Final Environmental Impact Statement - Appendices 

Wasatch-Cache National Forest B10 - 1 

APPENDIX B - 10 

Oil and Gas Leasing Analysis Assumption 

Introduction 

The Reasonably Foreseeable Development (RFD) scenario prepared in 1990 (USFS, 1994) is 

still a current representation of what level of activity could be reasonably anticipated based on 

the geology of the area. The one significant change since the completion of that report is the 

shift in demand and increased market for natural gas. The north slope is primarily an oil target 

with any gas being from production associated with oil so the increased demand for natural gas 

has not resulted in a need to change the RFD. New technology that allows for deeper wells to be 

drilled may expand the potential reserve models used to evaluate this area, but currently there is 

not enough known about the applicability of that technology to factor it into the RFD (Burkhardt, 

2000.) 

The RFD is an analytical tool not a ceiling or limit on activities. It provides the reasonably 

foreseeable projection that enables impacts analysis to occur. The number of wells projected 

could be exceeded or never realized but if monitoring indicates the level of impacts analyzed is 

being reached or exceeded, further evaluation would be conducted to determine if additional 

mitigation measures are necessary. 

The 1990 Oil and Gas Potential Report (Kaldenbach, 1990) analysis concluded that during the 

15-year period from 1991 through 2005 period, 11 exploration wells would be drilled in the 

Moxa Arch area with one or two exploration wells drilled in each of the other two areas. Because 

there are few, if any, roadless acres outside the wilderness along the Moxa Arch, it is reasonable 

to redefine the RFD for the roadless portion being addressed in the forest plan revision analysis. 

It is more likely to assume 7 exploration wells. Applying the unit’s historical discovery ratio of 

one field discovery per 5.6 exploration wells drilled indicates that the seven projected 

exploration wells could discover one new field (Burkhardt, 2000.) 

Exploration Activities 

The North Slope Oil and Gas Leasing Environmental Impact Statement (USDA Forest Service 

1994) estimated the number of acres of ground disturbance resulting from projected oil and gas 

exploration activities by extrapolating from past activities. This was shown in Appendix E of that 

document. Estimates were reviewed and still considered valid except for road reconstruction 

amounts. Because the area being analyzed is within the inventoried roadless area greater 

amounts of new road construction were estimated. 

• Each exploratory well pad would require an average of four acres. 

• Each exploratory well pad would require 1.7 mile of road construction. 

• Each mile of road reconstruction would have a net disturbance of 2.4 acres per mile after 

cut-and-fill slope reclamation. 
Final Environmental Impact Statement - Appendices 

Wasatch-Cache National Forest B10 - 2 

• Each mile of new road construction (relocation or new construction) would have a net 

disturbance of 3.6 acres per mile after cut-and-fill slope rehabilitation. 

The total area of ground disturbance would average about 10 acres for each exploratory well. 

Development Activities 

The discovery of a single field as a result of an exploration well discovery would result in the 

following activities: 

• “shooting” ten miles of seismic lines, which are composed of two lines laid out in a cross 

pattern 

• one or two wildcat wells to discover a field or “condemn” an exploration target 

The geologic, development, and production characteristics of a newly discovered filed would be 

similar to characteristics of fields in the Bridger Lake-Luckey Ditch producing trend. Fields in 

that area produce both oil and gas from mainly Dakota sandstone. Important characteristics of 

these fields are listed below. 

• Fields are spaces less than one to two miles apart. 

• Fields range from 640 acres to 6,400 acres. 

• Each field, at maximum development, contains between one and three exploration wells, 

between one and nine development wells, a maximum of one CO2 injection well for 

pressure maintenance or secondary recovery, and a maximum of one water disposal well. 

• Wells produce by gas lift. 

• Initial daily production potentials of wells range from 0 to 2,800 barrels of oil, 0 to 3,500 

mcf of gas, and 0 to 150 barrels of water. 

• Well depths range from 14,000 to 17,000 feet. 

• Ultimate recoverable reserves for fields range from less than 100,000 barrels of oil to 30 

million barrels of oil. 

• The lives of producing wells range from 12 to 35 years. 

• Wells are spaced from 0.5 to 1.0 mile apart (320- to 640-acre spacing). 

• Each well’s, lease equipment is configured on a site covering one to two acres. 

• Equipment for a single well includes: a wellhead valve assembly (Christmas tree), flow 

tubing (2- to 3-inch diameter), which connects the wellhead to a central tank battery, and 

a line heater unit which is located along the flow tubing. 

• A central tank battery serves each field. A tank battery is comprised of separation 

equipment, dehydration equipment, and storage tanks. Each tank battery generally 

requires between 0.5 and 1.0 acres per producing well. 

• A 2- to 3-inch diameter gas pipeline links the central tank battery to a refrigerated process 

gas processing plant. 

• The gas plant covers an average of five acres and processes gas for the entire field. 

• A 6- to 8- inch diameter gas pipeline transports gas from the plant to a regional pipeline 

off the forest. 
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Wasatch-Cache National Forest B10 - 3 

• Flow tubing and gas pipelines on the forest are buried along access roads; otherwise, they 

are constructed within a 30-foot-wide zone. 

• An average of 0.3 mile per well of buried flow tubing or gas pipelines are presumed 

outside road rights-of-way. 

• Development wells require 0.4 mile of reconstruction of roads and 0.4 mile of road 

reconstruction or new construction. 

• The land surface disturbance (after cut-and-fill reclamation) is 2.4 acres per mile for light 

reconstruction of raids and 3.6 acres per mile for heavy reconstruction or new 

construction of roads. 

• Most field development occurs within five years after discovery. 

The total land area that could be disturbed by development for each of the first two fields would 

be about 35 acres.