非常规油气藏不规则复杂裂缝表征方法

Characterization of irregular complex fractures in unconventional oil and gas reservoirs

何佑伟 谢义翔 乔宇 陈玉林 汤勇

HE Youwei XIE Yixiang QIAO Yu CHEN Yulin TANG Yong

西南石油大学 油气藏地质及开发工程全国重点实验室, 成都 610500

State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China

非常规油气资源储量大，开发难度高。储层压裂改造是非常规油气资源开发的关键技术手段。天然裂缝和压裂裂缝具有不规则性和复杂性。针对现有裂缝表征方法难以准确刻画裂缝真实形状和宽度变化等不规则特性这一问题，提出了基于非结构PEBI网格的不规则复杂裂缝表征方法。首先，建立基于PEBI网格的天然裂缝表征流程，实现对任意区域或限定区域天然裂缝的准确表征；其次，建立基于Delaunay三角形网格和PEBI网格的压裂裂缝表征及优化方法，分析网格尺寸及优化次数对裂缝表征精度的影响；第三，建立基于非结构网格的非平面裂缝表征方法，实现对弯曲裂缝的刻画和表征，裂缝形态和分布与实际情况更相符；第四，提出非均匀裂缝宽度表征方法，实现对变宽度即同一条裂缝宽度和导流能力不均匀分布裂缝的精细表征；第五，在全区域和限定区域内，实现耦合不规则压裂裂缝和不规则天然裂缝的复杂缝网表征。针对大规模天然裂缝与压裂裂缝相交、裂缝宽度非均匀分布、非平面裂缝等复杂条件下的裂缝网络表征，通过调整网格优化次数，能够提高缝网表征质量。利用PEBI网格能够灵活准确逼近裂缝复杂边界条件的优势，实现快速、准确地显示处理大量不规则天然裂缝和压裂裂缝。形成的不规则复杂裂缝表征方法，有助于提高非常规油气藏裂缝网络的表征精度和数值模拟计算准确性。

Unconventional oil and gas resources have large reserves and are difficult to develop. Reservoir fracturing is a key technical means for the development of unconventional oil and gas resources. Natural fractures and induced fractures are irregular and complex. To address the issue that existing fracture characterization methods cannot accurately depict the true shapes and width variations of fractures, a method based on unstructured PEBI grids for characterizing irregular and complex fractures was proposed. First, a natural fracture characterization process based on PEBI grids was established, allowing for accurate characterization of natural fractures in any region or a specified area. Second, a characterization and optimization method for induced fractures based on Delaunay triangulation and PEBI grids was developed, analyzing the impact of grid size and optimization iterations on fracture characterization accuracy. Third, a method for characterizing non-planar fractures using unstructured grids was established, enabling the depiction of curved fractures, making the fracture morphology and distribution more consistent with actual conditions. Fourth, a method for characterizing non-uniform fracture width was proposed, achieving fine characterization of fractures with non-uniform distribution of width and conductivity along the same fracture. Fifth, a complex fracture network characterization method coupling irregular induced fractures and irregular natural fractures in the whole area and specified regions was realized. For fracture network characterization under complex conditions such as large-scale intersections of natural and induced fractures, non-uniform fracture width distribution, and non-planar frac- tures, adjusting the number of grid optimization iterations could improve the quality of the fracture network characterization. Utilizing the advantage of PEBI grids to flexibly and accurately approximate complex fracture boundary conditions, this method enabled the rapid and accurate handling of a large number of irregular natural and induced fractures. The developed method for characterizing irregular and complex fractures helps improve the accuracy of fracture network characterization and numerical simulation calculations in unconventional oil and gas reservoirs.

国家自然科学基金委员会青年科学基金“致密气藏多井动态缝网数值试井理论研究”(52004238)资助。

https://doi.org/10.11781/sysydz202404748