川西致密砂岩气藏近井带复合污染治理技术研究

针对川西致密砂岩气藏近井带储层污染的问题，首先，开展了污染物特征及组分全分析，明确了川西致密砂岩气藏近井带主要的污染类型；其次，研发了多功能复合解堵剂，开展了新药剂物理特性、溶垢能力、破乳降黏、岩芯驱替等评价测试；再次，建立了压裂井近井带污染模型，提出了“大液量注入、液氮强顶替、放喷助排”的深度净化工艺；最后，在新场气田、中江气田及洛带气田10口井进行推广应用。结果表明，新工艺措施有效率90%，增产天然气1 923$\times$10$^4$m$^3$，取得了明显的经济效益。结果表明：（1）川西致密砂岩气藏近井带污染为液锁、起泡剂乳化、压裂液伤害、结垢结晶的复合型伤害；（2）多功能复合型解堵剂具有溶解无机垢、破乳降黏及解水锁等多项功能，驱替污染岩芯后渗透率提升1.74$\sim$2.40倍；（3）“大液量注入、液氮强顶替、放喷助排”的深度净化工艺，能够提高净化剂在致密储层的穿透深度，提高污染物返排效率，在同类气藏中具有推广价值。

A Study on Compound Pollution Control Technology Immediate Vicinity of Wellbore of Tight Gas Reservoir in Western Sichuan

Aiming at the problem of reservoir pollution in the near well zone of tight gas reservoir in Western Sichuan, the characteristics and components of pollutants are analyzed, and the main pollution types in the near well zone of tight sandstone gas reservoir in Western Sichuan are defined. Secondly, a multi-functional composite plugging removal agent was developed, and the evaluation tests of the physical properties, scale dissolution ability, demulsification and viscosity reduction, core displacement and so on of the new agent were carried out. Thirdly, the near well zone pollution model of fractured wells is established, and the deep purification process of "large liquid injection, strong liquid nitrogen displacement and blowout assistance" is put forward. Finally, it is popularized in Luokou Gas Field and Zhongjiang Gas Field. The results show that the efficiency of the new process measures is 90% and the natural gas production is increased by 1 923$\times$10$^4$ m$^3$, which has achieved obvious economic benefits. The conclusions are as follows:(1) the near well zone pollution of tight sandstone gas reservoir in Western Sichuan is the compound damage of liquid locking, foaming agent emulsification, fracturing fluid damage and scaling crystallization; (2) the multi-functional composite plugging remover has many functions, such as dissolving inorganic scale, breaking emulsion and reducing viscosity, and removing water lock. After displacing the polluted core, the permeability can be increased by 1.74$\sim$2.4 times; (3) the deep purification process of "large liquid injection, strong displacement of liquid nitrogen and blowout assistance" can improve the penetration depth of purification agent in tight reservoir and improve the pollutant flowback efficiency. It has popularization value in similar gas reservoirs.