裂缝性碳酸盐岩裂缝的双侧向测井响应特征及解释方法

Response of Dual Laterolog to Fractures in Fractured Carbonate Formation and Its Interpretation

裂缝评价是裂缝性碳酸盐岩储层评价的关键,其常规评价方法受到裂缝发育的不均匀性及储层各向异性的影响而存在诸多困难.采用三维数值算法,利用宏观各向异性地层模型,研究不同的裂缝参数条件下双侧向测井响应特征,由此导出一种用于裂缝孔隙度计算的快速算法.分析表明,裂缝的双侧向响应同裂缝孔隙度与孔隙流体电导率之间存在明显的线性关系,裂缝的倾角造成双侧向测井曲线幅度差异的变化;不同倾斜情况下,将双侧向测井响应近似表示为岩石基岩电阻率、裂缝孔隙度、裂缝流体电导率的函数,用于裂缝孔隙度的快速计算.实际资料处理表明,利用双侧向依据该方法确定的裂缝参数同成像测井资料具有良好的对应性.

The estimation of fractures is a key to the evaluation of the fractured carbonate reservoirs. Many obstacles are present for the evaluation of this kind of reservoir because of its heterogeneously-distributed fractures and anisotropies. A three-dimensional numerical algorithm based on a macro-isotropic anisotropic model, a fast fracture-computing method, may simulate the responses of the dual-laterolog in fractured formation. Firstly, the apparent conductivity of dual-laterolog is linearly related to the porosity of fracture and to the conductivity of pore fluid. Secondly, the amplitude difference of the deep and shallow apparent resistivity logs was dependent mainly on the dip angle of the fracture. Thirdly, the response of dual laterolog of formation with dip angle fractures is approximately depicted as a function of bulk resistivity of rock, porosity of fracture and conductivity of fracture fluid, for the rapid computation of the fracture porosity. The research data show that the fracture parameters determined by the dual laterolog coincide well with the formation micro-image log.