中国陆相页岩油完井方式优选的思考与建议

中国页岩油资源以陆相为主,在形成机理、成藏条件、赋存特征等方面与北美海相页岩油存在较大差异,具有油层平面分布范围小、纵向层系多、单层厚度薄、应力分布复杂等特点,利用水平井体积压裂技术开发呈现出油层钻遇率低、钻井周期长、压裂效果差、工程成本高等一系列不适应性,页岩油规模有效开发面临重大挑战,探索一条适合中国陆相页岩油特点的规模有效开发技术路线至关重要。为此,创新提出陆相页岩油直井高效的开发模式,通过直井和大斜度井大井丛平台式钻井,结合直井限流等压裂技术,纵向实现油层改造全覆盖,横向构建层内复杂体积缝网,实现页岩油分层立体开发,大幅提高页岩油开发效果。提出以下建议:①加强页岩油非均质性精细表征、直井多级精细限流压裂、多井协同压裂设计软件、细分层系开发等基础研究和技术攻关;②选取页岩纵向跨距较大、最大单层油层厚度较薄、甜点区存在多套夹隔层遮挡、砂地比适中的页岩油层开展直井全覆盖开发模式现场试验。

Considerations and suggestions on optimizing completion methods of continental shale oil in China

Shale oil resources in China are dominated by continental facies, which are quite different from marine shale oils in North America in terms of formation mechanism, reservoiring conditions, and occurrence characteristics; they are characterized by a small plane distribution range of oil reservoir, multiple vertical series of strata, thin single-layer thickness, and complicated stress distribution. A series of maladjustments embodied as the low ratio of the drilled payzone to the horizontal wellbore, prolonged drilling schedule, inferior fracturing performance and high engineering cost have been observed in the case of development based on the horizontal well volume fracturing technology. The large-scale and effective development of shale oil faces great challenges, and it is very important to explore a technology route suitable for the characteristics of continental shale oil in China. For this reason, this paper innovatively proposes an efficient development model for the vertical wells of continental shale oil. By combing the pad drilling with large well clusters of vertical and highly-deviated wells and fracturing technologies such as limited-entry fracturing, the full vertical coverage of oil payzone stimulation is achieved, and meanwhile complex three-dimensional fracture networks are created horizontally within the payzone. Thus, zonal three-dimensional recovery of shale oil is realized, which greatly improves the development performance of shale oil.This paper put forward the following suggestions:(1)To strengthen the basic researches on and make a technological breakthrough in the fine characterization of heterogeneity of shale oil, multi-stage fine limited entry fracturing for vertical wells, design software for multi-well cooperative fracturing, and development of subdivided stratum. (2)To select the shale reservoirs with large spans, thin maximum single-layer reservoir, multiple sets of interlayers in the sweet spot area and moderate sandstone thickness/formation thickness to carry out field tests for the development mode with full coverage for vertical wells.