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The AAPG/Datapages Combined Publications Database

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Abstract

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 core from potential gas-hydrate-bearing reservoirs in the Sagavanirktok, Prince Creek, and Schrader Bluff formations of Alaska's North Slope: Part 5—Acoustic Previous HitvelocityNext Hit core studiesast, 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. 657671.

DOI:10.1306/13201130M892598

Copyright copy2009 by The American Association of Petroleum Geologists.

Characterization of a Sediment Core from Potential Gas-hydrate-bearing Reservoirs in the Sagavanirktok, Prince Creek, and Schrader Bluff Formations of Alaska's North Slope: Part 5—Acoustic Previous HitVelocityNext Hit Core Studiesast

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 core 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 core measurements, including (part 1) project summary and geological description of the core; (part 2) porosity, permeability, grain density, and bulk modulus core studies; (part 3) electrical resistivity core studies; (part 4) nuclear magnetic resonance core studies; and (part 5) acoustic Previous HitvelocityNext Hit core studies.

ABSTRACT

The Anadarko Hot Ice 1 well was cored as part of a project to study the occurrence of gas hydrate on the North Slope of Alaska. The observations and measurements made at the drill site along with the subsequent core analysis are described in five individual reports published in this Memoir. This report deals with the acoustic Previous HitvelocityNext Hit measurements made on the recovered core.

Previous HitVelocityNext Hit measurements were made on the core-sample plugs from the sands recovered during both phase I and phase II coring operations at the Hot Ice 1 well. Polarized shear-wave and compressional-wave ultrasonic velocities at multiple confining stresses were measured on 1-in. (2.54-cm) horizontal plugs. The phase I unconsolidated sandstone-core samples were recovered from the permafrost zone; they were obtained frozen, and the velocities were measured in that recovered state. At 800 psi (5.5 MPa) confining stress, the median compressional Previous HitvelocityNext Hit is 3810 m/s (12,500 ft/s). Only a very weak dependence on temperature is observed. The median shear Previous HitvelocityNext Hit is 2170 m/s (7119 ft/s). No significant shear-wave anisotropy was observed. The trend of decreasing Previous HitvelocityNext Hit with increasing temperature is weak. Based on nuclear magnetic resonance and resistivity measurements, these samples had liquid porosities of a few percent. These velocities are consistent with a model in which ice acts as some combination of cement and a stress-supporting matrix material.

The phase II unconsolidated sand samples were recovered from unfrozen sediment. Polarized shear and compressional velocities were measured on cleaned, dried, and brine-resaturated samples. At 800 psi (5.5 MPa), the median compressional Previous HitvelocityNext Hit is 2040 m/s (6693 ft/s) and the shear Previous HitvelocityNext Hit is 1080 m/s (3543 ft/s). No significant shear-wave anisotropy was observed. The sands below 1900 ft (580 m) appear to be more consolidated than the shallower sands. This is reflected in a Previous HitvelocityNext Hit increase.

Two shale samples, one from 1800 ft (549 m) and one from 2000 ft (610 m), were selected for Previous HitvelocityNext Hit measurement. Measurements were made on horizontal, vertical, and 45deg plugs. At both depths at 800 psi (5.5 MPa), the compressional horizontal Previous HitvelocityNext Hit was 2100 m/s (6890 ft/s) and the vertical Previous HitvelocityNext Hit was 1900 m/s (6233 ft/s). Both components of shear-wave Previous HitvelocityTop at 800 psi (5.5 MPa) were approximately 1000 m/s (3281 ft/s).

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