盐间页岩油体积压裂技术研究与实践

盐间页岩油储层存在上下盐岩蠕变特征不清,压裂过程中易受上下塑性盐岩干扰;储层岩性组分多、敏感性复杂、孔隙连通性差,储层中可溶盐的溶解规律不清楚等特点。储层特点对体积压裂技术提出了较高要求,为寻求盐间页岩油高效开发手段,在潜江凹陷古近系盐间页岩油油藏的BYY1HF井试验采用CO₂增能复合压裂、耐酸压裂液加砂技术、密切割强加砂压裂技术和投球暂堵技术。CO₂增能复合压裂技术具有增加返排能力、改善基质孔渗性、穿透性强、返排率高的优势;耐酸压裂液体系在酸性环境(pH值为2～6)下性能稳定,携砂能力强,对储层伤害低;密切割强加砂压裂技术能克服“簇集效应”,促进各簇裂缝均匀开启及延伸,提高体积压裂效果。施工效果表明,该技术体系具有增强返排能力、改善储层孔渗性、提高岩石起裂能力及裂缝复杂度等优势,一定程度上提升了基质供油能力。该压裂技术试验对盐间页岩油大规模压裂改造具有较好的借鉴意义。

Research and Practice of SRV Fracturing Technology for Inter-salt Shale Oil

The inter-salt shale oil reservoirs are characterized by unclear creep characteristics of the upper and lower salt rocks, susceptibility to interference with the upper and lower plastic rocks during fracturing, multiple lithological components, complex sensitivity, poor pore connectivity, and unclear dissolution pattern of soluble salts. There are more stringent requirements for SRV fracturing due to reservoir characteristics. For efficient development of inter-salt shale oil, Well BYY1HF in Paleogene inter-salt shale oil reservoir, Qianjiang Sag was tested with such technologies as CO₂ enhanced composite fracturing, acid-resistant fracturing fluid plus sanding, dense cutting plus forced-sanding fracturing, and temporary plugging fracturing with ball casting. CO₂ enhanced composite fracturing had the advantages of increased flowback capacity, improved matrix porosity and permeability, strong penetration, and high flowback rate. The acid-resistant fracturing fluid system could maintain stable performance, strong sand carrying capacity and low damage to reservoirs in acidic environment (pH 2-6). The dense cutting plus forced-sanding fracturing technology could eliminate the "agglomeration effect", promote the uniform opening and propagation of each cluster of fractures, and improve the SRV fracturing effect. The construction results showed that the technical system was advantaged by enhancing the flowback capacity, improving the porosity and permeability of the reservoir, promoting the rock capacity of fracturing initiation, fracture complexity, etc., and improving the oil supply capacity of the matrix to a certain extent. The test of fracturing technology is of great significance in reference for the large-scale fracturing transformation of inter-salt shale oil.