注气辅助重力泄油开发油藏采收率预测方法

Prediction method of oil recovery in gas-assisted gravity drainage process

注气辅助重力泄油已成为油藏提高采收率的最新开发方式,可解决常规连续注气和水气交替注入体积波及系数低的主要问题,大幅度提高最终采收率,然而还未有相对应有效的采收率预测方法。通过对注气辅助重力泄油开发机理研究,利用量纲分析方法,对毛管数、邦德数及重力数进行分析,评价其对采收率影响的相对作用,然后通过考虑储层润湿性、油气密度差与粘度比,重新修正重力数和重力泄油数,利用实验及现场数据,确定其与采收率的关系,最后建立了注气辅助重力泄油开发油藏采收率预测方法。非混相驱替时,重力泄油数与采收率具有很好的相关性,修正重力泄油数与采收率的相关性更好;混相驱替时,重力泄油数与采收率的相关性差一些,但修正重力泄油数与采收率的相关性较好。实例应用表明,经过修正的采收率预测方法计算的结果更接近实际采收率。

Gas-Assisted Gravity Drainage(GAGD),solving the problem of low volume sweep coefficient for continuous gas injection(CGI) or water-alternating-gas injection(WAG) and increasing the ultimate recovery to a great extent,is a recent method for enhancing oil recovery.However,no effective predicting methods of oil recovery for GAGD exists.Based on the study of producing mechanism of GAGD and dimensional analysis method,this paper analyzed three dimensionless varies,Capillary Number,Bond Number and Gravity Drainage Number,and evaluated its relative influence on oil recovery.Considering the effect of wettability,viscosity ratio,and the difference between oil density and gas density,Bond Number and Gravity Drainage Number are modified and its relationship with recovery is established by experiment and field data.Finally,a new predicting method of oil recovery for GAGD is set up.Application shows that this method is far more suitable for GAGD and its predictive result is more reasonable.Therefore,it is quite significant for determining recovery of such type of development mode.