Title

Experiment of dynamic closure behavior of discontinuous sanding fracture

作者

何昀宾何封尹丛彬

单位

中国石油川庆钻探工程有限公司井下作业公司，四川成都 610000 中国石油集团油田技术服务有限公司，北京 100007

Organization

CCDC Downhole Service Company, CNPC, Chengdu 610000, China Oilfield Technology Service Company, Ltd., CNPC, Beijing 100007, China

摘要

采用脉冲式高频段塞压裂进行储层改造时，缝内支撑剂砂团在压后裂缝动态闭合过程中能否保持非连续有效分散，是工艺成功的关键因素。通过研制裂缝动态闭合过程模拟评价装置，对缝内压裂液滤失条件下的裂缝动态闭合过程开展了实验研究，分析了累计滤失量、缝宽及缝内流体压力等参数随裂缝动态闭合时间变化的情况。实验结果表明：压后裂缝动态闭合过程分缝内流体承压、承压过渡、支撑剂砂团承压3个阶段，且各阶段主控影响因素不同，分别受流体滤失、支撑剂砂团受压形变及局部嵌入破碎等因素控制；闭合过程各阶段缝宽变化及累计滤失量随闭合时间的增加，呈现出前期平缓、中期激增、后期平缓的阶段特征；同时结合非连续铺砂裂缝缝内支撑剂的分布状态，定义了缝内孔道率和缝宽持有率，可作为数学表征的参考值，能够精确描述非连续铺砂裂缝缝内孔道特征及动态缝宽特征。利用实验结果修正了滤失系数、支撑剂砂团高度及裂缝形变量等参数计算模型，可用于指导压裂参数优化设计以获取最优缝内孔道率。

Abstract

Whether the proppant group could maintain the state of effective discontinuous dispersion during the process of dynamic closure of fracture is the key factor to the success of discontinuous sanding fracture in unconventional reservoir. The prototype devices simulating fracture dynamic closing process were developed to perform corresponding experimental tests which consider the leak off of fracturing fluid. The variation of accumulative fluid loss amount, fracture width and fluid pressure in the fracture with the dynamic fracture closure time were analyzed. The experiment results show that the dynamic fracture closure process can be divided into three stages, initial stage of fluid pressurization in fracture, middle stage of transition, later stage of proppant group pressurization, which are respectively controlled by fluid leak off, deformation of compressed proppant group, partial embedding and crush. Meanwhile accumulative fluid loss amount and fracture width present a sharply increasing middle stage and a steady trend in the initial and later stage with closure time. Combined with the distribution state of proppant in non-continuous sanding fracture, channel rate within fracture and holding rate of fracture width were defined to characterize the feature of channel and dynamic fracture width in discontinuous sanding fracture precisely in the form of mathematical formula. Based on the experiment results, the mathematical model parameters such as leak off coefficient of fracturing fluid, proppant group height, deformation of fracture were corrected to optimize the fracturing and acquire the optimal channel rate within fracture.

关键词：

非连续铺砂; 动态闭合; 阶段式承压; 缝内孔道率; 缝宽持有率; 支撑剂砂团高度; 裂缝形变

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Keywords:

discontinuous sanding; dynamic closure behavior; episodic pressurization; channel rate within fracture; holding rate of fracture width; proppant group height; fracture deformation

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基金项目

DOI

10.6056/dkyqt201803027

非连续铺砂裂缝动态闭合实验