压裂压力递减分析三维模型与应用

3-D MODEL OF ANALYZING FRAC PRESSURE DECLINE AND ITS APPLICATION

随着油气藏压裂技术的发展 ,压后评估技术越来越受到广泛重视。压裂压力递减资料分析是评价压裂裂缝形态、获取压裂设计重要参数的常用手段。对于压裂规模较大、施工排量较高的压裂井或上、下隔层较为薄弱的压裂井 ,采用二维或拟三维模型分析结果与实际情况偏差很大。文章推导建立了一套用于分析压裂压力递减资料的三维模型 ,模型综合考虑了压裂液续流对裂缝继续延伸的影响 ,提出了以压力平方差获取拟合压力 ,应用该模型和此拟合压力可以有效分析计算压后裂缝长度、宽度、高度、闭合时间、停泵后裂缝延伸时间、延伸长度、施工结束时压裂液效率、压裂液滤失系数和地层应力强度因子等参数。

Along with the development in reservoir fracturing techniques,more and more attention has been attached to the post fracturing assessment techniques.The analysis of frac pressure decline data is a common means of evaluating fracure patterns and of obtaining the important parameters for fracturing design.For these fractured wells with a large fracturing scale and high pumping rate or the ones with thin barrier beds at top and bottom,the result analyzed by use of 2 D or pseudo 3 D model was far diviated from the objective reality.A 3 D model applying to studying the frac pressure decline data is derived and set up in the paper.Because of considering comprehensively the influence of frac fluid afterflow on fracture propagation in the model,it is proposed that the matched pressure can be obtained from pressure square,difference.These parameters as the lengths,widths,heights and seal times of the post fracturing fractures,the extention times and lengths of the fractures after termination of pumping,the filtration efficiency and factor of the frac fluid by the end of operation,and the formation stress strength,etc.,can be effectively analyzed and calculated by applying the model and this matched pressure.The calculation results indicate that the 3 D model and mathematical fitting method are of high suitability and reliability.