煤层气储层裂隙阵列侧向测井响应数值模拟与分析

裂隙是煤层气储层重要的流体渗流通道，是煤层气有效储集体形成的重要条件。研究裂隙的测井响应特征是确定煤层裂隙参数的关键。利用三维有限元方法，确定不同裂隙条件的阵列侧向测井响应。研究表明：阵列侧向测井修正的视电导率与裂隙孔隙度、裂隙流体电导率基本为线性关系；随裂隙倾角增大，阵列侧向视电阻率升高；随基块电阻率增大，阵列侧向视电阻率增加；高角度裂隙(组)的阵列侧向测井深浅视电阻率呈现正差异，而基块电阻率较大的低角度裂隙(组)的响应可呈现负差异特征；相同裂隙孔隙度下，裂隙密度增加可能使裂隙组的阵列侧向视电阻率增加，当裂隙密度足够大时，测井响应基本不随裂隙密度发生变化；交叉裂隙的测井响应与平行裂隙组差异明显，且不同倾角组合的交叉裂隙的测井响应之间差异明显。

The simulation and analysis of array lateral log response of fracture in coalbed methane reservoir

Fracture is the important seepage channel of fluid in the coal bed methane reservoir.The fracture is very important for the formation of the effective strorage block of hydrocarbon.The study of log responses of fracture is the key to determining the fracture parameters.The fracture is usually developed in the form of fracture zone.Based on the fracture group model, a three-dimensional finite element method is used to simulate the responses of the array laterolog in fractured formation.The results show that conductivitites of array latero log are primarily linearly related to the porosity of fracture and the conductivity of pore fluid.With dip angle increasing, the array log apparent resistivity increases.With block resistivity increasing, the array log apparent resistivity increases too.Apparent resistivity is positive in the high-angle fractured formation and may be negative in the low-angle fractured formation with high block resistivity.Apparent resistivity increases gradually with fracture density increasing under the same porosity of fracture.If fracture density is large enough, the log response will not vary with essential fracture density.Log response of crossing fracture is apparently different from that of the parallel fracture group, and log response of crossing fracture is different under different dip grouping system.