Summary of “The Oil and Gas Resource Potential of the Artic National Wildlife Refuge 1002 Area, Alaska”

ANWR Assessment Team

Open File Report 98-34

US Geological Survey

Assessment Overview:

Abstract:

• Comprehensive 3 year study large team of scientists
• Last Assessment of 1002 was 1987
• Estimated technically recoverable and economically recoverable oil and gas resources in 10 plays
• TOTAL QUANTITY= 11.6 to 31.5 BBO, mean= 20.7 BBO
• TECHNICALLY RECOVERABLE= 4.3 to 11.8 BBO, mean= 7.7 BBO
• ECONOMICALLY RECOVERABLE- a curve shows increasing amounts of oil with increasing amounts of oil. 15 dollars/barrel, no oil, 16 d/b 1BBO, 20 d/b 3 BBO. Natural gas is non-economic for next 2 decades.
• This estimate is large than previous because of increased resolution of seismic data and geologic info. From the well drilled outside 1002 with producible oil.

Intro:

• 1002 is 8% of ANWR
• Currently off limits to oil exploration and production
• Only part of ANWR with significant amounts of oil.
• In between, Prudhoe Bay (produce ¼ of U.S. Daily oil production) and Mackenzie Delta (50 petroleum discoveries)
• Study extended 3 miles off shore
• Petroleum assessed- crude oil, natural gas, and natural gas liquids.

Assessment Project:

• 46 scientists at some time in the 3 years of study.
• Project-

·        New field studies

·        New well and sample data

·        New aeromagnetic data

·        Assessment method reviewed and modified

• Well near 1002 were controls for the evaluation of petroleum resources
• Made a data inventory from these wells- plots with boundaries, ages, lithologies, logs oil and gas indications, test results, engineering, thermal maturity, and source rock data
• Used this data to infer in 1002
• Reflection Seismic Data (required Act of Congress)

·        All 1,451 miles of seismic data from 1984-5 were reprocessed and interpreted.

·        Data was stacked, migrated and depth converted (previously only ¼ of the data was reprocessed and none was depth converted)

·        Interpreted seismic data, provided critical information on sizes, number of potential petroleum accumulations (traps)

·        Basic info- structural style, timing of deformation, seismic mappings, structural modeling, stratigraphic analysis

• Other geophysical methods- Aeromagnetic survey purchased

·        Location, size, continuity and faulting of structures shallow and deep

·        With seismic data- interpretations of rock units at depth, determining areal distribution

Project Schedule:

• At intervals of 6 to 9 months-workshops at Denver on Menlo Park to present geological data and interpretations
• Late April 1997, preliminary assessment
• January 1998- final assessment
• Following final -several reviews written examining assessment
• May 1998- results were released at annual AAPG meeting in Salt Lake City, Utah

Assessment Methodology:

• Play-analysis method
• Play- basic unit of assessment, defined as a volume of rock with common geologic attributes, such as source rock, reservoir rock, trapping mechanism, and timing.
• Ten plays defined and assessed
• Each play describes a number of prospects (potential oil or gas accumulation) as well as geologic and fluid characteristics
• A rang e of values for numbers show uncertainty in the process
• Also described as the deposit simulation method
• Good method in 1002- where no petroleum has been identified and there is a limited amount of data.
• Output- estimates of sizes, numbers, and depths of oil and gas accumulations- for economic analysis
• Origin of method- Geologic Survey of Canada in NPRA exploration, development and production
• Play definition- first step in assessment
• Process

·        For each play- potential petroleum estimated based on geological characteristics (reservoir thickness, porosity..)

·        restricted to estimations to larger that 50 MMBO (so assessment would not be influence by small accumulations tat are non-economic)

·        Risking procedure- weigh likelihood to generate 50 MMBO applied to in-place estimate.

·        Recovery factor- appropriate to each play applied to in-place estimate to find technically recoverable estimate