一种基于阵列声波测井的胶结指数计算方法在饱和度评价中的应用

利用饱和度公式评价储层含油性时,胶结指数一般在某一层位取某一固定值.在复杂岩性储层中,储层非均质性强,孔隙结构复杂,连通性差,导致胶结指数变化较大,利用常数胶结指数计算的含油饱和度精度降低,给储层测井评价带来了极大的困难.基于弹性介质理论,利用阵列声波数据得到地层骨架的剪切模量和体积模量,并计算出骨架的纵波速度.分析发现,地层和骨架的纵波速度比与地层孔隙度和胶结指数具有一定的函数关系,通过地层和骨架的纵波速度比和孔隙度可以计算出连续的胶结指数,进而得到地层饱和度.实验结果表明,本文方法计算得到的地层饱和度与岩心分析饱和度吻合较高,方法一定程度上克服了传统的饱和度模型在复杂岩性储层中的不适用性,为复杂岩性储层含油性准确评价提供了依据.

Application of saturation evaluation with cementation exponent based on array acoustic logging

When saturation model is applied to calculate water saturation of the reservoirs, the cementation factor is usually taken as a fixed value. In complex lithology reservoirs, the cementation factor varies significantly because of the anisotropism and complex pore structures, what will lead to the lower accuracy of saturation model and the difficulty of reservoir evaluation with well logging data. Based on elastic medium theory, shear modulus and bulk modulus of matrix are obtained by array acoustic logging. And then compressional velocity of matrix can be calculated. According to data analysis, cementation factor is a parameter which is related to the compressional velocity of formation and matrix and porosity. The statistical model of cementation factor is established and is applied to evaluating the hydrocarbon saturation. Practical application shows that the saturation by the method coincides with the core saturation well. The method overcomes the inapplicability of saturation model and provides an accurate way for quantitative interpretation in the complex lithology reservoirs.