Beluga River Gas Field, Cook Inlet, Alaska
The Beluga River gas field is a large, shallow gas accumulation located approximately 40 miles (64 km) west of Anchorage in the northern Cook Inlet Basin in south-central Alaska. The Beluga gas field was discovered in 1962 while exploring for a deeper oil objective. Production commenced in March 1968, and more than 1.2 TCF have been produced as of 2011. The Beluga River gas field is approximately 7.5 mi long by 2.5 mi wide (12 km × 4 km). The trap is the Beluga River structure, a broad north-northeast trending fault-propagation fold with a steeply dipping reverse fault along the west side. Basin fill consists of a thick sequence of nonmarine, fluvial-dominated, volcanic to arkosic sandstone, siltstone, mudstone, and coal deposited in a rapidly subsiding basin during Eocene to Pleistocene times. The field produces from two formations: the overlying high-net-to-gross Pliocene-age Sterling Formation and the underlying low-net-to-gross Miocene-age Beluga Formation. Gross reservoir thickness is up to 3400 ft (1036 m) and consists of dozens of stacked channel belt and crevasse splay sandstone beds separated by laterally continuous, relatively impermeable flood basin siltstone, mudstone, and coal. The domonate reservoir sandstone facies are characterized as relatively discontinuous channel belt or fan-shaped geometries. Reservoir connectivity is controlled by net-to-gross ratio, channel belt size and orientation relative to well spacing, and the presence of thin but widespread coal zones. The field is in the late stage of development, with many of the reservoir sandstones depleted to less than 40% of original pressure and with most down-structure wells experiencing water encroachment in reservoir sandstones. Declining and differential pressures, water breakthroughs, and sand production present significant operational issues. Pressure measurements indicate that much of the remaining gas resource resides in lower-quality, low-net-to-gross channel belt sand bodies in the lower portion of the reservoir.
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Oil and Gas Fields of the Cook Inlet Basin, Alaska
This volume is designed to showcase the geo-technical elements of oil and gas fields of the Cook Inlet Basin of southcentral Alaska. It contains 10 chapters written by 16 authors and co-authors who have extensive experience in the basin. All of the papers have been peer-reviewed. The first three chapters provide an introduction to exploration, stratigraphy, petroleum systems, seismic acquisition, and reservoirs of the basin. Following these are seven chapters that describe individual fields in detail. This volume is intended to serve as a key reference to the petroleum geology of the Cook Inlet Basin for a wide audience including oil and gas explorers, technical professionals, students and those seeking more information about the origin and habitat of oil and gas in the area.