CO2 Regional Enhanced Volumetric Fracturing Technology for Shale Oil Horizontal Wells in Ordos Basin
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摘要:
针对鄂尔多斯盆地页岩油储层压力低、缝网复杂程度低和黄土塬水资源缺乏等问题,以该盆地庆城油田页岩油为研究对象,进行了滑溜水和CO2压裂物理模拟试验,利用高能CT监测了CO2压裂裂缝扩展规律,分析了CO2压裂形成复杂裂缝的可行性;利用油藏数值模拟方法,优化了CO2注入关键参数,形成了适合庆城油田页岩油的CO2区域增能体积压裂技术。研究表明:前置CO2压裂可提高长7段页岩油储层裂缝复杂程度,裂缝沿层理弱面扩展并纵向穿层形成缝网;增能理念应由单井段间交替增能向平台整体注入实现井间、段间协同一体增能转变,单井采用全井段注入增能模式,可实现缝控区域全覆盖。庆城油田某平台进行了页岩油CO2区域增能体积压裂试验,与采用常规体积压裂技术的邻井相比,3口试验水平井平均压力保持程度提高1.5倍,单井平均初期产油量提高28.6%。研究和现场试验结果表明,CO2区域增能体积压裂能提高裂缝复杂程度,增加区域地层能量,提高单井产能,可为鄂尔多斯盆地页岩油开发提供技术支持。
Abstract:In response to the problems of low pressure, high fluid flow resistance, low energy enhancement efficiency of slick water fracturing, and low complexity of fracture networks in shale oil reservoirs in Ordos Basin, a physical simulation experiment of slick water and CO2 fracturing was conducted in the Qingcheng shale oil block of Ordos Basin. The expansion law of CO2 fracturing fractures was monitored using high-energy computerized tomography (CT) scanning, and the feasibility of CO2 fracturing to form complex fractures was analyzed. By using reservoir numerical simulation methods, the key parameters of CO2 injection were optimized, forming a CO2 regional energy enhancement and volumetric fracturing technology suitable for the Qingcheng shale oil block. Research showed that pre-CO2 fracturing could increase the complexity of fractures in Chang 7 shale oil, with fractures spreading along weak bedding planes and forming a fracture network through the layers vertically. The concept of energy enhancement should be achieved by injecting energy into the platform as a whole instead of alternating energy enhancement between single well sections and injecting energy into the platform as a whole, achieving a transformation of integrated energy enhancement between wells and sections. The single well that adopted the full well section injection energy enhancement mode could achieve full coverage of the fracture control area. Based on a platform in the Qingcheng shale oil block, a shale oil CO2 regional energy enhancement and volumetric fracturing test was conducted. Compared with conventional volumetric fracturing adjacent wells, the average pressure retention of the three test horizontal wells increased by 1.5 times, and the average initial oil production of a single well increased by 28.6%. Research and on-site experiments showed that CO2 regional energy enhancement and volumetric fracturing could increase the complexity of fractures, enhance regional formation energy, and improve single well productivity, providing technical support for shale oil development in Ordos Basin.
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表 1 庆城油田页岩油与国内外典型页岩油特征参数的对比
Table 1 Characteristic parameter comparison of shale oil in Ordos Basin and other typical shale oil in China and abroad
特征参数 庆城油田 国内 国外 准噶尔盆地芦草沟组 三塘湖盆地条湖组 松辽盆地白垩系 北美二叠盆地 沉积环境 湖相 湖相 湖相 湖相 浅海相 埋深/m 1 600~2 200 2 700~3 900 2 000~2 800 1 700~2 200 2 134~2 895 油层厚度/m 5~15 10~13 5~20 10~30 400~600 孔隙度,% 6.0~11.0 8.0~14.6 8.0~18.0 5.0~18.0 8.0~12.0 渗透率/mD 0.11~0.14 0.010~0.012 0.1~0.5 0.02~0.50 0.01~1.00 含油饱和度,% 67.7~72.4 78.0~80.0 55.0~76.5 48.0~55.0 75.0~88.0 油气比/(m3·t−1) 75~122 18~22 50~140 原油黏度/(mPa·s) 1.2~2.4 11.7~21.5 58.0~83.0 4.0~8.0 0.15~0.53 压力系数 0.77~0.84 1.20~1.60 0.90 1.10~1.32 1.05~1.50 水平应力差/MPa 4~6 5~9 1~5 3~6 1~3 脆性指数,% 35~45 50~51 31~54 45~60 -
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