Shale Gas Well Casing Deformation in Longwall Chain Pillars Under Deep Cover – Field Measurement and Numerical Modeling

Details

• Personal Author:
  Dougherty H ; Kim BH ; Su D ; Van Dyke M ; Zhang P
• Description:
  The integrity of shale gas wells in longwall chain pillars under the influence of longwall mining is a safety concern for both coal and gas operators. Previous modeling studies of gas wells in longwall pillars have shown that a FLAC3D model can predict longwall-induced stresses and deformations in gas well casings with reasonable accuracy. The predicted casing deformations can be verified by multi-finger caliper survey. This study concerns the influence of longwall mining on eight shale gas wells in a shale gas well pad located in the chain pillars between two adjacent longwall panels under 1,030 feet of cover. FLAC3D modeling was performed to predict longwall-induced deformations in gas well casings based on site-specific mining and geological conditions. Small deformations less than 0.5 in were predicted in the intermediate casing above 600 ft depth, and very small casing deformations less than 0.15 in were predicted below 600 ft due to high abutment pressure and high frictional resistance along the weak bedding interfaces. After the first panel was mined, a 56-arm caliper survey was performed on one of the wells to measure the longwall-induced casing deformations in the intermediate casing. The predicted casing deformations were then compared with the measured deformations, which indicated that the prediction was generally in good agreement with the measurement in terms of deformation locations and magnitudes. Findings from this study provide valuable information not only for stability assessment of shale gas wells in longwall chain pillars but also for developing engineering guidelines to preserve casing integrity through adequate pillar and casing design. [Description provided by NIOSH]
• Subjects:
  Coal Coal Mining Mining Occupational Health Safety
• Keywords:
  Coal Mining Gases Longwall Mining Models Pillar Mechanics Stress Underground Mines
• Series:
  Mining Publications
• ISBN:
  9781713863700
• Publisher:
  Society for Mining, Metallurgy & Exploration (SME)
• 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
• Pages in Document:
  301-315
• NIOSHTIC Number:
  nn:20067520
• Citation:
  Proceedings of the 41st International Conference on Ground Control in Mining (ICGCM 2022), July 26-28, 2022, Canonsburg, Pennsylvania. Englewood, CO: Society for Mining, Metallurgy & Exploration (SME), 2022 Jul; :301-315
• Federal Fiscal Year:
  2022
• Peer Reviewed:
  False
• Source Full Name:
  Proceedings of the 41st International Conference on Ground Control in Mining (ICGCM 2022), July 26-28, 2022, Canonsburg, Pennsylvania
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:3b378a6ec58d3d91dcd335f48c468a70775013aa7bef91c7079c827784ae2a2a1ca5c6a2b9aae307029be0fdc34e99ea02a7ad073db66faab746f12c7a8168ff
• Download URL:
  https://stacks.cdc.gov/view/cdc/215553/cdc_215553_DS1.pdf
• File Type:
  [PDF - 2.89 MB ]