鄂尔多斯盆地页岩油水平井细切割体积压裂技术

Fracturing technology of stimulated reservoir volume with subdivision cutting for shale oil horizontal wells in Ordos Basin

鄂尔多斯盆地页岩油资源丰富,而受储层物性致密、原始油藏压力系数低和湖相沉积非均质性强等因素影响,常规直井开发单井产量极低。2011年以来针对页岩油Ⅰ与Ⅱ类储层,水平井+分段体积压裂技术攻关试验成功,单井产量突破10 t/d,但仍面临规模开发单井产量递减大、低油价下效益差的问题,资源向储量、储量向产量和产量向效益转化速度极慢。为进一步提高单井产量和采出程度,从水力裂缝扩展规律及裂缝形态综合认识评价入手,瞄准优质储量裂缝最大化控制,综合岩性、物性、含油性和可压性评价,建立了水平段储层品质和工程品质一体化分级评价标准;创新了基于水平段分类的非均匀细切割多簇裂缝设计和缝控体积压裂参数优化方法;利用限流和架桥原理,集成配套了极限分簇射孔、动态暂堵转向等裂缝控制技术提高多簇有效性;采用可溶桥塞压裂工具、低成本滑溜水压裂液和组合粒径石英砂支撑剂,实现细切割体积压裂成本控降。通过研究与实践,形成了页岩油Ⅰ与Ⅱ类储层规模效益开发的长水平井细切割体积压裂技术模式,2017～2018年共实施85口水平井,初期日产油达到16 t以上,12个月累产油达到4 850 t,较前期提高1 120 t,第一年递减率下降15%,预测单井产量可提高近1×104t,盈亏平衡点由63美元/桶下降至42美元/桶。矿场实践证实,采用长水平井+细切割压裂+高强度改造是实现页岩油效益开发的有效技术途径,该技术为其它页岩油资源高效动用和效益开发提供了借鉴。

The Ordos Basin is rich in shale oil resources.But due to factors such as tight reservoir,low primary reservoir pressure coefficient and high heterogeneity of lacustrine sedimentation,the production of early conventional vertical single well is extremely low.Since 2011,the multistage SRV(stimulated reservoir volume) fracturing technology for horizontal wells has been successfully applied to shale oil reservoirs of Type I and II,and the daily production per well has increased to more than 10t/d.However,we still have to face the problems including high decline rate of production,poor benefit under low oil price in large-scale development,and a fairly low transmission efficiency from resource to reserve,then to production,and finally to economical development.With a view to further improving the individual well production and recovery degree,an integrated set of evaluation criteria for horizontal reservoir quality and engineering quality has been established based on the composite evaluation of hydraulic fracture propagation patterns and fracture geometry,and combined with the evaluation of lithology,physical property,oil-bearing property and compressibility,targeting at maximizing the fracture-controlled reserves.The nonhomogeneous multi-cluster fracturing design with subdivision cutting based on the classification of horizontal laterals and the method to optimize the fracture-controlled volume fracturing parameters have been improved.In view of the theory of limited entry and bridging,the fracture-controlled technologies such as limit multi-cluster perforation and dynamic temporary plugging diversion have been integrated to improve the multi-cluster effectiveness.The cost of SRV fracturing with subdivision cutting can be controlled and reduced by applying dissolvable bridge plug fracturing tools,low-cost slick water fracturing fluid and combined particle-size quartz sand proppants.Following multiple researches and practices,the fracturing technology of SRV with subdivision cutting for long horizontal wells has been created and applied to develop shale oil reservoirs of Type Ⅰ and Ⅱ economically.From 2017 to 2018,this technology were put into effect on 85 horizontal wells with the initial oil production per well reaching above 16 t.And their accumulative production was 4 850 t for the first year,which was 1 120 t more year-on-year.While the decline rate fell by 15 % in the first year and the single-well production was predicted to be improved by 10,000 t or so.The Break Even Point (BEP)has declined from $ 60 per barrel to around $ 40.Field practice has proved that the technique of fracturing with subdivision cutting and intensive reformation for long horizontal wells is effective to efficiently develop shale oil,and it is of reference value for improving the efficient mobilization and development of other shale oil resources.