亲油碳酸盐岩基质岩块系统的重力驱替作用

Gravity drainage in oil-wet carbonate matrix rock system

重力驱替作用是塔河油田缝洞型单元体中水驱油的重要作用力。基于油润湿条件下的碳酸盐岩岩心,建立油藏条件下的毛细管渗流方程,讨论重力驱替作用对采出程度的贡献及其影响因素。计算结果表明,对于亲油的基质岩块系统,岩块越高,油水密度差越大,产生的驱替作用力越大,原油采出程度越高。采用离心法模拟重力驱替作用,实验结果证明,在底水能量作用下,重力驱替作用与底水驱替作用对原油采出程度的贡献相当。结合压力恢复数据、测井曲线和取心层段含油性数据综合分析塔河油田7区典型井采油曲线,证实在底水能量作用下,发育裂缝-溶洞和裂缝-溶孔的储集体中,底水突破前,依靠油水密度差产生的重力作用驱替基质岩块系统中的油,能维持较长的低产、稳产期。

Gravity drainage is an important acting force in fracture-cavity reservoir units of the Tahe Oilfield,Tarim Basin,NW China.With the oil wetting carbonate matrix rock,capillary flowing equation was established under reservoir condition,and the contribution of gravity drainage and influential factors to oil recovery was discussed.For oil wetting matrix rock,the higher the rock and the greater the density difference between oil and water,the larger the displacement force generated and the higher the oil recovery.Gravity drainage was simulated by the centrifugal method.Under the condition of bottom water flooding,the contribution of gravity drainage to oil recovery is almost equal to that of bottom water flooding.With pressure buildup data,log curves and oil saturation data in coring layer,production curves of representative wells from 7 blocks were analyzed in the Tahe Oilfield.It shows that under the condition of bottom water flooding,before bottom water breakthrough,using the gravity force due to density difference between oil and water to displace oil in matrix rock can maintain a long period of low and stabilized production in reservoirs with fracutes-cavities and fractures-dissolved pores.