Comparison of Measured and Modeled Casing Deformations of a Test Well in a Longwall Abutment Pillar

Details

• Personal Author:
  Kim BH ; Midler E ; Su D ; Zhang P
• Description:
  Shale gas wells in longwall abutment pillars are subjected to longwall-induced ground movements, and their stability has been a safety concern for both the mining and gas industries. To understand the impact of longwall mining on the stability of gas wells in longwall abutment pillars, a test well was drilled in a longwall pillar between two adjacent longwall panels to measure longwall-induced deformations in the casing as the two longwall panels on either side were retreated. The longwall panels extracted the Pittsburgh coal seam under a depth of 177 m and were developed with a 3-entry system with 52-m-wide chain pillars and 366-m-wide panels. Casing deformations induced by longwall mining were measured by 60-arm caliper logging and observed with a downhole camera. A FLAC3D model was set up to predict longwall-induced stresses and deformations in the test well casing. The model was validated with measured surface subsidence and longwall-induced pillar pressure. Both measurements and numerical modeling showed that the casing deformed because of relative displacements along distinct weak rock interfaces. Casing deformations at the weak claystone interfaces were found to be confined within the claystone layers. In this case, casing deformations occurred at the same locations with both first and second panel mining. Second panel mining caused additional deformations as the relative horizontal displacements along the interfaces shifted in the opposite direction. The FLAC3D model proved to be capable of predicting the locations and magnitudes of casing deformations with reasonable accuracy. [Description provided by NIOSH]
• Subjects:
  Occupational Health Safety
• Keywords:
  3D Environmental Stress Gases Geologic Models Ground Control Longwall Mining Pillar Mechanics 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 ; West Virginia
• 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:20067129
• 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-2022-0280
• 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:d3fd966705cf97a2de697d1f19c67863d4325ba10255c9b217c0f6103facb2e1054204ea460df6a257b1401c6541362937c7199fc354a83d2febc250b761efac
• Download URL:
  https://stacks.cdc.gov/view/cdc/215539/cdc_215539_DS1.pdf
• File Type:
  [PDF - 1.97 MB ]