基于薄板理论的碳酸盐岩地层压力检测方法探讨

现有碳酸盐岩地层压力检测方法均存在不足，因此，为保证Y油田F地层碳酸盐岩地层的钻井安全，开展了碳酸盐岩地层压力的检测方法研究。基于薄板理论，考虑体积弹性模量的影响，结合碳酸盐岩特征，建立了构造挤压条件下的地层压力地质力学识别模型；通过分析F地层碳酸盐岩的地质构造、异常高压及测井响应特征分布规律，结合排除法研究了异常高压的成因机制；形成的碳酸盐岩地层压力检测方法在Y油田F层进行了实例应用。F层小断层发育，纵波速度在5 500 m/s左右；FU层和FL层的地层压力系数分别约为1.45和1.30；FU层岩石骨架变形量大于FL层，构造挤压是异常高压产生的主要成因机制。应用结果表明，该模型检测值与SFT实测值间的相对误差小于10%；地层压力随构造变形曲率、地层压力系数、弹性模量的增大而增大，随泊松比的增大而减小，且呈线性关系。研究认为，基于薄板理论的碳酸盐岩地层压力检测方法，能够比较准确地检测由构造挤压作用下的碳酸盐岩地层压力。 

Discussion on a Formation Pore Pressure Detection Method for Carbonate Rocks Based on the Thin Plate Theory

The current formation pore pressure detection methods for carbonate rock have shortcomings.In order to ensure drilling safety of carbonate rock in the F formation,Y Oilfield,the formation pore pressure detection method was studied.The geo-mechanical model of formation pore pressure was proposed under tectonic compression,based on the thin plate theory,considering the effect of bulk modulus and in accordance with carbonate rock characteristics.Based on the analysis of the geological structure,abnormal over-pressure and logging response of carbonate rock in F formation,combined with exclusive method,the generation mechanism of abnormal over-pressure was studied.When a formation pore pressure detection method was applied to F formation,Y Oilfield,the study showed that the minor faults were developed and the P-wave velocity is about 5 500 m/s in F formation.Formation pore pressure coefficient of FU formation and FL formation was about 1.45 and 1.30 respectively.The deformation of rock framework of FU formation was larger than that of FL formation,and the main generation mechanism of abnormal over-pressure was based on tectonic compression.The application results showed that the error of formation pore pressure detected value was less than 10% when compared with SFT measured value.Formation pore pressure increased with the increase of tectonic deformation curvature,formation pore pressure coefficient and elasticity modulus,and decreased with the increase of Poisson’s ratio,which was shown in the linear relationship.The study suggests that formation pore pressure detection method of carbonate rock based on the thin plate theory could be used to detect pore pressure of carbonate rock caused by tectonic compression.