The present-day in-situ stress filed characteristic of deep shale reservoirs and its effect on the reconstruction of shale reservoirs:A case study of the Yongchuan shale gas field in South Sichuan Basin
LI Yong
HE Jianhua
DENG Hucheng
WEI Limin
WANG Yuanyuan
LI Ruixue
CAO Feng
YIN Shuai
Abstract：The present-day in-situ stress characteristic of deep shale reservoirs and the impact of fracture efficacy and fracturing effect under their control is still unclear.Taking the Yongchuan shale gas play in southeastern Sichuan baisn as an example,the hydraulic fracturing method,rock acoustic emission experiment,logging data,and numerical simulation were used to clarify the stress characteristic of deep shale reservoirs and its effect on the reconstruction of shale reservoirs.Our findings demonstrate that the deep shale reservoirs in the southeast Sichuan ba-sin are currently experiencing strike-slip and strike-slip with the tension,and some areas are experiencing strike-slip with the compression.Its difference of in-situ horizontal stresses mostly range from 10 to 30 MPa[0.05～0.3 Sv(Sv:Vertical principal stress)],a prevailing near EW(92°～105°)trending SHmax orientation,and obviously affected by faults and folds.The buried depth has little impact on the lateral stress coefficient(K),which typically ranges from 0.9 to 1.1 and is close to 1.0.Deep shale reservoirs have a low fracture friction coefficient(typically less than 0.2),and natural fractures with a medium-high dip angle(＞45°±10°)and an angle between 15° and 65° with the maximum horizontal stress have favorable mechanical ef-fectiveness following transformation.The present-day in-situ stress has a certain control effect on the permeability.As the difference of in-situ horizontal stresses increases,the complexity of the fracture network gradually decreases,and the fracturing impact deteriorates.The shear stress produced by the off-azimuth well induce the hydraulic fracture to produce a larger kin-king angle(＞40°).Deep shale forms a stress barrier in the longitudinal direction due to litho-facies differences.The region of strike-slip with tension has a better overall reconstruction im-pact.Our results can provide a reference for the study of in-situ stress in deep shale reservoirs and the efficient exploration and development of deep shale gas.
Keywords：deep shaleSouth Sichuan BasinWufeng-Longmaxi Formationin-situ stress charac-teristicreservoir engineering qualityfracture mechanical effectivenesshydraulic fracturing
Publication Date：2024-05-30
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：18( 546-563 )