Rockmass Permeability Induced by Longwall Mining Under Deep Cover: Potential Gas Inflow from a Sheared Gas Well

Details

• Personal Author:
  Ajayi KM ; Esterhuizen, Gabriel S. ; Khademian Z ; Kim BH ; Schatzel, Steven J.
• Description:
  The stability of shale gas wells drilled through current and future coal reserves can be compromised by ground deformations due to nearby longwall mining. Depending on the longwall-induced rockmass permeability, the high-pressure explosive gas from the damaged well may reach mine workings and overwhelm the mine ventilation systems. This study uses geomechanical models to estimate the rockmass permeability induced by mining. A two-panel longwall model of a deep, 341-m-cover mining site in southwestern Pennsylvania is constructed in 3DEC to explicitly model the rockmass by a discrete fracture network (DFN) technique. Stress-induced fracture apertures and permeabilities are calculated across the model and are validated against permeability measurements. A fracture flow code (FFC) is developed to use these results to predict potential inflow to the mine should a gas well breach occur. One hundred DFN realizations are simulated, and the results show that for a gas pressure of 2.4 MPa, the average of the predicted inflow rates to this deep-cover mine is 0.006 m3/s, significantly lower than the average inflow of 0.22 m3/s for a shallow-cover mine (145-m deep) studied in the previous work (Khademian, et al. 2021). The result can help assess the potential hazards of a shale gas well breach for mine safety and evaluate the ventilation requirements to mitigate the risk. [Description provided by NIOSH]
• Subjects:
  Geology Mining Occupational Health Safety Ventilation
• Keywords:
  Explosive Gases Fracturing Longwall Mining Mining Industry Rock Mechanics Ventilation Systems
• Series:
  Mining Publications
• ISSN:
  2524-3462
• Document Type:
  Text
• Genre:
  Journal Article
• 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
• Volume:
  39
• Issue:
  4
• NIOSHTIC Number:
  nn:20065516
• Citation:
  Min Metall Explor 2022 Aug; 39(4):1465-1473
• Contact Point Address:
  Zoheir Khademian, Pittsburgh Mining Research Division, CDC NIOSH, Pittsburgh, PA, USA
• Email:
  opv9@cdc.gov
• Federal Fiscal Year:
  2022
• NORA Priority Area:
  Mining
• Peer Reviewed:
  True
• Source Full Name:
  Mining, Metallurgy & Exploration
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:643d98b6fb3938eb13bd557135c26716d7f3bb9442dfb4218f46fa83a6b652d68b12063717272f75f33dc667f7bbdd1efe31dcd6f0a849f7e5265905caa6a8ad
• Download URL:
  https://stacks.cdc.gov/view/cdc/215558/cdc_215558_DS1.pdf
• File Type:
  [PDF - 1.10 MB ]