Natural gas hydrates on the North Slope of Alaska

• Main Author: Collett, T.S.
• Other Authors: United States. Department of Energy.
• Format: Report
• Language: English
• Published: Geological Survey (U.S.). Western Region. Administrative Division. 1991
• Subjects: Origin; Federal Region X; Well Logging; Hydrates; Geology; Alaska; Porosity; Natural Gas Hydrate Deposits; Chemistry; Geochemistry; North America; Gas Hydrates; Progress Report; 03 Natural Gas; Document Types; Usa 030200* > Natural Gas > Reserves; & Exploration; Geologic Deposits; Arctic; Mackenzie River; Mackenzie river; Methane hydrate; north slope; Prudhoe Bay; Siberia
• Online Access: https://doi.org/10.2172/5745610; https://digital.library.unt.edu/ark:/67531/metadc1101156/

Gas hydrates are crystalline substances composed of water and gas, mainly methane, in which a solid-water lattice accommodates gas molecules in a cage-like structure, or clathrate. These substances often have been regarded as a potential (unconventional) source of natural gas. Significant quantities of naturally occurring gas hydrates have been detected in many regions of the Arctic including Siberia, the Mackenzie River Delta, and the North Slope of Alaska. On the North Slope, the methane-hydrate stability zone is areally extensive beneath most of the coastal plain province and has thicknesses as great as 1000 meters in the Prudhoe Bay area. Gas hydrates have been identified in 50 exploratory and production wells using well-log responses calibrated to the response of an interval in one well where gas hydrates were recovered in a core by ARCO Alaska and EXXON. Most of these gas hydrates occur in six laterally continuous Upper Cretaceous and lower Tertiary sandstone and conglomerate units; all these gas hydrates are geographically restricted to the area overlying the eastern part of the Kuparuk River Oil Field and the western part of the Prudhoe Bay Oil Field. The volume of gas within these gas hydrates is estimated to be about 1.0 {times} 10{sup 12} to 1.2 {times} 10{sup 12} cubic meters (37 to 44 trillion cubic feet), or about twice the volume of conventional gas in the Prudhoe Bay Field. Geochemical analyses of well samples suggest that the identified hydrates probably contain a mixture of deep-source thermogenic gas and shallow microbial gas that was either directly converted to gas hydrate or first concentrated in existing traps and later converted to gas hydrate. The thermogenic gas probably migrated from deeper reservoirs along the same faults thought to be migration pathways for the large volumes of shallow, heavy oil that occur in this area. 51 refs., 11 figs., 3 tabs.