Time: 2022-03-10 | Counts: |
doi:10.16186/j.cnki.1673-9787.2020060037
Received:2020/06/12
Revised:2020/09/04
Published:2022/03/15
Numerical simulation study on stress distribution around the roadway-type horizontal wells in coal reservoirs: A case study of Hudi coal mine of Jincheng mining area
ZHANG Xiaodong1,2, SUN Feiyang1, ZHANG Bin3, HENG Shuai1, LI Xianzhong 1
1.School ofEnergy Science and Engineering, Henan Polytechnic University, Jiaozuo 454000 , Henan, China;2.Henan Province Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region, Jiaozuo 454000 , Henan, China;3.CBM and Gas Storage Business Department of Huabei Oilfield Company, PetroChina , Renqiu 062552 , Hebei, China
Abstract: To clarify the stress distribution of a large-diameter roadway-type horizontal well drilled in coal reservoirs,Hudi coal mine in Jincheng mining area was taken as a case study.Based on the reservoir conditions and rock mechanics properties of coal seam and its roof and floor,a calculation model of stress field around the roadway-type horizontal wells during excavation was established by the numerical simulation software ABAQUS,and the stress distribution characteristics around the wells under different conditions of wellbore shapes,sizes and excavation directions were discussed.The results showed that: (1) The existence of roof and floor obviously changed the stress distribution in the vertical direction,which made the stress discontinuous and incongruous,and increase the stress concentration at the interface to a certain extent.The stress concentration at the interface was more conducive to the excavation of horizontal wells; (2) Circular and rectangular roadwaytype horizontal wells had the same range of stress influence zone.But the severe stress release of circular roadway-type horizontal wells was easy to cause wellbore instability and breakdown,thus it was conducive to enlarging wellbore diameter; (3) The range of the stress releasing zone and the stress influence zone around circular roadway-type horizontal wells increased with the increase of the wellbore size,and the range of the stress influence zone increased more obviously; (4) The roadway-type horizontal wells showed stress concentration in the vertical direction and stress release in the horizontal direction,whether the horizontal wells were excavated along the direction of the maximum horizontal principal stress or the minimum horizontal principal stress.By contrast,the stress release was more severe when the roadway-type horizontal well was excavated along the direction of the minimum horizontal principal stress.On the other hand,compared with the rectangular roadwaytype horizontal wells,the circular roadway-type horizontal wells had more significant diameter enlargement.Meanwhile the larger wellbore size was,the larger stress influence zone was.Furthermore,in the excavation direction,the excavation along the minimum horizontal principal stress was better than that along the maximum horizontal principal stress.
Key words:Hudi coal mine;coal reservoir;roadway-type horizontal well;borehole geometric size;stress distribution around the well