大尺寸套管井多级酸化技术

南苏丹ANANAS区块部分大尺寸套管井采用土酸和桥塞酸化工艺解堵增产，但土酸反应过快，桥塞管柱操作复杂且存在酸液泄漏风险，因此亟需研制大尺寸套管井多级酸化技术。通过设计小截面定活塞、分离进液口与注酸口、选定T型密封圈密封注酸口，研制了新型注酸器；通过酸液缓蚀性能评价、络合性能测试及配伍性试验，优选出一种适用于该区块储层的HV缓速酸液体系。室内试验表明:新型注酸器开启压力高达8 MPa以上，能使?147 mm封隔器稳定坐封；理论上单趟管柱可酸化15段且可用于套管验漏；HV缓速酸液体系缓蚀性能优于常规土酸体系，能够有效络合储层金属离子，抑制二次沉淀产生，与多种添加剂配伍性能良好。该技术可用于大尺寸套管井3段以上酸化增产，采用HV缓速酸体系能有效扩大酸液作用距离，解除近井地带伤害，措施效果显著，建议今后考虑转向酸压，以进一步提高储层改造程度。

Multi-stage acidizing technology of large-size cased well

In the ANANAS Block of the South Sudan, mud acid and bridge plug acidizing technology are adopted in some of the large-size cased wells for blockage removing and stimulation, but the reaction of mud acid is too fast and the bridge string has complicated operation and the risk of acid leak, so it is in urgent need to develop the multi-stage acidizing technology of large-size cased well. A new type of acid injector was developed by designing small-section fixed piston, separating liquid inlet and acid injection port and selecting T-shaped seal ring to seal the acid injection port. In addition, the HV retarded acid system suitable for the reservoirs in the ANANAS Block was selected by means of corrosion inhibition evaluation, complexation testing and compatibility testing. The laboratory tests show that the opening force of the new type of acid injector is up to 8 MPa, which can realize the stable setting of ?147 mm packer; one-trip string can theoretically realize acidizing of 15 stages and casing leak detection; HV retarded acid system is superior to the conventional mud acid system in term of corrosion inhibition, can effectively complex with reservoir metal ions to inhibit the generation of secondary deposits, and is well compatible with various additives. This technology can be used for the multi-stage (＞3) acidizing stimulation of large-size cased wells and HV retarded acid system can increase the action distance of acid effectively and remove near well damage, presenting remarkable application effects. It is suggested to take the diverting and acid fracturing into consideration to improve the reservoir stimulation degree further.