Geomechanical Modeling of Mining-Induced Permeability: Implications for Potential Gas Inflow from a Sheared Gas Well

Details

• Personal Author:
  Ajayi KM ; Esterhuizen, Gabriel S. ; Khademian Z ; Schatzel, Steven J. ; Su, Daniel W. H.
• Description:
  Stability and integrity of unconventional shale gas wells drilled through current and future coal reserves can be compromised by ground deformations induced by nearby longwall mining operations. Due to the enhancement of the surrounding rockmass permeability by longwall mining, the high-pressure gas from a damaged, breached well may reach mine workings and overwhelm ventilation system capability to dilute the hazardous atmosphere. This paper describes a set of in-situ measurements coupled with a modeling procedure that uses geomechanical analyses for estimating longwall-induced rockmass permeability and estimates potential inflow to the mining area by a fracture flow analysis. A two-panel longwall model is constructed to represent a shallow 147 m-deep mining site in the southwestern Pennsylvania coal region. A Distinct Element Code (3DEC) is used to explicitly model the rockmass by a Discrete Fracture Network (DFN) logic. Field observation, surface subsidence measurement, underground coal pillar stress measurements, and in-situ permeability measurements are used for calibrating DFN geometries and initial aperture values. The fracture aperture distribution across the model is used for predicting potential shale gas inflow to the mine using a Fracture Flow Code (FFC) developed for this study. Several realizations are simulated to cover worst-case scenarios for the maximum inflow into the mining area in a comparative analysis. The presented modeling approach will help investigate the potential hazards of a shale gas well for mine safety should the well casing integrity be compromised by mining operations. [Description provided by NIOSH]
• Subjects:
  Coal Coal Mining Geology Mining Occupational Health Safety
• Keywords:
  Coal Mining Gases Gas Flow Geologic Models Ground Control Ground Monitoring Longwall Mining Rock Mechanics Underground Mines
• Series:
  Mining Publications
• Publisher:
  Society for Mining, Metallurgy & Exploration, Inc. (SME)
• Document Type:
  Text
• Genre:
  Proceedings
• Place as Subject:
  OSHA Region 3 ; Pennsylvania
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  PMRD - Pittsburgh Mining Research Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-10
• NIOSHTIC Number:
  nn:20064712
• Citation:
  Proceedings of the 40th International Conference on Ground Control in Mining (ICGCM 2021), July 27-28, 2021, virtual event. Englewood, CO: Society for Mining, Metallurgy & Exploration, Inc. (SME), 2021 Jul; :1-10
• Federal Fiscal Year:
  2021
• NORA Priority Area:
  Mining
• Peer Reviewed:
  False
• Source Full Name:
  Proceedings of the 40th International Conference on Ground Control in Mining (ICGCM 2021), July 27-28, 2021, virtual event
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:e7e4049d6842ab112b14b61dd010d9f04d3a55f1975064d80d3975f58905067751b5ee0053ff23f632c38cf0a4b5cf07fc73fafdffbdf8ef4433ee6eb957db7e
• Download URL:
  https://stacks.cdc.gov/view/cdc/215461/cdc_215461_DS1.pdf
• File Type:
  [PDF - 1.55 MB ]