聚合物驱后热化学沉淀调剖提高采收率技术研究

Enhanced oil recovery for profile control by thermo-chemical precipitation after polymer flooding

在探讨聚合物驱油后油层物性变化及剩余油分布特点的基础上,提出利用热化学沉淀进行油藏深部调剖提 高采收率的方法。该方法的调剖原理不同于传统的调剖,主要通过缩小孔隙体积而达到降低高渗透层渗透率的目 的。初步的物理模拟研究表明,选用硼酸钠溶液进行结晶沉淀,可以明显降低高渗透层的渗透率,且在10倍孔隙 体积水洗后渗透率降低幅度仍可保持在55.8％～60.2％,并且"堵而不死",实现真正意义上的调剖。在二维纵向 非均质模型上的热化学沉淀调剖驱油实验表明,在聚合物驱后可继续提高采收率7.8％-9.2％,效果同于聚合物 凝胶,并且具有注入粘度低、可进入残余油不连续分布的油藏深处等特点,尤其适合于温度适中的油藏。

A method of enhanced oil recovery for deep profile control in reservoirs by thermo-chemical precipitation was introduced based on the study about the change of reservoir physical properties and the characteristics of remaining oil distribution after polymer flooding. The profile control principle of this technique is to reduce the permeability of a high permeability formation through reducing pore volume, which is different from traditional profile control. Preliminary physical simulation research indicates that the crystallization precipitation of selected sodium borate solution can significantly reduce the permeability of high -permeability formations, and reduced permeability range of 55.8% -60.2% can still last after flooding by ten -times pore volume of water wash. In addition, formations may be plugged, but were not totally be killed by this technique, so it can perform a 'real' profile control. Oil displacement test on 2 -D Ingitudinally heterogeneous models indicates that the technique of profile control by thermo - chemical precipitation after polymer flooding can further improve oil recovery of 7. 8% - 9. 2% , which is equivalent to the effect of polymer gel tech- nique. It has low injection viscosity, can penetrate deep into formations, with uncontinuous distribution, and is especially suitable for a polymer-flooded reservoir with a moderate temperature.