Research On Immiscible Carbon Dioxide Flooding Technology For Enhancing Oil Recovery In Yaoyingtai Oilfield

There has been a lot of successful applications of CO₂ EOR technology in foreign countries,however,the research on this technology in China started relatively late.In recent years,China got some CO₂ EOR experience through the CO₂ flooding pilot tests in Daqing,Jilin,Shengli oilfields.Though Yaoyingtai oilfield obtained some certain effect since starting to conduct CO₂ EOR pilot test in 2011,many problems need to be solved also exposed,such as the unclarity of the formation of CO₂ phase underground,the unclarity of the primary factor affecting CO₂ flooding effect,the lack of an effective evaluation method for CO₂ immiscible flooding,the urgent need of countermeasures to improve the effect of CO₂ flooding in Yaoyingtai oilfield.In order to solve the problems above,change law of CO₂ phase was researched with the the method of wellbore multiphase pipe flow calculation,the results showed that the injected CO₂ existed in the 3 different stages?miscible stage,supercritical fluid stage and gas stage?and the most in the supercritical fluid stage;the effect factors of CO₂ flooding were researched with grey correlation analysis and fuzzy mathematics methods,the results showed that the ratio of current reservoir pressure and CO₂ miscible pressure whose weight was 39% was the primary factor affecting the CO₂ flooding effect;the effect of CO₂ immiscible flooding in Yaoyingta oilfield was evaluated with support vector machine,the results showed that the CO₂ immiscible flooding effect on improving production in Yaoyingtai oilfield was not ideal which have not reached the domestic other immiscible CO₂ flooding pilots' average level so far;frother B with good foaming ability and foam stability was selected from 4 kinds of frothers and the optimal injection parameters of CO₂ foam generated with frother B were optimized with the method of physical model experiment,the results showed that the best injection method was injection at the same time,the optimal injection speed was 0.7m L/min,gas/liquid ratio was 1:1 and frother concentration was 0.5%;the countermeasures to improve the effect of CO₂ flooding in the block were researched with the method of reservoir numerical simulation and the countermeasures that stratified gas injection technology,intermittent gas injection technology,cyclic gas injection technology and changing immiscible flooding into miscible flooding technology were suggested.