鄂尔多斯盆地页岩油水平井扇形井网地质工程一体化开发实践

Geology and engineering integrated development practice of fan well pattern shale oil horizontal wells in Ordos Basin

多平台大范围规模布井是非常规资源高效动用的关键。由于黄土塬地貌特征和林缘区、水源区的限制,鄂尔多斯盆地庆城三叠系延长组长7页岩油的布井模式存在局限性。为进一步实现平台动用储量最大化,创新提出扇形井网布井方式。文章采用地质工程一体化方法,探究扇形井网不同布井方位对裂缝扩展和产能的影响,对扇形井网开展相应的裂缝间距和压裂次序优化,同时结合实际案例分析扇形井网下的压裂特征并对产能效果进行对比。研究结果表明,斜交水平井(水平段井轨迹与最小水平主应力夹角大于或等于15°)与常规水平井(水平段井轨迹与最小水平主应力夹角小于15°)相比,预测产能随偏转角度(布井方向与最小水平主应力方向的夹角)的增大而减小,当偏转角度大于45°时,产能差异进一步放大,同时模拟结果下的经济评价情况表明,当偏转角度为90°时,经济可行性最差,不建议布井;扇形井网模式下通过扩大裂缝间距和采用“从外到内”的压裂次序可以提高预测产能;斜交水平井裂缝首先沿垂直井筒方向延伸且震级较大,但在远场尺度下最大水平主应力方向仍然是裂缝扩展的主导因素;与常规水平井相比,斜交水平井储层改造体积小,但裂缝复杂程度高,缝网改造更充分;对比实际投产效果来看,斜交水平井累计产量低于常规水平井,但液面高度高且目前日产油量接近,存在一定开发潜力。

Multi-platform and large-area well deployment is the key to high-efficiency unconventional resource utilization.Due to the geomorphic characteristics of loess tableland,as well as forest edge and water source areas in Qingcheng area in Ordos Basin,well placement for the development of the Triassic Chang 7 member shale oil is restricted.As a result,an innovative fan well pattern is proposed to further maximize the producing reserves of the platform.Based on the geology and engineering integrated method,the influence of various azimuths of fan well pattern on fracture propagation and production capacity is analyzed,and the fracture spacing and fracturing sequence are optimized of fan well pattern.Meanwhile,the practical cases are combined to analyze fracturing characteristics and compare production results of various fan well patterns.The study results show that,compared with conventional horizontal wells(the angle between the horizontal trajectory and the minimum horizontal principal stress is less than 15°),the predicted production capacity of oblique horizontal wells(the angle between the horizontal trajectory and the minimum horizontal principal stress is greater than or equal to 15°)decreases with the increasing deflection angle(the angle between the well placement and the minimum horizontal principal stress).When the deflection angle is greater than 45°,the difference in production capacity is further expanded with the increase of the deflection angle.In addition,the economic evaluation results of various simulation scenarios show that the economic feasibility is the worst when the deflection angle is 90°,and well deployment is not recommended.The predicted production capacity can be improved by increasing fracture spacing and adopting the“outside-in”fracturing sequence of fan well pattern.The fractures in oblique horizontal well first propagate along the vertical wellbore direction with a large microseismic magnitude,but the direction of the maximum horizontal principal stress is still the dominant factor for fracture propagation at a far-field scale.Compared with conventional horizontal well,the oblique horizontal well is characterized by a smaller stimulated reservoir volume,but more complex fractures,and more reconstructed fracture network.In terms of the actual production results,the cumulative production of oblique horizontal wells is lower than that of conventional horizontal wells,but the liquid level is higher and the daily oil production is close at present,indicating a promising development potential.