APPENDIX 13

APPENDIX 13

OIL AND GAS AND

COALBED METHANE RESOURCES

IN THE JACK MORROW HILLS PLANNING AREA

(Part of The Reasonably Foreseeable Development Scenario - 1998 Through 2017) 

The Reasonably Foreseeable Development (RFD) comprises this appendix, the Minerals Assumptions (Appendix 

10), and Minerals impacts (Chapter 4). 

The RFD considers current management of the planning 

area and the proposed management for each proposed alternative. Past hydrocarbon development and relevant research on 

hydrocarbon potential is used to make assumptions about the 

kind and amount of development likely to occur for these 

alternatives during the period of analysis for the JMHCAP 

(1998 through 2017). 

The planning area is considered to have a high potential for 

the occurrence of oil and gas. This rating considers a variety 

of geologic characteristics, including: 

• Presence of hydrocarbon source rocks 

• Presence of reservoir rocks with adequate porosity/ 

permeability 

• Potential for structural/stratigraphic traps to exist 

• Opportunity for migration from source to trap and 

• Other conditions, such as temperature, depth of burial, 

and subsurface pressures 

For the “Green River Resource Area Resource Management Plan and Final Environmental Impact Statement” (1996) 

a determination was made of the potential for development. It 

used high, moderate, and low potential values for each part of 

the planning area (Map 45) and is considered to still be 

reasonable for that part covering the planning area. Drilling 

activity is likely to occur in all areas. The highest rate of 

activity is expected to occur in the high potential area and the 

lowest rate is expected in the low potential area. 

EXPLORATION AND 

DRILLING HISTORY 

Exploration History 

Analysis of past exploration activity indicates how the 

hydrocarbon resource has been developed in the planning 

area. Exploration history can be tracked by reviewing information on past Federal Exploratory Units that have been 

proposed and drilled in the area. Most exploratory wells have 

been drilled as part of Federal Exploratory Units. Table A13-

1 lists Federal Exploratory Units known to have been located 

entirely or partially within the limits of the planning area. To 

date, 52 units are known to have been approved or proposed. 

The large number of approved exploratory units shows that 

unitization has been a popular method for orderly exploration 

for hydrocarbons. 

Early Units. Easily mapped surface structures in Wyoming 

were located and tested through the 1940s. In the planning 

area, the only surface structures were those thought to lie 

against a long fault system on its north edge. These potential 

structural traps have occasionally been tested over the years 

but have not been productive. The first exploratory unit was 

the Pacific Creek unit (1943) which tested a potential structural trap in this area. No production was found in this 

Mesaverde Group test and the unit terminated in 1947. 

After the Pacific Creek unit test and through the 1960s, 11 

more units were tested and one was proposed and latter 

withdrawn with no test. Only the Nitchie Gulch unit test found 

commercial hydrocarbons. The Nitchie Gulch unit/field is a 

combination stratigraphic-structural trap, producing mostly 

gas from the Frontier and Dakota formations. Little exploration activity occurred in the planning area during this early 

period because it was thought to be gas prone and gas resources were of minor interest. Industry was concentrating its 

exploration in areas of Wyoming that were oil prone. 

1970-1993. Between 1970 and 1984 an additional 30 exploratory units were created. This period of increased exploratory 

activity coincided with a nation-wide boom in drilling activity, mainly due to price increases for oil and gas. Of the 30 new 

units, hydrocarbons were found in eight units (Table A13-2). 

The traps associated with production from the units named in 

Table A13-2 are stratigraphic and produce mostly gas. 

No exploratory units were proposed for a ten-year period 

after the Essex Mountain unit terminated in 1984. This was 

partially due to deteriorating prices, generally low volumes of 

gas produced from many of the producing units other than 

Nitchie Gulch unit/field, and a reduced area available for 

exploration and production due to WSA withdrawals and 

limitations placed on development. The core area was withheld from leasing in 1992 and the rest of the planning area was 

removed in 1998. All unleased areas will continue to be 

suspended until this plan is completed. 

Recent Units. Since 1994, increased emphasis on gas exploration in the region has resulted in nine new unit proposals 

(despite large areas being unavailable for exploration activity) 

in the planning area. Also, drilling successes to the southwest 

at Stagecoach Draw and Clay Buttes fields and to the east and 

southeast in the Great Divide Basin have contributed to 

increased interest in the area. The recent exploratory unit 

targets have been stratigraphic trapped Cretaceous-aged sediments. 

Within the planning area, the first test of the Big Bear unit 

was oil productive in the Rock Springs formation. The unit 

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APPENDIX 13

terminated, in 1996, due to low production rates from this 

well. The Northern Lights unit was proposed, but withdrawn 

November 3, 1998. 

Three recently terminated exploratory units covered part 

of the planning area and the first well for each was drilled 

outside the planning area. 

Riva Exploratory Unit overlapped the planning 

area on its eastern boundary and terminated June 

22, 1995. The operator tested and abandoned a 

Lewis Shale well drilled in sec. 36 T. 25 N., R. 98 

W. 

The Encore Exploratory Unit overlapped the planning area on its southeast edge and terminated 

February 17, 1998. The formation targets were 

the Almond, Lewis, and Ericson. The well drilled 

in sec. 32 T. 24 N., R. 99 W. was abandoned. 

The Jade Exploratory Unit overlapped the planning area on its eastern boundary and terminated 

July 1, 1998. The formation targets were the 

Almond and Lewis. The first well was completed 

as a Lewis producer in sec. 11 T. 24 N., R. 98 W. 

It was a low volume gas producer causing unit 

termination. 

Active and pending exploratory units (Map 44) are: 

Johnson Gap (Deep), approved effective February 28, 1994. The first well is proposed for sec. 1 

T. 23 N., R. 103 W. A “Suspension of Operations 

and Production” has been granted for this well 

until this environmental analysis can be completed. 

Gold Coast, approved effective January 30, 1998. 

The first well is proposed for sec. 6 T. 25 N., R. 

102 W. A “Suspension of Operations and Production” has been granted for this well until an 

environmental analysis can be completed. 

West 187, approved effective February 25, 1998. 

The first well is presently pending drilling in sec. 

25 T. 23 N., R. 105 W. 

Jack Morrow Creek, drilling is pending final 

approval. The proposal lies in T. 25 N., Rs. 104 

and 105 W. and T. 26 N., R. 104 W. 

Of the 52 exploratory units, five units are productive and 

still active; five units have productive wells, but they did not 

produce in great quantities and have been terminated; 35 did 

not find productive hydrocarbons and were terminated; three 

proposed units were withdrawn or canceled; and four exploratory units are pending approval or are waiting to be drilled. 

Drilling History 

Drilling and completion data were obtained from PI/ 

Dwights LLC., BLM well files, and Wyoming Oil and Gas 

Conservation Commission well files for Map 65, showing the 

location of drilled wells in the planning area. Most drilling 

activity has been concentrated in the south central part of the 

planning area (Nitchie Gulch unit/field) with additional exploratory wells scattered across the rest of the area. The 

concentration area lies along the crest of the Rock Springs 

Uplift structural high, a good geologic target. 

Table 3-06 (Wells Drilled in the JMH) shows the history of 

drilling activity in the planning area. The first test well in the 

planning area was drilled in 1927, in sec. 16 T. 23 N., R. 104 

W. It was a shallow (1,529 feet) Mesaverde Group dry hole 

drilled by Boars Tusk Oil Company (now defunct). Two 

additional nonproductive shallow Tertiary-age tests were 

made in the north part of the planning area in the 1940s. 

The first known hydrocarbon show was in the El Paso 

Natural Gas Company (now defunct) well drilled in 1954 in 

sec. 29 T. 25 N., R. 103 W. This well tested gas in a number 

of zones in the Upper Cretaceous section, with a maximum 

recovery of 240 thousand cubic feet of gas per day recovered 

from one zone, before the well was abandoned. An additional 

12 wells were drilled and abandoned before the first economically productive well was completed in November of 1961. 

Trigood Oil Company (now defunct) completed the first 

productive well in sec. 17 T. 23 N., R. 103 W. Gas and some 

condensate (light oil) production was obtained from both the 

Frontier and Dakota formations. This was the discovery well 

for the Nitchie Gulch unit/field. 

Wells Drilled. In the planning area 153 wells have been 

drilled. Of these wells, 66 were completed as producers. 

Three of these wells were completed as coalbed methane 

wells. The coalbed methane wells have been tested but have 

not been put on production. The remaining 87 drilled wells 

were abandoned after drilling (Map 66). 

Units/Fields. A number of units/fields have been found to be 

productive (Table A13-3). Information about these fields and 

individual wells is available in the publications “Wyoming 

Geological Association Symposium, Oil and Gas Fields, 

Greater Green River Basin” (1979 and 1992) and in BLM and 

Wyoming Oil and Gas Conservation Commission files. 

Drilling Targets. Past drilling targets have been formations 

of Cretaceous age (145 of the 153 wells drilled). Only two 

wells have tested formations deeper than the Cretaceous. The 

Eden Unit #5-11 in sec. 11 T. 22 N., R. 105 W. was proposed 

as a test of Mississippian-age rocks at 19,500 feet. The well 

reached 18,150 feet in the Mississippian Madison Formation 

and was abandoned. No hydrocarbons were discovered in 

these older sediments. A test of the Madison recovered a small 

amount of nonflammable gas. Other deep tests further south 

on the Rock Springs Uplift have tested some nonflammable 

carbon dioxide gas in the Madison. Carbon dioxide is likely 

the nonflammable gas recovered on this test. 

The other deep test was the Indian Gap unit #1 which 

reached 10,066 feet in the Nugget formation and was abandoned. No hydrocarbons are known to have been discovered 

in this well’s older sediments. 

One other well was expected to test formations older than 

Cretaceous age. The South Pass Unit #1 in sec. 17 T. 27 N., 

R. 100 W. was expected to test the Mississippian Madison at 

22,000. Instead the well drilled Precambrian granite in the 

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APPENDIX 13

near surface, crossed the Wind River thrust fault and drilled 

Cretaceous-aged sediments to a depth of 22,947 feet. 

Six wells were shallow Tertiary targets and none were 

productive. 

Well Elevations and Depths. Well elevations in the planning 

area have ranged from about 6,400 feet to 8,100 feet. Well 

depths have ranged from only 218 feet to 22,947 feet. The 

number of wells drilled by 5,000-foot depth ranges are: 

• < 5,000 feet 18 wells 

• 5,000 - 9,999 feet 80 wells 

• 10,000 - 14,999 feet 42 wells 

• 15,000 - 19,999 feet 12 wells 

• > 20,000 feet 1 well 

Most wells in the 5,000 to 10,000 range lie in the Nitchie 

Gulch unit/field area because it is the highest structural 

location on the Rock Springs Uplift. Wells must be drilled 

deeper outside the Nitchie Gulch unit/field area to reach the 

same target formations (Frontier and Dakota). The deepest 

wells to Cretaceous formations have been drilled on the north 

part of the planning area. 

Drilling Rates and Success. Drilling rates and success 

percentages are shown in Table A13-4. 

The drilling rate history shows that there have been two 

periods of increased activity. The first was centered on the 

period when the Nitchie Gulch unit/field was first discovered 

(1961) and developed. Development was on 640-acre spacing. Drilling decreased in the late 1960s and early 1970s 

because most 640-acre spacing units had been developed. 

Drilling increases culminating in 48 wells being drilled in 

the 1978-1982 period were due to: 

• improvements in drilling and completion technology 

that allow areas with lower gas reserves to be developed; 

• the recognition of the importance of stratigraphic traps 

that contain much of the planning area gas; 

• exploration for deeper drilling targets which favor gas 

over oil; and 

• the general increase in gas prices. 

During this period well spacing was decreased to 160 acres 

in much of the Nitchie Gulch unit/field and increased exploration for deeper reserves occurred in the area north and east 

of the field. Additional exploration is expected to have 

occurred west of Nitchie Gulch unit/field, but, this area had 

been withdrawn from leasing because of wilderness characteristics. 

Improved success rates in each five year period after the 

1968-1972 period have been due to industry’s concentration 

on development drilling in the Nitchie Gulch unit/field, improvements in geologic analysis, and improvements in drilling and completion technology. 

Coalbed Methane Drilling History 

Tyler, et al. (1997) have reviewed drilling history of the 

coalbed methane resource in the planning area. In this area 

coals of the Fort Union, Almond, and Rock Springs Formations were tested. Development of the two coalbed wells on 

the south boundary of the planning area was stopped in 1992, 

primarily by low gas prices and disappointing test results and 

secondarily by environmental concern over disposal of produced water. 

EVALUATION OF POTENTIAL 

PLAYS AND DRILLING AND 

EXPLORATION TRENDS 

Information on potential plays is available and four exploratory unit proposals have been made. The information from 

these unit proposals is confidential and only general information can be released. Some additional information has been 

made available through public comment and personal communication. Drilling projections for each alternative have 

been made based on this available information and from 

restrictions (no leasing, no surface occupancy, stage leasing, 

and controlled surface use) that will be placed on activity. 

Information Resources Used 

A number of documents are available that have evaluated 

gas reservoirs and exploration trends for the Greater Green 

River Basin area. These documents were used to help evaluate 

the gas reservoirs present in the planning area and determine 

levels of future activity. 

The CD-ROM “Emerging Resources in the Greater Green 

River Basin” (Gas Research Institute, 1996) is an atlas of the 

Upper Cretaceous that provided access to geological, production, engineering, and land use data for some of the productive 

and potentially productive reservoirs in the planning area. 

A three CD-ROM set “1995 National Assessment of United 

States Oil and Gas Resources” (U.S. Geological Survey, 

1996) provides a discussion of some of the potential hydrocarbon plays in the planning area. The potential plays discussed 

are: 

• Rock Springs Uplift Play 

• Basin Margin Anticline Play 

• Subthrust Play 

The “Atlas of Major Rocky Mountain Gas Reservoirs” 

(New Mexico Bureau of Mines & Mineral Resources, 1993) 

summarizes information on those gas reservoirs with cumulative production of at least 5 billion cubic feet of gas. The 

reservoirs and their associated plays are discussed. Some of 

the relevant parameters discussed are reservoir and lithologic 

data, production data, compositional analyses of produced 

gas, reservoir engineering parameters, and estimates of proved 

developed reserves. 

The Barlow & Haun, Inc. (1994) publication “Accessibility to the Greater Green River Basin Gas Supply, Southwestern Wyoming” provides additional discussion of plays and 

maps of play boundaries. It also evaluates the limitations on 

production and increased costs associated with access to 

public lands. 

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APPENDIX 13

The paper “The Potential for Coalbed Gas Exploration and 

Production in the Greater Green River Basin, Southwest 

Wyoming and Northwest Colorado” (Tyler, et al. 1997) 

presents a discussion of the coalbed gas resource for the 

planning area and was used to prepare the map of coalbed 

methane development potential (Map 46). 

The comment letter from Barlow & Haun, Inc. (1998) was 

used as the most up-to-date reference for the plays present and 

their potential future resource. The plays and their potential 

future resource are shown in Table A13-5. In addition, 

Diedrich (1999) has projected that 88 to 111 wells could be 

drilled in the planning area if areas outside of WSAs is 

available for development. Landreth (1999) has indicated the 

producing Frontier and Dakota wells in the Nitchie Gulch unit 

are being produced to their economic limit and no additional 

in-fill drilling is anticipated. 

Determining Undiscovered 

Hydrocarbon Accumulations 

Two methods were used to help determine the number of 

wells required to develop undiscovered hydrocarbon accumulations (other than coalbed methane deposits) in the planning 

area. Both methods derived about the same number of wells 

from these undiscovered wells. 

“Resource Method” - This method was developed from information received in the Barlow & 

Haun, Inc. (1998) comment letter and information obtained developing this RFD. Barlow & 

Haun determined a potential future gas resource 

(not including the coalbed methane resource) of 

2,150 billion cubic feet. Present producing wells 

indicate an average well will produce 2.2 billion 

cubic feet of gas. To recover the estimated 2,150 

billion cubic feet from wells that recover an 

average of 2.2 billion cubic feet would require 

977 producing wells. 

“Checkerboard Method” - Stanley’s (1995) 

“Checkerboard Method” is intended as a simple 

and quick way of estimating the number of undiscovered accumulations were some past activity 

has occurred. When this procedure was followed 

for the planning area we determined that 359 

sections could contain producible hydrocarbons. 

Assuming development of each section would 

require 2.5 to 3 producing wells, 897 to 1,077 

wells would be needed to develop these sections. 

Exploratory Unit Activity 

The large number of past approved exploratory units 

shows that unitization has been a popular method for orderly 

exploration. Recent exploratory unit proposals indicate new 

exploration interest in the planning area if activity continues 

to be allowed. Over the busiest past period, 1978-1983, 25 

exploratory units were proposed. This rate is assumed to be 

the maximum rate that could be expected between 1998 and 

2017. This rate applied to the 20-year study period means a 

maximum of 83 exploratory unit proposals could be made for 

lands in or partially in the planning area. About 20 percent of 

past exploratory units have been successful (at least one 

productive well was drilled) and this success ratio is expected 

to continue. 

Total Projected Wells 

Most drilling activity has been concentrated in the south 

central part of the planning area (Nitchie Gulch unit/field) 

with additional exploratory wells scattered across the rest of 

the area. If allowed, most future activity would spread out and 

down the flanks of the Rock Springs Uplift from present areas 

of production. Exploration activity is also expected to be 

concentrated in the areas were exploratory unit proposals have 

been made, but, have not yet been tested. Scattered tests will 

continue to be drilled throughout the area with concentrations 

of wells being drilled around new successful wells. Lowest 

rates of activity are expected to be on the north edge of the 

planning area were targets are deep and lie below granites of 

the Wind River Thrust. 

Since no drilling programs have been proposed by industry, a statistical analysis was developed to determine the 

number of wells that could be drilled. It is difficult to do a 

statistical analysis of past drilling rates to help predict future 

rates. Since the 1980s, large parts of the planning area have 

not been available for development or have had development 

restrictions and this distorts the data from this period. 

A review of past activity and success rates for the planning 

area shows that the highest 5-year rate was during the 1978-

1982 period when 48 wells were drilled. Assuming this 

highest rate can be projected over a 20 year period, a maximum rate of drilling activity can be projected. At this rate an 

additional 192 wells could be drilled in the planning area. 

A drilling success rate for these wells is expected to be 53 

percent. This rate was determined by comparing wells drilled 

in the period 1978-1997 against the number completed as 

producers. During this period 46 non-coalbed methane producers have been completed out of the 86 non coalbed methane wells drilled. Recent success rates have been high and are 

expected to remain relatively high due to continued improvements in geologic analysis and in drilling and completion 

technology and due to the expected general step-out drilling 

from already producing areas. 

Costs of Time Delays Related to 

Restrictions 

Barlow & Haun (1994) project an increased demand for 

clean-burning, affordable, natural gas in the area of the planning area. This increased demand coupled with slower 

drilling response time, due to high level of restriction on 

activity, does not allow for timely development of drilling 

programs. This adversely impacts economics for companies 

trying to develop the resource. Seasonal access restrictions 

increase the time needed to acquire seismic data, drill individual wells, and develop discovered fields. These delays do 

not generally prevent an individual operator from developing 

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APPENDIX 13

the resource, but they do increase costs of field development 

and slow the industry’s response time to attractive increases in 

product prices. These time delays coupled with the many 

other restrictions on activity in the planning area are expected 

to discourage interest in the area and cause some wells to not 

be drilled. Barlow & Haun (1994) found that “cumulative 

costs associated with access in the NEPA process can add 

$9,500 to $21,000 on a per well basis.” 

Other Mineral Conflicts 

Conflicts with other mineral resources can cause restriction to development of the hydrocarbon resource. No conflicts with other mineral resources are expected over the life 

of this plan. 

715
TABLE A-13-01 

FEDERAL EXPLORATORY UNITS 

Unit Name Effective Date Status Term. Date Acres Exploration Targets Trap Type Producing Formation 

Big Bear 19950531 Productive Terminated 19960725 25,625 Lance, Lewis, Mesaverde, Frontier, and Dakota Stratigraphic Rock Springs 

Big Dune 19590121 Terminated 19620501 17,675 Fort Union, Lewis, and Almond Stratigraphic 

Boars Tusk 19790625 Productive Terminated 19861009 11,520 Frontier and Dakota Stratigraphic Frontier and Dakota 

Buccaneer 19801216 Productive Active 12,160 Fort Union, Lance, and Mesaverde Stratigraphic Dakota 

Centurion 19810428 Terminated 19810716 24,988 Lewis Stratigraphic 

Circle Bar 19710115 Terminated 19720613 56,877 Lewis and Mesaverde Structural closure against Continental fault 

Citation 19811130 Terminated 19820517 24,949 Mesaverde Stratigraphic 

Continental Peak 19820617 Terminated 19820827 12,813 Granite Wash Structural, near Continental Fault 

Dickie Springs 19700428 Terminated 19701215 13,074 Mesaverde Structural closure against Continental fault 

Eden 19720818 Terminated 19750901 39,127 Tertiary and Mesaverde Stratigraphic with fault control 

Encore 19970325 Terminated 19980217 4,407 Lewis, Almond, Ericson Stratigraphic 

Essex Mountain 19840506 Productive Terminated 19841018 10,116 Frontier Stratigraphic Frontier 

Freighter Gap 19810209 Productive Terminated 19870711 24,656 Rock Springs Stratigraphic Mowry 

Gold Coast 19980130 Exploratory Suspended 25,585 Confidential Confidential 

Greater Pacific Creek 19780310 Terminated 19801001 31,338 Frontier, Dakota, Nugget, Structural closure 

Phosphoria, Tensleep, and Madison 

Harris Slough 19800812 Terminated 19810715 24,983 Lewis Stratigraphic 

Honeycomb Buttes 19790329 Terminated 19800403 24,969 Mesaverde ? Unknown 

Hourglass 19800530 Terminated 19810528 24,453 Mesaverde Stratigraphic 

Indian Gap 19550916 Terminated 19580301 19,826 Nugget Unknown 

Jack Morrow Creek Exploratory Proposed 24,921 Confidential Confidential 

Jade 19970219 Productive Terminated 19980701 19,034 Lewis and Almond Overpressured Stratigraphic Lewis 

Johnson Gap (Deep) 19940228 Exploratory Suspended 25,970 Confidential Confidential 

Lost Valley 19780807 Productive Terminated 19851130 40,371 Lewis Stratigraphic Mesaverde 

Monument Draw 19810917 Terminated 19811229 13,389 Granite Wash Structural closure 

Monument Ridge 19630529 Terminated 19640201 31,644 Lewis and Rock Springs Stratigraphic 

Morrow Creek 19541112 Terminated 19560701 25,126 Mesaverde Structural (seismic) closure against fault 

Morrow Creek 19590917 Terminated 19600501 8,160 Lewis and Mesaverde Stratigraphic/Structural 

Morrow Creek 19660624 Terminated 19680201 79,301 Almond Stratigraphic 

Musketeer 19810630 Terminated 19820517 23,626 Mesaverde Stratigraphic 

Nitchie Gulch 19621001 Productive Active 7,154 Frontier and Dakota Stratigraphic/Structural Frontier and Dakota 

Northern Lights Withdrawn 26,908 Confidential Confidential 

Oasis 19831227 Terminated 19840515 24,677 Morrison Stratigraphic 

Oregon Trail 19460000 Terminated ? 15,000? Unknown Structural closure against Continental fault 

Pacific Creek 19430527 Terminated 19471231 23,036 Mesaverde Structural closure against Continental fault 

Pacific Creek 19590113 Withdrawn 19610414 27,514 Mesaverde Structural closure 

Pacific Creek II 19730927 Terminated 19750723 15,939 Ericson Structural closure 

Packsaddle 19790227 Terminated 19790730 24,779 Frontier Stratigraphic 

716 
TABLE A-13-01 

FEDERAL EXPLORATORY UNITS 

Packsaddle Canyon Cancelled 19821015 24,927 Frontier Stratigraphic 

Parnell Creek 19611103 Terminated 19620501 26,183 Almond Stratigraphic 

Pinnacles 19670321 Terminated 19680601 150,024 Lewis and Almond Stratigraphic 

Pirate 19801031 Terminated 19810227 10,165 Mesaverde Stratigraphic 

Plunge 19600311 Terminated 19620801 21,087 Almond Unknown 

Rim Rock 19800229 Productive Active 24,816 Frontier Stratigraphic Dakota 

Riva 19941202 Terminated 19950622 13,179 Lewis Stratigraphic 

Rock Cabin 19800627 Terminated 19820328 15,336 Lewis, Mesaverde, and Frontier Stratigraphic 

Saddle Bag 19810528 Terminated 19821024 26,083 Rock Springs Stratigraphic 

Sands of Time 19830311 Terminated 19830519 24,879 Lewis Stratigraphic 

Scotty Lake 19781102 Terminated 19800721 23,240 Lewis Stratigraphic 

South Pass 19810323 Terminated 19830624 24,920 Lewis Structural closure 

Steamboat 19780418 Productive Active 14,132 Frontier Stratigraphic Frontier 

Treasure 19790620 Productive Active 24,797 Lewis Stratigraphic Dakota 

West 187 19980225 Exploratory Active 4,493 Confidential Confidential 

717 
TABLE A13-2

UNITS WITH HYDROCARBONS

Exploratory Unit Producing Zone(s) 

Steamboat Frontier Formation 

Lost Valley Mesaverde Group (production from outside 

planning area) 

Treasure Dakota Formation 

Boars Tusk Frontier and Dakota formations 

Rim Rock Dakota Formation 

Buccaneer Dakota Formation 

Freighter Gap Mowry Shale 

Essex Mountain Frontier Formation 

TABLE A13-3

PRODUCTIVE UNITS OR FIELDS

Unit and/or Field Name Number of Producing 

Wells 

Nitchie Gulch 48 

Boars Tusk 1 

Pine Canyon 4 

Treasure 2 

Essex Mountain 2 

Rim Rock 2 

Buccaneer 1 

Steamboat Mountain 1 

Freighter Gap 1 

Big Bear 1 

Unnamed coalbed methane wells 3 

718
TABLE A13-4

DRILLING RATES AND SUCCESS PERCENTAGES

Time Period Wells Drilled Producers Success 

Pre-1952 3 0 0% 

1953-1957 3 0 0% 

1958-1962 16 3 19% 

1963-1967 19 9 47% 

1968-1972 9 1 11% 

1973-1977 14 4 29% 

1978-1982 48 17 35% 

1983-1987 20 13 65% 

1988-1992 19 17 89% 

1993-1997 2 2 100% 

TABLE A13-5

PLAYS AND THEIR POTENTIAL FUTURE RESOURCE

Play Play Type Gas Resource BCF 

(billion cubic feet) 

Fort Union and Lance basin-centered gas 200 BCF 

Lewis Shale deep water marine sandstone 150 BCF 

Upper Almond Sandstone shore-face sandstone 100 BCF

 " " " marine bar sandstone 100 BCF 

Lower Almond-Ericson basin-centered gas 500 BCF 

Rock Springs Formation coalbed methane 50 BCF 

Frontier Formation fluvial sandstone 100 BCF

 " " marine sandstone 100 BCF 

Muddy Sandstone Marine sandstone 200 BCF

 " " fluvial sandstone 100 BCF 

Dakota Sandstone fluvial sandstone 100 BCF 

Structural Accumulations multiple objectives 400 BCF 

719