瓜尔胶压裂返排液回用技术在气井中的应用

Application of recycling technology for flow-back guar fracturing fluid in gas field

储层改造规模的加大对水资源的需求逐渐增加,压裂返排液的重复利用越来越受到关注。根据硼酸根离子的水解、络合反应机理,加入配位体PWT-2调节瓜尓胶压裂液返排液处理水(简称处理水)中硼酸根离子的有效含量,保持处理水中瓜尓胶压裂液的基液黏度及交联延迟时间与清水配置的一致,基液黏度约28~32 m Pa·s,交联延迟时间为75~150 s。通过加入缓冲剂HC-J调节瓜尓胶压裂液p H约为10.0,控制体系硼离子的有效浓度,降低多价阳离子的含量;将处理水与现场清水按照体积比2∶1的比例配置瓜尓胶压裂液,提高体系的耐温性能;稀释后配置的瓜尓胶压裂液在110℃剪切120 min,黏度保持250 m Pa·s以上,若加入胶囊破胶剂剪切50 min后黏度可降低至40 m Pa·s以下。

The recycling of flow-back water（ FB-W） of guar fracturing fluid are increasingly attracting more and more attention because the increasing scale of reservoir reformation drives the demand for water to rise gradually.According to the reaction mechanisms of hydrolysis and complexation of borate ion,the effective content of borate ion in the treated flow back water of guar fracturing fluid is adjusted by adding PWT-2 ligand,and the linear gel viscosity and crosslinking delay time of guar fracturing fluid in water being treated shall be kept at the same as that in clean water.The linear gel viscosity shall be around 30 m Pa·s and the crosslinking delay time shall be 75 to 150 s.The pH value of guar fracturing fluid is regulated to about 10 through adding buffer HC-J,which can help to keep the effective concentration of boric ion in system and reduce the content of multivalent cations. The temperature resistance of the system can be improved by configuring guar fracturing fluid with treated water and spot clean water in a volumetric ratio of 2 ∶ 1. The viscosity of dilute guar fracturing fluid configured with treated flow-back water remains above 250 m Pa·s after being sheared at 110℃ for 120 min. If capsule gel-breaker is added,the viscosity can be decreased to 40 m Pa·s after it is sheared for 50 min at the same temperature.