Cr3+聚合物弱凝胶调驱剖面变化规律及改善方法

采用分子内交联为主的Cr³⁺聚合物弱凝胶，通过“分注分采”岩心驱替实验研究调驱剂段塞尺寸、岩石渗透率和原油黏度对储层吸液剖面和产液剖面的影响。针对渤海油田LD10-1区块渐新统东营组进行了“堵/调/驱”实验。研究结果表明：①调驱剂段塞尺寸对注采两端液流转向和剖面返转时机没有影响，但超过0.3 PV后单位体积段塞尺寸Cr³⁺聚合物弱凝胶提高原油采收率增幅减小，随储层渗透率级差和原油黏度增大，注采两端液流转向时机延后，剖面返转时机提前；②“有机/无机”复合凝胶体系封堵高渗透率层、聚合物微球调控微观非均质性和稠油流度改善剂提高驱油效率等3种措施同时实施，可提高聚合物弱凝胶调驱后的采收率；③“堵/调/驱”组合提高采收率机理为：封堵优势渗流通道扩大非均质储层宏观波及体积、聚合物微球在变径孔隙或喉道处发生桥堵实现微观液流转向、高效驱油剂可进入未波及孔喉区域发挥降黏原油、降低油水界面张力和高效驱替等3种作用。

Profile change rule during Cr3+ polymer weak gel flooding and related improving method

The Cr³⁺ polymer week gel with molecular intra-crosslinking was used to study the influences of slug size， core permeability and crude oil viscosity on reservoir absorption profile and production profile by core displacement experiment. The experiments of plugging/profile control/flooding were carried out in Oligocene Dongying Formation in LD10-1 block of Bohai Oilfield. The results show that： （1）The slug size of profile control agent has no effect on the turning of fluid flow at both ends of injection and production and the turning time of profile，but when the slug size per unit volume exceeds 0.3 PV，the increase rate of Cr³⁺ polymer weak gel to enhance crude oil recovery decreases. With the increase of reservoir permeability ratio and crude oil viscosity，the turning time of fluid flow at both ends of injection and production is delayed and the turning time of profile is advanced.（2）Three measures including organic and inorganic composite gel system plugging high permeability layer，polymer microspheres regulating micro heterogeneity， and heavy oil mobility improver improving oil displacement efficiency，can be implemented at the same time，which can improve the recovery after polymer weak gel profile control and flooding.（3）The EOR mechanism of plugging/profile control/flooding combination is： plugging the dominant seepage channel to expand the macro swept volume of heterogeneous reservoir， bridging and blocking polymer microspheres in variable diameter pores or throats to realize micro fluid flow diversion， and high-efficiency oil displacement agent can enter the unswept pore throat area to play three roles， including reducing viscosity crude oil， reducing oil-water interfacial tension， and high-efficiency displacement.