碳酸盐岩地层中裂缝孔隙度的定量解释

Quantitative Interpretation of Fracture Porosity in Carbonates.

李善军，肖承文等．碳酸盐岩地层中裂缝孔隙度的定量解释．测井技术，１９９７，２１（３）：２０５～２１４从理论上证明了等间距平行裂缝组与宏观均匀各向异性介质的等价性，通过三维有限元模拟，找出了各种裂缝倾角下单一裂缝、等间距平行裂缝组、宏观均匀各向异性介质的裂缝双侧向测井响应的变化规律。根据各向异性介质的双侧向测井响应与裂缝倾角之间的关系，将裂缝分为低角度裂缝、倾斜裂缝、高角度裂缝３种状态。给出了判别裂缝状态的方法，建立了裂缝的双侧向测井响应与裂缝的地层参数之间的函数关系，得出人工估算和计算机精确计算裂缝孔隙度的两套解释公式及相应计算方法。通过岩心分析，得出了塔里木盆地碳酸盐岩裂缝型储集层中，单一裂缝张开度的分布规律和裂缝孔隙度的分布规律。利用统计出的单元层的裂缝孔隙度对计算裂缝孔隙度的解释公式进行刻度。建立了碳酸盐岩裂缝性地层中，利用双侧向测井响应计算裂缝孔隙度的定量解释模型，将该模型应用于塔里木盆地碳酸盐岩裂缝性储集层中裂缝孔隙度的定量解释，取得了较好的效果。

In this paper, the equivalence between response of a medium with paralell fractures of equal spacing and that of a macroscopically anisotropic medium is proved theoretically. With 3 D FEM, the responses of dual laterolog to single fracture, parallel fractures with equal spacing and anisotropic medium are obtained at different fracture dip, and it is found that the equivalence holds only when the fracture spacing is small enough. According to the functional dependence of the response of anisotropic medium upon the fracture dip, the fractures are classified into three kinds: subhorizontal fracture, dipping fracture and subvertical fracture. A method of fracture classification is given. The functional relationships between the response and the physical parameters of the fractured formation are set up. Two sets of formulae for the estimation of fracture porosity are presented, among which one for manual application, the other for computer. The distribution characteristics of the fracture aperture in the carbonate fracture type reservoir of Tarim basin are obtained through core analysis. The core is divided into a series of elementary segments of unit length, which is assumed to be the vertical resolution of the dual laterolog (about 0 5 m). The porosity of them are calculated, from which the distribution characteristics of the fracture porosity are derived. The fracture porosity of the elementary segment is used to calibrate the aforementioned formulae for estimation of fracture porosity. Also, the quantitative interpretation models are established, which can be used to compute the fracture porosity with the dual laterolog data. Application of the above models for quantitative estimation of the fracture porosity in the carbonate fracture type reservoir of Tarim basin has yielded good results.