|
|||||
|
|
Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope |
|
| Authors: | William Winters Michael WalkerRobert Hunter Timothy CollettRay Boswell Kelly RoseWilliam Waite Marta TorresShirish Patil Abhijit Dandekar |
| Institution: | a U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543, USA b Weatherford Laboratories, 8845 Fallbrook Drive, Houston, TX 77064, USA c ASRC Energy Services, 3900 C Street, Suite 702, Anchorage, AK 99503, USA d U.S. Geological Survey, Box 25046, MS-939, Denver, CO 80225, USA e U.S. Department of Energy, National Energy Technology Laboratory, 3610 Collins Ferry Road, Morgantown, WV 26507, USA f Oregon State University, 104 COAS Administration Building, Corvallis, OR 97331, USA g University of Alaska, P.O. Box 755880, Fairbanks, AK 99775, USA |
| Abstract: | This study characterizes cored and logged sedimentary strata from the February 2007 BP Exploration Alaska, Department of Energy, U.S. Geological Survey (BPXA-DOE-USGS) Mount Elbert Gas Hydrate Stratigraphic Test Well on the Alaska North Slope (ANS). The physical-properties program analyzed core samples recovered from the well, and in conjunction with downhole geophysical logs, produced an extensive dataset including grain size, water content, porosity, grain density, bulk density, permeability, X-ray diffraction (XRD) mineralogy, nuclear magnetic resonance (NMR), and petrography.This study documents the physical property interrelationships in the well and demonstrates their correlation with the occurrence of gas hydrate. Gas hydrate (GH) occurs in three unconsolidated, coarse silt to fine sand intervals within the Paleocene and Eocene beds of the Sagavanirktok Formation: Unit D-GH (614.4 m-627.9 m); unit C-GH1 (649.8 m-660.8 m); and unit C-GH2 (663.2 m-666.3 m). These intervals are overlain by fine to coarse silt intervals with greater clay content. A deeper interval (unit B) is similar lithologically to the gas-hydrate-bearing strata; however, it is water-saturated and contains no hydrate.In this system it appears that high sediment permeability (k) is critical to the formation of concentrated hydrate deposits. Intervals D-GH and C-GH1 have average “plug” intrinsic permeability to nitrogen values of 1700 mD and 675 mD, respectively. These values are in strong contrast with those of the overlying, gas-hydrate-free sediments, which have k values of 5.7 mD and 49 mD, respectively, and thus would have provided effective seals to trap free gas. The relation between permeability and porosity critically influences the occurrence of GH. For example, an average increase of 4% in porosity increases permeability by an order of magnitude, but the presence of a second fluid (e.g., methane from dissociating gas hydrate) in the reservoir reduces permeability by more than an order of magnitude. |
| Keywords: | Gas hydrate Sagavanirktok Formation Milne Point Physical properties Grain size Mineralogy Porosity Permeability |
| 本文献已被 ScienceDirect 等数据库收录！ | |