The Effect of Overburden Depth on Casing Deformations of Shale Gas Wells in Longwall Chain Pillars – Recent Mine-By Experiences

Details

• Personal Author:
  Khademian Z ; Kim BH ; Su D ; Tulu B ; Zhang P
• Description:
  Over 2,000 shale gas wells have been drilled in the Pittsburgh Seam longwall reserves. As longwall panels are laid out, some of these shale gas wells must be located in longwall chain pillars. With longwall mining on both sides and the constraint of chain pillar size, gas wells in chain pillars are subjected to longwall-induced ground movements and stresses, which could induce deformations in gas well casings. Casing deformations are associated with several factors such as overburden geology, surface topography, setback distance, and casing construction. Overburden geology is one important factor that largely determines the locations and levels of deformations in gas well casings. Previous NIOSH gas well research has found that casing deformations above the coal seam horizon are smaller under deep cover than under shallow cover and that casing deformations could occur at the coal seam horizon under deep cover. Recent mine-by cases have provided more insights into the locations and amount of longwall-induced casing deformations as well as the potential occurrence of a large casing deformation at the coal seam horizon. This paper presents three recent mine-by cases with shale gas wells in the chain pillars between two adjacent longwall panels under different overburden depths. Casing deformations were measured by multi-finger caliper surveys and predicted with numerical modeling. With the established numerical model, the effect of overburden depth was further analyzed to investigate the potential occurrence of a large casing deformation at the coal seam horizon under deep cover. These mine-by cases not only provide a general demonstration of how overburden depths can affect longwall-induced stresses and deformations but also give a good indication about the level of casing deformations that could occur under different overburden depths. The study concludes that (1) casing deformations reduce with increase of overburden depths at the gas well; (2) a cementing alternative with production casing uncemented is an effective means to eliminate production casing deformations; and (3) large plastic casing deformation could occur in the production casing at the coal seam horizon under deep cover. The experience and knowledge gained from these mine-by cases would help longwall operators and gas companies to take appropriate measures to minimize the influence of longwall mining in shale gas wells in chain pillars. [Description provided by NIOSH]
• Subjects:
  Occupational Health Safety
• Keywords:
  Ground Control Longwall Mining Mining Engineering Pillar Design Pillar Mechanics
• Series:
  Mining Publications
• ISBN:
  97808733551
• 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:
  114-128
• NIOSHTIC Number:
  nn:20070526
• Citation:
  Proceedings of the 43rd International Conference on Ground Control in Mining (ICGCM 2024), July 22-25, 2024, Canonsburg, Pennsylvania. Klemetti T, Mitra R, Perry K, Murphy M, Tulu IB, eds. Englewood, CO: Society for Mining, Metallurgy & Exploration (SME), 2024 Jul; :114-128
• Editor(s):
  Klemetti T; Mitra R; Perry K; Murphy M; Tulu IB
• Federal Fiscal Year:
  2024
• Peer Reviewed:
  False
• Source Full Name:
  Proceedings of the 43rd International Conference on Ground Control in Mining (ICGCM 2024), July 22-25, 2024, Canonsburg, Pennsylvania
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:63449a6278f8029c3bdb877de9b0cbd3225fcb147d6c47618c7a880ef0893d213875ebc7b17cdc82a66aa453b1e9987ce939afe61143f73c326ea323562de112
• Download URL:
  https://stacks.cdc.gov/view/cdc/215717/cdc_215717_DS1.pdf
• File Type:
  [PDF - 3.36 MB ]