陆相盆地页岩油储层天然裂缝识别与建模——以苏北盆地溱潼凹陷QY4井周为例

Natural fracture identification and modeling for shale oil reservoirs in continental basins: a case study from vicinity of well QY4 in Qintong Sag, Subei Basin

  • 摘要: 我国蕴含丰富的页岩油资源,但陆相页岩储层非均质性强、裂缝发育复杂导致勘探开发进展缓慢。以苏北盆地溱潼凹陷QY4井区阜二段页岩油储层为研究对象,通过裂缝识别技术,构建高精度三维离散裂缝网络模型,为甜点段优选和高效开发提供支撑。利用岩心观察、薄片分析、扫描电镜等手段,系统表征裂缝类型、产状及分布规律。基于常规测井数据,通过对比裂缝与非裂缝段响应特征,构建新型裂缝识别参数nfra,并引入分形理论对测井曲线进行优化处理,以提升识别敏感度和准确性。结合电成像测井资料,定量计算单井裂缝发育强度,并在地质构造等条件和裂缝发育强度的约束下,建立三维裂缝强度模型和离散裂缝网络模型,确保模型与实际地质条件一致。研究结果表明:区内主要发育北东向和北西向两组高角度剪切缝,其中北东向为优势走向,反映了多期构造应力场的影响。改进的nfra参数经分形处理后,裂缝识别能力显著增强,在QY4井阜二段成功识别出8处裂缝发育段,与岩心、成像测井等实测数据吻合度高。裂缝发育强度分析显示,北东向强度为0~0.5 m,北西向为0~0.18 m,体现出明显的各向异性特征。所建三维模型能够精细刻画裂缝空间展布,符合地质认识,为压裂设计和井位部署提供了可靠依据。该综合方法有效解决了陆相页岩油储层裂缝识别精度低、建模难的问题,提升了勘探开发效率,对类似盆地页岩油资源评价与开发提供参考。

     

    Abstract: China possesses abundant shale oil resources, but exploration and development have progressed slowly due to the strong heterogeneity and complex fracture development in continental shale reservoirs. In this study, the shale oil reservoir in the second member of the Funing Formation in the well QY4 area of the Qintong Sag, Subei Basin, was taken as the research object. Through fracture identification technologies, a high-precision three-dimensional discrete fracture network (DFN) model was established to support sweet spot prediction optimization and efficient reservoir development. Through core observation, thin-section analysis, and scanning electron microscopy (SEM), fracture types, occurrence, and distribution patterns were systematically characterized. Based on conventional logging data, a novel fracture identification parameter (nfra) was constructed by comparing the response characteristics of fractured and non-fractured intervals. Fractal theory was introduced to optimize the logging curves, thereby enhancing identification sensitivity and accuracy. Combined with electrical imaging logging data, the fracture intensity of individual wells was quantitatively calculated. Under the constraints of geological structure and fracture intensity, a three-dimensional fracture intensity model and a DFN model were established to ensure consistency with actual geological conditions. The results indicated that the study area mainly developed NE-trending and NW-trending high-angle shear fractures, with NE orientation being the dominant trend, reflecting the influence of multi-stage tectonic stress fields. The improved nfra parameter after fractal processing significantly enhanced fracture identification capability, successfully identifying eight fracture-developed intervals in the second member of the Funing Formation in well QY4, with high consistency with core and imaging logging data. Fracture intensity analysis showed that the NE-trending fractures had an intensity of 0-0.5 m, and the NW-trending ranged 0~0.18 m, demonstrating distinct anisotropic characteristics. The established 3D models accurately characterize the spatial distribution of fractures, align with geological understanding, and provide a reliable basis for fracturing design and well location deployment. This integrated approach effectively addresses the problems of low accuracy in fracture identification and difficulties in modeling for continental shale oil reservoirs, thereby improving exploration and development efficiency and providing a reference for shale oil resource evaluation and development in similar basins.

     

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