Prediction of Present-day in-situ Stress in No.5 Coal Seam of Daning-Jixian Area:Implications for Coalbed Methane Development
The present-day in-situ stress field has an extremely important controlling effect on the permeability of coal reservoirs.The Daning-Jixian area of eastern Ordos Basin is rich in coalbed methane(CBM)resources,however,the present-day in-situ stress in this area has been studied to a low degree,which is not conducive to the efficient development of CBM in this area.To investigate the current characteristics of the geostress field in the main coal seam of Daning-Jixian area,a three-dimensional finite element numerical simulation method was used to predict the present-day distribution of No.5 coal seam in the Shanxi Formation of the Lower Permian.The results show that the present-day in-situ stress in No.5 coal seam was characterized by a positive break-type stress mechanism.The maximum horizontal principal stresses in No.5 coal seam in the eastern Ordos Basin range from 15.4 Mpa to 21.6 Mpa,and the minimum horizontal principal stresses range from 9.8 Mpa to 14.4 Mpa,and the complexity of tectonic deformation affects the distribution of in-situ stresses.The present-day stress controls the expansion of fracturing cracks,and the fracturing cracks in the study area under the present-day stress state expand vertically along the NNW-SSE direction.Most of the stress differences in the No.5 coal seams in the study area are less than 6 Mpa,which provides a foundation for the formation of complex fracture networks.The permeability of the coal seams decreases exponentially with the increase of effective ground stress,and the higher the effective ground stress,the worse the permeability of the coal reservoirs.The southeastern part of the study area is far away from the faults and is a stress reduction area,where coalbed methane is easy to gather,forming a rich area for coalbed methane storage.The research results can provide geological basis and scientific guidance for the beneficial development of coalbed methane in the study area.
万方数据
维普
