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 New Zealand ....................................................................... 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 Taranaki 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, New Plymouth.............................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