考虑裂隙发育的碳酸盐岩地层孔隙压力预测新模型

利用深、浅侧向电阻率差值定量计算裂缝孔隙度,以有效应力原理为理论基础,结合碳酸盐岩声波试验,研究多因素协同作用机制下的地层波速的总体响应特征,分析孔隙度一定条件下声波波速与有效应力之间的关系,利用回归分析法建立一套适合碳酸盐岩地层的压力预测新模型。结果表明:利用深、浅电阻率差值可以判断地层裂缝的产状,并定量计算裂缝孔隙度和裂缝张开度;在孔隙度一定的条件下,纵、横波速随有效应力的增大而增大;在有效应力一定的条件下,纵、横波速随孔隙度的增大而减小;建立的模型比传统方法具有更好的可靠性和预测精度。

A novel pore pressure prediction model of carbonate formation with fracture development

The fracture porosity was calculated by the difference of deep and shallow lateral resistivity quantitatively. Based on the effective stress theory, the integration of sonic velocity experiments was presented to imply the different responses to complex mechanisms of generating pore pressure. In addition, the correlation between sonic velocity and the effective stress was analyzed and a new pore pressure prediction model for carbonate formation was established by regression analysis method. The results show that the attitude of formation fractures can be justified by the difference of deep and shallow lateral resistivity. Moreover, the fracture porosity and fracture opening width can be also calculated quantitatively. When the porosity is an constant, both shear and compressional wave travel time increase with the rise of the effective stress. Otherwise, when the effective stress is an constant, both shear and compressional wave travel time decrease with the rise of porosity. The reliability and better accuracy are also testified compared with conventional methods.