可回收再利用的低分子胍胶压裂液技术研究

为解决压裂作业水资源缺乏和返排液难处理的问题,利用pH值控制硼酸盐离解平衡移动原理来改变胍胶压裂液的交联状态,使其在酸性条件下非降解性破胶,胍胶分子结构不被破坏,可实现重复交联。采用生物降解技术,对胍胶进行降解,通过控制降解条件来控制胍胶的降解程度,从而控制胍胶的相对分子质量,制备出了相对分子质量为30×104~50×104、在硼酸盐条件下可交联的低分子胍胶,其水溶液黏度较低,水不溶物质量分数≤4%。并以某固体酸为囊芯、在水中可逐渐溶解的某高聚物为囊衣,采用空气悬浮成膜法制备出了一种胶囊破胶剂,在地面条件下显中性,保证胍胶压裂液顺利交联,而在地层温度和压力条件下逐渐释放出固体酸物质对压裂液非降解性破胶。以低分子胍胶为稠化剂,包裹固体酸的胶囊为破胶剂,开发出了可回收再利用的低分子胍胶压裂液,在四川须家河组储层改造中得到了广泛应用,对返排出的压裂液进行了回收再利用,节能减排效果显著。

Technology research of the recycled low molecular guar gum fracturing fluid

To solve the problems of water shortage in fracturing operation and fracturing outlet liquid handling difficulty, the borate dissociation equilibrium principle is controlled by pH value to change the crosslinked state of guar gum fracturing fluid for the degradability of gel breaking under acidic condition. The molecular structure of guar gum is not damaged, so it can be crosslinked again. This paper used the biodegradation technology to degrade guar gum, and controlled the molecular weight of the guar gum by controlling the degradation conditions to control the degree of degradation of guar gum, eventually a low molecular crosslinked guar gum have been developed with molecular weight from 30×10⁴ to 50×10⁴ under the condition of borate. The viscosity of aqueous solution of the low molecular guar gum was low,and the water insoluble content was less than or equal to 4%. Taking a solid acid as a capsule core, a polymer being gradually dissolved in the water as the capsule dressing, a capsule breaker have been prepared using the method of air suspension film. The capsule breaker is not acidic on the ground for ensuring the fracturing fluid to be crosslinked well, and under formation temperature and pressure conditions the capsule breaker can gradually release the solid acid for the fracturing fluid degradability gel breaking. Taking the low molecular guar gum as the thickening agent, the capsule breaker parceling solid acid as the breaker, a recycled low molecular guar gum fracturing fluid has been developed. The fracturing fluid has been widely used in Sichuan Xu Jiahe reservoir reconstruction, and a lot of fracturing outlet liquids have been recycled. The effect of energy conservation and emissions reduction is remarkable.