低初黏型凝胶调堵体系驱油效果实验研究

Experimental study on Oil Displacement Effect of Low Initial Viscosity Gel Plugging System

大庆油田聚合物驱后地层非均质性加剧,致使二次聚驱窜流严重。为实现老油田进一步开发,本文确立了调、堵、驱综合治理开发思路。根据堵调需求,研发出一种低初黏型凝胶调堵体系,该凝胶体系初始黏度小于20 mPa·s,10~40 d内黏度小于300 mPa·s,成胶黏度2500 mPa·s以上。为探究该体系对驱油效果的影响,开展三管并联岩心驱油实验。结果表明:适量的凝胶体系可以有效改善岩心的非均质性,实现高渗层的有效封堵;然而注入量过大时,会造成中、低渗透层的污染;实验优化结果为,当凝胶注入量为0.1 PV,可实现对中、低渗透层无污染,此时再进行二次聚驱,采收率可增幅13.6%,较单纯高浓度聚驱可多提高采收率4.4%。

The formation heterogeneity intensified after polymer flooding in Daqing Oilfield,resulting in severe cross-flow during the secondary polymer flooding.To achieve further development of the old oilfields,the development strategy of comprehensive profile modification,water plugging and flooding was established.According to the plugging requirements,a low initial viscosity gel plugging system was developed.The initial viscosity of the system is less than 20 mPa·s,during 10~40 days,the system viscosity is less than 300 mPa·s,and the gel viscosity is above 2500 m Pa·s.In order to explore the effect of this system on oil displacement,a three-pipe parallel core oil displacement experiment was carried out.The results showed that the proper amount of gel system could effectively improve the heterogeneity of the core and achieve the effective plugging of the high permeability layer.However,when the injection volume was too large,it could cause the pollution of the middle and low permeability layers.The experimental optimization results were as follows:when the injection volume of the gel was 0.1 PV,the middle and low permeability layers were not polluted.At this time,the secondary polymer flooding increased the recovery rate by 13.6%,which can increase the recovery rate by 4.4%compared with the simple high concentration polymer flooding.