川南龙马溪组深层页岩现今地应力场特征

Characteristics of Current In-Situ Stress of the Longmaxi Formation Deep Shale, Southern Sichuan Basin

摘要: 页岩气应力场特征的分析评价是深层页岩气勘探开发的重要环节，对压裂预测走向和井网部署具有重要指导意义。四川盆地储藏大量页岩气，由于页岩气储层孔隙度和渗透率较低，需要通过水力压裂技术实现页岩气效益开发，而岩石力学参数和地应力特征是影响裂缝扩展的重要因素。以川南页岩气储层龙马溪组龙-₁¹小层为研究对象，结合室内实验和现场测井资料，计算岩石力学参数，分析单井地应力大小、方向。结果表明，岩石动态杨氏模量介于33.6~47.1 GPa，动态泊松比介于0.20~0.23，明确静态杨氏模量为39.4~46.9 GPa，静态泊松比为0.25~0.28，动静态参数具有良好的线性关系。利用组合弹簧模型计算单井最大水平主应力97~115 MPa，最小水平主应力77~99 MPa，垂向应力86~106 MPa，地层主要呈走滑应力状态σ_H > σ_V > σ_h；单井地应力方向NE向(100˚~120˚)为主，岩石力学参数和地应力特征的研究为油气勘探开发提供了可靠的技术支撑。

Abstract: The analysis and evaluation of stress field characteristics constitute a critical component of deep shale gas exploration and development, providing essential guidance for fracture prediction and well pattern deployment. Shale in the Sichuan Basin is widespread and shale gas resources are abundant. Due to low porosity and low permeability of shale reservoirs, the hydraulic fracturing is a key technology for the benefits development of shale gas resources. Rock mechanical parameters and in-situ stress significantly influence fracture propagation. This study focuses on the Long-₁¹ small layer in southern Sichuan basin. Integrating laboratory experiments and field logging data, we calculated rock mechanical parameters and analyzed individual well stress characteristics. The results indicate that the dynamic Young’s modulus of is 33.6~47.1 GPa, with a dynamic Poisson’s ratio is 0.20~0.23. Static Young’s modulus is 39.4~46.9 GPa, and static Poisson’s ratio is 0.25~0.28, showing a good linear relationship between dynamic and static rock mechanical parameters. Using the combined spring model, the maximum horizontal principal stress was calculated at 97~115 MPa, with minimum horizontal principal stress at 77~99 MPa and vertical stress at 86~106 MPa. The stress regime primarily exhibited strike-slip (σ_Hmax > σ_V > σ_hmin), with the maximum horizontal principal stress orientation being northeast (100˚~120˚). The study of rock mechanics parameters and in-situ stress characteristics provide reliable technical support for oil and gas exploration and development.