裂缝性致密油藏非稳态窜流规律

Transient cross flow law for fractured tight oil reservoirs

王璐 姚约东 黄山 耿丹丹 刘显东 张羽

 （中国石油大学（北京）石油工程教育部重点实验室，北京 102249）

(MOE key Laboratory of Petroleum Engineering, China University of Petroleum, Beijing 102249, China)

 对裂缝性油藏渗流过程中基质-裂缝间窜流规律的研究发现，其形状因子是随着时间发生变化的。裂缝性致密油藏传统模型通常将形状因子考虑为常数，无法准确描述双重介质油藏的渗流规律，因此，文中考虑致密油藏应力敏感特征，引入与压力有关的变渗透率系数，建立了裂缝性致密油藏不稳定渗流方程。综合运用分离变量法和幂级数法对该模型进行求解，得出时变形状因子表达式。将推导的时变形状因子应用到典型双重介质模型中，计算结果表明，运用所推导的时变形状因子的预测结果和精细网格模型一致，较准确地反映了裂缝性致密油藏基质-裂缝系统间窜流规律，简化了基质-裂缝系统间窜流过程的定量数学模拟，为类似油藏进行试井分析和产能评价提供了更准确的理论依据。

 Based on the study of the cross flow law between matrix and fracture in seepage process, it is found that the shape factor varies with time. However, conventional models for fractured tight oil reservoirs usually consider the shape factor as a constant value, which can not describe the seepage law of dual medium reservoir precisely. This paper introduces the variable coefficient of apparent permeability related with pressure based on stress sensitivity of the tight oil reservoir, and establishes transient seepage equation. This equation is solved using separation of variables method and power series method synthetically, then the time-dependent shape factor expression is obtained. Finally, the time-dependent shape factor is applied to typical dual medium model. The computed results indicate that the prediction of the model using time-dependent shape factor is consistent with the fine grid model, which validates the accuracy of new shape factor expression in describing the unsteady cross flow law between matrix and fracture systems. This model simplifies quantitative mathematical description of cross flow law between matrix and fracture systems, and provides more accurate theoretical basis for well test analysis and productivity evaluation in the similar reservoirs.

10.6056/dkyqt201603012