特低渗透油层CO_2与N_2驱替方式
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摘要
针对特低渗透油层CO_2驱效果好而气源有限、N_2驱气源广而效果差的实际情况,以YS油田为实际背景,依据该油田地层及流体物性参数,对连续注CO_2、CO_2和N_2混注以及CO_2前置段塞+N_2等三种驱油方式进行了一维数值模拟,研究了CO_2混入N_2后与原油最小混相压力的变化规律,分析了不同尺寸CO_2前置段塞+N_2驱油过程中CO_2和N_2在油相气相中的分布规律,以及C2—C4和C+22在油相中的摩尔分数变化,对比了不同驱油方式的驱油效率。结果表明:特低渗透油层CO_2与N_2复合驱不宜采用CO_2与N_2混合气驱方式,而应采用CO_2段塞+N_2的驱油方式;且一次注入的CO_2段塞至少应有0.3 PV才能有效地阻止N_2的窜逸对最终采收率的影响;于此同时,0.3 PV CO_2段塞+N_2的驱油方式不仅可以减少CO_2用量,而且可以充分发挥CO_2与N_2各自的优势,获得与连续注CO_2驱相同的驱油效果。
In the light of the actual situation the good-effects of carbon dioxide flooding but the shortage of the gas resource and the abundant gas resource while the poor effects of the nitrogen flooding in ultra-low permeability oil reservoirs,taking Oilfield YS as the actual background,according to the physical property parameters of the reservoir and fluids,the one-dimensional numerical simulation was conducted for the following three displacing methods:continuous carbon dioxide injection,mixed injection of the carbon dioxide with the nitrogen and the carbon dioxide front slug + nitrogen,the MMP changing law of the oil after the mixture was researched,the distribution rules of the carbon dioxide and the nitrogen in the oil and gas phases and moreover the mole fraction changes of C2-C4 and C22 +in the oil phase were analyzed during the oil displaced process of different-size carbon dioxide front slugs + nitrogen,finally the oil displaced efficiencies were contrasted for the different oil flooding ways. The results show that the mixed flooding is not good to adapt the combined displacing,while the third oil flooding method should be adap-ted for the ultra-low permeability oil reservoir; for once injected CO_2,the carbon dioxide slug size may not be less in 0. 3 PV so as to effectively prevent the influence of the nitrogen escaping on the ultimate oil recovery; meanwhile,the flooding mode of 0. 3 PV carbon dioxide slug + nitrogen can not only reduce the carbon dioxide consumption,but also can gain full advantages of the carbon dioxide and nitrogen,and moreover can obtain the same oil flooded efficiency as that of the continuous injection of the carbon dioxide.
In the light of the actual situation the good-effects of carbon dioxide flooding but the shortage of the gas resource and the abundant gas resource while the poor effects of the nitrogen flooding in ultra-low permeability oil reservoirs,taking Oilfield YS as the actual background,according to the physical property parameters of the reservoir and fluids,the one-dimensional numerical simulation was conducted for the following three displacing methods:continuous carbon dioxide injection,mixed injection of the carbon dioxide with the nitrogen and the carbon dioxide front slug + nitrogen,the MMP changing law of the oil after the mixture was researched,the distribution rules of the carbon dioxide and the nitrogen in the oil and gas phases and moreover the mole fraction changes of C2-C4 and C22 +in the oil phase were analyzed during the oil displaced process of different-size carbon dioxide front slugs + nitrogen,finally the oil displaced efficiencies were contrasted for the different oil flooding ways. The results show that the mixed flooding is not good to adapt the combined displacing,while the third oil flooding method should be adap-ted for the ultra-low permeability oil reservoir; for once injected CO_2,the carbon dioxide slug size may not be less in 0. 3 PV so as to effectively prevent the influence of the nitrogen escaping on the ultimate oil recovery; meanwhile,the flooding mode of 0. 3 PV carbon dioxide slug + nitrogen can not only reduce the carbon dioxide consumption,but also can gain full advantages of the carbon dioxide and nitrogen,and moreover can obtain the same oil flooded efficiency as that of the continuous injection of the carbon dioxide.
引文
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[2]Bachu S,Shaw J C,Pearson R M.Estimation of oil recovery and CO2storage capacity in CO2EOR incorporating the effect of underlying aquifers[R].SPE 89340,2004.
[3]沈平平.提高采收率技术[M].北京:石油工业出版社,2006.
[4]苗国锋.龙虎泡油田高台子油层CO2驱最小混相压力研究[J].石油地质与工程,2010,24(3):70-72.
[5]刘英杰.改善榆树林油田CO2驱油效果技术研究[D].大庆:东北石油大学,2016.
[6]张勇.苏北低渗透油藏CO2混相驱油方案优化研究[D].青岛:中国石油大学(华东),2012.
[7]白素.榆树林油田CO2驱非达西渗流数值模拟研究[D].大庆:东北石油大学,2011.
[8]王进安,岳陆,袁广钧,等.N2驱室内实验研究[J].石油勘探与开发,2004,31(3):119-121.
[9]陈兴隆,秦积舜,张可.CO2-原油体系混相状态的渗流特性[J].地球科学(中国地质大学学报),2009,34(5):94-98.
[10]孙杨,杜志敏,孙雷,等.注CO2前置段塞+N2顶替提高采收率机理[J].西南石油大学学报(自然科学版),2012,34(3):89-96.