关键词: 评价标准, 页岩油, 水平井, 细切割压裂, 缝控储量, 效益开发, 延长组, 鄂尔多斯盆地

Abstract: 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.

Key words: evaluation criteria, shale oil, horizontal well, fracturing with subdivision cutting, fracture-controlled reserve, efficient development, Yanchang Formation, Ordos Basin