CO₂ Huff-n-puff Sensitivity Simulation On JD Oilfield

With the successful of the CO₂ huff-n-puff technology used on USA's tight oil production,CO₂ huff-n-puff technology gained more and more attention.However,that technology started late in China,we are lack of both theory and practice.Therefore,this article is based on the actual situation of JD oilfield,carried out research on CO₂ flooding related issues.Its research results have certain reference significance for mine production.In this paper,the mechanism of CO₂ enhanced oil recovery,the phase change of crude oil injected into the formation by CO₂ and the sensitivity parameters of CO₂ stimulation laboratory experiment to increase recovery were studied.The research has achieved the following results:1.Deepen the understanding of the mechanism of CO₂ stimulation to improve the recovery factor of crude oil.The article sorts out the CO₂-EOR mechanism,including viscosity reduction,improved water-oil mobility ratio,and increased sweep efficiency;dissolved CO₂ on the one hand extracts light components in crude oil,and expands the volume of crude oil,the fluid pressure in the pores increases,on the other hand, exacerbates dissolved gas flooding.What's more,as a acid gas CO₂ has the functions of acidizing and unblocking,inhibiting the expansion of viscosity minerals,and blicking water and profile control.2.Establish a phase model based on PVT of formation fluid in Jidong Oilfield.Using the obtained physical data of the underground fluid,the WinProp module of the CMG software is used to perform phase state fitting to obtain the composition of the formation fluid.Final we gain 6 quasi-compnents.What's more,it is concluded that the miscibility pressure of CO₂ and formation fluid under reservoir conditions is 15MPa,and CO₂ and formation crude oil can be miscible smoothly under formation conditions.3.Done a CO₂ throughput laboratory experiment.3 sensitive parameters?CO₂injection pressure,stew time,huff-n-puff circle?were analyzed.Meantime got the solution that the lager the injection pressure of CO₂ injection,the larger the oil production;the more the huff-n-puff circles,the lower single production;when the well time is 8H, the oil production is higher and the throughput effect is good.4.Done a CO₂ huff-n-puff reservoir numerical simulation.Taking a typical well in JD oilfield as an example,using CMG numerical simulation method,6 parameters?CO₂injection volume,CO₂ injection speed,CO₂ injection pressure,huff time,liquid production rate,huff-n-puff circle?were compared.Got the solution that the greater the amount of CO₂ injection,the greater the oil production;60m³/d is the best CO₂ injection speed,after which the oil production changed a few;15MPa is the best CO₂ injecting pressure,which is the CO₂ miscibility pressure under the reservoir of JD;8-day stewing is the best stew time,when the oil production increased largest;The liquid production rate has little to do with oil production;The more the huff-n-puff circles,the lower the single-circle production,etc.Providing a basis for the CO₂ huff and puff field experiment in JD Oilfield.5.Obtained the optimal parameter range of CO₂ huff and puff in JD oilfield.Combining the laboratory experiment and the CMG reservoir numerical simulation results,the optimal parameters for CO₂ huff and puff in JD Oilfield were obtained,which is the basis for the improvement of mineral production.