新疆油田中深层稠油CO_(2)驱/吞吐实验研究

Experimental study on CO_(2) flooding/huff and puff of medium-deep heavy oil in Xinjiang Oilfield

针对新疆油田中深层稠油油藏的“中等偏强—强”速敏伤害以及“强—极强”水敏伤害引起的注水开发效果不理想的问题,基于CO_(2)独特的物理和化学性质,借助高温高压PVT实验仪和长岩心驱替装置,开展CO_(2)-原油高压物性测定和CO_(2)驱/吞吐提高采收率可行性研究,结合气相色谱和高温高压流变仪表征产出油的组成及黏度变化。实验结果表明,57.345%摩尔分数的CO_(2)能将溶解气油比(GOR)从32 m^(3)/m^(3)增大至149.3 m^(3)/m^(3)、泡点压力(pb)从6.8 MPa增大至15.7 MPa,原油体积系数从1.06增大至1.27,原油密度从0.8965 g/cm^(3)降低至0.8548 g/cm^(3),原油黏度从419.3 mPa·s降低至253.4 mPa·s,因此CO_(2)能有效补充地层能量,增大原油弹性能,减小渗流阻力。第一轮次0.95 PV(孔隙体积)的CO_(2)驱的原油采出程度为32.8%,焖井24 h后多孔介质中的流体重新分布,第二轮次0.5 PV的CO_(2)驱能提高原油采出程度17.9%。而5轮次CO_(2)吞吐的原油采出程度为63.5%。产出油的黏度呈降低的趋势,主要原因是原油中的沥青质在多孔介质中发生沉积。实验结果明确了CO_(2)驱/吞吐在新疆油田中深层稠油提高采收率的可行性。

Addressing the challenges of moderate to strong velocity sensitivity damage and strong to extremely strong water sensitivity damage in the medium and deep heavy oil reservoirs of Xinjiang oilfields,which lead to suboptimal waterflooding outcomes,a study was conducted leveraging the unique physical and chemical properties of CO_(2).Utilizing high-temperature,high-pressure PVT apparatus and long core displacement equipment,the feasibility of enhancing oil recovery through CO_(2) flooding/huff and puff was explored by determining the high-pressure physical properties of CO_(2)-crude oil and analyzing the composition and viscosity changes of the produced oil with gas chromatography and high-temperature,high-pressure rheometry.The experimental results show that 57.345%mole fraction of CO_(2) can increase the dissolved gas-oil ratio(GOR)from 32 m^(3)/m^(3) to 149.3 m^(3)/m^(3),the bubble point pressure(pb)from 6.8 MPa to 15.7 MPa,the volume coefficient of crude oil from 1.06 to 1.27,the density of crude oil from 0.8965 g/cm^(3) to 0.8548 g/cm^(3),and the viscosity of crude oil from 419.3 mPa·s to 253.4 mPa·s.Therefore,CO_(2) can effectively supplement the formation energy,increase the elastic energy of crude oil and reduce the seepage resistance.The first round of 0.95 PV(pore volume)CO_(2) flooding has a crude oil recovery of 32.8%,and the fluid in the porous medium is redistributed after 24 hours of shut-in.The second round of 0.5 PV CO_(2) flooding can increase the crude oil recovery by 17.9%.The crude oil recovery of five rounds of CO_(2) huff and puff is 63.5%.The viscosity of the produced oil tends to decrease,mainly due to the deposition of asphaltenes in crude oil in porous media.The experimental results have confirmed the feasibility of CO_(2) flooding/huff and puff in the recovery of heavy oil in the middle and deep layers of Xinjiang Oilfield.