低渗油藏CO_2驱中注采方式优化设计

OPTIMIZATION OF THE INJECTION AND PRODUCTION SCHEMES DURING CO2 FLOODING FOR TIGHT RESERVOIR

低渗油藏储层致密,衰竭与注水效果差,由于CO2具有易流动、降黏、体积膨胀的特点,在解决低渗透油藏开发方面表现出独特的优势。讨论了低渗油藏CO2驱中的注采方式,分析了目前常用的连续注气、水气交替和生产井控制等注采方式的优缺点,提出应综合考虑原油采收率、CO2埋存量、经济效益及其在低渗油藏中的适用性。并针对以上方法的不足提出了另外3种改进注采方式,通过油藏工程研究、典型模型和实例油藏的数值模拟进行测试分析,表明改进的依据生产井气油比和平均静压两种指标实施开关井控制的CO2驱注采方法能够满足低渗油藏注气能力需要,且具有开发周期短、油藏采收率高、CO2埋存潜力大等特点,油田实施简易,能够取得较好经济、社会效益。

Due to the tight nature of low-permeability reservoir,recoveries from depletion,water flooding and normal EOR methods are greatly limited.However,gases like CO2 with lower viscosity have higher injectivity which can co-optimize oil recovery and CO2 sequestration.In this study,reservoir engineering analysis and simulations are performed to investigate the best injection and production schemes in tight reservoirs among continuous gas injection,water alternative gas injection and producer control according to GOR and average reservoir pressure,periodical injection and production,improved well control production method,etc.The three objective functions are oil recovery,amount of CO2 sequestered and net present value.Result shows that continuous CO2 injection by using directional injectors coupled producers′ well control method according to oil well static pressure and gas oil ratio is the best scheme during CO2 flooding in tight reservoirs,which can give higher oil recovery and the most CO2 sequestration with higher injectivity,shorter developing period and feasibility.