高黏土疏松低渗透砂岩储层注水过程中梯度防堵体系的防堵降压效果

Anti-blocking and Depressurization Effect of Gradient Anti-blocking System in Water Injection Process of Low Permeability Loose Sandstone Reservoir with High Content Clay

针对高黏土疏松低渗透砂岩油藏注水过程中微粒运移堵塞储层孔喉导致注水压力高的难题,通过室内实验优选出一种中性梯度防堵体系。低速梯度防堵体系由0.5%KCl黏土稳定剂组成,高速梯度防堵体系由0.2%KCl和0.3%有机阳离子黏土稳定剂(YN)组成。考察了梯度防堵体系的防膨性能、驱替过程中岩心压力和渗透率的变化。结果表明,该体系的防膨率约为91%。与空白生产水(0.75 mL/min)驱替对比,较低的速度(0.25 mL/min)下,经0.5%KCl驱替后,压力增长倍数由5.41降为2.03,渗透率保留率由18.49%提高到49.15%;较高的速度(0.50 mL/min)下,经0.2%KCl+0.3%YN体系驱替后,岩心渗透率逐渐恢复;转生产水以0.75 mL/min驱替8 PV后,渗透率保留率由10.56%提高至91.58%,压力增长倍数由9.47降为3.28。通过速度梯度和防堵体系的协同作用,获得了明显的防堵降压效果。

Aiming at the problem of high injection pressure caused by particle migration and the blocking of reservoir pore throat in the water injection process of loose low permeability sandstone reservoir with high content clay,a neutral gradient anti-plugging system was optimized through laboratory experiments.The lower speed gradient anti-plugging system consisted of 0.5%KCl clay stabilizer,and the higher speed gradient anti-plugging system consisted of 0.2%KCl and 0.3%organic cationic clay stabilizer(YN).The anti-swelling performance of the gradient anti-plugging system and the changes of core pressure and permeability during displacement were investigated.The results showed that the anti-swelling rate of the system was about 91%.Compared with blank produced water(0.75 mL/min)displacement,at a lower speed(0.25 mL/min),the pressure growth multiple was reduced from 5.41 to 2.03 after 0.5%KCl displacement,and the permeability retention rate was increased from 18.49%to 49.15%.At higher speed(0.50 mL/min),the core permeability was gradually restored after displacement by 0.2%KCl and 0.3%YN system.After produced water displacement of 8 PV by 0.75 mL/min,the permeability retention rate was increased from 10.56%to 91.58%,and the pressure growth multiple was reduced from 9.47 to 3.28.Through the synergistic effect of velocity gradient and plugging prevention system,obvious plugging prevention and pressure reduction effect was obtained.