缝-洞型地层缝洞的双侧向测井响应数值模拟

为研究缝-洞型地层的双侧向测井响应特征,建立洞穴和裂缝组合的介质模型,利用三维有限元方法对缝洞的双侧向测井响应进行数值模拟。结果表明,洞穴在一定尺度和范围内影响双侧向测井响应,随着洞穴尺度的增大,双侧向测井视电阻率降低,且深浅侧向视电阻率比值降低,但双侧向测井响应对离开井壁洞穴的较敏感范围不大于一个洞穴半径尺度。缝-洞型地层的双侧向测井响应主要受裂缝影响,低角度缝双侧向测井呈现负差异,而高角度缝双侧向测井为正差异,洞穴的存在不改变双侧向测井响应深浅侧向视电阻率与裂缝倾角的匹配关系。缝-洞型地层的双侧向测井视电导率与裂缝张开度存在线性关系。

Numerical simulation of the dual laterolog response to fractures and caves in fractured-cavernous formation

To study the response characteristics of dual laterolog in fractured-cavernous reservoirs, a model of fractures and caves was built, and the 3-D finite element method was utilized to simulate its logging responses. Caves of certain size have influence on the response of dual laterolog within certain space. With the cave size increasing, the logging apparent resistivity becomes lower, and the apparent resistivity ratio of deep laterolog to shallow laterolog decreases. Within less than the one-cave radius scope, the dual laterolog is more sensitive to the cave to borehole wall. The logging response of fractured-cavernous formation is mainly affected by fractures, and low angle fractures result in a negative difference of dual laterolog which is contrary to high angle fractures, but the existing caves do not change the matching relationship between the shallow and deep resistivity and fracture dip. The apparent conductivity of dual laterolog in fracture-cave formation presents a linear relationship with fracture aperture.