Abstract:
[Objective] The sweet spot intervals of shale oil reservoirs exhibit rapid vertical variations, are characterized by centimeter-scale thin interbeds and well-developed bedding planes, and possess strong anisotropy. Traditional isotropic models are therefore inadequate for detailed geomechanical modeling and characterization, posing significant challenges for reservoir stimulation and hydraulic fracturing design. [Methods] Geomechanics is key to the cost-effective development of oil and gas reservoirs with complex geological features. To establish a high-precision 1D geomechanical model, anisotropy experiments on shale oil reservoirs were conducted in the laboratory, perform 1D geomechanical modeling using well log data to analyze geomechanical characteristics. [Results]Systematically obtaining the anisotropic rock mechanical parameters of shale. Based on the rock mechanics experimental results and the anisotropic model, the depth-wise anisotropic stiffness matrix of the formation was derived from acoustic logging data, thereby obtaining anisotropic characterizations of mechanical parameters such as Young’s modulus, Poisson’s ratio, and compressive strength. Based on the acoustic-density log curves, the unloading characteristics of the study block were identified. Pore pressure was calculated using the Bowers unloading theory and calibrated with field Modular Formation Dynamics Tester data. By integrating a high-precision anisotropic rock mechanics model with pore pressure data, a higher-accuracy two-way horizontal principal stress field was derived using an anisotropic elastic model. This enabled the construction of a high-precision 1D anisotropic geomechanical model, demonstrating significantly improved accuracy compared to the isotropic model. [Conclusions] This study established an anisotropic 1D geomechanical modeling workflow, which provides a theoretical basis and technical support for oil and gas reservoir stimulation and fracturing program design. Systematic laboratory experimental studies on shale oil reservoir anisotropy were conducted to obtain the anisotropic rock mechanical parameters of the shale. These parameters were used to provide anisotropic rock mechanical data for the 1D geomechanical modeling. Based on the high-precision anisotropic rock mechanical model and pore pressure, the anisotropic elastic model was employed to determine the two-way horizontal principal stress with higher accuracy. The precision was significantly improved by approximately 7% compared to the isotropic model. The model was validated against field data such as well history records, revealing the distribution characteristics of anisotropic geomechanical parameters and in-situ stress along the wellbore. [Significance] The research findings serve as a foundational basis for the integration of Geo-engineering Integration, providing theoretical guidance and technical support for reservoir stimulation and hydraulic fracturing design.