An Improved Method for Predicting Horizontal Principal Stress: A Case Involving a P Gas Field in Northeastern Sichuan

In situ stress is an important parameter in the context of petroleum exploration and development. Triaxial mechanical experiments, acoustic emission analyses, and logging interpretation were performed on sandstone, mudstone, and carbonate rocks obtained from northeast Sichuan. Subsequently, the radial deformation characteristics caused by vertical stress were examined. Furthermore, a new in situ stress prediction model was derived based on the experimental results. The experimental results demonstrate that the assumption of the radial strain constraint based on uniaxial strain theory is inconsistent with actual rock deformation, as vertical stress will produce radial strain. Additionally, geo-temperature can also affect Poisson's ratio and Young's modulus of rock, thus resulting in the production of a temperature stress component that cannot be ignored. The newly derived in situ stress prediction model consisted of a skeleton stress component, a tectonic stress component, a pore stress component, and a temperature stress component. Compared to the acoustic emission test results, the prediction error of the new model is less than 8%, thus confirming that the new model conforms to actual geological characteristics, meets the needs of oilfield production, and possesses a certain reliability and scientific meaning.