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Title: Pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate-bearing reservoirs in the Krishna-Godavari Basin, offshore India

Abstract

Physical properties of the sediment directly overlying a gas hydrate reservoir provide important controls on the effectiveness of depressurizing that reservoir to extract methane from gas hydrate as an energy resource. The permeability of overlying sediment determines if a gas hydrate reservoir’s upper contact will provide an effective seal that enables efficient reservoir depressurization. Compressibility, stiffness and strength indicate how overlying sediment will deform as the in situ stress changes during production, providing engineering data for well designs. Assessing these properties requires minimally-disturbed sediment. India’s National Gas Hydrates Program Expedition 2 (NGHP-02) provided an opportunity to study these seal sediment properties, reducing disturbance from gas exsolution and bubble growth by collecting a pressure core from the seal sediment just above the primary gas hydrate reservoir at Site NGHP-02-08 in Area C of the Krishna-Godavari Basin. The effective stress chamber (ESC) and the direct shear chamber (DSC) devices in the suite of Pressure Core Characterization Tools (PCCTs) were used to measure permeability, compressibility, stiffness and shear strength at the in situ vertical stress. Geotechnical properties of the predominantly fine-grained seal layer at in situ vertical stress are in typical clay sediment ranges, with low measured permeability (0.02 mD), high compressibility (Ccmore » = 0.26 – 0.33) and low shear strength (404 kPa). Though pressure and temperature were maintained throughout the collection and measurement process to stabilize gas hydrate, the lack of effective stress in the pressure core storage chamber and the chamber pressurization with methane-free water caused core expansion and gas hydrate in a thin coarser-grained layer to dissolve. The PCCTs can reapply in situ stress with incremental loading steps during a consolidation test to account for sediment compaction. Lastly, gas hydrate dissolution can be limited by storing cores just above freezing temperatures, and by using solid spacers to reduce the storage chamber’s free volume.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [4];  [6];  [7]
  1. U. S. Geological Survey, Woods Hole, MA (United States). Integrated Statistics Inc.
  2. Georgia Inst. of Technology, Atlanta, GA (United States)
  3. National Inst. of Advanced Industrial Science and Technology, Sapporo (Japan)
  4. U. S. Geological Survey, Woods Hole, MA (United States)
  5. U. S. Geological Survey, Menlo Park, CA (United States)
  6. U. S. Geological Survey, Denver, CO (United States)
  7. Oil and Natural Gas Corporation, Panvel, Navi, Mumbai, (India)
Publication Date:
Research Org.:
Louisiana State Univ., Baton Rouge, LA (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE); USGS; National Institute of Advanced Industrial Science and Technology (AIST); Japan Oil, Gas and Metals National Corporation (JOGMEC)
OSTI Identifier:
1469805
Grant/Contract Number:  
FE0028966
Resource Type:
Accepted Manuscript
Journal Name:
Marine and Petroleum Geology
Additional Journal Information:
Journal Volume: 108; Related Information: U. S. Geological Survey Data Release, https://doi.org/10.5066/P91XJ7DP.; Journal ID: ISSN 0264-8172
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; National Gas Hydrate Program Expedition 02; pressure core characterization tools; gas hydrate-bearing sediments; geotechnical properties; seal layers

Citation Formats

Jang, Junbong, Dai, Sheng, Yoneda, Jun, Waite, William F., Stern, Laura A., Boze, Lee-Gray, Collett, Timothy S., and Kumar, Pushpendra. Pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate-bearing reservoirs in the Krishna-Godavari Basin, offshore India. United States: N. p., 2018. Web. https://doi.org/10.1016/j.marpetgeo.2018.08.015.
Jang, Junbong, Dai, Sheng, Yoneda, Jun, Waite, William F., Stern, Laura A., Boze, Lee-Gray, Collett, Timothy S., & Kumar, Pushpendra. Pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate-bearing reservoirs in the Krishna-Godavari Basin, offshore India. United States. https://doi.org/10.1016/j.marpetgeo.2018.08.015
Jang, Junbong, Dai, Sheng, Yoneda, Jun, Waite, William F., Stern, Laura A., Boze, Lee-Gray, Collett, Timothy S., and Kumar, Pushpendra. Sat . "Pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate-bearing reservoirs in the Krishna-Godavari Basin, offshore India". United States. https://doi.org/10.1016/j.marpetgeo.2018.08.015. https://www.osti.gov/servlets/purl/1469805.
@article{osti_1469805,
title = {Pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate-bearing reservoirs in the Krishna-Godavari Basin, offshore India},
author = {Jang, Junbong and Dai, Sheng and Yoneda, Jun and Waite, William F. and Stern, Laura A. and Boze, Lee-Gray and Collett, Timothy S. and Kumar, Pushpendra},
abstractNote = {Physical properties of the sediment directly overlying a gas hydrate reservoir provide important controls on the effectiveness of depressurizing that reservoir to extract methane from gas hydrate as an energy resource. The permeability of overlying sediment determines if a gas hydrate reservoir’s upper contact will provide an effective seal that enables efficient reservoir depressurization. Compressibility, stiffness and strength indicate how overlying sediment will deform as the in situ stress changes during production, providing engineering data for well designs. Assessing these properties requires minimally-disturbed sediment. India’s National Gas Hydrates Program Expedition 2 (NGHP-02) provided an opportunity to study these seal sediment properties, reducing disturbance from gas exsolution and bubble growth by collecting a pressure core from the seal sediment just above the primary gas hydrate reservoir at Site NGHP-02-08 in Area C of the Krishna-Godavari Basin. The effective stress chamber (ESC) and the direct shear chamber (DSC) devices in the suite of Pressure Core Characterization Tools (PCCTs) were used to measure permeability, compressibility, stiffness and shear strength at the in situ vertical stress. Geotechnical properties of the predominantly fine-grained seal layer at in situ vertical stress are in typical clay sediment ranges, with low measured permeability (0.02 mD), high compressibility (Cc = 0.26 – 0.33) and low shear strength (404 kPa). Though pressure and temperature were maintained throughout the collection and measurement process to stabilize gas hydrate, the lack of effective stress in the pressure core storage chamber and the chamber pressurization with methane-free water caused core expansion and gas hydrate in a thin coarser-grained layer to dissolve. The PCCTs can reapply in situ stress with incremental loading steps during a consolidation test to account for sediment compaction. Lastly, gas hydrate dissolution can be limited by storing cores just above freezing temperatures, and by using solid spacers to reduce the storage chamber’s free volume.},
doi = {10.1016/j.marpetgeo.2018.08.015},
journal = {Marine and Petroleum Geology},
number = ,
volume = 108,
place = {United States},
year = {2018},
month = {8}
}

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