Research And Application Of Geostress In The Shale-Gas-bearing Area In Yichang

Shale gas has become one of the important unconventional oil and gas resources.Results of early-stage prospecting in Yichang,Hubei province exhibit good shale gas potential.Geostress distribution is the important basic data in process of shale gas development,while the geostress data in the shale-gas-bearing area in Yichang are still blank.Thus,it is of great significance to carry out geostress measurement and simulation of geostress field.The geostress data were obtained from 4 wells in Yichang,i.e.well EYY3,YY1 l,ZD2 and YD2 by means of hydraulic fracturing method,anelastic strain recovery method(ASR)and borehole caving method.Subsequently,these data were used to simulate the geostress field by using finite element analysis method with ANSYS aiming at the 2000 m depth stratum in the study area.Finally,based on the Coulomb-Mohr criterion and Griffith criterion,the fracture rate I of the target formation was calculated,and the distribution of tensile and shear fractures in the study area is predicted.Results show that the maximum horizontal principal stress is about 65 MPa ?69MPa at the 2000 m depth in the study area,and the minimum horizontal principal stress is about 45MPa?49MPa.Comparison with the measured fitting results and small relative error(<7%)validates the simulated results.The maximum horizontal principal stress direction is about NE30°?NE65°.The result of simulation shows that the fractures in the south wing of Zigui syncline,south wing of Huangling anticline,Changyang anticline and Yichang slope zone in the region are relatively less developed.In process of design of well locations,special attention should be paid to areas and strata with high rupture rates to avoid well collapse and leakage.