地层测试中不同探针污染驱替效率研究

Research on the Pollution Elimination Efficiency of Different Probes in Formation Testing

钻井过程中钻井液和固体碎屑混合而成的泥浆滤液渗透进入地层,对原始地层液体造成了不可避免的污染。取样探针的形状和布局对于在短时间内获取低污染样品有着十分重要的影响。采用合理简化,针对污染侵入和取样2个阶段建立了相关联的一系列模型,对不同类型探针和不同地层条件下的抽取过程用ECLIPSE软件进行数值模拟。通过对各个实例模拟结果的分析比较,为探针的设计和选择提供了依据。采用扩大探针口尺寸、在垂直方向上拉长探针、增加同一组件上的探针口数量和同一地层测试器(MDT)上携带更多探针组件的方式都增加了探针口面积,从而缩短达标作业时间。对于竖向与水平向渗透率比较小的地层环境,在探针口面积相同的情况下,竖直方向尺度较小的探针能更有效率地获得达标样品。

During drilling,the miscible filtrate,a mixture of drilling fluid,mud and rock debris,would inevitably pollute the original reservoir area with the formation of a compact mudcake layer.When acquiring fluid samples,it takes time to eliminate the portion of the filtrate and gets pure sample with a MDT probe and the time is closely linked with the shape and arrangement of the probe.In this work,it is required to construct proper model to study several probe factors' influence on wireline formation testing with ECLIPSE based on reasonable assumptions.The study of the different probe cases serves as important reference for probe design.Some valuable conclusions are obtained.The probe could be designed with larger area to achieve the shorter operation time by increasing probe diameter,stretching probe vertically,and adding drains to one packer.Further more,the ratio of permeability in vertical and horizontal directions can be reference to select probe.Namely low height probe should be used in the low ratio condition while high height probe should be selected in the high ratio condition to reach a highly efficient sample collection.