A Case Study on Longwall-Induced Rockmass Permeability Under Medium Cover: Potential Gas Inflow Implications

Details

• Personal Author:
  Ajayi KM ; Khademian Z ; Kim BH
• Description:
  In the Northern Appalachian Basin of the United States, most of the production wells in shale gas reservoirs intersect with a bedded sequence of minable coal layers. The gas wells are often positioned in the coal mine abutment pillars for protection, but longwall-induced stresses may lead to excessive deformation in the gas well casing and potentially leak high-pressure gas to the mining area. Quantitative analyses of the potential gas inflow need an understanding of the rockmass permeability evolution during longwall mining. For this study, a medium-cover (198-m deep) mining site in eastern West Virginia was selected to calculate longwall mining-induced permeability changes. A model in 3DEC numerical modeling code was constructed using the Discrete Fracture Network (DFN) technique to explicitly create fracture systems in the model and calculate fracture apertures under longwall-induced stress and deformations. The calculated fracture apertures are used in a fracture flow code (FFC) to predict the volumetric gas inflow to the mine in the case of a hypothetical breach in a gas well casing. The potential breach location was identified using a 60-arm caliper survey in a test well in abutment pillar, showing that the maximum horizontal displacement occurs 51 m below the surface. The results of FFC simulation for the breach in this location shows that in 100 different DFN realizations, there is no sign of gas reaching the mine workings. [Description provided by NIOSH]
• Subjects:
  Coal Coal Mining Mining Occupational Health Safety Software
• Keywords:
  3D Coal Mining Computer Models Fracture Zones Gases Ground Control Longwall Mining Rock Mechanics Three Dimensional
• Series:
  Mining Publications
• ISBN:
  9780979497575
• Publisher:
  American Rock Mechanics Association (ARMA)
• Document Type:
  Text
• Genre:
  Proceedings
• Place as Subject:
  OSHA Region 10 ; OSHA Region 3 ; Pennsylvania ; Washington
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  PMRD - Pittsburgh Mining Research Division ; SMRD - Spokane Mining Research Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• NIOSHTIC Number:
  nn:20067126
• Citation:
  56th US Rock Mechanics/Geomechanics Symposium, June 26-29, 2022, Santa Fe, New Mexico. Alexandria, VA: American Rock Mechanics Association (ARMA), 2022 Jun; :ARMA-2022-0387
• Federal Fiscal Year:
  2022
• Peer Reviewed:
  False
• Source Full Name:
  56th US Rock Mechanics/Geomechanics Symposium, June 26-29, 2022, Santa Fe, New Mexico
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:408ac851083add7320b6aa12df111da09659dce8c248faeea3117e098d4485264260177c5148a656f0c6526c19e60fd130ab2e5d8207b8770167f2d2bc91ea45
• Download URL:
  https://stacks.cdc.gov/view/cdc/215537/cdc_215537_DS1.pdf
• File Type:
  [PDF - 1.73 MB ]