DALLEGGE, TODD A., University of Alaska Fairbanks, Department of Geology and Geophysics, Fairbanks, AK

ABSTRACT: Coalbed Methane Assessment Using High-Resolution Chronostratigraphy, Vitrinite Reflectance and Burial History Modeling, Cook Inlet, Alaska

Natural gas reserves in conventional traps are well known in Alaska, but methane reserves in coalbeds associated with these gas fields remain undetermined. Methane stored in coalbeds can be modeled if the coalbed burial history is well documented. Burial history is dependent upon determining the stratigraphic, structural, thermal, and depositional histories of the basin. The Cook Inlet Basin is both stratigrahically and structurally difficult.

I propose the construction of a model for assessing the coalbed methane potential of the Kenai Group in Cook Inlet Basin by using high-resolution chronostratigraphy and burial history modeling. Ash bed partings and vitrinite reflectance samples from coalbeds will be collected from core and outcrop. ⁴⁰Ar/³⁹Ar dating and vitrinite reflectance measurements will be completed on these samples. Published data, including well logs, regional tectonic studies, coal-quality, and seismic data, will be used to supplement this information.

The data produced will be used to formulate a chronostratigraphic and thermal framework for the basin. Multiple ⁴⁰Ar/³⁹Ar dates will allow for complete correlation and delineation of stratigraphic relations between wells and outcrops across the basin. Vitrinite reflectance measurements will determine the thermal histories at these locations. Basin-mod software will be to model the burial history of the basin. Using this data, a model will be constructed to produce basin-wide, maturity isopach maps showing areas of potential coalbed methane generation and storage. These factors make the Cook Inlet Basin an ideal setting to document and test a high-resolution, thermal maturation model for coalbed methane resource potential.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid