泡沫酸化工艺技术在页岩井中的应用

The application of foam acidizing technology in shale wells

川东南区块页岩储层徽裂缝发育,黏土矿物丰富,潜在较强应力敏感性。PY3井由于外源入井液体互相发生物理化学反应,严重影响了储层渗透性。针对该区块地层压力系数低、黏土矿物含量高、井筒污染严重等井况,提出了氮气泡沫酸化技术进行解堵。前置酸采用盐酸体系,溶解地层灰质组分,主体酸采用土酸体系有效解除近井筒污染堵塞,同时加快残酸液的返排效率,酸液体系中加入密度0.5~0.7 g/cm^3起泡剂。经泡沫酸化作业后,该井产能由6 000 m^3/d上升至16 800 m^3/d,从电潜泵排采转为自喷生产,该技术对川东南区块污染的页岩储层改造效果明显,对国内页岩储层解堵具有参考价值。

The shale reservoir in southeast Sichuan basin has the characteristics of microfracture development, rich clay minerals and strong potentially stress sensitivity. Because the allogenes enter the well PY3, physical and chemical reaction takes place, which seriously affect reservoir permeability. Aiming at low formation pressure coefficient, high content of clay minerals and seri- ous wellbore damage, nitrogen foam acidizing technology is put forward for broken down. The lead acid adopts hydrochloric acid system, and the dissolved formation calcareous components and main acid adopts mud acid system, which can effectively remove near wellbore pollution and jam, and speed up the efficiency of the residual acid flowback at the same time. Foaming agent is add- ed to acid system, whose density is 0.5 - 0.7 g/cm3. By adopting foam acidizing treatment, the productivity rises from 6 000 m3/d to 16 800 m3/d, and electrical submersible pump production turns into flow production. The results have obvious reform effects on polluted shale reservoir in southeast Sichuan basin and provide references for break down of domestic shale reservoir.