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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes

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Sigal, R. F., C. Rai, C. Sondergeld, B. Spears, W. J. Ebanks Jr., W. D. Zogg, N. Emery, G. McCardle, R. Schweizer, W. G. McLeod, and J. Van Eerde, 2009, Characterization of a sediment Previous HitcoreNext Hit from potential gas-hydrate-bearing reservoirs in the Sagavanirktok, Prince Creek, and Schrader Bluff formations of Alaska's North Slope: Part 1—Project summary and geological Previous HitdescriptionNext Hit of the Previous HitcoreNext Hit, in T. Collett, A. Johnson, C. Knapp, and R. Boswell, eds., Natural gas hydrates—Energy resource potential and associated geologic hazards: AAPG Memoir 89, p. 598607.

DOI:10.1306/13201126M892598

Copyright copy2009 by The American Association of Petroleum Geologists.

Characterization of a Sediment Previous HitCoreNext Hit from Potential Gas-hydrate-bearing Reservoirs in the Sagavanirktok, Prince Creek, and Schrader Bluff Formations of Alaska's North Slope: Part 1—Project Summary and Geological Previous HitDescriptionNext Hit of the Previous HitCoreNext Hit*

R. F. Sigal,1 C. Rai,2 C. Sondergeld,3 B. Spears,4 W. J. Ebanks Jr.,5 W. D. Zogg,6 N. Emery,7 G. McCardle,8 R. Schweizer,9 W. G. McLeod,10 J. Van Eerde11

1Mewbourne School of Petroleum and Geological Engineering, University of Oklahoma, Norman, Oklahoma, U.S.A.
2Mewbourne School of Petroleum and Geological Engineering, University of Oklahoma, Norman, Oklahoma, U.S.A.
3Mewbourne School of Petroleum and Geological Engineering, University of Oklahoma, Norman, Oklahoma, U.S.A.
4Mewbourne School of Petroleum and Geological Engineering, University of Oklahoma, Norman, Oklahoma, U.S.A.
5Consultant, College Station, Texas, U.S.A.
6PTS Labs, Houston, Texas, U.S.A.; Present address: Marathon Oil Corp., Houston, Texas, U.S.A.
7PTS Labs, Houston, Texas, U.S.A.
8PTS Labs, Houston, Texas, U.S.A.
9PTS Labs, Houston, Texas, U.S.A.
10Lone Wolf Oilfield Consulting, Calgary, Alberta, Canada
11Consultant, Calgary, Alberta, Canada
astEditor's note: This report is part of a five-report series on the geologic, petrophysical, and geophysical analysis of a sediment Previous HitcoreNext Hit recovered from the Hot Ice 1 gas-hydrate research well drilled in northern Alaska during 2003–2004. Each of these reports (Chapters 25–29 of this volume) deals with specific topical observations and/or Previous HitcoreNext Hit measurements, including (part 1) project summary and geological Previous HitdescriptionNext Hit of the Previous HitcoreNext Hit; (part 2) porosity, permeability, grain density, and bulk modulus Previous HitcoreNext Hit studies; (part 3) electrical resistivity Previous HitcoreNext Hit studies; (part 4) nuclear magnetic resonance Previous HitcoreNext Hit studies; and (part 5) acoustic velocity Previous HitcoreNext Hit studies.

ABSTRACT

The Anadarko Hot Ice 1 well was cored with a continuous coring system that recovered a 3.25-in.-diameter (8.25-cm-diameter) Previous HitcoreNext Hit from 107 to 2300 ft (33 to 701 m) below the surface. Previous HitCoreNext Hit recovery was 94.5%. The coring proceeded in two phases, separated by a summer of no activity. In phase I, the Previous HitcoreNext Hit was acquired from 107 to 1400 ft (33 to 427 m). With the exception of the bottom 140 ft (43 m), the phase I Previous HitcoreNext Hit was from the permafrost interval. The base of the permafrost interval was identified at a depth of 1260 ft (384 m). The Previous HitcoreNext Hit from the permafrost zone was recovered in a frozen state. The recovered Previous HitcoreNext Hit was described and characterized at the drill site.

The observations and measurements made at the drill site along with the subsequent analysis are described in five individual reports published in this Memoir. This Project Summary and Geological Previous HitDescriptionNext Hit of the Previous HitCoreNext Hit report contains a detailed project review and Previous HitdescriptionNext Hit of the Hot Ice project and highlights from each of the five technical reports included in this volume.

The Hot Ice Previous HitcoreNext Hit penetrated 7 ft (2 m) of surface gravel and then entered the Sagavanirktok Formation. The Hot Ice well cored through the early Tertiary age sediments of the Sagavanirktok Formation, the Tertiary and Upper Cretaceous Prince Creek Formation (which includes the informally named Ugnu sandstones), and the Schrader Bluff Formation (which includes the informally named West Sak sandstones); the Previous HitcoreNext Hit ended in 42 ft (13 m). of what appears to be a marine section of fine-grained sediments. The sediments above the marine section were identified from the visual Previous HitcoreNext Hit Previous HitdescriptionNext Hit as deposited in environments that ranged from fluvial to marginal marine and upper deltaic. Alternating sandstone, mudstone, conglomerate, and coal formations form sequences that indicate an overall progradation and shallowing of environments of deposition with time.

The Previous HitcoreNext Hit from the first phase of the project, phase I, after the melting of the pore ice was completely unconsolidated. Previous HitCoreNext Hit recovery through the bottom of the mudstone in which phase I drilling was terminated was 96.3%. The Previous HitcoreNext Hit recovered from this interval contains 12.4% conglomerate, 43.50% sandstone, 37.8% mudstone, and 6.3% coal.

The second phase of the coring program, phase II, recovered Previous HitcoreNext Hit from 1403 ft (428 m) subsurface to 2300 ft (701 m). The bottom of the hole was estimated to be below the base of the hydrate stability zone at the Hot Ice location. The first 59 ft (18 m) of the Previous HitcoreNext Hit from phase II consisted of the marine sediments in which the phase I drilling program ended. The remainder of the Previous HitcoreNext Hit was composed of sediments from the Schrader Bluff Formation (West Sak section).

The sediments cored during phase II are not as variable in character as those encountered during phase I and are finer grained. Layers of shell fragments and whole bivalve shells are common. The sandstones and mudstones in this interval form upward-coarsening sequences and have gradational contacts with the sediments above and below. These features suggest that the sediments in this interval may have been deposited in a shallow marine shelf environment.

Unlike the phase I Previous HitcoreNext Hit, the phase II Previous HitcoreNext Hit contains no conglomerate or coal. The Previous HitcoreNext Hit recovered below the marine sand in which phase I terminated contains 68% mudstone, 26.3% sandstone, and 5.7% siltstone. In general, the sandstones were finer grained than those of the Ugnu sands.

Gas hydrate was not encountered at the site of the Hot Ice 1 well; however, the recovered cores and associated laboratory Previous HitcoreTop observations and analysis provide a critical data set for understanding the nature of the sediments that have been shown to be gas-hydrate-bearing in nearby wells.

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