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NONTRIBUTARY GROUNDWATER ASSESSMENT: AND - ,

Submitted to: OXY USA INC. AND OXY USA WTP LP

Date: November 4, 2009

Norwest Corporation 950 South Cherry Street, Suite 800 Denver, CO 80246 Tel: (303) 782-0164 Fax: (303) 782-2560 Email [email protected] www.norwestcorp.com

004280

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...... 1 1 INTRODUCTION...... 1-1 2 CONCEPTUAL MODEL ...... 2-1 2.1 GEOLOGIC SETTING ...... 2-1 2.1.1 Mancos ...... 2-1 2.1.2 Iles Formation ...... 2-2 2.1.3 ...... 2-2 2.1.4 Wasatch Formation...... 2-3 2.2 HYDROLOGIC DATA ...... 2-3 3 HYDROLOGEOLOGIC PARAMETERS...... 3-1 3.1 PERMEABILITY...... 3-1 3.1.1 Oxy Reported Permeability – Mesaverde ...... 3-2 3.1.2 Permeability information – Wasatch ...... 3-2 3.2 SPECIFIC STORAGE ...... 3-2 4 NONTRIBUTARY GROUNDWATER EVALUATION...... 4-1 5 SUMMARY...... 5-1 6 REFERENCES...... 6-1

LIST OF TABLES

Table 3-1. Literature Values for Mesaverde Group and Wasatch Formation Producing Units .3-3 Table 3-2. Summary of Mesaverde Group Permeability Data Provided by Oxy ...... 3-5 Table 4-1. Parameters Used in Nontributary Analysis ...... 4-3

LIST OF FIGURES

Figure 1-1. Site Location ...... 1-2 Figure 2-1. Surficial Geologic Map...... 2-4 Figure 2-2. General Stratigraphic Column near Grand Junction (from Cole and Cumella, 2003) ...... 2-5 Figure 2-3. Generalized West to East Cross Section of the Mesaverde and Mancos (from Johnson and Roberts, 2003)...... 2-6 Figure 2-4. Depositional and Stratigraphic Framework of the Piceance Basin ...... 2-7 (from Yurewicz, 2005)...... 2-7 Figure 2-5. Geologic Map of Project Area with Perennial Streams...... 2-8 Figure 4-1. Mesaverde Group Nontributary Groundwater Zone ...... 4-4 Figure 4-2. Wasatch Formation Nontributary Groundwater Zone ...... 4-5

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT TOC - 1 004281

LIST OF APPENDICES Appendix A Mesaverde Group Permeability Data Provided by Oxy Appendix B Wasatch Formation Permeability Data Appendix C Nontributary Distance Calculations

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT TOC - 2 004282

EXECUTIVE SUMMARY

OXY USA Inc. and Oxy USA WTP LP (Oxy) engaged Norwest Corporation (Norwest) to evaluate the nontributary status of groundwater associated with formations Oxy is producing natural gas from in the Piceance Basin in Garfield and Mesa Counties Colorado. Oxy is producing unconventional (tight) gas from the Wasatch Formation (Wasatch) and Mesaverde Group (Mesaverde) in the southern Piceance Basin.

The Norwest evaluation of nontributary status of groundwater from the producing formations utilized the Glover-Balmer equation. This equation is a commonly used method for evaluating the timing and magnitude of depletions to surface water from pumping tributary groundwater. The Glover-Balmer equation requires simplification of the groundwater system, and assumes it is a semi-infinite, homogeneous, confined aquifer in perfect connection to a fully penetrating stream. For this analysis, the formation parameters based on the assumption that the gas producing formations were a confined groundwater-saturated aquifer in perfect connection with the stream were input into the Glover-Balmer equation. The oversimplification required by the Glover-Balmer equation results in an extremely conservative evaluation of the potential depletions that producing groundwater during natural gas production from the Mesaverde and Wasatch may have on surface streams. Permeability data that is site- specific to Oxy’s operations were used for the Mesaverde analysis and data from surrounding operators were used for the Wasatch analysis.

For the purposes of this assessment the potential points of depletion were considered to be the location where the Mesaverde or Wasatch lie directly beneath a mapped perennial stream or the of a mapped perennial stream. The calculated distances from points of depletion where the groundwater was nontributary were 6,160 ft (1.17 miles) and 6,450 ft (1.22 miles) for the Mesaverde and Wasatch respectively. Areas where groundwater was within these distances from perennial streams in or crossing the Mesaverde or Wasatch outcrops were excluded from the nontributary groundwater zones.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT ES-1 004283

1 INTRODUCTION

Oxy engaged Norwest to evaluate the nontributary status of groundwater associated with formations Oxy is producing natural gas from in the Piceance Basin in Colorado. Groundwater in Colorado is presumed by law to be tributary water, the pumping of which may have injurious impacts on vested tributary water rights in over-appropriated stream systems in Colorado.

Oxy is producing unconventional (tight) gas from the Wasatch Formation (Wasatch) and Mesaverde Group (Mesaverde) in the southern Piceance Basin. Oxy’s primary holdings are in the Cascade Creek Field located north, north-east of DeBeque, CO and the Collbran Field located near Collbran, CO. The major surface water drainage through the area is the Colorado River with tributaries joining the river from both the south and north. The lease locations, topographic relief, and perennial streams are shown on Figure 1-1.

The study area that Norwest evaluated is physically bounded by the outcrops of the Wasatch and Mesaverde and is limited to Garfield, Mesa, and Pitkin Counties. The watershed of the North Fork of the was used as a southern boundary for the study area since Oxy does not have operations in this watershed. The study area is shown on Figure 1-1.

Oxy is producing natural gas from in the targeted formations. Natural gas is a hydrocarbon that has lower viscosity and is much less dense than water or brine. The lower viscosity of natural gas and significant buoyancy forces compared to water would drive the natural gas to discharge from the formations if this was physically possible. Natural gas remaining trapped in these formations over geologic time indicates the natural gas is isolated by extremely low permeability rock from the surface. Water in these zones is not in the active groundwater cycle (i.e. recharge to a formation outcrop, movement of groundwater through an aquifer, and discharge to a surface stream).

The Norwest evaluation of nontributary status of groundwater in Garfield, Mesa, and Pitkin Counties of the Piceance Basin from the producing formations utilized the Glover-Balmer equation. The Glover-Balmer equation is a commonly used analytical method for evaluating the timing and magnitude of depletions to surface water from pumping tributary groundwater. The conceptual model used in the Glover-Balmer equation is a semi-infinite, homogeneous, confined aquifer in perfect connection to a fully penetrating stream. The Glover-Balmer equation was used with formation parameters based on the assumption that the producing zones were a confined groundwater-saturated aquifer in perfect connection with a surface stream. This conceptual model gives an extremely conservative evaluation of the potential impacts that producing groundwater during natural gas production from the Mesaverde and Wasatch may have on surface streams.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 1-1 004284 r e v i

R

n e e r G

Yam Moffat pa Riv e r Routt

Rio Blanco White River

Garfield Eagle Rifle Roaring Fork River

Cascade Creek Lease Colorado River

De Beque

Collbran Lease Collbran Pitkin

Mesa Grand Junction

G un n i son R i v e Delta r

Uncom pa Gunnison hg r e

R

i v

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r

Legend Projection Information: UTM ZoneMontrose 13N FIGURE 1-1 Oxy USA Inc. Leases Elevation North American Datum 1983 Gunnison River feet Map Area Mesaverde Group Outcrop 4388 m Project Area Geology Souce: Project Location USGS OFR-92-507, Rivers 1172 m based on Tweto 1979 Perennial Streams 0 2.5 5 7.5 10 Counties 004285 MilesOuray

2 CONCEPTUAL MODEL

The Piceance Basin is a structural and sedimentary basin created by Laramide tectonism from late through time located in northwest Colorado. It is an asymmetrical basin with a gently dipping west and southwest flank and steeply dipping eastern flank (Johnson, 1989).

2.1 GEOLOGIC SETTING

Figure 2-1 shows the surficial geology of the Piceance Basin from the USGS 1:500,000 digital geologic mapping (Green, 1992) with the Mesaverde and Wasatch outcrops shown. A generalized stratigraphic column by Cole and Cumella (2003) for the Grand Junction area is shown in Figure 2-2. This report focuses on the Upper Cretaceous Mesaverde and the Tertiary Wasatch. Oxy produces natural gas primarily from the lithology in the Mesaverde with some natural gas production from the Wasatch “G” sandstone.

For the purposes of this report, the Mesaverde is divided into the Iles and Williams Fork Formations following the stratigraphic terminology suggested by Hettinger and Kirschbaum (2002, 2003) as follows. The Iles Formation nomenclature includes those parts of the Mesaverde and Mount Garfield Formations that lie below the top of the Rollins Sandstone Member. The Iles Formation includes the Corcoran, Cozzette, and Rollins Sandstone Members. The Williams Fork includes the (1) the Bowie Shale and Paonia Shale Members and an undifferentiated member in the and areas, (2) the part of the Mount Garfield that lies above the Rollins Sandstone Member in the eastern area, (3) the Hunter Canyon Formation in the eastern Book Cliffs area, and (4) all strata that are equivalent to the Ohio Creek .

A generalized cross section illustrating the stratigraphic relationship of the units in the southern Piceance Basin is shown on Figure 2-3. The general depositional environment for the basin is shown on Figure 2-4 which is broken into the northern and southern parts of the basin. A short description of each of the relevant units for this analysis follows.

2.1.1 The Mancos Shale is dominated by that accumulated in offshore and open-marine environments of the Cretaceous Interior seaway with the upper part of the formation grading into and intertongueing with the Mesaverde (Hettinger and Kirschbaum, 2003). Figure 2-3 shows the relationship of the Mancos Shale tongues with the sandstone members of the Iles Formation. These members were deposited during several regressive marine cycles (Johnson, 1989) with the basal part of each shale tongue representing the transgressive phase of each marine cycle. (Hettinger and Kirschbaum, 2003).

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2.1.2 Iles Formation The Iles Formation includes the Corcoran, Cozzette, and Rollins Sandstone Members. These members were deposited during regressive marine cycles and divided by tongues of the Mancos Shale. The sandstones are laterally continuous and can be correlated across much of the southern and eastern Piceance Basin (Cumella and Ostby, 2003).

North of Palisade, the Corcoran is about 100 ft thick and consists of very fine grained to fine-grained sandstone, siltstone, shale, and . The Cozzette is as much as 230 ft thick and consists of very fine grained to fine-grained sandstone, siltstone, shale, and coal. The Rollins Sandstone Member is 0 to 200 ft thick and consists of very fine grained to coarse-grained, cliff forming sandstone that accumulated in a regressive nearshore marine environment (Hettinger and Kirschbaum, 2003).

2.1.3 Williams Fork Formation The Williams Fork Formation was deposited on a broad coastal plain west of the prograding shorelines. The fluvial and coastal plain strata intertongue with marine deposits in the Bowie Shale Member of the Williams Fork Formation in the vicinity of the Grand Hogback and areas (Hettinger and Kirschbaum, 2003). The Williams Fork is thickest in the east including about 3,600 to 5,155 ft of strata between the Iles and Wasatch Formations along the Grand Hogback and thinning to about 1,200 ft thick in the west. The upper, “undifferentiated” part of the Williams Fork is about 2,000 to 4,000 ft thick and dominated by fluvial deposits of sandstone, conglomeratic sandstone, conglomerate, siltstone, and shale (Hettinger and Kirschbaum, 2003).

Coal is present in the Cameo-Wheeler coal zone of the Williams Fork Formation (Johnson, 1989; SSP&A, 2007). It overlies and intertongues with the Rollins Sandstone member of the Iles Formation and extends westward from the Grand Hogback to near the Colorado- State line (Hettinger and Kirschbaum, 2003). The Cameo-Wheeler coal zone is about 50-450 ft thick and contains as much as 87 ft of net coal in 1-21 beds that are 1-44 ft thick (Hettinger and others, 2000).

A critical characteristic of the lower Williams Fork Formation sandstones for the purposes of this study are their lenticular nature. Cole and Cumella (2005) conducted a sedimentological and stratigraphic examination of the lower 700 ft of the Williams Fork Formation, as exposed in Coal Canyon, near Palisade, Colorado. This Lower Williams Fork includes the Cameo-Wheeler coal zone and is stratigraphically equivalent to part of the gas productive interval in the southern Piceance Basin. Cole and Cumella (2005) noted the interval was less than 50% sandstone with a total of 136 sand bodies identified. The average sand-body thickness was 9 ft with and a mean apparent width of 528 ft. The 10-acre spacing of gas wells in the Piceance Basin is driven by the short apparent width of the target sand bodies.

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2.1.4 Wasatch Formation The Wasatch Formation was subdivided into the Atwell Gulch, Molina, and Shire members by Donnell (1969) in the southwest portion of the basin. The Atwell Gulch member is known as the in the northern half of the basin (Donnell, 1969). The Atwell Gulch/Fort Union is overlain by the Molina Member which generally correlates with the productive fluvial sandstone interval known as the Wasatch “G” (Carlstrom, 2003).

Overall, the lower Tertiary strata in the Piceance Basin are much more highly mud-dominated than the underlying Upper Cretaceous Mesaverde (Johnson and Flores, 2003).

2.2 HYDROLOGIC DATA

For the purposes of this assessment, the point of evaluation (POE), i.e. the potential point of depletion, is considered to be the location where the Mesaverde or Wasatch lies directly beneath a mapped perennial stream or the alluvium of a mapped perennial stream. Perennial stream locations were obtained from the USGS National Hydrography Dataset (NHD). This is the surface water component of The National Map. The NHD is a comprehensive set of digital spatial data representing the surface water of the using common features such as , ponds, streams, rivers, canals, and oceans. These data are designed to be used in general mapping and in analysis of surface-water systems using geographic information systems (GIS).

The locations of perennial streams were overlain on the geologic mapping. Figure 2-5 shows the mapped lakes and perennial streams used in the assessment.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 2-3 004288 Moffat

Routt

Rio Blanco

Garfield Rifle

De Beque

Collbran Pitkin

Grand Junction Mesa

Delta

Gunnison

Montrose

Projection Information: Legend UTM Zone 13N FIGURE 2-1 Project Area Geology Tertiary Sediments North American Datum 1983 feet Map Area Counties Quarternary, Undifferentiated Wasatch Formation Geologic Map of Alluvium Mesaverde Group Geology Souce: USGS OFR-92-507, Piceance Basin Tertiary Intrusions Mancos Shale based on Tweto 1979 Tertiary Volcanic Flows 0 2.5 5 7.5 10 004289 Miles

FIGURE 2-2. GENERAL STRATIGRAPHIC COLUMN NEAR GRAND JUNCTION (FROM COLE AND CUMELLA, 2003)

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 2-5 004290

FIGURE 2-3. GENERALIZED WEST TO EAST CROSS SECTION OF THE MESAVERDE AND MANCOS (FROM JOHNSON AND ROBERTS, 2003)

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 2-6 004291

FIGURE 2-4. DEPOSITIONAL AND STRATIGRAPHIC FRAMEWORK OF THE PICEANCE BASIN (FROM YUREWICZ, 2005)

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 2-7 004292 Rio Blanco

Rifle Garfield

De Beque

Collbran Pitkin

Mesa

Grand Junction Gunnison

Legend Projection Information: UTM Zone 13N FIGURE 2-5 Geology Tertiary Sediments Counties North American Datum 1983 Map Area Quarternary, Undifferentiated Wasatch Formation Project Area feet Delta Geologic Map of Alluvium Mesaverde Group Perennial Streams Geology Souce: Piceance Basin Tertiary Intrusions Mancos Shale USGS OFR-92-507, with Perennial Streams based on Tweto 1979 Tertiary Volcanic Flows 0 2.5 5 7.5 10 004293 Miles

3 HYDROLOGEOLOGIC PARAMETERS

There is a limited set of published hydrogeologic data available for the Mesaverde and Wasatch in the Piceance Basin as noted by SSP&A, 2007. It is important to note that published hydrogeologic parameters are biased towards formations and zones that produce water in useable quantities instead of hydrocarbon production zones. There has been ongoing research in natural gas production from tight sandstones of the Mesaverde with some literature data available. Site specific data were also obtained from Oxy and other operators. This section describes the available hydrogeologic data for formation permeability and water storage that was evaluated for use in the nontributary analysis.

3.1 PERMEABILITY

Table 3-1 summarizes permeability data assembled for the Mesaverde and Wasatch. This collection of permeability data combines several types of reported permeability, primarily from core samples. In most low-permeability sandstones, in situ high-pressure gas or liquid permeability values range from 10 to 1,000 times less than routine air permeability values (Byrnes, 1996). Core analysis methods commonly use gas as the flowing phase. To obtain equivalent reservoir pressure gas permeability values, an adjustment called the Klinkenberg correction must be made to account for the fact the gas molecules used in the laboratory testing do not collide as often as do liquid molecules. Permeability values for hydrocarbon reservoirs are commonly reported in milliDarcies (mD) with 365 mD approximately equal to a hydraulic conductivity of 1 ft/day.

Published literature values for permeability in Table 3-1 for the Mesaverde sandstones are upwards of 0.1 mD with most reported values orders of magnitude lower. A major study to characterize critical permeability, capillary pressure, and electrical properties for Mesaverde tight gas sandstones from western U.S. basins was sponsored by the U.S. Department of Energy under DOE Contract DE-FC26-05NT42660. As part of this effort, a data set from six wells and two shallow boreholes in the Piceance Basin was analyzed. For 577 samples, the geometric average permeability was 0.0011 mD (Byrnes and others, 2009). Given the low permeability of the core samples, a single high permeability sample from a large data set can result in misleadingly high average formation permeability. Permeability values are commonly log normally distributed and a geometric mean is a more appropriate method for calculating average formation permeability.

A high quality set of permeability data from 21 cored wells was used in a nontributary groundwater determination in the northeastern portion of the Piceance Basin (WWE, 2009). Permeability data from several other operators was obtained for production intervals in the Wasatch. Additionally, Oxy provided a high quality data set of permeability data from seven cored wells from its Cascade Creek and Collbran lease areas in the more central part of the basin. This section describes the available hydrogeologic data for the nontributary groundwater analysis.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 3-1 004294

3.1.1 Oxy Reported Permeability – Mesaverde Oxy provided a dataset of Klinkenberg permeabilities for seven wells with permeability values reported for the Ohio Creek, Upper Williams Fork, Lower Williams Fork, Corocoran, Cozzette, and Cameo zones. These analyses were conducted at varying confining stresses and for one well the samples were run at both 1,500 and 3,000 psi confining stress. As a conservative measure, the 1,500 psi permeabilities were used instead of the 3,000 psi permeabilities which were lower. The Oxy data is shown in Appendix A and a summary of the Oxy data is shown in Table 3-2.

The zone with the highest geometric mean permeability was the Cozzette at 0.0175 mD. The value of 0.0175 mD was used as a conservative measure when calculating the Mesaverde nontributary groundwater distance since a higher permeability value increases the distance that groundwater is tributary. This is a site-specific permeability value from Oxy’s lease areas that is representative of the permeability of the formations that groundwater is withdrawn from in conjunction with the exploration and production of oil and gas. This value is almost twice the geometric mean of all of Oxy’s Mesaverde data (0.0105 mD), more than three times higher than the geometric mean of all of the ExxonMobil permeability values (0.0047 mD), and within the range of Mesaverde permeabilities summarized in Table 3-1.

3.1.2 Permeability information – Wasatch Oxy did not have any site specific Wasatch permeability data for their lease areas. There is limited published permeability data for the Wasatch in the Piceance Basin but several other operators provided permeability data for the Wasatch for this effort. Data was obtained from ExxonMobil (WWE, 2009) Chevron, and Williams Production Company. This permeability data are shown in Appendix B. The data are from production zones in the Wasatch, including the Wasatch G which generally correlates to the Molina Member of the Wasatch (Carlstrom, 2003)

The Klinkenberg permeability data for the Wasatch sands was assembled and analyzed. If the permeability was calculated at several confining stresses, the 1,500 psi value was used for consistency with the Mesaverde analysis. The geometric mean of the Klinkenberg permeability values is 0.0192 mD which was used in the calculation of the nontributary groundwater distance.

3.2 SPECIFIC STORAGE

Specific storage describes the amount of water a confined aquifer will produce from a unit volume for a unit decline in potentiometric head. No site-specific specific storage values were available, so a common default value of 1x10-6 ft-1 for a confined aquifer (Lohman, 1972) was used. This value is at the lower end of a range of specific storage values (2.1 x 10-5 to 1x10-6 ft-1) provided by Anderson and Woessner (1992) for fissured and jointed rock. Give the lack of site- specific values, this is a reasonable and conservative specific storage to use and is consistent with the value used in recent evaluations of nontributary groundwater status in the Piceance Basin by SSP&A, 2007 and WWE, 2009.

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TABLE 3-1. LITERATURE VALUES FOR MESAVERDE GROUP AND WASATCH FORMATION PRODUCING UNITS

Permeability (mD) Formation or Unit Source Notes Williams Fork Sandstones at at 6 to 12% for approximately 4,100 ft of Mesaverde Core at 0.0001 to 0.002 reservoir pressure and water Cumella and Ostby, 2003 the MWX wells, net sandstone pay of 300-400 ft for Williams Fork in saturation GV-P-R Statement of David S. George on Dynamic Formation Injectivity Test (DFIT) well Cascade Creek 797-05- 0.02 Iles Formation Cause No. 510 Docket No. 0903- 36D AW-01 Cozzettte, Corcoran, and 0.002 to 0.08 Brown and others, 1986 In situ gas permeabilities of Cozzette, Corcoran, and Rollins Rollins Sandstones Productive sandstones of 0.02 Olson, 2003 Average of pressure buildup tests in 7 wells in White River Dome Williams Fork microdarcy matrix Iles and Williams Fork Koepsell and others, 2003 Soeder and Randolph, 1987 Based on 44 tight Mesaverde Sandstone samples from US DOE MWX 0.0005 to 0.009 Mesaverde cited in Nelson, 2009 site - geometric mean of 2.1 uD 0.0002 to 0.08 Mesaverde Byrnes, 1996 Table is after Dutton et al. 1993. 0.0011 Mesaverde Byrnes and others, 2009 Value is geometric mean for 577 samples

0.01 to 0.1 Mesaverde group reservoirs Johnson and Roberts, 2003 Citing Pitman and Spencer (1984), locally as low as 0.0006 mD

0.0071 to 0.0117 Mesaverde group reservoirs Craig and others, 2002 Geometric means of 244 and 503 tests

Reporting values from Rio Blanco Natural Gas Company, 1980 - 0.0006 to 0.055 fluvial part of the Mesaverde Johnson, 1989 conventional dry core measurement Corcoran, Cozzette, and Reporting values from Tichy and Rettger, 1961. Up to 0.1 mD for 0.06 Johnson, 1989 Rollins productive Corcoran and Cozzette on the Divide Creek anticline

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Table 3-1. Literature Values for Mesaverde Group and Wasatch Formation Producing Units (continued) Permeability (mD) Formation or Unit Source Notes

0.007 to 0.092 Subunits in Williams Fork WWE (2009) for ExxonMobil Arithmetic mean values of core data, not geometric mean. 0.003 and 0.042 Cameo and Rollins WWE (2009) for ExxonMobil Arithmetic mean values of core data, not geometric mean. Trans-Cozzette thru 0.005 WWE (2009) for ExxonMobil Arithmetic mean values of core data, not geometric mean. Castlegate in Mesaverde 0.026 to 0.034 Wasatch sandstones WWE (2009) for ExxonMobil Arithmetic mean values of core data, not geometric mean Less than 0.1 Wasatch Johnson and Roberts, 2003 Fluvial Sandstones in Wasatch in

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TABLE 3-2. SUMMARY OF MESAVERDE GROUP PERMEABILITY DATA PROVIDED BY OXY

Hydraulic Permeability (mD) Conductivity Zone Geometric Mean (ft/day)

Ohio Creek 0.0140 3.836E-05

Upper Williams Fork 0.0099 2.712E-05

Lower Williams Fork 0.0135 3.699E-05

Cameo 0.0096 2.630E-05

Corocoran 0.0075 2.055E-05

Cozzette 0.0175 4.795E-05

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4 NONTRIBUTARY GROUNDWATER EVALUATION

The nontributary groundwater analysis used the Glover-Balmer equation (Glover and Balmer, 1954). This is an analytical solution for stream depletions over time caused by a well pumping in an idealized, homogeneous, semi-infinite aquifer that the stream fully penetrates. The idealized aquifer geometry and perfect connection between the stream and the formation being pumped from results in a highly conservative, worst case analysis of stream depletions which makes the Glover-Balmer analysis a widely used screening level tool for estimating stream depletions.

The Glover-Balmer equation requires input values for distance from pumping well to the point of depletion, length of time the pumping has occurred, aquifer storativity and aquifer transmissivity. The equation is shown below:

The Glover-Balmer Equation is as shown below:

q ⎛ Sα 2 ⎞ = erfc⎜ ⎟ ...... (Equation 1) ⎜ ⎟ Q ⎝ 4tT ⎠

Input parameters for Equation 1 are in terms of length (L) and time (T) as follows:

q/Q = ratio of the quantity of stream depletion (L3/T) to pumping rate (L3/T)

erfc = complementary error function that returns a value between 0 and 1

S = storativity of water-bearing materials (unitless)

α = distance from pumping well to the point of stream depletion (L)

t = time (T)

T = transmissivity of water-bearing materials (L2/T)

Storativity can be calculated as follows:

S = Ss x b

Transmissivity (T) can be calculated as follows:

T = K x b

Where:

Ss = specific storage (1/L)

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 4-1 004299

K = hydraulic conductivity (L/T) b = formation thickness (L)

As b appears in both the numerator and the denominator in Equation 1, it cancels out and Equation 1 reduces to:

q ⎛ Ssα 2 ⎞ = erfc⎜ ⎟ ...... Equation 2 ⎜ ⎟ Q ⎝ 4tk ⎠

Using the statutory definition of nontributary groundwater (q/Q < 0.001 after 100 years [36,500 days]), the Glover-Balmer Equation was used to establish the location of the nontributary boundary as the distance from the POE where q/Q is equal to 0.001. This analysis was performed using an Excel spreadsheet with the parameters shown in Table 4-1. Copies of the spreadsheet calculations are included in Appendix C.

The calculated distance from a stream/outcrop intersection to nontributary groundwater is 6,160 ft for the Mesaverde Group and 6,450 ft for the Wasatch Formation as shown in Table 4-1. Arcs with these distances were established from stream/outcrop intersection points and overlapping areas were combined using GIS. The nontributary groundwater zone for the Mesaverde is shown on Figure 4-1 and for the Wasatch on Figure 4-2. Small areas where the Wasatch was not present at the surface but surrounded by zones of Wasatch outcrop were excluded from the nontributary groundwater zone as a conservative measure. The nontributary zones were also limited as described in Section 1 and the northern and southern boundaries of the nontributary groundwater are shown with a dashed line to reflect that these are project boundaries rather than the physical end of the nontributary groundwater zones.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 4-2 004300

TABLE 4-1. PARAMETERS USED IN NONTRIBUTARY ANALYSIS

Parameter Value Basis Mesaverde Hydraulic Geometric mean of Oxy permeability data for 4.79 x 10-5 ft/day Conductivity Cozzette Sandstone is 0.0175 mD.

Mesaverde Specific Default specific storage value suggested by Lohman, 1x10-6 ft-1 Storage 1972 and used by WWE, 2009 and SSP&A, 2007.

Mesaverde Nontributary 6,160 ft Calculated using Glover-Balmer Equation Groundwater Distance Wasatch Hydraulic 5.26 x 10-5 ft/day Geometric mean of permeability data is 0.0192 mD. Conductivity

Wasatch Specific Default specific storage value suggested by Lohman, 1x10-6 ft-1 Storage 1972 and used by WWE, 2009 and SSP&A, 2007.

Wasatch Nontributary 6,450 ft Calculated using Glover-Balmer Equation Groundwater Distance

Time 36,500 days Equal to 100

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 4-3 004301 T4S R103W T4S R102W Rio Blanco T4S R100W T4S R99W T4S R98W T4S R97W T4S R96W T4S R95W T4S R101W T4S R94W T4S R93W T4S R92W T4S R91W T4S R90W 013A T4S R89W T4S R88W

T5S R103W T5S R102W 325A T5S R101W T5S R100W T5S R99W T5S R98W T5S R97W T5S R96W T5S R95W T5S R94W T5S R93W T5S R92W T5S R91W T5S R90W T5S R89.5W T5S R89W T5S R88W T6S R104W

T6S R103W T6S R102W T6S R101W T6S R98W T6S R100W Rifle 070E 006D T6S R99W 006K T6S R97W Garfield T6S R96W 006L T6S R95W T6S R94W T6S R92W T6S R91W T6S R90W T6S R93W T6S R89W T6S R88W

T7S R104W T7S R103W T7S R102W T7S R101W T7S R100W T7S R99W T7S R98W T7S R97W 082A T7S R93W T7S R96W T7S R95W T7S R94W T7S R92W T7S R91W 006M T7S R90W T7S R89W T7S R88W

T8S R104W T8S R103W T8S R102W T8S R101W T8S R100W T8S R99W T8S R98W T8S R97W T8S R93W 139A De Beque T8S R95W T8S R94W T8S R92W T8S R91W T8S R96W T8S R90W T8S R89W T8S R88W

T9S R102W T9S R101W T8.5S R94W T8.5S R93W T9S R103W

T9S R100W 070A T9S R99W T9S R98W T9S R97W T9S R95W T9S R94W T9S R96W T9S R93W T9S R89W PM 31 T2N R3W PM 31 T2N R2W T9S R92W T9S R91W Collbran T9S R90W T9S R88W 006A Pitkin

T10S R101W T10S R100W

T10S R103W T10S R99W

T10S R98W 330A T10S R97W T10S R96W T10S R95W T10S R94W PM 31 T1N R3W T10S R93W PM 31 T1N R2W T10S R92W T10S R91W PM 31 T1N R1W T10S R90W T10S R89W T10S R88W PM 31 T1N R1E Mesa 340A T11S R99W T11S R98W

T11S R103W 070B 006C T11S R102W T11S R101W T11S R97W 006B T11S R96W T11S R95W T11S R94W T11S R93W T11S R92W T11S R91W PM 31 T1S R1W 070Z T11S R90W T11S R89W PM 31 T1S R1E T11S R88W PM 31 T1S R2E

Grand Junction T12S R103W 141B T12S R102W PM 31 T2S R1W 065A T12S R101W Gunnison PM 31 T2S R1E T12S R98W T12S R100W T12S R97W T12S R96W T12S R95W T12S R94W T12S R93W T12S R92W Projection Information: T12S R91W Legend T12S R90W T12S R89W T12S R88W T12S R99W PM 31 T2S R2E UTM Zone 13N FIGURE 4-1 Project Area Counties Perennial Streams North American Datum 1983 050A feet Map Area Mesaverde Group Townships & Ranges Interstate Delta Mesaverde Group T13S R103W Nontributary Area T13S R102W Sections Geology Souce: T13S R101W U.S. Highway Mesaverde Group Outcrop T13S R100W USGS OFR-92-507, Nontributary Boundary T13S R99W T13S R98W State Highway T13S R97W T13S R96W based on Tweto 1979 T13S R95W T13S R94W 133B 141A T13S R93W T13S R92W T13S R89W PM 31 T3S R2E T13S R91W T13S R90W T13S R88W 0 2.5 5 7.5 10 004302 T14S R103W T14S R102W T14S R101W T14S R100W Miles T14S R99W T14S R98W T14S R97W T14S R96W T4S R103W T4S R102W Rio Blanco T4S R100W T4S R99W T4S R98W T4S R97W T4S R96W T4S R95W T4S R101W T4S R94W T4S R93W T4S R92W T4S R91W T4S R90W 013A T4S R89W T4S R88W

T5S R103W T5S R102W 325A T5S R101W T5S R100W T5S R99W T5S R98W T5S R97W T5S R96W T5S R95W T5S R94W T5S R93W T5S R92W T5S R91W T5S R90W T5S R89.5W T5S R89W T5S R88W T6S R104W

T6S R103W T6S R102W T6S R101W T6S R98W T6S R100W Rifle 070E 006D T6S R99W 006K T6S R97W Garfield T6S R96W 006L T6S R95W T6S R94W T6S R92W T6S R91W T6S R90W T6S R93W T6S R89W T6S R88W

T7S R104W T7S R103W T7S R102W T7S R101W T7S R100W T7S R99W T7S R98W T7S R97W 082A T7S R93W T7S R96W T7S R95W T7S R94W T7S R92W T7S R91W 006M T7S R90W T7S R89W T7S R88W

T8S R104W T8S R103W T8S R102W T8S R101W T8S R100W T8S R99W T8S R98W T8S R97W T8S R93W 139A De Beque T8S R95W T8S R94W T8S R92W T8S R91W T8S R96W T8S R90W T8S R89W T8S R88W

T9S R102W T9S R101W T8.5S R94W T8.5S R93W T9S R103W

T9S R100W 070A T9S R99W T9S R98W T9S R97W T9S R95W T9S R94W T9S R96W T9S R93W T9S R89W PM 31 T2N R3W PM 31 T2N R2W T9S R92W T9S R91W Collbran T9S R90W T9S R88W 006A Pitkin

T10S R101W T10S R100W

T10S R103W T10S R99W

T10S R98W 330A T10S R97W T10S R96W T10S R95W T10S R94W PM 31 T1N R3W T10S R93W PM 31 T1N R2W T10S R92W T10S R91W PM 31 T1N R1W T10S R90W T10S R89W T10S R88W PM 31 T1N R1E Mesa 340A T11S R99W T11S R98W

T11S R103W 070B 006C T11S R102W T11S R101W T11S R97W 006B T11S R96W T11S R95W T11S R94W T11S R93W T11S R92W T11S R91W PM 31 T1S R1W 070Z T11S R90W T11S R89W PM 31 T1S R1E T11S R88W PM 31 T1S R2E

Grand Junction T12S R103W 141B T12S R102W PM 31 T2S R1W 065A T12S R101W Gunnison PM 31 T2S R1E T12S R98W T12S R100W T12S R97W T12S R96W T12S R95W T12S R94W Projection Information: T12S R93W T12S R92W T12S R91W T12S R89W T12S R99W T12S R90W T12S R88W Legend PM 31 T2S R2E UTM Zone 13N FIGURE 4-2 North American Datum 1983 050A Map Area Project Area Counties Perennial Streams feet Delta T13S R103W Wasatch Formation WasatchT13S FormationR102W Townships & Ranges Interstate Geology Souce: T13S R101W Nontributary Area T13S R100W USGS OFR-92-507, Sections T13S R99W Nontributary Boundary U.S. Highway T13S R98W T13S R97W T13S R96W T13S R95W based on Tweto 1979 Wasatch Formation Outcrop T13S R94W T13S R93W 133B 141A T13S R92W T13S R91W T13S R89W T13S R88W StatePM 31 Highway T3S R2E T13S R90W Mesaverde Group Outcrop 0 2.5 5 7.5 10 004303 T14S R103W T14S R102W T14S R101W T14S R100W Miles T14S R99W T14S R98W T14S R97W T14S R96W

5 SUMMARY

Nontributary groundwater zones were determined for Mesaverde and the Wasatch for water produced during natural gas production. The zones were determined using the Glover-Balmer equation. The equation was solved for a distance over which a well pumping for 100 years would not deplete surface water at a rate meeting the statutory definition of tributary groundwater (q/Q < 0.001 after 100 years) for a stream that fully penetrates an semi-infinite, homogeneous aquifer that is in perfect contact with the stream. These distances were calculated with Oxy site-specific permeability data from gas production wells for the Mesaverde and with data from surrounding operators for the Wasatch. The calculated distances were 6,160 ft (1.17 miles) and 6,450 ft (1.22 miles) for the Mesaverde and Wasatch respectively. Areas where groundwater was within these distances from perennial streams in or crossing the Mesaverde or Wasatch outcrops were excluded from the nontributary groundwater zones.

The calculated distances are conservative because:

• The use of absolute instead of effective permeability values.

• The analysis assumed lateral hydraulic continuity of permeable lithology between the producing zones and potential points of impact at the outcrop.

• Calculated nontributary distances were from the top of the evaluated zones, making stratigraphically lower production intervals closer for the purposes of the evaluation.

• Calculated nontributary distances from the outcrop were measured horizontally rather than along a flow path. This is especially relevant on the eastern portion of the basin where the Mesaverde Group is steeply dipping.

• The highest geometric mean permeability value for the zones within the Mesaverde Group was used to calculate the nontributary boundary for the group.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 5-1 004304

6 REFERENCES

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Byrnes, A.P., 1996. Reservoir Characteristics of Low-Permeability Sandstones in the Rocky Mountains. The Mountain Geologist 34(1): 39-51.

Byrnes, A.P., Cluff R.M., Webb J.C., Krygowski D.A., and Whittaker S.D., 2009. Lithofacies and Petrophysical Properties of Mesaverde Tight-Gas Sandstones in Western U.S. Basins: A Short Course. 2009 AAPG Annual Convention Short Course #1. 6 June 2009, Denver, Colorado.

Carlstrom G.M., 2003. Wasatch “G” Sand – A Conventional Reservoir in a Non-conventional Basin. In Piceance Basin 2003 Guidebook. Edited by Peterson, K.R., Olson T.M., and Anderson D.S. Rocky Mountain Association of Geologists, Denver, CO.

Cole R.D. and Cumella, S.P., 2003. Field Trip Guidebook: Stratigraphic Architecture and Reservoir Characteristics of the Mesaverde Group, Southern Piceance Basin, Colorado in Piceance Basin 2003 Guidebook. Edited by Peterson, K.R., Olson T.M., and Anderson D.S. Rocky Mountain Association of Geologists, Denver, CO.

Cole R.D. and Cumella, S.P., 2005. Sand-Body Architecture in the Lower Williams-Fork Formation (Upper Cretaceous), Coal Canyon, Colorado, with Comparison to the Piceance Basin Subsurface. The Mountain Geologist 42(3): 85-107.

Craig, D.P., Eberhard M.J., Odegard C.E., Ramurthy M., and Mullen R., 2002. Permeability, Pore Pressure, and Leakoff-Type Distributions in Rocky Mountain Basins. Paper SPE 75717 presented at the SPE Gas Technology Symposium, Calgary, Alberta, Canada. 30 April-2 May 2002.

Cumella, S.P. and Ostby D.B., 2003. Geology of the Basin-Centered Gas Accumulation, Piceance Basin, Colorado. In Piceance Basin 2003 Guidebook. Edited by Peterson, K.R., Olson T.M., and Anderson D.S. Rocky Mountain Association of Geologists, Denver, CO.

Donnell, J.R. 1969. Paleocene and Lower Units in the Southern Part of the Piceance Creek Basin, Colorado. U.S. Geological Survey Bulletin 1274-M.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 6-1 004305

George, D.S. 2009. Verified Statement for COGCC Director Approval in Cause No. 510, Docket no. 0903-AW-01

Glover R.E. and Balmer, G.G., 1954. River Depletion Resulting from Pumping a well near a River. Transactions American Geophysical Union 35: 468-470.

Green, G.N. 1992. The Digital Geologic Map of Colorado in ARC/INFO Format: U.S. Geological Survey Open-File Report 92-507.

Hettinger, R.D., Roberts, L.N.R., and Gognat, T.A.., 2000. Investigations of the Distribution and Resources of coal in the southern part of the Piceance Basin, Colorado. Chapter O in Geologic assessment of coal in the , Colorado, , and Utah: edited by Kirschbaum, M.A., Roberts, L.N.R., and Biewick, L.R.H., U.S. Geological Survey Geologic Professional Paper 1625-B.

Hettinger, R.D. and Kirschbaum M.A., 2002. of the Upper Cretaceous Mancos Shale (Upper Part) and Mesaverde Group in the Southern Part of the Uinta and Piceance Basins, Utah and Colorado. U.S. Geological Survey Geologic Investigations Series I-2764.

Hettinger, R.D. and Kirschbaum M.A., 2003. Stratigraphy of the Upper Cretaceous Mancos Shale (Upper Part) and Mesaverde Group in the Southern Part of the Uinta and Piceance Basins, Utah and Colorado. In Petroleum Systems and Geological Assessment of Oil and Gas in the Uinta-Piceance Province, Utah and Colorado. U.S. Geological Survey Digital Data Series DDS-69-B.

Johnson R.C., 1989. Geologic History and Hydrocarbon Potential of -Age, Low- Permeability Reservoirs, Piceance Basin, Western Colorado. U.S. Geological Survey Bulletin 1787-E.

Johnson, R.C. and Flores R.M., 2003. History of the Piceance Basin from Latest Cretaceous through Early Eocene and the Characterization of Lower Tertiary Sandstone Reservoirs. In Piceance Basin 2003 Guidebook. Edited by Peterson, K.R., Olson T.M., and Anderson D.S. Rocky Mountain Association of Geologists, Denver, CO.

Johnson, R.C. and Roberts, S.B., 2003. The Mesaverde Total Petroleum System, Uinta-Piceance Province, Utah and Colorado. In Petroleum Systems and Geological Assessment of Oil and Gas in the Uinta-Piceance Province, Utah and Colorado. U.S. Geological Survey Digital Data Series DDS- 69-B.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 6-2 004306

Koepsell, R., Cumella, S.P., and Uhl D., 2003. The Practical Use and Application of the Magnetic Resonance Imaging Log in the Piceance Basin. In Piceance Basin 2003 Guidebook. Edited by Peterson, K.R., Olson T.M., and Anderson D.S. Rocky Mountain Association of Geologists, Denver, CO. Lohman, S.W., 1972. Ground-Water Hydraulics. U.S. Geological Survey Professional Paper 708.

Nelson, P.H. 2009. Pore-throat Sizes in Sandstones, Tight Sandstones, and . AAPG Bulletin, 93(3): 319-340.

Olson, T.M., 2003. White River Dome Field: Gas Production from Deep and Sandstones of the Cretaceous Williams Fork Formation. In Piceance Basin 2003 Guidebook. Edited by Peterson, K.R., Olson T.M., and Anderson D.S. Rocky Mountain Association of Geologists, Denver, CO.

S.S. Papadopulos & Associates, Inc. and Colorado Geological Survey, 2007. Draft Stream Depletion Assessment Study – Piceance Basin, Colorado. S.S. Papadopulos & Associates, Inc., Boulder, Colorado.

Spencer, C. W., 1989. Review of Characteristics of Low-Permeability Gas Reservoirs in the . AAPG Bulletin, 73(5): 613-629.

Wright Water Engineers, Inc., 2009. ExxonMobil Nontributary Groundwater Assessment. Piceance Basin, Colorado. Prepared for Exxon Mobil Corporation. Houston, Texas. February, 2009.

Yurewicz D., 2005. Controls on Gas and Water Distribution, Mesaverde Basin Center Gas Play, Piceance Basin, Colorado. Extended Abstract for 2005 Vail Hedberg Conference.

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 6-3 004307

APPENDIX A MESAVERDE GROUP PERMEABILITY DATA PROVIDED BY OXY

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT A-1 004308 Occidental Oil & Gas Corporation Cascade Creek 697-20-28: Conventional Core Cascade Creek Field Garfield County, Colorado

CMS-300 CONVENTIONAL PLUG ANALYSIS

Sample Depth Net Confin Permeability Formation Number Stress KlinkenbergKair ft psig % mD mD 1 4680.35 1500 4.01 0.011 0.022 Upper Williams Fork 2 4685 1500 1.61 0.001 0.001 (Non Productive) 3 4690.5 1500 1.37 0.0001 0.0004 4 4694.6 1500 9.13 0.006 0.014 5 4699 1500 4.62 0.003 0.006 6 4704 1500 5.56 0.003 0.006 7 4710 1500 6.02 0.004 0.01 8 4713.3 1500 6.54 0.013 0.016 9 4720 1500 6.57 0.025 0.033 10 4725.15 1500 8.26 0.027 0.034 11 4730 1500 8.97 0.042 0.048 12 4735.2 1500 3.79 0.016 0.022 13 4742.2 1500 3.39 0.001 0.002 14 4754 1500 4.53 0.002 0.005 15 4759 1500 5.49 0.027 0.031 16 4764.1 1500 2.86 0.002 0.004 17 4769.2 1500 6.88 0.016 0.02 18 4774 1500 5.61 0.017 0.024 19 4779 1500 7.16 0.018 0.023 20 4784.25 1500 7.47 0.043 0.058 21 4784.5 1500 6.52 0.015 0.018 22 4789.2 1500 8 0.072 0.091 23 4794 1500 8.1 0.071 0.084 24 4804.6 1500 5.2 0.001 0.002 25 4809.7 1500 6.43 0.005 0.012 26 4814.6 1500 7.68 0.006 0.013 27 4819.6 1500 8.25 0.034 0.044 28 4824.5 1500 7.72 0.007 0.015 29 4829.6 1500 8.7 0.019 0.022 30 4834 1500 10.19 0.008 0.016 31 4839.6 1500 8.5 0.041 0.052 32 4853 1500 3.61 0.001 0.003 33 4859 1500 2.25 0.533 0.56

34 5180.2 1500 8.87 0.019 0.025 Lower Williams Fork 35 5188.5 1500 3.62 0.001 0.002 (Productive) 36 5194.3 1500 6.05 0.014 0.016 37 5199.5 1500 6.34 0.003 0.006 38 5205.4 1500 4.36 0.001 0.002 39 5210.5 1500 6.04 0.005 0.01 40 5214.2 1500 3.88 0.006 0.013 41 5218.5 1500 2.95 0.001 0.002 42 5223.3 1500 3.45 0.001 0.003 45 5240.7 1500 5.18 0.001 0.001 46 5248 1500 1.76 0.006 0.014 47 5253 1500 6.46 0.005 0.011 48 5258.3 1500 1.12 0.0002 0.001 49 5263 1500 4.16 0.003 0.006 51 5280.5 1500 5.39 0.008 0.01 52 5285 1500 0.4 0.0004 0.001 53 5293.5 1500 3.89 0.004 0.009 54 5298.3 1500 9.04 0.009 0.02 55 5303 1500 8.53 0.041 0.051 56 5308.6 1500 9.14 0.033 0.042 57 5313 1500 7.85 0.03 0.038 58 5318.4 1500 9.87 0.06 0.075 59 5326.3 1500 4.02 0.001 0.003 60 5331.3 1500 8.42 0.054 0.068 61 5336 1500 8.98 0.036 0.045 62 5341.3 1500 8.4 0.02 0.025 63 5347.4 1500 2.71 0.0003 0.001 64 5352.3 1500 4.95 0.012 0.017 65 5358.3 1500 5.08 0.013 0.017

66 6112.3 1500 9.63 0.009 0.019 67 6117 1500 10.46 0.012 0.024 68 6124.3 1500 4.6 0.015 0.03 69 6129.5 1500 3.11 0.001 0.003 70 6134 1500 7.24 0.014 0.017 72 6139.5 1500 6.52 0.447 0.459 73 6145.3 1500 4.04 0.001 0.004 Cameo 74 6154.3 1500 2.25 0.001 0.002 (Productive) 75 6162.3 1500 4.14 0.448 0.493 76 6167.3 1500 3.49 0.013 0.026 78 6183.5 1500 3.91 0.013 0.026 79 6209 1500 5.38 0.012 0.025 80 6214.3 1500 11.86 0.023 0.032 81 6216.6 1500 10.84 0.016 0.019 82 6220.9 1500 10.95 0.014 0.02 83 6225.9 1500 5.76 0.033 0.059 84 6231 1500 4.34 0.004 0.009 85 6235.5 1500 4.28 0.105 0.162 86 6248.2 1500 2.66 0.0002 0.001 87 6263.4 1500 3.73 0.164 0.171 88 6268.4 1500 3.52 0.073 0.118 89 6278.4 1500 2.92 0.0002 0.001 91 6288.3 1500 5.64 0.006 0.013 92 6294 1500 7.28 0.059 0.098 93 6299 1500 9.76 0.007 0.015 94 6304.1 1500 6.88 0.015 0.031

004309 CORE LABORATORIES, INC. HOUSTON ADVANCED TECHNOLOGY CENTER

Occidental Oil & Gas Corporation Cascade Creek Project

CMS-300 ROTARY SIDEWALL CORE ANALYSIS DATA Sample Net Confining Porosity Permeability Number Depth Stress Klinkenberg Kair Footnote (ft) (psig) (%) (mD) (mD) Formation

Cascade Creek 620-24-43 Well 4A 4014.00 1500 8.56 0.060 0.076 Upper Williams Fork 4A 4014.00 3000 8.34 0.034 0.045 (Non Prod) 11A 4566.00 1500 6.82 0.028 0.037 Lower Williams Fork 11A 4566.00 3000 6.55 0.014 0.020 (Prod) 13A 4692.00 1500 9.69 0.044 0.059 (1),(3) 13A 4692.00 3000 9.30 0.025 0.034 (1),(3) 15A 4766.00 1500 10.74 0.052 0.067 (1),(3) 15A 4766.00 3000 10.14 0.031 0.042 (1),(3) 17A 4874.00 1500 9.23 0.020 0.028 17A 4874.00 3000 8.94 0.008 0.012 18A 4948.00 1500 5.75 0.002 0.005 18A 4948.00 3000 5.47 0.001 0.003 20A 5201.00 1500 7.57 0.014 0.021 20A 5201.00 3000 7.28 0.007 0.011 21A 5256.00 1500 8.67 0.021 0.030 21A 5256.00 3000 8.39 0.011 0.017 22A 5304.00 1500 8.58 0.013 0.018 22A 5304.00 3000 8.34 0.004 0.010 23A 5394.00 1500 6.66 0.006 0.009 23A 5394.00 3000 6.41 0.003 0.006 24A 5497.00 1500 9.35 0.012 0.018 (3) 24A 5497.00 3000 8.96 0.008 0.012 (3) 25A 5650.00 1500 5.29 0.003 0.005 25A 5650.00 3000 5.05 0.001 0.003 27A 5874.00 1500 10.29 0.005 0.009 27A 5874.00 3000 10.04 0.003 0.006 28A 5978.00 1500 10.55 0.020 0.030 Cameo 28A 5978.00 3000 10.33 0.013 0.020 (Prod) 29A 6086.00 1500 9.65 0.010 0.015 29A 6086.00 3000 9.35 0.005 0.009 34A 6296.00 1500 3.09 0.0004 0.001 (3) 34A 6296.00 3000 2.78 0.0002 0.001 (3)

Cascade Creek 629-23-42 Well 2B 3600.00 1500 7.71 0.014 0.020 Ohio Creek 2B 3600.00 3000 7.43 0.006 0.009 (Non Prod) 6B 3774.00 1500 8.11 0.016 0.024 Upper Williams Fork 6B 3774.00 3000 7.80 0.007 0.011 (Non Prod) 7B 3844.00 1500 8.34 0.006 0.010 7B 3844.00 3000 8.02 0.002 0.005 12B 3966.00 1500 5.75 0.003 0.006 12B 3966.00 3000 5.44 0.001 0.003 15B 4101.00 1500 6.56 0.002 0.004 15B 4101.00 3000 6.22 0.001 0.002 16B 4114.00 1500 8.35 0.006 0.010 16B 4114.00 3000 8.12 0.003 0.005 20B 4210.00 1500 16.07 0.127 0.207 (3) 20B 4210.00 3000 15.81 0.089 0.154 (3) 22B 4234.00 1500 10.62 0.052 0.069 (1),(3) 22B 4234.00 3000 10.40 0.030 0.042 (1),(3) 23B 4248.00 1500 9.84 0.008 0.013 (3) 23B 4248.00 3000 9.75 0.003 0.007 (3) 36B 4696.00 1500 8.51 0.038 0.050 Lower Williams Fork 36B 4696.00 3000 8.11 0.017 0.025 (Prod) 38B 4823.00 1500 8.66 0.006 0.010 41B 4909.00 1500 7.58 0.016 0.023 (1) 41B 4909.00 3000 7.33 0.008 0.013 (1) 42B 4958.00 1500 10.16 0.050 0.067 (3) 42B 4958.00 3000 9.97 0.027 0.038 (3) 45B 5149.00 1500 9.38 0.017 0.025 (3) 45B 5149.00 3000 8.91 0.009 0.014 (3) 47B 5298.00 1500 4.85 0.002 0.006 47B 5298.00 3000 4.48 0.001 0.003 48B 5314.00 1500 9.49 0.027 0.037 (3) 48B 5314.00 3000 9.07 0.015 0.022 (3) 51B 5386.00 1500 8.67 0.006 0.009 51B 5386.00 3000 8.27 0.002 0.006 53B 5663.00 1500 8.18 0.004 0.007 (3) 53B 5663.00 3000 7.47 0.002 0.005 (3) 54B 5846.00 1500 3.56 0.0003 0.001 Cameo 54B 5846.00 3000 3.07 0.0002 0.001 (Prod) 55B 5865.00 1500 3.19 0.192 0.206 (1) 55B 5865.00 3000 2.82 0.080 0.084 (1) 56B 5938.00 1500 11.18 0.011 0.017 (3) 56B 5938.00 3000 10.45 0.007 0.012 (3) 61B 5210.00 1500 9.06 0.022 0.031 (3) 61B 5210.00 3000 8.52 0.014 0.021 (3) 62B 5218.00 1500 10.49 0.026 0.037 (3) 62B 5218.00 3000 9.45 0.016 0.024 (3)

Footnotes : (1) : Denotes fractured or chipped sample. Permeability and/or porosity may be optimistic. (3) : Denotes very short sample, porosity may be optimistic due to lack of conformation of boot material to plug surface. (5) : Denotes sample unsuitable for measurement at stress. Porosity determined using Archimedes bulk volume at ambient conditions.

Page 1 004310 Collabran Area: Sidewall Core Data Summary (by Producing Interval)

Sample Depth Net Confining Porosity Permeability Number Stress Klinkenberg Kair ft psig % md Lower Williams Fork (Productive) Esperanza 7 4723.0 400 8.0 0.071 0.118 Ranch (ER) 9-5 8 4731.0 400 8.1 not suitable 9 4779.0 400 8.8 0.120 0.188 10 4790.0 400 8.7 0.146 0.224 11 4962.0 400 9.0 0.031 0.059 12 5064.0 400 8.0 0.034 0.062 13 5147.0 400 6.7 0.012 0.026 14 5295.0 400 7.4 not suitable Gipp 13-7 4 6746.0 400 6.0 0.006 0.014 5 6880.0 400 9.7 0.021 0.042 6 6891.0 400 9.2 0.060 0.102 7 6906.0 400 8.9 0.021 0.042 Gunderson 13-12 7 6724.0 400 8.6 0.019 0.039 8 6730.0 400 8.2 0.016 0.033 9 6742.0 400 8.6 0.016 0.033 10 6747.0 400 10.4 0.079 0.131 11 6804.0 400 9.9 0.027 0.052 12 6808.0 400 9.6 0.046 0.082 13 6824.0 400 6.9 0.012 0.026 14 6854.0 400 10.5 0.030 0.057 15 7021.0 400 5.1 0.004 0.011 16 7024.0 400 9.7 0.030 0.057 Hells Gulch 23-11 1 6372.0 400 8.2 0.117 0.184 2 6424.0 400 4.3 0.010 0.023 3 6530.0 400 6.6 0.019 0.038 4 6540.0 400 7.9 not suitable 5 6598.0 400 8.0 not suitable 6 6704.0 400 6.4 0.014 0.030 7 6800.0 400 9.9 0.010 0.023 8 6900.0 400 7.6 0.012 0.027 9 6919.0 400 7.8 0.047 0.083 10 6980.0 400 10.4 0.057 0.098 11 7142.0 400 7.7 0.009 0.022

Cameo (Productive) ER 9-5 17 5703.0 400 8.3 0.017 0.035 MWR 6-9 2 5909 1450 5.4 0.004 1 5828 1450 5.2 0.002 Gipp 13-7 8 7048.0 400 3.5 0.002 0.007 9 7052.0 400 8.1 0.009 0.021 10 7196.0 400 7.4 0.004 0.010 11 7235.0 400 9.3 0.007 0.017 12 7298.0 400 7.8 0.005 0.014 13 7498.0 400 10.6 0.017 0.036 14 7507.0 400 7.7 0.019 0.039 15 7510.0 400 7.1 0.015 0.033 16 7526.0 400 6.4 0.006 0.015 Gund 13-12 17 7224.0 400 2.8 0.002 0.005 18 7384.0 401 6.4 0.003 0.009 20 7398.0 403 4.3 0.007 0.017 21 7402.0 404 5.9 0.005 0.014 HG 23-11 12 7326.0 400 2.7 0.884 1.149 13 7424.0 400 7.9 0.005 0.012 14 7622.0 400 6.4 0.007 0.016 15 7640.0 400 8.9 0.022 0.044 16 7668.0 400 7.3 0.011 0.025 17 7688.0 1450 8.8 0.006 18 7711.0 400 9.7 0.017 0.034 19 7809.0 1450 8.8 0.004 20 7819.0 400 8.9 0.005 0.012 Cozzette (Productive) ER 9-5 20 6298.0 400 5.0 0.015 0.032 21 6305.0 400 10.7 0.022 0.045 22 6351.0 400 7.5 not suitable Gund 13-12 22 7888.0 405 6.7 0.007 0.018 23 7892.0 406 10.4 0.046 0.082 24 7894.0 407 11.1 0.048 0.084 25 7898.0 408 7.5 0.005 0.014

Corocoran (Productive) ER 9-5 23 6455.0 not suitable 24 6470.0 400 5.7 not suitable 25 6495.0 400 4.4 0.003 0.010 Gipp 13-7 17 8182.0 400 2.3 0.003 0.008 18 8184.0 400 6.9 0.007 0.017 19 8186.0 400 7.5 0.015 0.032 20 8188.0 400 7.9 0.008 0.020 21 8190.0 400 6.9 22 8195.0 400 6.8 0.005 0.013 23 8197.0 400 6.2 0.036 0.067 24 8215.0 400 5.8 0.007 0.017

004311

APPENDIX B WASATCH FORMATION PERMEABILITY DATA

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT 1 004312 Wasatch Permeability Data from ExxonMobil

WELL SSI EOD CTYPE CSTRS CNCS MD-DR TVD-SS MD-CORE CPHI CPERM CPERM Well Name Sequence Environment Core Type Core ‐ Stress Core ‐ Net Measured True Vertical Measured Core Core Core Stratigraphic of Value Confining Drilling Depth Depth ‐ Sub Sea Coring Depth Porosity Permeability Permeability 2 Index Deposition Stress (ft) (ft) (ft) (%) (mD) (gpd/ft ) PCBMEXOM‐F31X35G Twasatch_G Fluv‐Lacst Rot SW‐Plug Measured NCS 1900 5860.0 131.8 5860.0 8.00% 0.03080 0.00062 PCBMEXOM‐F31X35G Twasatch_G Fluv‐Lacst Rot SW‐Plug Measured NCS 1900 5943.0 48.8 5943.0 11.40% 0.02310 0.00047 PCUMEXOM‐T78X12G Twasatch_G Fluv‐Lacst Rot SW‐Plug Measured NCS 1834 5514.0 1779.7 5514.0 10.20% 0.07900 0.00160 PCUMEXOM‐T78X12G Twasatch_G Fluv‐Lacst Rot SW‐Plug Measured NCS 1921 5775.0 1519.0 5775.0 6.50% 0.00200 0.00004 Twasatch_G Average 1889 5773.0 869.8 5773.0 9.03% 0.03373 0.00068 LVRMECUSA‐LVR‐01 Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2020 6055.0 96.1 6055.0 8.40% 0.02520 0.00051 LVRMECUSA‐LVR‐01 Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2040 6120.0 31.1 6120.0 7.40% 0.02500 0.00050 PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2150 6740.0 ‐747.7 6740.0 7.40% 0.00890 0.00018 PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2300 7128.0 ‐1135.7 7128.0 7.70% 0.02520 0.00051 PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2300 7148.0 ‐1155.7 7148.0 9.30% PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2300 7258.0 ‐1265.7 7258.0 9.40% 0.00980 0.00020 PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2350 7420.0 ‐1427.6 7420.0 5.70% 0.00790 0.00016 PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2400 7431.0 ‐1438.6 7431.0 6.70% 0.01000 0.00020 PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2400 7555.0 ‐1562.6 7555.0 10.10% 0.02490 0.00050 PCBMEXOM‐F31X35G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2450 7668.0 ‐1675.5 7668.0 8.30% 0.01840 0.00037 PCBMEXOM‐T52X29G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2170 6778.5 403.6 6778.5 7.90% 0.00450 0.00009 PCUMEXOM‐T78X12G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2000 6013.0 1281.2 6013.0 13.20% 0.17900 0.00362 PCUMEXOM‐T78X12G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2128 6398.0 896.5 6398.0 8.00% 0.03500 0.00071 PCUMEXOM‐T78X12G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2214 6657.0 637.6 6657.0 3.40% 0.00300 0.00006 PCUMEXOM‐T78X12G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2264 6808.0 486.6 6808.0 9.30% 0.01500 0.00030 PCUMEXOM‐T78X12G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2404 7228.0 66.6 7228.0 8.50% 0.01400 0.00028 PCUMEXOM‐T78X12G Twasatch_I Fluv‐Lacst Rot SW‐Plug Measured NCS 2417 7262.0 32.6 7262.0 5.60% 0.00300 0.00006 PCUMEXOM‐T25X25G Twasatch_I UNASSIGNED Rot SW‐Plug Measured NCS 2320 7258.0 ‐346.5 7258.0 9.70% 0.06610 0.00133 PCUMEXOM‐T25X25G Twasatch_I UNASSIGNED Rot SW‐Plug Measured NCS 2380 7447.0 ‐534.9 7447.0 9.20% 0.02080 0.00042 PCUMEXOM‐T25X25G Twasatch_I UNASSIGNED Rot SW‐Plug Measured NCS 2460 7680.0 ‐767.3 7680.0 8.90% 0.00460 0.00009 Twasatch_I Average 2273 7002.6 ‐406.3 7002.6 8.21% 0.02633 0.00053 Grand Average 2209 6797.7 ‐193.6 6797.7 8.34% 0.03311 0.00056

004313 Chevron Poro/Perm data for Wasatch formation

Fresh state Clean state Klinkenberg- Sample Sample Total porosity, % Effective Kg, mD Total porosity, % corrected number depth permeability, mD feet no confining stress 800-1250 psi NCS 800-1250 psi NCS

SKR 598-36-AV-11, Wasatch G (Molina member) 11A 2277.97 5.4 0.000024 - -

SKR 598-26-AV-02, Ft. Union (aka Lower Wasatch, Atwell Gulch Member) 1 2170.00 13.6 0.0000002 10.2 0.111 2 2226.00 11.9 0.0023869 8.7 0.065

SKR 598-36-AV-11, Ft. Union (aka Lower Wasatch, Atwell Gulch Member) 8A 2398.45 6.1 0.000068 11.4* 0.224* 7A 2452.00 5.5 0.000054 - - 5A 2548.02 4.9 0.000023 9.5* 0.125* 2A 2745.93 3.2 0.000015 - - 27 3040.02 9.3 0.001325 11.0 0.307 26 3109.01 3.9 0.011312 - -

*measurements performed on companion plugs

004314 4-30-08

SUMMARY OF ROTARY CORE ANALYSES RESULTS Humidity Dried at 140°F

Williams Exploration & Production Garfield County, Colorado RPW 533-25-596 Well File: HH-38701 Red Point West

Permeability, Sample millidarcys Porosity, Grain Run Sample Depth, to Air Klinkenberg percent Density, Lithological Number Number feet 800 psi 1500 psi 3000 psi 800 psi 1500 psi 3000 psi Ambient 800 psi 1500 psi 3000 psi gm/cc Descriptions

1 1-1R 2893.0 + 11.4 2.62 Ss fg frac 1 1-2R 3212.5 0.051 0.037 0.026 0.018 6.1 6.0 5.9 2.67 Ss mg scalc 1 1-3R 3217.0 0.194 0.139 0.124 0.084 11.2 11.1 11.0 2.63 Ss fg-mg spyr w/thn shly streaks 1 1-4R 3483.0 0.014 0.0091 0.0053 0.0032 5.9 5.8 5.7 2.69 Ss fg vcalc spyr 1 1-5R 3490.0 0.015 0.011 0.0059 0.0040 5.9 5.8 5.7 2.67 Ss fg calc 1 1-7R 3578.0 + 14.0 2.65 Ss fg-mg frac 1 1-9R 3640.0 0.039 0.018 0.019 0.0072 7.1 7.1 7.0 2.65 Ss fg-mg 1 1-10R 3663.0 0.0042 0.0025 0.0012 0.0006 2.4 2.3 2.2 2.66 Ss fg-mg vcalc 1 1-13R 4591.5 0.056 0.041 0.026 0.029 0.020 0.012 8.2 8.2 8.0 7.9 2.66 Ss fg-mg 1 1-14R 4759.0 + 4.2 4.1 4.0 3.8 2.67 Ss fg-mg scalc w/shly lam 1 1-15R 4766.0 0.493 0.217 0.119 0.357 0.141 0.071 9.6 9.6 9.5 9.3 2.68 Ss mg-crs scalc 1 1-16R 5049.0 + 4.3 4.2 4.1 3.9 2.65 Ss fg-crs scalc frac 1 1-17R 5080.0 0.033 0.023 0.013 0.016 0.010 0.0051 7.7 7.6 7.5 7.3 2.66 Ss fg-mg 1 1-18R 5092.0 0.279 0.135 0.065 0.187 0.082 0.035 9.5 9.4 9.3 9.1 2.66 Ss mg-crs 1 1-19R 5389.0 + 8.1 2.63 Ss mg-cs frac 1 1-20R 5414.0 0.017 0.013 0.0096 0.007 0.0049 0.0033 10.2 10.1 10.0 9.8 2.66 Ss mg-crs

+ Indicates the sample is unsuitable for this type of measurement

004315

APPENDIX C NONTRIBUTARY DISTANCE CALCULATIONS

OXY USA 4010-000023 PB NONTRIBUTARY GROUNDWATER ASSESSMENT B-1 004316 Glover-Balmer Analysis for Mesaverde Group

Conversions 1 ft/day = 365 mD

Parameter or Function Symbol Value Used Units Notes Well Pumping Volume Q n/a ft3/day Stream Depletion Volume q n/a ft3/day Stream Depletion Ratio q/Q <0.001 unitless Nontributary ratio is <0.001 Complementary Error Function erfc Formation Thickness b 500 ft Drops out of equation Formation Permeability k 0.0175 mD Hydraulic Conductivity K 4.79E-05 ft/day Specific Storage Ss 1.00E-06 1/ft Storativity S 5.00E-04 unitless Equal to Ss*b Transmissivity T 2.40E-02 K*b Equal to K*b Time t 36,500 days Equal to 100 years Distance from well to stream α ft Value to be solved for

Calculating q/Q ratio for specified distance Distance (ft) q/Q 6,160 0.000992 Depletion ratio is less than 0.001

004317 Glover-Balmer Analysis for Wasatch Formation

Conversions 1 ft/day = 365 mD

Parameter or Function Symbol Value Used Units Notes Well Pumping Volume Q n/a ft3/day Stream Depletion Volume q n/a ft3/day Stream Depletion Ratio q/Q <0.001 unitless Nontributary ratio is <0.001 Complementary Error Function erfc Formation Thickness b 500 ft Drops out of equation Formation Permeability k 0.0192 mD Hydraulic Conductivity K 5.26E-05 ft/day Specific Storage Ss 1.00E-06 1/ft Storativity S 5.00E-04 unitless Equal to Ss*b Transmissivity T 2.63E-02 K*b Equal to K*b Time t 36,500 days Equal to 100 years Distance from well to stream α ft Value to be solved for

Calculating q/Q ratio for specified distance Distance (ft) q/Q 6,450 0.000997 Depletion ratio is less than 0.001

004318