Distribution of in-situ stress and prediction of critical depth for deep coalbed methane in Enhong Block of eastern Yunnan region

The Permian layers in Enhong Block of eastern Yunnan region have abundant in coalbed methane resources， a potential key block for future coalbed methane development.It is well documented that in-situ stress distribution has significant impact on coalbed methane development projects such as hydraulic fracturing.In this study， the revised Anderson Model was employed to predict the stress distributions with in Enhong Block with the constraint from measured stress data from injection pressure decline approach.In general， the horizontal maximum principal stress (SH，max)， the horizontal minimum principal stress (Sh，min) and the vertical stress (Sv) follow different stress mechanisms in different burial depths， which changes from reverse faulting stress regime ， then strike-slip faulting stress regime and final normal to strike-slip faulting stress regime as the burial depth increases.The study results reveal: within this block of Permian Xuanwei Formation， the stresses have the relationship of SH，max≥Sv ＞Sh，min， indicating the existing of normal faulting to strikeslip stress regime.However， within this specific coal seams， stress magnitudes are relatively lower compared to those within the floor，showing the normal faulting stress regime.Due to the fact that burial depth and rock types have great impact on in-situ stress distribution.The horizontal stresses linearly increase along with burial depth； Furthermore， stress magnitude reaches the minimum in coal seams with lower Young's Modulus.In Enhong Block，the critical depth for deep coalbed methane reservoir is about 700 m.The results from this study may provide new geological references for future coalbed methane development in Enhong Block of eastern Yunnan region.