井旁裂缝的双侧向测井物理模拟及特征分析

摘要

为深入认识裂缝性地层的双侧向测井响应特征, 指导裂缝识别及裂缝参数表征, 基于数值仿真开展了井旁裂缝的缩小比例物理模拟.在物理模拟平台构建的基础上, 用不同浓度的氯化钠溶液模拟基岩, 用不同宽度的镀锌板来模拟高导裂缝, 实现测量过程的可视化.通过实验分析井旁裂缝的规模、发育位置和产状等因素对深、浅侧向电阻率的影响.研究表明:在仪器有效探测范围内, 垂直缝延伸长度对深浅侧向电阻率的数值影响较小;裂缝离井壁越远, 双侧向电阻率明显增大, 但深浅侧向电阻率值的降低幅度不同;随着裂缝倾角增大, 深侧向电阻率增大, 浅侧向电阻率无明显变化, 深浅侧向电阻率从负幅度差向正幅度差过渡, 但临界角的观测十分困难, 应用双侧向测井判断地层产状时, 需特别注意其适用条件.%We developed a scaling-down proportional physical simulation on the near borehole fractures based on the numerical results to investigate the response characteristics of dual lateral log in fractured reservoirs, aiming to improve the precision of the fracture identification and parameter characterization.Based on the physical simulation platform, the bedrock was simulated with sodium chloride solution of different concentrations, and the high conductive fractures were simulated with galvanized sheets of different widths, to make the measurement process visible.The effects of the scales, fracture location, and occurrence of near borehole fractures on dual lateral resistivity are analyzed via comparative experiments.The results show that the fracture scale has little effect on the value of dual lateral resistivity, while has a direct relationship with the amplitude of dual lateral resistivity in the effective detection range of the instrument;the farther away from the borehole, the higher of the dual lateral resistivity.But the reduction extents of shallow and deep resistivity are different.The deep lateral resistivity is positively correlated with the fracture dip, but the shallow lateral resistivity does not change obviously.With the increase of the fracture dip, the difference between the deep and the shallow lateral resistivity transits from the negative value to the positive value, it is hard to observe the critical dip.The phenomenon indicates that it is necessary to pay special attention to the applicable conditions of the dual lateral log to judge the formation occurrence.