Influence of longwall mining on the stability of gas wells in chain pillars
Longwall mining has a significant influence on gas wells located within longwall chain pillars. Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well casings. If the gas well casings are compromised or ruptured, natural gas c...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2020-01-01
|
| Series: | International Journal of Mining Science and Technology |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2095268619306032 |
| _version_ | 1811341273396674560 |
|---|---|
| author | Peter Zhang Heather Dougherty Daniel Su Jack Trackemas Berk Tulu |
| author_facet | Peter Zhang Heather Dougherty Daniel Su Jack Trackemas Berk Tulu |
| author_sort | Peter Zhang |
| collection | DOAJ |
| description | Longwall mining has a significant influence on gas wells located within longwall chain pillars. Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well casings. If the gas well casings are compromised or ruptured, natural gas could migrate into the mine workings, potentially causing a fire or explosion. By the current safety regulations, the gas wells in the chain pillars have to be either plugged or protected by adequate coal pillars. The current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar study. The study provided guidelines for gas well pillars by considering their support area and overburden depth as well as the location of the gas wells within the pillars. As the guidelines were developed for room-and-pillar mining under shallow cover, they are no longer applicable to modern longwall coal mining, particularly, under deep cover. Gas well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 study. This study, conducted by the National Institute for Occupational Safety and Health (NIOSH), presents seven cases of conventional gas wells penetrating through longwall chain pillars in the Pittsburgh Coal Seam. The study results indicate that overburden depth and pillar size are not the only determining factors for gas well stability. The other important factors include subsurface ground movement, overburden geology, weak floor, as well as the type of the construction of gas wells. Numerical modeling was used to model abutment pressure, subsurface deformations, and the response of gas well casings. The study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above, within, and below the chain pillars, and the potential location and modes of gas well failures, thereby providing a more quantifiable approach to assess the stability of the gas wells in longwall chain pillars. Keywords: Longwall mining, Gas well, Chain pillar, Casing stability |
| first_indexed | 2024-04-13T18:53:35Z |
| format | Article |
| id | doaj.art-62cbf1fc444a4c388193bd63bb5e3098 |
| institution | Directory Open Access Journal |
| issn | 2095-2686 |
| language | English |
| last_indexed | 2024-04-13T18:53:35Z |
| publishDate | 2020-01-01 |
| publisher | Elsevier |
| record_format | Article |
| series | International Journal of Mining Science and Technology |
| spelling | doaj.art-62cbf1fc444a4c388193bd63bb5e30982022-12-22T02:34:19ZengElsevierInternational Journal of Mining Science and Technology2095-26862020-01-0130139Influence of longwall mining on the stability of gas wells in chain pillarsPeter Zhang0Heather Dougherty1Daniel Su2Jack Trackemas3Berk Tulu4CDC NIOSH, Pittsburgh Mining Research Division (PMRD), Pittsburgh, PA 15236, USA; Corresponding author.CDC NIOSH, Pittsburgh Mining Research Division (PMRD), Pittsburgh, PA 15236, USACDC NIOSH, Pittsburgh Mining Research Division (PMRD), Pittsburgh, PA 15236, USACDC NIOSH, Pittsburgh Mining Research Division (PMRD), Pittsburgh, PA 15236, USADepartment of Mining Engineering, West Virginia University, Morgantown, WV 26505, USALongwall mining has a significant influence on gas wells located within longwall chain pillars. Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well casings. If the gas well casings are compromised or ruptured, natural gas could migrate into the mine workings, potentially causing a fire or explosion. By the current safety regulations, the gas wells in the chain pillars have to be either plugged or protected by adequate coal pillars. The current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar study. The study provided guidelines for gas well pillars by considering their support area and overburden depth as well as the location of the gas wells within the pillars. As the guidelines were developed for room-and-pillar mining under shallow cover, they are no longer applicable to modern longwall coal mining, particularly, under deep cover. Gas well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 study. This study, conducted by the National Institute for Occupational Safety and Health (NIOSH), presents seven cases of conventional gas wells penetrating through longwall chain pillars in the Pittsburgh Coal Seam. The study results indicate that overburden depth and pillar size are not the only determining factors for gas well stability. The other important factors include subsurface ground movement, overburden geology, weak floor, as well as the type of the construction of gas wells. Numerical modeling was used to model abutment pressure, subsurface deformations, and the response of gas well casings. The study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above, within, and below the chain pillars, and the potential location and modes of gas well failures, thereby providing a more quantifiable approach to assess the stability of the gas wells in longwall chain pillars. Keywords: Longwall mining, Gas well, Chain pillar, Casing stabilityhttp://www.sciencedirect.com/science/article/pii/S2095268619306032 |
| spellingShingle | Peter Zhang Heather Dougherty Daniel Su Jack Trackemas Berk Tulu Influence of longwall mining on the stability of gas wells in chain pillars International Journal of Mining Science and Technology |
| title | Influence of longwall mining on the stability of gas wells in chain pillars |
| title_full | Influence of longwall mining on the stability of gas wells in chain pillars |
| title_fullStr | Influence of longwall mining on the stability of gas wells in chain pillars |
| title_full_unstemmed | Influence of longwall mining on the stability of gas wells in chain pillars |
| title_short | Influence of longwall mining on the stability of gas wells in chain pillars |
| title_sort | influence of longwall mining on the stability of gas wells in chain pillars |
| url | http://www.sciencedirect.com/science/article/pii/S2095268619306032 |
| work_keys_str_mv | AT peterzhang influenceoflongwallminingonthestabilityofgaswellsinchainpillars AT heatherdougherty influenceoflongwallminingonthestabilityofgaswellsinchainpillars AT danielsu influenceoflongwallminingonthestabilityofgaswellsinchainpillars AT jacktrackemas influenceoflongwallminingonthestabilityofgaswellsinchainpillars AT berktulu influenceoflongwallminingonthestabilityofgaswellsinchainpillars |