川东南茅口组泥灰岩复合酸压技术

Study on Compound Fracturing of Maokou Formation Marl in Southeast Sichuan

针对川东南区块茅口组基质储层埋藏浅,敏感性矿物含量高且储层低孔低渗,采用了多簇限流射孔+降阻水加砂+清洁酸复合酸压工艺,扩大了储层改造体积,提升了地层裂缝导流能力。结合岩石力学参数,采用密切割射孔增加人工裂缝密度,通过增大簇间诱导应力优化了裂缝间距为10~15 m,当单段液量为1600~1800 m^(3),降阻水与清洁酸配比为6∶4时,可实现裂缝壁面的刻蚀,提升裂缝导流能力,强化渗流通道。研选了耐酸、高降阻率的清洁稠化剂,形成的清洁酸体系降阻率达63.5%,有效地降低了酸压施工摩阻,有利于大排量酸压施工,在闭合压力为30 MPa下的酸蚀裂缝导流能力达14.9μm^(2)·cm,且清洁酸与岩石反应前后的岩石表面结构特征基本一致,酸蚀蚓孔及裂缝表面无附着物,对储层伤害较小。并在FM1HF井成功应用,取得了Φ12 mm油嘴放喷条件下,日产4.12×10^(4)m^(3)工业气流,首次在川东南地区茅口组获得稳定工业气流,验证了该项技术在泥灰岩气藏中的应用可行性,对国内类似储层改造提供良好的借鉴和推广应用价值。

The Maokou formation in the southeast Sichuan is shallow buried.It is rich in sensitive minerals and has low porosity and low permeability.In reservoir stimulation operations,multi-cluster limited entry perforation,friction-reduced water with sand and fracturing with compound clear acids techniques were used to increase the volume of reservoir formations to be stimulated and to improve the conductivity of formation fractures.Based on the rock mechanics parameters,the artificial fracture density was increased using intensive cut perforation technique,the spacing between two fractures was optimized to 10–15 m by increasing the inducing force.When the fluid volume in a single section was 1,600–1,800 m 3,and the ratio of friction-reduced water to clear acid was 6:4,the surfaces of the fractures can be itched away,thereby increasing the conductivity of the fractures and strengthening the seepage channels.A clear thickening agent with acid tolerance and high friction-reducing capacity was selected and used to formulate a clear acid with percent friction reduction of 63.5%.With this acid,the friction of acid fracturing operation was effectively reduced,which is beneficial to high flow rate acid fracturing job.At closure pressure of 30 MPa,the conductivity of the acid-itched fractures reached 14.9μm^(2)∙cm.The rocks,after being itched by the clear acid,had basically unform surface structures.The acid-itched wormholes and the surfaces of the factures are free of any attachment,which is less damaging to the reservoirs.This acid was used in the fracturing of the well FM1HF.Using aΦ12 mm choke,the daily gas production rate of the well reached 4.12×10^(4) m ^(3),a stable industrial gas production rate first obtained from the Maokou formation in southeast Sichuan,which proves the feasibility of this fracturing technology in stimulating marl reservoirs.This technology will provide a good reference and popularization value for stimulating similar reservoirs in China.