Abondoned oil and gas wells - a reconnaissance study of an unconventional geothermal resource

A. G. Reyes

GNS SCIENCE REPORT 2007/23

July 2007 Abandoned oil and gas wells - a reconnaissance study of an unconventional geothermal resource

A. G. Reyes

GNS Science Report 2007/23 July 2007

GNS Science BIBLIOGRAPHIC REFERENCE

Reyes A.G. 2007. Abandoned oil and gas wells – a reconnaissance study of an unconventional geothermal resource, GNS Science Report 2007/23 41 p.

A. G. Reyes, GNS Science, 1 Fairway Drive, Avalon, PO Box 30368, Lower Hutt

© Institute of Geological and Nuclear Sciences Limited, 2007 ISSN 1177-2425 ISBN 978-0-478-09988-1

CONTENTS

ABSTRACT...... iii KEYWORDS ...... iii 1.0 INTRODUCTION ...... 1 1.1 Geothermal Resources in ...... 1 1.2 Objectives of Study...... 2 2.0 ABANDONED OIL AND GAS WELLS IN OTHER COUNTRIES ...... 4 3.0 ABANDONED OIL AND GAS WELLS IN NEW ZEALAND ...... 4 3.1 Distribution and Dates of Completion...... 4 3.2 Well Depths and Estimated Bottom hole Temperatures ...... 7 3.3 Reasons for abandoning wells ...... 14 4.0 HARNESSING GEOTHERMAL ENERGY FROM ABANDONED HYDROCARBON WELLS14 4.1 Geothermal Potential Projections...... 14 4.2 Sedimentary basins and other areas outside the Taupo Volcanic Zone...... 16 5.0 CURRENT GEOTHERMAL USE OF ABANDONED HYDROCARBON WELLS...... 18 6.0 INITIAL STEPS FOR USE OF WELLS ...... 20 7.0 RECOMMENDATIONS FOR FUTURE WORK ...... 23 8.0 SUMMARY AND CONCLUSIONS ...... 24 9.0 ACKNOWLEDGMENTS ...... 25 10.0 REFERENCES ...... 25

FIGURES

Figure 1 Temperature, depth and permeability ranges of conventional and unconventional sources of geothermal energy in New Zealand...... 2 Figure 2 Distribution of conventional and unconventional geothermal resources in New Zealand...... 3 Figure 3 Distribution of offshore and onshore abandoned wells in various hydrocarbon basins. ...5 Figure 4 Number of offshore and onshore abandoned wells in hydrocarbon basins and non- basins of New Zealand...... 5 Figure 5 Map showing the distribution of abandoned oil and gas wells with date of drilling completion and the general location of sedimentary basins...... 6 Figure 6 Drilled vertical depths of abandoned onshore hydrocarbon wells...... 8 Figure 7 Estimated bottom hole temperatures in abandoned onshore hydrocarbon wells...... 9 Figure 8 Temperature ranges of abandoned oil and gas wells ...... 13 Figure 9 Depth vs estimated bottom hole temperatures of offshore and onshore abandoned hydrocarbon wells and possible geothermal uses...... 14 Figure 10 Depth vs formation pressure in wells ...... 17 Figure 11 Possible geothermal uses of abandoned hydrocarbon wells...... 15 Figure 12 Map showing areas where temperatures >120oC could be intersected at >3200m...... 17 Figure 13 Direct heat use of 29oC waters from well Bonithon-1, ...... 18 Figure 14 A. Bonithon-1 in New Plymouth B. Kotuku borehole forming a pseudo-warm spring. ...18

GNS Science Report 2007/23 i

Figure 15 Distribution of abandoned onshore hydrocarbon wells in Taranaki showing (A) vertical depths and (B) estimated bottomhole temperatures with roads and population centres...... 21 Figure 16 Abandoned hydrocarbon wells in Taranaki (squares) that may be converted for geothermal use...... 22

TABLES

Table 1 Number of wells within a range of temperatures ...... 15 Table 2 Potential energy from wells ...... 16 Table 3 Potential energy from drilling new wells in high heat flow regions ...... 22 Table 4 Proposed wells for a 0.5 to 1 MWe pilot geothermal plant in Taranaki ...... 23 Table 5 Main points of presentations during the Oil and Gas conference held in March 2006....29 Table 6 Basic well data...... 32

APPENDICES

Appendix 1 Notes on the Geothermal Energy Generation in Oil and Gas Settings Conference ...... 27 Appendix 2 Abandoned onshore hydrocarbon wells in New Zealand...... 31

GNS Science Report 2007/23 ii ABSTRACT

There are 349 abandoned onshore oil and gas wells in New Zealand that can potentially be harnessed for geothermal energy for direct usage of heat, power production and development as pseudo hot spring systems for tourism. Well depths range from 17 to 5064m vertical. Estimated bottom hole temperatures range from ambient temperatures (about 12 to 18oC) to 172oC. Of these wells 65% are located in the North Island, the rest in South Island. Taranaki, the only oil and gas producing hydrocarbon basin in the country, has the largest number of abandoned oil and gas wells at 140 or about 40% of all onshore wells.

The use of abandoned hydrocarbon wells for direct heat utilisation and power generation could add another 6.1 PJ to the geothermal energy potential of New Zealand. Of these 1.4 PJ is for use with ground source heat pumps from 123 wells with bottomhole temperatures of <30oC drilled to depths of 17m to 686m for space heating and heating of domestic water; 4.54 PJ for other direct heat uses from 206 wells with temperatures of 31-120oC; and 0.15 PJ from 20 wells with bottomhole temperatures of 120-172oC drilled to 3131-5064m. The total power that could be produced from the 20 high temperature wells, assuming a flow of about 4 L s-1 and a capacity factor of 10% is 4772 kWe (kilowatt electric) or an average of about 238 kWe per well.

The requisite temperature may be present in abandoned hydrocarbon wells for a wide range of geothermal energy uses but there are many geoscientific, technical and non technical problems to be considered before oil and gas wells can be used for geothermal power generation or cogeneration of geothermal and hydrocarbon energy. However New Zealand has the available expertise in the geothermal and oil and gas industries and access to the requisite technology, making this scheme of converting old hydrocarbon wells for geothermal use viable.

Taranaki has a large energy-intensive dairy industry that would benefit from the cogeneration of geothermal and oil and gas wells and the conversion of abandoned oil and gas wells for geothermal use. Possible sites for a 200 kWe binary cycle pilot plant have been selected, preferably using two wells, one for production and the other for reinjection of waste fluids.

KEYWORDS

Geothermal, oil and gas, hydrocarbon, direct heat, power, binary cycle.

GNS Science Report 2007/23 iii 1.0 INTRODUCTION

With the technological advances in the last 20 years the definition of an economically viable geothermal resource has broadened to a resource that extracts heat from the rock or circulating aquifer waters at temperatures ranging from as low as 4oC (Lund and Freeston, 2001) to as high as sub-magmatic (400oC) and from about 15m to >3500m depths. At shallow depths and temperatures of 10-35oC heat can be harnessed from the ground or circulating water in boreholes or warm water in abandoned mines using ground source heat pumps (Lund et al, 2005). In Central and Northern Europe, for example, all heat energy stored below about 15m from the surface is considered geothermal energy (Rybach and Sanner, 2000).

For some of the unconventional sources of geothermal energy, such as heat from sedimentary basins and hot dry rock (HDR), permeability or the volume of circulating fluids may be too low to economically extract heat. To increase the productivity and lifetime of these marginal geothermal sources for power generation, enhanced or engineered geothermal systems (EGS) technology may be required where, essentially, low permeability hot rock at depth is artificially fractured and fluid is introduced into the newly-fractured rock where it is heated by conduction. The heated fluids are recirculated to the surface by pumps and the heat extracted by a heat exchanger (e.g. Smith, 1983; White, 1983).

1.1 GEOTHERMAL RESOURCES IN NEW ZEALAND

There are conventional and non-conventional sources of geothermal energy for power generation and direct heat utilisation in New Zealand (Figure 1) ranging in temperature from about 12 to 15oC at about 15m to as high as >330oC at >3,500m. Power can be generated by steam turbines or by binary cycle systems using the Organic Rankine Cycle (ORC) where the working organic fluid has a low boiling temperature such as isopentane, or the Kalina Cycle which uses ammonia/water.

The newest system is called the NE (Natural Energy) Engine that operates on hot and cold water and uses liquid CO2 as a working fluid in the heat exchanger engine (www.fossil.energy.gov).

Conventional sources include (1) high enthalpy hot spring systems in the Taupo Volcanic Zone (TVZ) and Ngawha in Northland some of which are now harnessed for power production, (2) waste-water from high enthalpy power-generating systems such as Wairakei, Mokai, Ohaaki-Broadlands, Kawerau, Rotokawa and Ngawha and (3) hot spring systems outside the Taupo Volcanic Zone and Ngawha and including springs in the North Island, islands in the Bay of Plenty and Hauraki Gulf and in the South Island (Figure 2).

Nonconventional sources of geothermal energy include: (1) most of the TVZ outside high enthalpy geothermal systems, where thermal gradients range from 40oC/km to >50oC/km but permeability low, (2) 12oC to 170oC waters in abandoned oil and gas (hydrocarbon) wells, (3) heated waters in abandoned flooded coal and mineral mines, (4) conductive heat from shallow depths (<250m) for ground source heat pump harnessing, (5) conductive heat at depth in high-heat flow (>70 mW/m2) sedimentary basins, metamorphic terrain and rapidly rising regions of the country such as the Raukumara Peninsula (Mazengarb and Speden, 2000) and the Southern Alps (Allis and Shi, 1995) and regions outside high heat flow regions. The location of some of the nonconventional heat sources available in New Zealand are shown in Figure 2.

GNS Science Report 2007/23 1 Figure 1. Temperature, depth and permeability ranges of conventional and unconventional sources of geothermal energy in New Zealand. The temperature and depth range of abandoned oil and gas wells in New Zealand are highlighted in red.

Geothermal energy in this country is associated with power generation in the Taupo Volcanic Zone and Ngawha where volcanism is recent. New Zealand has a total installed power generating capacity of 435 MWe provided by six geothermal systems in the Taupo Volcanic Zone and one at Ngawha in Northland, where a binary plant produces 9 MWe (http://www.crownminerals.govt.nz).

The installed capacity for direct usage of geothermal energy in the country is 448 MWt (White, 2006), 62% of which is produced from waste water and waste steam or dedicated wells in the power-generating Kawerau, Mokai, Ohaaki-Broadlands and Wairakei geothermal systems. About 170 MWt is used for bathing in more than 30 commercial swimming pools and in ad hoc holes dug for hot water at the edges of rivers or at tide level along the sea shore, space-heating, fruit irrigation, plant or fish cultivation, and health and beauty therapy.

1.2 OBJECTIVES OF STUDY

This is reconnaissance study on the potential of extracting geothermal energy from abandoned oil and gas wells and regions outside the Taupo Volcanic Zone (TVZ) and Ngawha. Assumptions are broad and conservative, calculations are basic.

GNS Science Report 2007/23 2 Figure 2. Distribution of conventional and nonconventional geothermal resources in New Zealand including hot springs, abandoned oil and gas wells, abandoned flooded underground coal and mineral mines and stored heat in the rock. Conductive heat flow contours are from Allis et al, 1998.

GNS Science Report 2007/23 3 2.0 ABANDONED OIL AND GAS WELLS IN OTHER COUNTRIES

The idea of using abandoned oil and gas (hydrocarbon) wells and drilling wells in sedimentary basins to produce geothermal energy is not new. Low enthalpy geothermal resources in sedimentary basins in France have been tapped by wells for district heating since 1969. At present there are 41 plants in the Paris basin including 15 in the Aquitane basin and five in other regions producing hot water for a total of 200,000 households and supplanting about 170,000 TOE (Laplaige et al, 2000). Albania, Poland, Germany, Switzerland, USA, France and Australia are exploring the possibility of recovering heat from hydrocarbon wells (e.g., Bodvarrsson and Reistad, 1983; White, 1983; Barbacki, 2000; Schellshmidt et al, 2000; Lund et al, 2005).

In the USA abandoned hydrocarbon wells, in regions of high heat flow (>75 mW/m2) and sufficient water flow such as Texas and Oklahoma, are estimated to have a power generating potential at the gigawatt level (Appendix 2). Using the existing wells minimises the initial costs of geothermal power production. The main capital funding input is fitting existing wells with heat exchangers and small power plants (McKenna et al, 2005). In March 2006, the Southern Methodist University in Texas held the first conference on the potential of harnessing geothermal power from abandoned hydrocarbon wells (Appendix 1).

3.0 ABANDONED OIL AND GAS WELLS IN NEW ZEALAND

Although the number of abandoned hydrocarbon wells in New Zealand is <1% that of the USA several factors indicate that abandoned oil and gas wells can be harnessed for geothermal energy, including (1) bottomhole temperatures >50oC in more than 150 wells drilled to depths >625m, (2) the presence of nonsaline or saline waters in most of the abandoned wells that may be discharged using artesian pressures inherent in the wells or through downhole pumps, (3) over pressuring in some wells in Taranaki (King and Thrasher, 1996), the East Coast (Field et al) and Northland (Isaac et al) indicate that some wells are artesian and will flow without the need for well stimulation or hydrofracturing, (4) mud losses during drilling indicate permeability in several wells e.g., Kiakia-1/1A in the East Coast, and (4) large areas of high heat flow cover parts of the Northland, Taranaki, Wanganui and East Coast basins in the North Island and parts of the West Coast basin of the South Island (Figures 2 and 3) where the surface conductive heat flow of >70 mW/m2 indicate thermal gradients of >33oC/km.

3.1 DISTRIBUTION AND DATES OF COMPLETION

There are about 450 onshore and offshore abandoned hydrocarbon wells in New Zealand (Figure 3). Of these wells, 349 are onshore with the offshore wells drilled mostly in waters <150m deep.

Thirty-six of the onshore wells were drilled out of basins and the rest are located in eight of the 18 hydrocarbon basins in the country (Figures 3 and 4). Of the onshore wells, 65% are located in the North Island and the rest in the South Island. The highest number of abandoned hydrocarbon wells, at 140, are found in Taranaki, the only basin producing oil and gas in the country.

GNS Science Report 2007/23 4 Figure 3. Distribution of offshore and onshore abandoned wells in various hydrocarbon basins (data from http://www.crownminerals.govt.nz).

Figure 4. Number of offshore and onshore abandoned wells in New Zealand.

GNS Science Report 2007/23 5 Figure 5. Map showing the distribution of abandoned oil and gas wells with date of drilling completion and the general location of sedimentary basins (data from http://www.crownminerals.govt.nz). Active fault lines are shown as grey lines (data from www.gns.cri.nz). Red line defines the boundaries of the Taupo Volcanic Zone.

GNS Science Report 2007/23 6 The onshore wells were drilled from 1866 to 2005 with the two late-19th century ones located in Taranaki (Figure 5). The completion dates of 93 wells are unknown. Of those with known dates, 19 wells drilled from 1903-1944 are located in Taranaki, 16 in the East Coast of North Island, two in the Wanganui basin, 15 in the West Coast of South Island and one in Canterbury. These were drilled to depths of 19 to 3331m. Thirty-four wells were drilled before 1970, 33 before 1980, 68 before 1990, 41 from 1990-1999 and 27 after 2000. The date of completion nearly a century ago does not preclude development. For example, Bonithon-1, a well used today for the Taranaki baths in New Plymouth was drilled in 1908. However, Bonithon-2 sited nearby and drilled nearly at the same time could not be located. Well diameters below the production casing shoe range from about 2.5” to 12”. A liner is sometimes installed and sometimes perforated. However, the liner is retrieved prior to abandoning the wells. Hence the age of the boreholes may, however, affect the degree of cave-ins in wells without liners.

3.2 WELL DEPTHS AND ESTIMATED BOTTOM HOLE TEMPERATURES

Abandoned wells have total vertical depths ranging from 17m to 5064m (Figure 6). Twelve of the 13 wells drilled deeper than 4000m are located in Taranaki e.g., Inglewood-1 (5061m) and Cardiff-1 (5064m). The one well deeper than 4000m outside Taranaki is located in the East Coast i.e., Rere-1 (4351m; Figure 2).

Down hole temperatures, after the well had stabilised after drilling, are often not measured in hydrocarbon wells although temperatures during or just a few hours after drilling have been measured in some wells.

Since stable downhole temperatures are not available for most wells, bottom hole temperatures are roughly estimated using published surface conductive heat flow data (Funnell et al, 1996; King and Thrasher, 1996; Funnell and Allis, 1997; Field et al, 1997; Allis et al, 1998, Cook et al, 1999) and converted to thermal gradient, in oC/km, using a factor of 2.1 (Funnell, pers. comm., 2003) and an average surface temperature of 15oC. In two wells, Kowai-1 and Hohonu-1, the bottom temperatures measured a few hours after drilling are higher by 8oC and 3oC, respectively than calculated bottomhole temperatures, i.e., 60oC vs 52oC for Hohonu-1 and 52oC vs 49oC for Kowai-1. Thus calculated bottomhole temperatures are most likely minimum values. Homogenisation temperatures in the latest aqueous fluid inclusions in quartz in abandoned and active hydrocarbon wells in Taranaki are often about +10oC of the estimated bottomhole temperatures (Reyes unpublished data, Reyes, 1998).

The estimated bottomhole temperatures in the onshore abandoned hydrocarbon wells range from ambient to as high as 172oC at 4451m in well New Plymouth-2 in Taranaki (Figures 7 and 8; Table 1). About 34% of all the onshore wells (120) have bottom hole temperatures of <30oC suitable for harnessing with ground source heat pumps (Figure 8).

Temperatures of 30-100oC were intersected in 57% (199) of the onshore wells and another 18 wells (5%) have estimated bottomhole temperatures of 100-120oC, suitable for other direct uses of heat. Except for four wells, all wells with bottomhole temperatures of 120- 172oC are located in Taranaki (Figure 7). The four wells outside Taranaki are: Waimamaku-2 in Northland (124oC), Rere-1 in the East Coast (147oC), Bounty-1 (131oC) and Kokiri-1 (122oC) in the West Coast, South Island (Figures 2 and 7).

GNS Science Report 2007/23 7 Figure 6. Drilled vertical depths of abandoned onshore hydrocarbon wells. Grey lines are active faults (www.gns.cri.nz) and the red line defines the boundaries of the Taupo Volcanic Zone.

GNS Science Report 2007/23 8 Figure 7. Estimated bottom hole temperatures in abandoned onshore hydrocarbon wells. Grey lines are active faults (www.gns.cri.nz) and the red line defines the boundaries of the Taupo Volcanic Zone.

GNS Science Report 2007/23 9 Figure 8. Temperatures ranges of onshore and offshore abandoned oil and gas wells.

In contrast to onshore wells about 92% of abandoned offshore wells (97 wells) have bottomhole temperatures >50oC (Figure 8) because these are all drilled deeper than 700m. One offshore well, Clipper-1 in the Great South basin, has a calculated bottomhole temperature of nearly 185oC at 4742m.

A plot of total depth versus estimated bottom hole temperatures (Figure 9) show three onshore wells with thermal gradients higher than most wells: Rotokautuku-1 in the East Cape, Bounty-1 in the West Coast and New Plymouth-2 in Taranaki (Figures 2 and 9). Rotokautuku-1 is located in a region of active landmass uplift in the Raukumara Peninsula where the surface heat flow is high at 170 mW/m2 believed to be caused by the advection of rising hot fluids from depth (Field et al, 1997). The thermal gradient in Rotokautuku is about 80oC/km.

Well Bounty-1 in the West Coast is 3131m deep, drilled in an isolated region with a heat flow of 80 mW/m2 heat flux (Figure 3) where the landmass is rapidly rising (Allis and Shi, 1995). Well New Plymouth-2 is drilled to 4451m in a region of 70 mW/m2 heat flux and is located near the Pliocene to Quaternary and Paritutu volcanic centres which may still possess vestigial heat at depth.

The thermal gradient is about 40oC/km in wells Bounty-1 and New Plymouth-2. The three offshore wells with the highest thermal gradients at 40-50oC/km are wells Takapu-1 and Clipper-1 in the Great South basin and well Cook-1 in offshore Taranaki.

GNS Science Report 2007/23 10 Figure 9. Depth versus estimated bottom hole temperatures of all offshore and onshore abandoned hydrocarbon wells and possible uses of geothermal fluids.

GNS Science Report 2007/23 11 Table 1. Number of wells within a range of calculated bottomhole temperatures and corresponding depth ranges, in North island and South Island onshore basins and non- basins. BHT= bottomhole temperature. Number of BHT(oC) Depth Region <30oC 30-50oC 50-80oC 80-100oC 100-120oC >120oC wells range range (m) North Island Northland 10 17-127 44-3357 5 3 1 - - 1 Taranaki 140 17-172 48-5064 22 23 27 36 16 16 Wanganui 15 22 – 90 295-3495 3 7 4 1 - - East Coast 62 16-150 55-4351 21 20 16 3 1 1 Other areas 27 16 – 66 45-1684 17 9 1 - - - South Island West Coast 70 16-134 122-3749 43 9 13 2 1 2 Canterbury 8 29 - 70 661-1696 1 4 3 - - - Southland 8 17-106 61-3131 4 - 3 - 1 - Other areas 9 17 - 81 73-2135 7 1 - 1 - - Total 349 123 76 68 43 19 20

GNS Science Report 2007/23 12 Table 2. Potential energy in kW from oil and gas wells assuming flow of 4L s-1. The conversion factor (CF) used for calculating kWt (kilowatt-thermal) is 0.7 for wells with bottomhole temperatures <120oC to be harnessed for direct heat uses. For power generation using a binary system a conversion factor of 0.1 is used. Conversion factors of 0.7 and 0.1 refer to the conversion efficiency from one form of energy to another and are geothermal industry standards e.g., Lund and Freeston, 2001. The factor 0.1 is used because power generation using steam is very inefficient and only about 10% is converted to electrical energy. Region/ Estimated Energy in kW kWt kWe Basin CF=0.7 CF=0.1

<30oC 30-50oC 50-80oC 80-100oC 100-120oC >120oC <120oC >120oC North Island Northland 1,900 1,800 1,100 - - 2,100 3,360 210 Taranaki 8,400 15,600 31,000 53,400 28,600 38,800 95,900 3,880 Wanganui 1,300 5,100 4,400 1,500 - - 8,610 0.0 East Coast 7,800 13,000 18,200 4,500 1,900 2,500 31,780 250 Non-basin 5,900 6,200 1,100 - - - 9,240 0 Subtotal 25,300 41,700 55,800 59,400 30,500 43,400 148,890 4,340 South Island West Coast 14,800 6,200 13,900 2,900 1,900 4,320 27,790 432 Canterbury 500 3,000 2,100 - - - 9,240 0.0 Southland 1,400 - 3,300 - 1,800 - 4,550 0.0 Non-basin 2,500 800 - 1,400 - - 3,290 0.0 Subtotal 19,200 10,000 19,300 4,300 3,700 4,320 39,550 432 Total 44,500 51,700 75,100 63,700 34,200 47,720 188,440 4,772

GNS Science Report 2007/23 13 3.3 REASONS FOR ABANDONING WELLS

Most wells were abandoned because of low or total lack of hydrocarbon shows. The reservoirs are, instead, often saturated with fresh or saline waters and are a boon to geothermal exploitation. Others were abandoned because of drilling problems e.g., swelling clays and oil and sand bursts.

Abandoned wells are plugged. In most cases liners are not installed or are pulled out upon abandonment. Hence cave-ins may occur in some older wells.

Permeability is apparently present in most of the wells as indicated by the discharge of water from some wells; however the water level in the wells is unknown. In Taranaki, there is a widespread zone of over pressuring with respect to the hydrostatic gradient at >3000m (King and Thrasher, 1996) indicating that these wells may be artesian (Figure 10) and hence will flow without the need for downhole heat pumps.

Figure 10. Depth versus formation pressure derived from measured values or mud weights in several Taranaki wells showing over pressuring with respect to hydrostatic pressure at about >3km depths (Figure 6.12 of King and Thrasher, 1996)

4.0 HARNESSING GEOTHERMAL ENERGY FROM ABANDONED HYDROCARBON WELLS

4.1 GEOTHERMAL POTENTIAL PROJECTIONS

As shown in Figures 9 and 11 geothermal energy from abandoned oil and gas wells can be harnessed for direct heat using ground source heat pumps at temperatures of about <30oC for space heating and heating water for domestic use. Wells with bottomhole temperatures from 30o to 120oC can be harnessed for other direct heat uses, and wells with waters >120oC and sufficient water flow can potentially be used for power generation.

There are 123 onshore wells with bottomhole temperatures <30oC (Table 1) that can potentially yield a total of 31,150 kWt (44,500 x 0.7=31,500) as shown in Table 2. On the other hand, if a 6 kW capacity closed loop ground source heat pump system is installed in each well, then a total of 738 kWt can be produced.

GNS Science Report 2007/23 14 Figure 11. Possible geothermal uses of abandoned hydrocarbon wells. Grey lines are active faults (www.gns.cri.nz) and the red line defines the boundaries of the Taupo Volcanic Zone.

GNS Science Report 2007/23 15 Assuming a flow of 4 L s-1, the 206 wells with bottomhole temperatures of 30 to 120oC can potentially produce 166,754 kWt of energy (238,220 x 0.7 = 166,754) for various direct heat uses.

For the 20 wells with temperatures of 120-172oC, the hot fluids can be used to generate power using a down hole heat pump (to enhance the flow rate and keep the resource under pressure to prevent formation of a vapour phase (Hance, 2005) and a binary cycle system. A down hole pump can be used up to about 200oC (Hance, 2005) which is well above the highest temperatures in the abandoned wells. The total power that could be produced from these wells, assuming a flow of about 4 L s-1 and a capacity factor of 10% is 4,772 kWe (kilowatt electric) or an average of about 238 kWe per well.

The use of abandoned hydrocarbon wells for direct heat utilisation and power generation could add another 6.1 PJ to the geothermal energy potential of New Zealand. Of these 1.4 PJ is for use with ground source heat pumps from 123 wells with bottomhole temperatures of <30oC drilled to depths of 17m to 686m; 4.54 PJ for other direct heat uses from 206 wells with temperatures of 31-120oC; and 0.15 PJ from 20 wells at temperatures of 120-172oC drilled to 3131-5064m.

4.2 SEDIMENTARY BASINS AND OTHER AREAS OUTSIDE THE TAUPO VOLCANIC ZONE

The region with surface conductive heat flow of >70 mW/m2 (>33oC/km), outside the Taupo Volcanic Zone, Ngawha and land administered by the Department of Conservation, covers an area of about 31,520km2 or about 12% of the New Zealand landmass (Figure 12). In these regions, a temperature of 120oC will be intersected at about 2,600m in Northland and the Coromandel and at least 3,200m in the rest of the North Island and in South Island (Figures 2 and 12; Table 3).

Drilling new wells in these areas is dependent on accessibility (access factor) dictated by topography (e.g., slip-prone rugged Alpine slopes are problematic), land usage (e.g., national parks, private property, Maori-owned may not be accessible for drilling) and geology (e.g. proximity to faults may contribute to permeability at depth and are therefore attractive for drilling; areas best drilled for coal, hydrocarbons or precious metals may not be immediately accessible for deep drilling; regions with swelling clays or highly silicified rocks may cause drilling problems). The success rate of 0.40, used in Table 3, is the lowest success rate in exploration geothermal drilling in New Zealand, based on the percentage of geothermal wells that would successfully produce 1 MWe per five wells drilled (Barr et al, 1984).

Assuming that the areas to be drilled, at 2 wells/100 km2, have enough permeability where heated water circulates, the temperature of extraction is 100oC, and the drilled wells will have a flow of at least 4 L s-1 then another 21,100 kWe can be potentially produced or 0.67 PJ of geothermal energy generated (Table 3).

However, before drilling new deep wells in high heat flow regions outside the Taupo Volcanic Zone and Ngawha, geothermal energy from existing abandoned hydrocarbon wells should be explored first.

GNS Science Report 2007/23 16 Figure 12. Map showing areas where temperatures >120oC could be intersected at >3200m. Blue areas are under the jurisdiction of the Department of Conservation and cannot be drilled.

GNS Science Report 2007/23 17 5.0 CURRENT GEOTHERMAL USE OF ABANDONED HYDROCARBON WELLS

In Taranaki, warm bicarbonate water (27oC) from the 910m deep Bonithon-1, an abandoned hydrocarbon well drilled in 1908, is heated to 33-38oC by gas and fed into the therapy and private pools of a commercial spa enterprise. The bore water is also bottled and sold as therapeutic mineral water (Figure 13). In Kotuku, West Coast, a leaking hydrocarbon well discharged 21oC (ambient temperature=13oC) effervescent bicarbonate waters at 3 kg s-1 for years and formed a pseudo warm spring pool that could be used as a tourist attraction (Figure 14). However in early 2006 the well ceased to flow due probably to sealing by carbonate deposition and the lowered water level caused by drought in the region. A warm spring in Lake Omapere, Northland was also originally a well. These examples show that it is possible to harness abandoned hydrocarbon wells for direct utilisation of heat or turn them into “pseudo hot springs” for tourism.

Despite the projections of extracting gigawatts of geothermal power from abandoned hydrocarbon wells in the Gulf regions of the USA, only one hydrocarbon well is producing 1.5 MWe of geothermal power, located in a geopressured sedimentary basin in Pleasant Bayou, Louisiana (Campbell and Hattar, 1990; Griggs, 2005).

The well is 5030m deep, and intersected a leaky fault, a fault that leaks due to pressure differentials in the reservoir. Wellhead pressure is 20.7 MPa. Fluids contain 87% CH4. The hybrid cycle power plant is equipped with a pressure reduction turbine, with the gas providing 690 kW, the binary cycle turbine 535 kW and a parasitic load of 270 kW. Problems with corrosive saline solutions were solved by using 16 gauge steel; scaling problems from 130,000 mg/kg TDS waters by using inhibitors, and carbon fouling by regularly shutting and opening the plant (www.smu.edu/geothermal/Oil&Gas/Oil&Gas_SMUmeeting_summary; Appendix 1).

Figure 13. Direct heat use of 29oC waters Figure 14. Kotuku borehole forming a pseudo-warm spring from well Bonithon-1, New Plymouth (21oC) in 2003. Flow is 3 kg/s (photo by A.G.Reyes).

GNS Science Report 2007/23 18 Table 3. Drilling new wells in regions with heat flow >70 mW/m2 where the geothermal gradient is >33oC/km. Two wells are proposed for each 100 km2 area. One is for production, the other for reinjection. CF= conversion factor

No. of Thermal Temperature 2 Area in Temperature Enthalpy Flow wells for kWe Region gradient of extraction wells/100 Success kW TJ PJ km2 at depth (kJ/kg) (kg/s) power (0.1 CF) (oC/km) (oC) km2 generation 3,200m North Island 33 7,865 120oC 100 419 4 157 0.4 31 52,727 5,273 166 0.17 South Island 33 18,800 120oC 100 419 4 376 0.4 75 126,035 12,604 398 0.40

2,600m Coromandel 40 1,610 120oC 100 419 4 32 0.4 6 10,793 1,079 34 0.03 Northland 40 3,245 120oC 100 419 4 65 0.4 13 21,754 2,175 69 0.07 TOTAL 31,520 125 21,131 667 0.67

GNS Science Report 2007/23 19 In New Zealand temperature may be present but there are many technical and non technical problems to be considered when converting oil and gas wells for geothermal extraction e.g.,

1. Marginal permeability and fluid flow in a number of oil and gas wells may require hydrofracturing and/or well stimulation, 2. The state of the casing and grouting jobs of wells drilled before 1980, which comprise about 45% of the onshore wells, may not be satisfactory and the wells not usable, 3. Wells are filled and plugged when abandoned and will require drilling out the fills and cement before use, 4. Some wells may be difficult to locate because all surface traces are covered (Funnell, pers comm. 2007), 5. Oil fouling of geothermal turbines is possible when producing some wells for geothermal power, 6. Liner tubings may need to be converted to slotted liners (or the tubings perforated), 7. Liners have either been pulled out or not installed at all and rock may have caved-in in some wells, 8. Casing corrosion, whether internally or externally induced, is probable, 9. Access to the wells owned by oil companies, Maori tribes, other private owners or the New Zealand government, 10. Acceptance and support of the government to the idea of converting hydrocarbon wells for geothermal use.

In Taranaki cogeneration and colocation of geothermal and hydrocarbon energy sources may affect reinjection strategies because water reinjection may hasten water flooding in structurally or stratigraphically-connected hydrocarbon-bearing zones in nearby producing gas and condensate wells. Other factors that should be considered include finding methods of stimulating water flow in abandoned oil and gas wells, determining the type of binary cycle system to be used (Rankine, Kalina or NE Engine) and the feasibility of using hybrid power plant systems to cogenerate power from geothermal fluids and methane from the same well, and later, investigating EGS (Enhanced or Engineered Geothermal Systems) technology to exploit deep oil and gas wells.

6.0 INITIAL STEPS FOR USE OF WELLS

A pilot plant could be set up in Taranaki to demonstrate the viability of this hydrocarbon-to- geothermal energy scheme. Taranaki has the most number of abandoned hydrocarbon wells with some of the highest estimated bottom hole temperatures and artesian pressures below 3000m (Figures 15A and B). It is the centre of oil, gas and petrochemical production in the country. It is one of the most energy-hungry regions of the country that could benefit from cogeneration and colocation of hydrocarbon and geothermal energy sources to support its dairying, horticultural and food processing industries. Low temperature wells could be harnessed to provide heat for space heating of dairy farm buildings, milk pasteurisation, greenhouses, swimming pools and spas. Higher temperature wells (16 wells) can be used for power generation.

GNS Science Report 2007/23 20 The 16 high temperature wells selected for possible geothermal power generation (Figure 15) have estimated bottom hole temperatures 120oC to 172oC, drilled to >3100m and are mostly artesian. However four of these (with yellow crosses) were drilled prior to 1980 and the state of the casing, liners and grouting jobs is uncertain and need to be examined. All 16 wells have been plugged with cement upon abandonment.

For a binary cycle pilot plant with a capacity of about 200 kW five wells were selected based on their bottomhole temperatures, proximity to a population centre or an industrial complex such as Fonterra and proximity to another abandoned well that can be possibly used as a reinjection well. These wells include Tipoka-1, Te Kiri-1, Toko-1, New Plymouth-2 or Inglewood-1 (Table 4), listed according to priority, and shown in Figure 16. A downhole pump may be needed in some wells to increase or sustain fluid flow. Electricity generated from Tipoka-1 or Te Kiri-1 can be used by nearby dairy farms or Fonterra while other wells such as from Toko-1, New Plymouth-2 and Inglewood-1 may supplement electricity from the grid for Stratford, New Plymouth and Inglewood, respectively. Other wells with bottomhole temperatures >120oC near Stratford are Wharehuia-1, Piakau-1 and Waihapa-1. Another well that could be harnessed in Inglewood is Tauteka-1. Cardiff-1, a well with a bottomhole temperature of 153oC may be reactivated as a source of hydrocarbons and hence not included in the list.

More geoscientific studies need to be done on these wells before any power harnessing could be done. The effect of drawing out large volumes of hot water on nearby actively- producing hydrocarbon wells is not known.

A B

Figure 15. Distribution of abandoned onshore hydrocarbon wells in Taranaki showing (A) vertical depths and (B) estimated bottomhole temperatures with roads and population centres. Haloed wells may be used for geothermal power production.

GNS Science Report 2007/23 21 Figure 16. Abandoned hydrocarbon wells in Taranaki (squares) that may be converted for geothermal use. All plotted abandoned hydrocarbon wells have estimated bottom hole temperatures (BHT) >120oC and depths from 3131 – 5064m.

GNS Science Report 2007/23 22 Table 4. Proposed wells for 200 kWe pilot geothermal plant in Taranaki. Refer to Appendix 3 for well details. BHT= bottom hole temperature.

Estimated Well Priority Comments kWe Tipoka-1 fluids (BHT= 142oC at 4360m) can be reinjected in Tipoka-2, Tipoka-1 1 240 1.1 km away, which has BHT= 88oC at 2504m. Power can be used by nearby dairy farms. Well (154oC at 4710m) near dairy farms associated with Fonterra. Te Kiri-1 2 260 There may be a need to drill a nearby reinjection well Fluids from Toko-1 with BHT=150oC at 4900m can be reinjected into Toko-2 with BHT = 103oC at 3200m, 1.2km away. There is a seal between the Mangahewa Fm in Toko-1 and the shallower Fm in Toko-2. Power can be used for Stratford. Other wells near Toko-1 3 250 Stratford that can be used for power generation are: Wharehuia-1 (114oC at 3595m) with fluids reinjected into Piakau-1 1.0km away or Waihapa-1 (144oC at 4942m) using Waihapa-2, 1.8km away, as a reinjection well Highest BHT of all onshore wells at 172oC; located in middle of New New Plymouth- Plymouth. Fluids can be reinjected in numerous adjacent abandoned 4 290 2 wells. This was drilled before 1980 and the state of the casings and grouts is unknown. BHT= 164oC at 5061m. This was drilled before 1980. There may be a need to drill a nearby reinjection well. The nearest abandoned well that could be used for reinjection is Ngatoro-1 about 2.1km away. Inglewood-1 5 275 Power can be used by Inglewood. Another well near Inglewood is Manganui-1 (131oC at 3753m) with Tauteka-1, 830m away, as a reinjection well

7.0 RECOMMENDATIONS FOR FUTURE WORK

This is merely a reconnaissance study whose main goal is to present an idea and the basic data of wells that could be used for geothermal energy purposes. Before any wells could be used the following studies should be done:

1. Review all literature on wells regarding water reservoirs, fault and stratigraphic permeability, stratigraphic connectivity among abandoned and actively-producing wells, downhole pressure and temperature measurements and geology.

2. Determine the state of the casing/tubings, liners and cementing jobs of selected wells.

3. Determine the corrosion state of the well pipes.

4. Measure downhole temperatures of selected wells.

5. Determine flow rates of well discharges and methods of stimulating water flow.

6. Find out if hydrofracturing is necessary or possible to enhance permeability.

7. Find out the maximum working temperatures of down hole pumps.

8. Determine fluid discharge chemistry to find out if a hybrid plants can be used to tap both gas and geothermal fluids, predict fouling problems to the plant, determine ways of disposing well fluids (use a reinjection well or dispose fluids into the waterways?).

9. Determine fluid pathways and temperatures using petrological and geochemical methods.

GNS Science Report 2007/23 23 10. Determine how geothermal production will affect the hydrocarbon reservoirs.

11. Study the economic viability of converting extant hydrocarbon wells for geothermal direct heat use or for power production.

8.0 SUMMARY AND CONCLUSIONS

The 349 abandoned onshore oil and gas wells in New Zealand have total vertical depths of 17 to 5064m and estimated bottom hole temperatures ranging from ambient temperatures (about 12 to 18oC) to 172oC. Of these wells 65% are located in the North Island, the rest in South Island. Taranaki, the only oil and gas producing hydrocarbon basin in the country, has the largest number of abandoned oil and gas wells at 140 or about 40% of all onshore wells and also contains 16 of the 20 wells with bottomhole temperatures >120oC.

Thus the use of abandoned hydrocarbon wells for direct heat utilisation and power generation could add another 6.1 PJ to the geothermal energy potential of New Zealand. Of these 1.4 PJ is for use with ground source heat pumps from 123 wells with bottomhole temperatures of <30oC drilled to depths of 17m to 686m for space heating and heating of domestic water; 4.54 PJ for other direct heat uses from 206 wells with temperatures of 31- 120oC; and 0.15 PJ from 20 wells with bottomhole temperatures of 120-172oC drilled to 3131-5064m. The total power that could be produced from the 20 high temperature wells, assuming a flow of about 4 L s-1 and a capacity factor of 10% is 4,772 kWe (kilowatt electric) or an average of about 238 kWe per well.

Taranaki has a large energy-intensive dairy industry that would benefit from the cogeneration of geothermal and oil and gas wells and the conversion of abandoned oil and gas wells for geothermal use. Possible sites for a 200 kWe binary cycle pilot plant have been selected using wells with bottomhole temperatures >120oC and include, with decreasing priority, Tipoka-1, Te Kiri-1, Toko-1, New Plymouth-2 or Inglewood-1. The selected wells are either near dairy farms or an industrial complex like Fonterra or within a population centre such as Stratford, new Plymouth and Inglewood. Three of the sites are within a 1.8 km radius from another abandoned well, but with lower temperatures, that can be used for reinjection. Well Inglewood-1, however, is 2.1 km from the nearest abandoned well and a reinjection may need to be drilled nearer the well and there is no nearby well for Te Kiri-1.

New wells in high heat flow regions of the country, outside the Taupo Volcanic Zone, Ngawha and Department of Conservation land, may provide another 0.67 PJ of energy assuming production of energy from waters extracted at 100oC and a flow of about 4 L s-1. However, these will only be drilled once the viability of geothermal power outside the Taupo Volcanic Zone and Ngawha have been proven by harnessing geothermal energy from abandoned hydrocarbon wells.

The requisite temperature may be present in abandoned hydrocarbon wells for a wide range of geothermal energy uses but there are many geoscientific, technical and non technical problems to be considered before oil and gas wells can be used for geothermal power generation or cogeneration of geothermal and hydrocarbon energy. However New Zealand has the available expertise in the geothermal and oil and gas industries and access to the requisite technology, making this scheme of converting old hydrocarbon wells for geothermal use viable.

GNS Science Report 2007/23 24 Converting at least a pair of abandoned hydrocarbon wells (one for production the other for reinjection) in Taranaki for use in a 200 kWe pilot plant may prove the viability of this scheme.

9.0 ACKNOWLEDGMENTS

Thank you to D. Darby and E. Mroczek for reviewing the report whose comments and suggestions have contributed to the improvement of the report. Discussions with D. Darby, E Mroczek, and J. Callan and speakers of the conference on Geothermal Energy Generation in Oil and Gas Settings Conference held in the Southern Methodist University, Texas in 13-14 March 2006 have helped in writing this report. Thank you to K. Hunt for her expert word processing.

10.0 REFERENCES

Allis R G and Shi Y (1995) New insights to temperature and pressure beneath the central southern Alps, New Zealand. NZ J Geol Geophysics, 38, 585-592. Allis R G, Funnell R and Zhan X (1998) From basins to mountains and back again: NZ basin evolution since 10 Ma. Proceedings 9th International Symposium on Water-Rock Interaction, Taupo New Zealand, 3-7. Barbacki A (2000) The use of abandoned oil and gas wells in Poland for recovering geothermal heat. Proceedings World Geothermal Congress 2000, Kyushu Japan, 3361-3365. Barr H, Grant M A and Mclachlan R (1984) Proving and development of geothermal fields, DSIR Report 116, Wellington New Zealand. Barry J M, Duff S W and MacFarlan D A B (1994) Coal resources of New Zealand. Coal report series CR3132, NZ Ministry of Commerce, 73 p. Bodvarrsson G and Reistad G M (1983) Forced geoheat recovery for moderate temperature uses. J Volcanol and Geoth Res, 15, 247-267. Campbell R G and Hattar M M (1990) Operation of a geopressured hybrid power system at Pleasant Bayou. Proceedings Energy Conversion Engineering Conference, 1990, IECEC-90 25th Intersociety, 91-101. Cook R A, Sutherland, R, Zhu H and others (1999) Cretaceous-Cenozoic geology and petroleum systems of the Great South basin, New Zealand. Institute of Geological and Nuclear Sciences Monograph 20, Lower Hutt New Zealand, 188 p. Dunstall M (2005) 2000-2005 New Zealand country update. Proceedings World Geothermal Congress 2005, Turkey. Field B D, Uruski C I and others (1997) Cretaceous-Cenozoic geology and petroleum systems of the East Coast region, New Zealand. Institute of Geological and Nuclear Sciences Monograph 19, Lower Hutt New Zealand, 301 p. Funnell R and Allis R G (1997) Hydrocarbon maturation potential of offshore Canterbury and Great South basins. Proceedings New Zealand Petroleum Conference, 22-30. Funnell R, Chapman D, Allis R and Armstrong P (1996) Thermal state of the Taranaki Basin, New Zealand. JGR, V 101 (B11), 25197-25215. Griggs J (2005) A reevaluation of geopressured-geothermal aquifers as an energy source. Proceedings 30th workshop on geothermal reservoir engineering, Stanford University, California. Hance C N (2005) Factors affecting costs of geothermal power development. Geothermal Energy Association for the US Department of Energy, 61 p.

GNS Science Report 2007/23 25 Isaac M J, Herzer R H, Brook F J and Hayward B W (1994) Cretaceous and Cenozoic sedimentary basins of Northland, New Zealand, Inst. of Geol and Nuclear Sciences Monograph 8, 203 p. King P R and Thrasher G P (1996) Cretaceous-Cenozoic geology and petroleum systems of the Taranaki Basin, New Zealand. Institute of Geological and Nuclear Sciences Monograph 13, Lower Hutt New Zealand, 243 p. Klein C W, Lovekin J W and Sanyal S K (2004) New geothermal site identification and qualification. GeothermEx Inc. report. Laplaige P, Jaudin F, Desplan A and Demange J (2000) the French geothermal experience review and perspectives. Proceedings World Geothermal Congress 2000, Kyushu Japan, 283-294. Lund, J, Freeston D H and Boyd T L (2005) World-wide direct uses of geothermal energy 2005. Proceedings World Geothermal Congress 2005, Turkey. Mazengarb C and Speden I G (2000) Geology of the Raukumara area. Institute of Geological and Nuclear Sciences 1:250,000 Geological Map 6. Mckenna J, Blackwell D, Moyes C and Patterson D P (2005) Geothermal electric power supply possible from Gulf Coast, midcontinent oil field waters. Oil and Gas Journal, 34-39. Rybach L and Sanner B (2000) Ground source heat pump systems, the European experience. GHC Bull, 16-26. Reyes A G (2001) Mineral alteration in a low-enthalpy hydrocarbon well, Taranaki, New Zealand. Proceedings 23rd New Zealand Geothermal Workshop. Schellschmidt R, Clauser C, and Sanner B (2000) Geothermal energy use in Germany at the turn of the millenium. Proceedings World Geothermal Congress 2000, Kyushu Japan, 427-432. Smith M (1983) A history of hot dry rock geothermal energy systems. J Volcanol and Geoth Res, 15, 1-20. White A A L (1983) Sedimentary formations as sources of geothermal heat. J Volcanol and Geoth Res, 15, 269-284.

Websites http://www.crownminerals.govt.nz www.fossil.energy.gov

GNS Science Report 2007/23 26 APPENDIX 1

NOTES ON THE GEOTHERMAL ENERGY GENERATION IN OIL AND GAS SETTINGS CONFERENCE

GNS Science Report 2007/23 27 APPENDIX 1 NOTES ON THE GEOTHERMAL ENERGY GENERATION IN OIL AND GAS SETTINGS CONFERENCE

The conference was held in March 2006 at the Southern Methodist University (SMU) in Texas, organised by D. Blackwell. The main point of the conference is the enormous potential of oil and gas settings in providing geothermal power. What oil and gas operators view as the death of a fossil fuel system is viewed as the source of another energy by the geothermal industry that also has the blessings of the environmentally conscious population.

Talks were about 75% technical, 25% laws and regulations affecting geothermal and oil and gas systems in the USA (main points of talks are in Table 4).

The most interesting talks and posters were centred on the heat flow map of the USA that SMU had published at the AAPG. The map making was led by David Blackwell of SMU. One of the main offshoots of this map is the reestimation of the geothermal potential of the USA using oil and gas wells and EGS technology (EGS= Enhanced or Engineered Geothermal Systems). The total conservative geothermal potential of the USA is 43,617,976 MWe. At present geothermal provides 8900 MWe of power to 24 countries world-wide.

The oil and gas operators view water flooding as the end of the field whereas geothermal operators see this phenomenon as the start of a new source of energy. Some of the problems in harnessing geothermal energy from oil and gas wells are not technical but include the lack of communication between people in the oil and gas and geothermal industries and the lack of overt support from the federal government. During the meeting the discussion panel decided to write a one-page white paper report on “Geothermal Energy Generation in Oil and gas Settings”, to be submitted to the government and oil and gas operators. Interestingly, the convenors sent nearly 15,000 invitations to oil and gas operators and technical people, government officials and the media to attend this conference (which is the first in the world and quite important for the future energy outlook of the USA, at least) but there were only 90 attendees, <10 are oil and gas operators, one government representative, and mostly geothermal people.

GNS Science Report 2007/23 28 Table 5. Main points of presentations during the Oil and Gas conference held in March 2006.

Speaker Company/Agency Topic Main Points of Talk Ray US DOE Geothermal Dept. of Energy Geothermal DOE’s geothermal budget for 2007: $0.00 yet they plan to have 40,000 MWe from LaSala Technologies Focus geothermal by 2040 at 80oC including overpressured Petty Geothermal System systems: 43,617,976 MWe @20% recovery, using ORC and conventional steam Resource Evaluation turbines (lots of very conservative assumptions in calculations) Dub State Energy Conservation Office Texas Renewable Program Texas is the 5th largest energy user in the world and most of the energy sources are Taylor (SECO)- Texas Renewable and Demonstration Sites from fossil fuels. Program Louis ThermaSource, Inc Comparison between Major differences: temperature, production pressures, rock formation characteristics, Capuano geothermal and oil & gas production rates and types of discharge fluids; tubings used in oil & gas, slotted liners drilling in geothermal Paul ORMAT Modular binary power Binary and flash steam turbines, modular (mainly an advertising spiel- presentation on Thomsen generators ORMAT data most people in the geothermal industry already know). Turbine efficiency is now 88%. David Southern Methodist University Geothermal resources in Discussed what factors SMU considered in making heat flow map of USA (AAPG Blackwell sedimentary basins publication) e.g., used several correction factors to estimate BHT’s at various depths. Scenarios for development of sedimentary basins: co-production of fluids, geopressured fluids, sedimentary EGS (enhanced geothermal systems) Will University of North Dakota, Dept Northern Great Plains Anomalously high temperatures in this region partly due to blanketing effect of shales Gosnold of Geol & Geol. Engg geothermal resources and heat advection in regional groundwater flow system. Berni Karl Chena Hot Springs Resort Geothermal electrical 74oC waters from well used to provide electricity for resort using ORC system of application in Alaska United Technologies where Carrier air conditioners are reengineered as reverse chillers (smallest module is 200kw). Used thermal waters are cascaded for use in greenhouse, space heating and an ice house (Kalina cycle) Dick Sustainable Solutions Scaling and corrosion Main problems in oil & gas wells that would be used as geothermal wells would be Benoit abatement carbonate scaling and corrosion due to hyper saline fluids Mike Chevron-Texaco Heat extraction from Modelled several scenarios on how heat can be extracted from oil & gas wells: best Shook sedimentary formations case is a vertical well dual doublet with a circulation rate of 6.31 kg/s. Inlet T (T of water being fed into well)= 27oC, fed water heated to 203oC. There is a need to balance circulation rate and temperatures for optimum energy efficiency- best model is use of horizontal wells but modelling study still ongoing. Geothermal production from mature watered-out oil & gas fields and from fields with on-going water-flooding Prentice Halliburton Well integrity to extend a Use of zoned seal foam cement extolled because of its high strength, high viscosity Creel well’s life and excellent displacement properties, resulting to better cementing jobs- the key to long lives of wells

GNS Science Report 2007/23 29 Speaker Company/Agency Topic Main Points of Talk Tim Smith Element Markets LP Renewable Energy Credits Regulations in the USA (REC’s) for the Gulf Coast 1REC= 1MWh of energy States Greg Idaho National laboratory Contributors to the cost of Regulations in the USA Mines geothermal power production Jason Engineer research and Geothermal potential in Water/oil ratio cut (water-flooding) = 95%. Thinking of using flooded oil & gas systems McKenna Development Center US Army military facilities in Iraq to increase country’s energy source base Corps of Engineers Richard University of Texas Permian Texas geothermal energy: a Erdlac Basin CEED focus on Permian basin and Trans-Pecos regions 7 posters Most interesting poster is a new system for harnessing energy using the movement of presented a magnet in a tube, by either a temperature or pressure gradient- still in development stage (Larry Shultz of Encore Clean Energy)

Richard TIC- The Industrial Company Results of the demonstration Well has WHP= 20.7 MPa. Fluids have 87% CH4. A hybrid cycle power plant is used, Campbell power plant on the Pleasant equipped with a pressure reduction turbine. Gas= 690 kW, binary cycle turbine = 535 Bayou geopressured kW and parasitic load = 270 kW. Heat exchanger uses the Rankine cycle. Hybrid resource system has a higher efficiency than 2 plants operating 2 different fluids. Problems from corrosive brine solved by using 16 gauge steel; scaling from 130,000 TDS waters by using inhibitors; carbon fouling by closing then opening plant regularly o Joel Idaho National Laboratory Pleasant Bayou, TX Geopressured systems: P range = 59.3-91.0MPa, T range = 110-180 C. In Pleasant Renner geopressured geothermal Bayou, TX well is 5030m deep, has salt domes and has intersected a leaky reservoir fault(leakage in fault due to pressure differentials in reservoir) Richard UT Permian Basin CEED Constraints and best use Main thesis of talk is to entice oil & gas operators and the Texas government to use oil Erdlac practices: the importance of & gas wells that are considered useless by the oil & gas industry for geothermal Texas geothermal electrical production. He emphasised that water in an oil & gas well is not a liability but an energy production asset. Encourages use of pinnate drilling system, often used in coal bed CH4 extraction, to be adapted to oil & gas cum geothermal wells. Mark Rocky Mountain Oilfield Testing Tea Pot Dome Case Study, Tap Cambrian sandstone and Pre-Cambrian basement for geothermal at T = 120- Millican Center Wyoming 125oC Susan Black Mountain Technology Geothermal power In Poplar Dome, present oil & gas wells need to be deepened to 3-4 km where T is as Petty generation potential- Poplar high as 135oC in fault zone. 3 scenarios for exploring geothermal energy in oil & gas Dome, MT systems: (1) use wells of opportunity (existing wells), (2) enhanced recovery, (3) EGS technology. Some of the problems: there is a need to get rid of most of the oil as this would foul up heat exchangers (use dispersants), may need electric submersible pumps, well stimulation, perforate oil & gas well tubings. In all her scenarios, Petty could only go down to $US0.0688/kwh which is 30% higher than the goal of US$0.05/kwh set by DOE

GNS Science Report 2007/23 30 APPENDIX 2

ABANDONED ONSHORE HYDROCARBON WELLS IN NEW ZEALAND

GNS Science Report 2007/23 31 Table 6. Basic well data for onshore abandoned hydrocarbon wells in New Zealand. BHT= bottom hole temperature calculated from heat flow data, MWt = megawatt thermal, MWe = megawatt electrical, MWh = megawatt-hour (8766 hours/year), TJ = terajoules, PJ= petajoules. In the calculations, the BHT is the same as the extraction temperature.

Total Date BHT MWt MWe Well Name Depth MW MWh TJ PJ Completed (oC) (CF=0.7) (CF=0.1) (m) NORTH ISLAND EAST COAST Awatere-1 2/06/1998 2136.0 69.9 1.2 0.8 7192 25.9 0.03 Back Ormond Road-1 1/12/1992 301.1 24.0 0.4 0.3 2479 8.9 0.01 Back Ormond Road-2 21/12/1992 300.1 24.0 0.4 0.3 2479 8.9 0.01 Gisborne-1 27/10/1928 927.0 40.6 0.7 0.5 4222 15.2 0.02 Gisborne-2 23/03/1930 1192.0 46.8 0.8 0.6 4835 17.4 0.02 Hukarere-1 24/11/2001 3213.2 94.6 1.6 1.1 9769 35.2 0.04 Kauhauroa-2 8/11/1998 2131.0 69.8 1.2 0.8 7192 25.9 0.03 Kauhauroa-5 16/06/1999 1751.0 60.0 1.0 0.7 6161 22.2 0.02 Kereru-1 30/11/1996 1939.0 56.6 0.9 0.7 5743 20.7 0.02 Kiakia-1/1A 21/08/1998 2225.0 72.2 1.2 0.8 7388 26.6 0.03 Koranga-1 18/04/1978 273.0 20.9 0.4 0.2 2160 7.8 0.01 Mangaone-1 20/04/1961 1550.0 56.3 0.9 0.7 5743 20.7 0.02 Mason Ridge-1 23/06/1971 1880.0 58.0 1.0 0.7 5964 21.5 0.02 Minerva Borehole 283.0 23.8 0.4 0.3 2479 8.9 0.01 Morere-1 20/11/1941 2037.0 69.3 1.2 0.8 7093 25.5 0.03 Ongaonga-1 2/05/1971 1573.0 48.7 0.8 0.6 5032 18.1 0.02 Opoho-1 20/12/1998 2320.0 76.9 1.3 0.9 7903 28.5 0.03 Opoutama-1 17/08/1967 3658.5 112.6 1.9 1.3 11634 41.9 0.04 Peep-O-Day 13/01/1914 917.0 34.7 0.6 0.4 3608 13.0 0.01 Rakaiatai-1 19/06/1969 685.7 29.7 0.5 0.4 3093 11.1 0.01 Rere-1 4/04/1986 4351.0 149.7 2.5 0.3 2216 8.0 0.01 Rotokautuku-1 13/03/1972 625.1 65.6 1.1 0.8 6774 24.4 0.02 Rotokautuku-1 (Southern 145.0 21.2 0.4 0.2 2160 7.8 0.01 Cross) Rotokautuku-2 172.0 22.4 0.4 0.3 2258 8.1 0.01 Rotokautuku-4 114.0 19.9 0.3 0.2 2062 7.4 0.01 Rotokautuku-5 560.0 33.7 0.6 0.4 3510 12.6 0.01 Ruakituri-1 1/01/1962 2745.0 85.6 1.4 1.0 8836 31.8 0.03 Speedy-1 20/07/2000 876.0 33.8 0.6 0.4 3510 12.6 0.01 Speedy-1 876.0 33.8 0.6 0.4 3510 12.6 0.01 Takapau-1 23/05/1971 1059.0 37.7 0.6 0.4 3903 14.0 0.01 Tane-1 (Mangaone) 13/01/1914 917.0 34.7 0.6 0.4 3608 13.0 0.01 Taradale-1 1/01/1969 1660.7 57.7 1.0 0.7 5964 21.5 0.02 Tautane-1 29/07/2001 1328.9 43.5 0.7 0.5 4516 16.3 0.02 Te Hoe-1 30/07/1990 627.0 32.3 0.5 0.4 3289 11.8 0.01 Te Horo-1 23/05/1972 1829.3 76.0 1.3 0.9 7805 28.1 0.03 Te Karaka-1 152.0 19.7 0.3 0.2 2062 7.4 0.01 Te Puia-1 5/08/1972 2042.7 80.2 1.3 0.9 8223 29.6 0.03 Toi Flat-1 1/01/1991 55.0 16.2 0.3 0.2 1645 5.9 0.01 Totangi-1 24/11/1939 103.0 18.1 0.3 0.2 1865 6.7 0.01 Totangi-1A 1903 64.0 17.0 0.3 0.2 1743 6.3 0.01 Totangi-1B 24/11/1939 1737.0 68.8 1.2 0.8 7093 25.5 0.03 Totangi-2 1903 154.0 19.7 0.3 0.2 2062 7.4 0.01 Totangi-2A 1903 156.0 19.8 0.3 0.2 2062 7.4 0.01 Tuhara-1B 24/06/2002 2169.3 70.8 1.2 0.8 7290 26.2 0.03 Waewaepa-1 1/01/1991 124.0 17.7 0.3 0.2 1865 6.7 0.01 Waiapu-1 774.0 40.8 0.7 0.5 4222 15.2 0.02 Waiapu-2 994.0 44.8 0.8 0.5 4614 16.6 0.02 Waihihere-1 421.0 27.6 0.5 0.3 2872 10.3 0.01 Waingaromia Bore 403.0 27.1 0.5 0.3 2774 10.0 0.01 Waingaromia-2 27/05/2002 502.1 30.1 0.5 0.4 3093 11.1 0.01 Waipatiki-1 1921 1097.0 38.5 0.7 0.5 4001 14.4 0.01 Waipatiki-2 1912 966.0 35.7 0.6 0.4 3706 13.3 0.01 Waitangi Hill-1 64.0 17.0 0.3 0.2 1743 6.3 0.01 Waitangi Station-1 9/07/1972 2135.0 79.1 1.3 0.9 8124 29.2 0.03 Waitangi-1 3/04/1931 512.7 30.6 0.5 0.4 3191 11.5 0.01 Waitangi-1 (Gisborne Oil) 1909 450.0 28.9 0.5 0.3 2994 10.8 0.01 Waitangi-1 (Taranaki Oilfields) 1930 513.0 30.9 0.5 0.4 3191 11.5 0.01 Waitangi-2 1931 662.0 35.2 0.6 0.4 3608 13.0 0.01 Waitaria-1B 27/08/1997 1150.0 49.0 0.8 0.6 5032 18.1 0.02 Waitaria-2 14/03/2001 2548.1 90.2 1.5 1.1 9253 33.3 0.03 Westcott-1 1/01/1991 67.0 16.4 0.3 0.2 1645 5.9 0.01 Whakatu-1 7/02/2000 1455.0 46.2 0.8 0.5 4737 17.1 0.02 NORTHLAND 0.0 Access Road 1963? 476.0 33.1 0.6 0.4 3387 12.2 0.01 Dargaville-1 1963? 248.0 23.3 0.4 0.3 2381 8.6 0.01 Dargaville-2 1963? 445.0 29.8 0.5 0.4 3093 11.1 0.01 Kaiaka-1 11/11/1957 625.0 35.8 0.6 0.4 3706 13.3 0.01 Kioreroa-1 148.0 21.0 0.4 0.2 2160 7.8 0.01

GNS Science Report 2007/23 32 Total Date BHT MWt MWe Well Name Depth o MW MWh TJ PJ Completed ( C) (CF=0.7) (CF=0.1) (m) NORTH ISLAND NORTHLAND 0.0 Kioreroa-2 109.0 19.4 0.3 0.2 1964 7.1 0.01 Kioreroa-3 54.0 17.1 0.3 0.2 1743 6.3 0.01 Northland-1 19/11/1972 625.9 38.8 0.7 0.5 4001 14.4 0.01 Waimamaku-1 1273.0 63.5 1.1 0.7 6480 23.3 0.02 Waimamaku-2 16/02/1972 3356.7 126.9 2.1 0.2 1872 6.7 0.01 NOT IN BASIN NORTH ISLAND Ardmore-1 137.0 19.6 0.3 0.2 1964 7.1 0.01 Great Barrier-1 226.0 24.7 0.4 0.3 2577 9.3 0.01 Great Barrier-2 92.0 18.9 0.3 0.2 1964 7.1 0.01 Horotiu Bore-1 137.0 19.2 0.3 0.2 1964 7.1 0.01 Horotiu Bore-2 137.0 19.2 0.3 0.2 1964 7.1 0.01 Horotiu Bore-3 195.0 20.9 0.4 0.2 2160 7.8 0.01 Horotiu Bore-4 229.0 22.0 0.4 0.3 2258 8.1 0.01 Horotiu-2 198.0 21.0 0.4 0.2 2160 7.8 0.01 Horotiu-5 198.0 21.0 0.4 0.2 2160 7.8 0.01 Kaiaua-1 2/02/1955 108.0 18.1 0.3 0.2 1865 6.7 0.01 Karaka-1 614.0 35.5 0.6 0.4 3706 13.3 0.01 Mangatawa-1 669.0 40.5 0.7 0.5 4222 15.2 0.02 Puketaha-1 24/10/1963 475.0 29.5 0.5 0.4 3093 11.1 0.01 Rangitaike-1 61.0 17.3 0.3 0.2 1743 6.3 0.01 Rangitaike-1A 479.0 33.2 0.6 0.4 3387 12.2 0.01 Rangitaike-2 194.0 22.4 0.4 0.3 2258 8.1 0.01 River Road-1 6/12/1963 789.0 39.0 0.7 0.5 4001 14.4 0.01 T.E. Weily-1 17/10/1966 1057.3 47.7 0.8 0.6 4934 17.8 0.02 Te Rapa-1 10/02/1964 1684.0 66.3 1.1 0.8 6774 24.4 0.02 Waikato-1 8/07/1971 1036.0 46.6 0.8 0.6 4835 17.4 0.02 Waikato-2 18/07/1971 1026.2 46.3 0.8 0.6 4835 17.4 0.02 Waikato-3 10/10/1972 320.1 24.8 0.4 0.3 2577 9.3 0.01 Waikato-4 29/11/1972 598.5 33.2 0.6 0.4 3387 12.2 0.01 Waikato-5 19/10/1972 1013.1 45.9 0.8 0.5 4737 17.1 0.02 Waiotapu-1 61.0 17.9 0.3 0.2 1865 6.7 0.01 Waiotapu-2 113.0 20.4 0.3 0.2 2062 7.4 0.01 Waipai-1 45.0 16.0 0.3 0.2 1645 5.9 0.01 TARANAKI Ahuroa-1 26/09/1986 3326.0 106.9 1.8 1.3 11021 39.7 0.04 Ahuroa-1A 11/10/1986 3153.0 102.1 1.7 1.2 10481 37.7 0.04 Ahuroa-2 10/12/1986 2465.0 83.1 1.4 1.0 8517 30.7 0.03 Bell Block-1 1/01/1913 1131.0 54.9 0.9 0.6 5645 20.3 0.02 Bell Block-2 8/02/1912 853.0 45.1 0.8 0.5 4614 16.6 0.02 Beta 208.0 21.9 0.4 0.3 2258 8.1 0.01 Blenheim-2 640.0 37.6 0.6 0.4 3903 14.0 0.01 Bonithon-1 1908 916.0 47.3 0.8 0.6 4835 17.4 0.02 Bonithon-2 1908 764.0 41.9 0.7 0.5 4320 15.6 0.02 Burgess-1 28/09/1989 3264.0 108.3 1.8 1.3 11217 40.4 0.04 Cape Egmont-1 17/11/1986 2435.0 84.6 1.4 1.0 8738 31.5 0.03 Cape Farewell-1 22/03/1986 2817.0 108.9 1.8 1.3 11217 40.4 0.04 Cardiff-1 21/08/1992 5064.0 152.5 2.6 1.8 0.3 2262 8.1 0.01 Carrington Road-1 1042.0 49.7 0.8 0.6 5130 18.5 0.02 Carrington Road-2 112.0 18.7 0.3 0.2 1964 7.1 0.01 Clematis-1 24/12/1999 1800.0 70.7 1.2 0.8 7290 26.2 0.03 Crusader-1 11/08/2000 2441.0 96.4 1.6 1.1 9867 35.5 0.04 Crusader-1A 19/09/2000 2060.0 83.7 1.4 1.0 8640 31.1 0.03 Cutters Bridge-1 48.0 16.8 0.3 0.2 1743 6.3 0.01 Devon-1 1/03/1943 2868.0 116.1 1.9 1.4 11953 43.0 0.04 Devon-2 16/07/1943 1883.0 77.8 1.3 0.9 8002 28.8 0.03 Dobson-1 682.0 37.7 0.6 0.4 3903 14.0 0.01 Dobson-2 611.0 35.4 0.6 0.4 3608 13.0 0.01 Durham-1 18/08/1989 2303.0 80.8 1.4 0.9 8321 30.0 0.03 Hu Road-1/1A 13/06/1991 3350.0 105.9 1.8 1.2 10898 39.2 0.04 Huinga-1, 1A, 1B 12/06/2002 4373.0 133.7 2.3 0.2 1974 7.1 0.01 Huiroa Bore 1500.0 56.4 0.9 0.7 5743 20.7 0.02 Inglewood-1 20/06/1963 5061.0 164.4 2.8 0.3 2430 8.7 0.01 Kaimiro-12 18/01/1996 835.0 40.8 0.7 0.5 4222 15.2 0.02 Kaimiro-14, 14A 14/02/1996 1843.0 76.4 1.3 0.9 7805 28.1 0.03 Kaipikari-1 10/10/1994 1854.0 70.6 1.2 0.8 7290 26.2 0.03 Kapuni-15 15/01/1992 4770.0 135.4 2.3 0.2 1992 7.2 0.01 Kiore-1 19/11/1964 536.6 30.3 0.5 0.4 3093 11.1 0.01 Koporongo-1 16/06/1971 590.9 31.6 0.5 0.4 3289 11.8 0.01 Makara-1 7/11/1984 2940.0 103.2 1.7 1.2 10603 38.2 0.04 Makara-1B 27/12/1984 2467.0 89.0 1.5 1.0 9155 33.0 0.03 Maketawa-1 30/10/2000 1135.4 47.4 0.8 0.6 4835 17.4 0.02 Makino-1, 1AA 17/02/2002 4100.0 116.5 1.9 1.4 11953 43.0 0.04 Makuri-1, 1A 18/08/1984 2500.0 86.4 1.4 1.0 8836 31.8 0.03

GNS Science Report 2007/23 33 Total Date BHT MWt MWe Well Name Depth o MW MWh TJ PJ Completed ( C) (CF=0.7) (CF=0.1) (m) NORTH ISLAND TARANAKI Mangamahoe-1 29/10/1993 802.0 41.7 0.7 0.5 4222 15.2 0.02 Manganui-1 30/06/1982 3975.0 138.0 2.3 0.2 2037 7.3 0.01 Manganui-2 31/05/1984 3753.0 131.2 2.2 0.2 1932 7.0 0.01 -1 2229.0 89.3 1.5 1.0 9155 33.0 0.03 McKee-13 28/01/1995 2278.0 80.1 1.3 0.9 8223 29.6 0.03 McKee-2B 8/07/2000 2237.0 78.9 1.3 0.9 8124 29.2 0.03 McKee-2C 15/06/2000 2316.0 81.2 1.4 0.9 8321 30.0 0.03 McKee-3 13/11/1981 2400.0 83.6 1.4 1.0 8640 31.1 0.03 McKee-6 6/05/1987 2227.0 78.6 1.3 0.9 8124 29.2 0.03 McKee-7 9/06/1987 2178.0 77.2 1.3 0.9 7903 28.5 0.03 Midhurst-1 14/02/1942 3330.8 105.4 1.8 1.2 10800 38.9 0.04 Moa Bore 140.0 18.5 0.3 0.2 1865 6.7 0.01 Mokoia-1 31/05/1989 3750.0 97.1 1.6 1.1 9965 35.9 0.04 Bore 1329.0 59.3 1.0 0.7 6063 21.8 0.02 Moturoa-3 31/05/1933 658.0 38.2 0.6 0.4 3903 14.0 0.01 New Plymouth-1 15/04/1975 655.0 38.1 0.6 0.4 3903 14.0 0.01 New Plymouth-2 4/10/1965 4451.6 171.9 2.9 0.3 2553 9.2 0.01 Ngatoro-1 27/03/1984 4126.0 146.6 2.5 0.2 2170 7.8 0.01 Norfolk Road Bore 762.0 36.8 0.6 0.4 3804 13.7 0.01 Oakura-1 13/11/1998 3220.0 100.9 1.7 1.2 10382 37.4 0.04 Okoke Bore 11/07/1927 61.0 16.8 0.3 0.2 1743 6.3 0.01 Bore-1 1930? 152.0 20.1 0.3 0.2 2062 7.4 0.01 Omata Bore-2 1930? 323.0 25.8 0.4 0.3 2675 9.6 0.01 Omata-1 1930? 960.0 47.0 0.8 0.6 4835 17.4 0.02 -1 14/12/1980 3590.0 124.4 2.1 0.2 1827 6.6 0.01 Oru-1 12/11/2005 1700.0 61.1 1.0 0.7 6259 22.5 0.02 Paritutu-1 24/09/1993 2400.0 95.0 1.6 1.1 9769 35.2 0.04 Patea East-1 11/08/2003 1082.5 39.2 0.7 0.5 4001 14.4 0.01 Patea-1 30/07/2003 1613.0 51.1 0.9 0.6 5253 18.9 0.02 Piakau-1 17/11/1986 2905.0 95.2 1.6 1.1 9769 35.2 0.04 Pohokura South-1 31/03/2001 3780.0 132.0 2.2 0.2 1946 7.0 0.01 Pouri-2 2/01/1997 2233.0 80.9 1.6 1.1 9793 35.3 0.04 Prospect Valley-1 29/09/1928 272.0 22.9 0.4 0.3 2258 8.1 0.01 Prospect Valley-2 430.0 27.5 0.5 0.3 2774 10.0 0.01 Pukearuhe-1 5/09/1986 3138.0 107.6 1.8 1.3 11119 40.0 0.04 Pukemai-1 10/07/1983 2293.0 83.8 1.4 1.0 8640 31.1 0.03 Pukemai-1A 24/07/1983 2432.0 88.0 1.5 1.0 9032 32.5 0.03 Pukemai-2 20/11/1983 2631.0 93.9 1.6 1.1 9671 34.8 0.03 Pukemai-3 6/03/1991 2098.0 77.9 1.3 0.9 8026 28.9 0.03 -1 21/01/2001 1597.0 62.1 1.1 0.7 6480 23.3 0.02 Rotary Bore 853.0 45.1 0.8 0.5 4614 16.6 0.02 Rotokare-1 23/02/1989 3232.7 102.7 1.7 1.2 10603 38.2 0.04 Salisbury-1 23/03/1996 2050.0 73.6 1.2 0.9 7609 27.4 0.03 Samuel Syndicate-1 283.0 24.4 0.4 0.3 2479 8.9 0.01 Samuel Syndicate-2 335.0 26.2 0.4 0.3 2675 9.6 0.01 Samuel Syndicate-3 468.0 30.6 0.5 0.4 3191 11.5 0.01 Samuel Syndicate-5 626.0 35.9 0.6 0.4 3706 13.3 0.01 Samuel Syndicate-6 92.0 18.1 0.3 0.2 1865 6.7 0.01 Samuel Syndicate-7 457.0 30.2 0.5 0.4 3093 11.1 0.01 Samuel Syndicate-8 625.0 35.8 0.6 0.4 3706 13.3 0.01 Samuel Syndicate-9 322.0 25.7 0.4 0.3 2675 9.6 0.01 Spotswood-1 925.0 45.8 0.8 0.5 4737 17.1 0.02 Standish-1 12/04/1993 1845.0 66.0 1.1 0.8 6774 24.4 0.02 Stent-1 5/09/2004 2710.0 93.7 1.6 1.1 9671 34.8 0.03 Taranaki Petroleum-1 (1866) 1866 94.0 18.1 0.3 0.2 1865 6.7 0.01 Taranaki Petroleum-2 (1866) 1866 97.0 18.2 0.3 0.2 1865 6.7 0.01 Taranaki Petroleum-4 511.0 33.0 0.6 0.4 3387 12.2 0.01 Tarata-1 7/05/1926 1527.0 60.8 1.0 0.7 6259 22.5 0.02 Tariki North-1 25/06/1987 2431.0 81.0 1.4 0.9 8321 30.0 0.03 Tariki North-1A 24/06/1987 3209.0 102.1 1.7 1.2 10382 37.4 0.04 Tariki-1 11/04/1986 3191.0 101.6 1.7 1.2 10382 37.4 0.04 Tariki-2 4/02/1987 3020.0 97.0 1.6 1.1 9965 35.9 0.04 Tariki-2A 10/03/1987 2564.5 84.6 1.4 1.0 8738 31.5 0.03 Tariki-4, 4C 1995 2777.0 90.4 1.5 1.1 9253 33.3 0.03 Tauteka-1 25/02/1983 2309.0 86.5 1.4 1.0 8836 31.8 0.03 Te Kiri-1 2/06/1986 4710.0 154.1 2.6 0.3 2276 8.2 0.01 Tikorangi-1 221.0 22.4 0.4 0.3 2258 8.1 0.01 Tipoka-1, 1A 21/10/1986 4359.0 141.6 2.4 0.2 2097 7.5 0.01 Tipoka-2 15/11/1993 2504.0 87.7 1.5 1.0 9057 32.6 0.03 Toetoe-1 11/09/1984 2310.0 84.3 1.4 1.0 8640 31.1 0.03 Toetoe-2 26/11/1984 2276.0 83.3 1.4 1.0 8517 30.7 0.03 Toetoe-2A, 2C 29/09/1987 1829.0 69.9 1.2 0.8 7192 25.9 0.03

GNS Science Report 2007/23 34 Total Date BHT MWt MWe Well Name Depth o MW MWh TJ PJ Completed ( C) (CF=0.7) (CF=0.1) (m) NORTH ISLAND TARANAKI Toetoe-3 23/02/1985 2618.0 93.5 1.6 1.1 9671 34.8 0.03 Toetoe-4A, B, C 8/05/1997 2326.0 87.0 1.5 1.0 8934 32.2 0.03 Toetoe-5 27/12/1988 2536.0 93.5 1.6 1.1 9671 34.8 0.03 Toetoe-6A 31/10/1999 1817.0 69.5 1.2 0.8 7192 25.9 0.03 Toetoe-7 27/07/1989 2315.0 84.5 1.4 1.0 8738 31.5 0.03 Toetoe-8 15/10/1992 1986.0 74.6 1.3 0.9 7707 27.7 0.03 Toetoe-9 3/09/1992 2027.0 75.8 1.3 0.9 7805 28.1 0.03 Toko-1 31/08/1979 4900.0 150.3 2.5 0.3 2216 8.0 0.01 Toko-2 30/04/1994 3202.0 103.4 1.7 1.2 10603 38.2 0.04 Totara-1 14/06/1987 3965.0 132.1 2.2 0.2 1946 7.0 0.01 Tuhua-1 Re-entry 1994 2564.0 88.3 1.5 1.0 9032 32.5 0.03 Tuhua-2, 2A 24/09/1983 2529.0 87.3 1.5 1.0 8934 32.2 0.03 Tuhua-3A, B, C 31/08/1988 2125.0 78.8 1.3 0.9 8124 29.2 0.03 Tuhua-5A 6/02/1991 2509.0 86.7 1.5 1.0 8934 32.2 0.03 Tuhua-8 30/08/1994 2471.0 85.6 1.4 1.0 8836 31.8 0.03 Tuihu-1, 1A 25/09/2003 4845.0 153.4 2.6 0.3 2276 8.2 0.01 Tupapakurua-1 1/06/1971 1150.0 47.3 0.8 0.6 4835 17.4 0.02 -1 7/10/1943 356.0 25.5 0.4 0.3 2675 9.6 0.01 Uruti-2 10/01/1944 1553.0 60.9 1.0 0.7 6259 22.5 0.02 Victoria 157.0 20.2 0.3 0.2 2062 7.4 0.01 Vogeltown Bore 1909 422.0 29.1 0.5 0.3 2994 10.8 0.01 Waihapa-1, 1A 7/07/1985 4942.0 144.4 2.4 0.2 2125 7.6 0.01 Waihapa-3 27/11/1988 2706.0 85.9 1.4 1.0 8836 31.8 0.03 Waihapa-6 18/11/1989 3245.0 100.0 1.7 1.2 10284 37.0 0.04 Whanga Road Bore 195.0 20.4 0.3 0.2 2062 7.4 0.01 Wharehuia-1 15/02/1985 3595.0 114.3 1.9 1.3 11732 42.2 0.04 Windsor-2 20/09/2000 1469.4 64.0 1.1 0.8 6578 23.7 0.02 Windsor-3 8/10/2000 1555.6 63.1 1.1 0.7 6480 23.3 0.02 Wingrove-1 1600.0 59.2 1.0 0.7 6063 21.8 0.02 WANGANUI Ararimu-1 26/03/1970 1057.6 50.3 0.8 0.6 5130 18.5 0.02 Kaitieke-1 4/02/1966 394.0 28.7 0.5 0.3 2994 10.8 0.01 Manutahi-1 19/05/1984 1391.0 46.1 0.8 0.5 4737 17.1 0.02 Ohaupo-1 1/01/1983 1207.0 57.0 1.0 0.7 5866 21.1 0.02 Ohura-1 1/01/1964 635.0 36.2 0.6 0.4 3706 13.3 0.01 Parikino-1 17/08/1964 2316.5 70.2 1.2 0.8 7192 25.9 0.03 Puniwhakau-1 25/01/1965 2146.0 75.3 1.3 0.9 7683 27.7 0.03 Santoft-1 13/03/1964 312.0 21.7 0.4 0.3 2258 8.1 0.01 Stantiall-1 5/11/1942 2096.0 59.9 1.0 0.7 6161 22.2 0.02 Tatu-1 28/10/1964 860.0 43.7 0.7 0.5 4516 16.3 0.02 Waikaka-1 12/03/1970 978.7 47.6 0.8 0.6 4934 17.8 0.02 Whakamaro-1 28/04/1969 916.0 45.5 0.8 0.5 4737 17.1 0.02 Whangaehu-1 20/02/1996 3495.0 89.9 1.5 1.1 9253 33.3 0.03 Whitianga-1 19/01/1964 295.0 24.1 0.4 0.3 2479 8.9 0.01 Young-1 4/11/1942 1035.0 37.2 0.6 0.4 3804 13.7 0.01 SOUTH ISLAND CANTERBURY Arcadia-1 24/11/2000 1479.0 20.9 0.9 0.6 5547 20.0 0.02 Chertsey Bore 16/09/1921 661.0 17.6 0.5 0.3 2994 10.8 0.01 Ealing-1 5/11/2000 1696.0 18.9 0.8 0.6 4934 17.8 0.02 J.D. George-1 5/10/1969 1649.9 24.8 1.2 0.8 7192 25.9 0.03 Kowai-1 23/03/1978 1410.0 20.7 0.9 0.6 5351 19.3 0.02 Leeston-1 26/08/1969 1158.5 18.6 0.7 0.5 4124 14.8 0.01 Oamaru-1 1954 908.0 21.3 0.8 0.5 4614 16.6 0.02 Oamaru-2 1961 665.0 22.9 0.7 0.5 4541 16.3 0.02 WEST COAST A1 1908? 122.0 19.4 0.3 0.2 1964 7.1 0.01 Ahaura-2 11/02/1978 1069.0 50.6 0.9 0.6 5253 18.9 0.02 Arahura-1 30/05/1964 1736.0 72.9 1.2 0.9 7511 27.0 0.03 Aratika-2 14/12/1977 1149.0 55.5 0.9 0.7 5743 20.7 0.02 Aratika-3 19/01/1978 1729.0 76.8 1.3 0.9 7903 28.5 0.03 Arnold River-1 18/01/1985 710.0 40.0 0.7 0.5 4124 14.8 0.01 B1 22.0 15.8 0.3 0.2 1645 5.9 0.01 B2 34.0 16.2 0.3 0.2 1645 5.9 0.01 B4 24.0 15.9 0.3 0.2 1645 5.9 0.01 Bore 251 123.0 18.5 0.3 0.2 1865 6.7 0.01 Bore 252 459.0 28.1 0.5 0.3 2872 10.3 0.01 Bounty-1 29/10/1970 3131.0 134.3 2.3 0.2 1974 7.1 0.01 Card Creek-1 15/02/1986 1342.0 53.3 0.9 0.6 5449 19.6 0.02 Corehole-10 1/01/1943 445.0 30.7 0.5 0.4 3191 11.5 0.01 Corehole-11 1/01/1942 423.0 27.1 0.5 0.3 2774 10.0 0.01 Corehole-8 7/10/1942 100.0 17.9 0.3 0.2 1865 6.7 0.01 Corehole-9 1/01/1942 215.2 22.7 0.4 0.3 2381 8.6 0.01

GNS Science Report 2007/23 35 Total Date BHT MWt MWe Well Name Depth o MW MWh TJ PJ Completed ( C) (CF=0.7) (CF=0.1) (m) SOUTH ISLAND WEST COAST Glenn Creek-1 29/09/1985 739.0 41.0 0.7 0.5 4222 15.2 0.02 Harihari-1 8/03/1971 2527.4 81.2 1.4 0.9 8321 30.0 0.03 Hohonu-1 28/06/1986 1039.0 51.6 0.9 0.6 5228 18.8 0.02 Bore 4/01/1918 407.0 29.3 0.5 0.3 2994 10.8 0.01 Kawhaka-1 6/06/1943 852.0 43.4 0.7 0.5 4418 15.9 0.02 Kokatahi-1 28/10/1987 1914.0 69.7 1.2 0.8 7192 25.9 0.03 Kokiri-1 16/07/1980 3233.0 122.8 2.1 0.2 1813 6.5 0.01 Kumara-2 19/07/1985 1756.0 65.2 1.1 0.8 6676 24.0 0.02 Kumara-2A 10/09/1985 1697.0 63.5 1.1 0.8 6578 23.7 0.02 Limestone Test Bore 148.0 20.3 0.3 0.2 2062 7.4 0.01 Matiri-1 29/12/1985 1467.0 70.9 1.2 0.8 7290 26.2 0.03 Mawhera-1 18/02/1985 697.0 39.9 0.7 0.5 4124 14.8 0.01 Murchison-1 1245.0 62.4 1.0 0.7 6357 22.9 0.02 Niagara-2 5/06/1986 952.0 48.5 0.8 0.6 5032 18.1 0.02 No1 Kotuku Consolidated 51.0 16.8 0.3 0.2 1743 6.3 0.01 No1 Kotuku Oilfields 290.0 25.4 0.4 0.3 2577 9.3 0.01 No1 Kotuku Petroleum 293.0 25.5 0.4 0.3 2577 9.3 0.01 No1 Lake Brunner 32.0 16.1 0.3 0.2 1645 5.9 0.01 No1 Maoriland 14/07/1936 44.0 16.6 0.3 0.2 1645 5.9 0.01 No2 Kotuku Oilfields 247.0 23.8 0.4 0.3 2479 8.9 0.01 No2 Kotuku Petroleum 187.0 21.7 0.4 0.3 2258 8.1 0.01 No2 Lake Brunner 229.0 23.2 0.4 0.3 2356 8.5 0.01 No2 Maoriland 22/07/1936 19.0 15.7 0.3 0.2 1645 5.9 0.01 No3 Bore 147.0 19.2 0.3 0.2 1964 7.1 0.01 No3 Kotuku Oilfields 183.0 21.5 0.4 0.3 2258 8.1 0.01 No3 Kotuku Petroleum 375.0 28.4 0.5 0.3 2872 10.3 0.01 No3 Lake Brunner 147.0 20.3 0.3 0.2 2062 7.4 0.01 No3 Maoriland 28/07/1936 40.0 16.4 0.3 0.2 1645 5.9 0.01 No4 Lake Brunner 32.0 16.1 0.3 0.2 1645 5.9 0.01 No4 Maoriland 15/08/1936 40.0 16.4 0.3 0.2 1645 5.9 0.01 No5 Lake Brunner 133.0 19.8 0.3 0.2 2062 7.4 0.01 No5 Maoriland 26/08/1936 41.0 16.5 0.3 0.2 1645 5.9 0.01 No6 Lake Brunner 98.0 18.5 0.3 0.2 1865 6.7 0.01 No7 Lake Brunner 38.0 16.4 0.3 0.2 1645 5.9 0.01 No8 Lake Brunner 137.0 19.9 0.3 0.2 2062 7.4 0.01 No9 Lake Brunner 265.0 24.5 0.4 0.3 2577 9.3 0.01 Notown-1 30/09/1944 2116.0 90.6 1.5 1.1 9352 33.7 0.03 Paddy Gully-1 294.0 25.5 0.4 0.3 2675 9.6 0.01 Petroleum Creek-1 13/11/1985 64.0 17.3 0.3 0.2 1743 6.3 0.01 Petroleum Creek-2 15/11/1985 59.0 17.1 0.3 0.2 1743 6.3 0.01 Petroleum Creek-5 20/11/1985 17.3 15.6 0.3 0.2 1645 5.9 0.01 RSE-1 22/04/2004 263.1 24.3 0.4 0.3 2479 8.9 0.01 RSE-2 3/05/2004 179.3 21.3 0.4 0.2 2160 7.8 0.01 Ruby Bay-1 1966 281.0 23.0 0.4 0.3 2356 8.5 0.01 SFL-1 10/12/1942 1663.0 62.5 1.1 0.7 6480 23.3 0.02 SFL-2 18/03/1943 908.0 40.9 0.7 0.5 4222 15.2 0.02 Shaft 25.0 15.9 0.3 0.2 1645 5.9 0.01 Taipo Creek-1 31/01/1985 679.0 39.3 0.7 0.5 4001 14.4 0.01 Tapawera-1 7/05/1988 1180.0 48.7 0.8 0.6 5032 18.1 0.02 Taramakau-1 14/02/1964 2129.0 75.8 1.3 0.9 7805 28.1 0.03 Waiho-1 16/07/1972 3749.4 113.2 1.9 1.3 11634 41.9 0.04 Westgas-1 1/02/1996 346.6 26.6 0.5 0.3 2774 10.0 0.01 Westgas-3 3/10/1997 310.6 25.4 0.4 0.3 2577 9.3 0.01 WEST SOUTHLAND - SOLANDER Alton 61.0 16.9 0.3 0.2 1743 6.3 0.01 Happy Valley-1 12/01/1988 1623.0 62.1 1.0 0.7 6357 22.9 0.02 Happy Valley-1A 6/02/1988 1600.0 61.5 1.0 0.7 6357 22.9 0.02 Happy Valley-1C 28/02/1987 3131.4 106.0 1.8 1.2 10898 39.2 0.04 Merryvale-1 239.0 21.8 0.4 0.3 2258 8.1 0.01 Papatotara-1 261.0 22.5 0.4 0.3 2258 8.1 0.01 Tuatapere-1 306.0 23.9 0.4 0.3 2479 8.9 0.01 Upukerora-1 15/12/1987 2009.0 72.4 1.2 0.8 7388 26.6 0.03 NOT IN BASIN SOUTH ISLAND Centre Bush-1 498.0 29.2 0.5 0.3 2994 10.8 0.01 J.T. Benny-1 6/01/1965 1013.0 46.4 0.8 0.5 4737 17.1 0.02 J.W. Laughton-1 5/04/1965 2135.0 81.1 1.4 0.9 8321 30.0 0.03 Kauana-1 179.0 20.5 0.4 0.2 2160 7.8 0.01 Pukerau-1 15/03/1970 73.0 17.4 0.3 0.2 1743 6.3 0.01 Pukerau-2 13/05/1972 118.0 18.9 0.3 0.2 1964 7.1 0.01 Pukerau-3 17/04/1971 165.0 20.5 0.4 0.2 2160 7.8 0.01 Waikaia-1 1/01/1974 197.0 20.6 0.4 0.2 2160 7.8 0.01 Waikaia-2 1/01/1975 121.0 18.5 0.3 0.2 1964 7.1 0.01 TOTAL ENERGY 317.5 190.6 4.8 1696547 6108 6.1

GNS Science Report 2007/23 36 Principal Location Other Locations

1 Fairway Drive Dunedin Research Centre Wairakei Research Centre National Isotope Centre Avalon 764 Cumberland Street 114 Karetoto Road 30 Gracefield Road PO Box 30368 Private Bag 1930 Wairakei PO Box 31312 Lower Hutt Dunedin Private Bag 2000, Taupo Lower Hutt New Zealand New Zealand New Zealand New Zealand T +64-4-570 1444 T +64-3-477 4050 T +64-7-374 8211 T +64-4-570 1444 www.gns.cri.nz F +64-4-570 4600 F +64-3-477 5232 F +64-7-374 8199 F +64-4-570 4657