长庆低压气井低伤害修井液研发

Research of low damage workover fluid in Changqing low-pressure gas wells

经过十多年的勘探开发,长庆气田地层压力系数严重下降,很多气井无法正常生产甚至被迫关井。为了提高产量、恢复生产,需进行相应的修井维护作业,而修井液是完成修井作业的一个关键因素。针对长庆低压气井修井液漏失严重、储层伤害大等问题,研发出一种自降解、抗高温的低伤害修井液体系,其配方为0.6%LH-1+0.5%LJ-1+0~16%WL-1+0.3%~0.5%SZ-2+0.25%GP-2。该体系密度调整范围为1.0~1.1 g/cm^(3);在100℃、170 s^(-1)剪切速率下剪切90 min后黏度仍保持在180 mPa·s;在80~100℃下,修井液具有较低的静态滤失系数;在100℃下修井液封堵承压能力达9 MPa;修井液破胶性能良好且破胶液对岩心的伤害率小于20%。该修井液体系具有“能压住、不漏失、易破胶、低伤害”的特点,在保证修井作业安全完成的同时,可有效降低修井作业对储层的伤害,在长庆低压气井修井作业中具有广阔的应用前景。

After more than ten years of exploration and development,formation pressure coefficient of Changqing gasfield has decreased seriously,and many gas wells cannot produce normally or even are forced to shut in.A workover fluid with excellent performance is a key factor in the maintenance of workover operations needed to increase production and restore production.Aiming at the common problems of vast loss and high reservoir damage of the workover fluid in low-pressure gas well of Changqing oilfield,a low-damage workover fluid system which can self-degrade and resist high temperature was developed.The formula of the system is 0.6%LH-1+0.5%LJ-1+0~16%WL-1+0.3%~0.5%SZ-2+0.25%GP-2. The density range of the workover fluid system is 1.0~1.1 g/cm^(3).The viscosity of the workover fluid remained 180 mPa·s after shear of 90 min at the shear rate of 170 s^(-1) at 100 ℃.The workover fluid has a low static filtration coefficient at 80~100 ℃.The plugging and bearing ability of the workover fluid reaches 9 MPa at 100 ℃. The breaking property of the workover fluid is excellent and the damage rate of the fluid to the core is less than 20%. This workover fluid system has the characteristics of good well-killing ability, low leakage, easy breaking and low damage. This workover fluid system can effectively reduce the damage to the reservoir caused by workover operation while ensuring the safety of workover operation, having a broad application prospect in the workover operation of low-pressure gas wells of Changqing oilfield.