Hydraulic-fracturing is an important well-stimulation technique, the fracture closure is inevitable during production. The existing pressure transient analysis models either ignore the length of fracture-closure segment that causes the explained fracture half-length to be smaller, or only use the fracture conductivity to evaluate fracture closure. To fully evaluate fracture closure and provide a reference for oilfield engineers determining whether need measures to improve the well performance, meanwhile considering the non-planar asymmetrical fracture is common met in low-permeability reservoirs, this paper proposes to use two parameters (flowrate proportion and conductivity of fracture-closure segment) to comprehensively evaluate fracture closure, and hence develops double-segment non-planar asymmetrical fracture model (DPAFM). Planar asymmetrical fracture model is simplified case of proposed model. The semi-analytical solution is obtained by using finite difference method (FDM) and Gonzalez-Chavez and Cinco-Ley (2006) model is used to verify the solution. The results of this work show that (a) The example of actual well simulation proves the model is more suitable for the actual field data, and the model established is better matched than the saphir software; (b) The proposed model can obtain production proportion and conductivity of fracture-closure segment to comprehensively evaluate fracture closure; (c) There are four typical flow regimes for the DPAFM, including bilinear flow, interference linear flow, formation linear flow, pseudo-radial flow. The interference linear flow regime with ‘V-shape’ characteristic is unique; (d) Conventional explanation thinks the ‘V-shape’ characteristic represents the secondary fracture developed (e.g., OFFN, TLFN and MOFN). However, this paper gives another possibility that the ‘V-shape’ reflects fracture closure.

The findings of this study can help for better understanding of illustrating the practicability of proposed methodology in evaluating the fracture closure and reservoir parameters. This research provides guidance for technicians to formulate the next step to increase production plan and helps the oilfield engineers determine whether take measures to improve the well performance.

水力压裂是一项重要的增产技术，在生产过程中不可避免地要关闭裂缝。现有的压力瞬态分析模型要么忽略裂缝闭合段的长度，否则导致解释的裂缝半长变短，或者仅使用裂缝传导率评估裂缝闭合。为了充分评价裂缝闭合性，为油田工程师确定是否需要采取措施提高油井性能提供参考，同时考虑到非渗透性非平面裂缝在低渗透油藏中很常见，本文提出使用两个参数（流量比和裂缝闭合段的电导率）以全面评估裂缝闭合，从而开发出双段非平面非对称裂缝模型（DPAFM）。平面非对称断裂模型是所提出模型的简化案例。使用有限差分法（FDM）获得半解析解，并使用Gonzalez-Chavez和Cinco-Ley（2006）模型验证该解。这项工作的结果表明：（a）实际油井模拟的例子证明该模型更适合实际的现场数据，并且所建立的模型比saphir软件具有更好的匹配性；（b）提出的模型可以获取裂缝闭合段的生产比例和电导率，从而对裂缝闭合进行综合评价；（c）DPAFM有四种典型的流态，包括双线性流，干涉线性流，地层线性流，伪径向流。具有“ V形”特性的干扰线性流态是唯一的；（d）传统解释认为，“ V形”特征代表发生的二次断裂（例如OFFN，TLFN和MOFN）。但是，本文给出了“ V形”反映裂缝闭合的另一种可能性。

这项研究的结果可以帮助更好地理解说明所提出的方法在评估裂缝闭合性和储层参数方面的实用性。该研究为技术人员制定下一步增加生产计划提供了指导，并帮助油田工程师确定是否采取措施改善油井性能。