CO_2复合驱油分子动力学模拟及微观机理研究
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摘要
为了探索较大幅度提高高含水期复杂断块油田剩余油采收率,提出了CO_2复合驱方式进行剩余油开采对策并在矿场先导试验井组取得了显著的增油降水效果,但对CO_2复合驱油体系微观增油机理的相关研究较少,亟需开展这方面的基础研究。基于CT扫描结果,结合油藏开发实际,明确了滴状和膜状剩余油为难以动用的2种剩余油类型;构建了溶解油滴模型和剥离油膜模型,利用分子动力学方法进行模拟。溶解油滴模拟结果表明,CO_2扩散至油滴中,增加其体积,然后油滴分子逐渐溶解在驱油体系中;剥离油膜分子动力学模拟结果表明,CO_2在油相中先形成扩散通道,随后CO_2优先通过扩散通道至岩石表面,CO_2在表面上形成氢键而产生吸附。
A CO_2 composite flooding method was proposed for remaining oil exploitation and achieved significant effects in pilot well tests in order to improve residual oil recovery efficiency in complex fault block oilfields during high water cut period. There are few related studies on the microscopic mechanism of CO_2 composite flooding, and the basic research in this field is urgently demanded. Based on the CT scanning results, combined with the actual development of reservoir, it was clear that the drop-like and film-like residual oil are two types of remain-ing oil that were difficult to recover. A dissolved oil droplet model and a stripped oil film model were constructed and simulated using a molecular dynamics method. The simulation results of the dissolved oil droplet method showed that CO_2 first diffused into oil droplets and increased their volume, and then the oil droplet molecules gradually dissolved into the oil displacement system. The molecular dynamics simulation results of the stripped oil film showed that CO_2 first formed diffusion channels in the oil phase, and then preferentially passed through the diffusion channels to the rock surface. CO_2 formed hydrogen bonds on the surface and generated adsorption.
A CO_2 composite flooding method was proposed for remaining oil exploitation and achieved significant effects in pilot well tests in order to improve residual oil recovery efficiency in complex fault block oilfields during high water cut period. There are few related studies on the microscopic mechanism of CO_2 composite flooding, and the basic research in this field is urgently demanded. Based on the CT scanning results, combined with the actual development of reservoir, it was clear that the drop-like and film-like residual oil are two types of remain-ing oil that were difficult to recover. A dissolved oil droplet model and a stripped oil film model were constructed and simulated using a molecular dynamics method. The simulation results of the dissolved oil droplet method showed that CO_2 first diffused into oil droplets and increased their volume, and then the oil droplet molecules gradually dissolved into the oil displacement system. The molecular dynamics simulation results of the stripped oil film showed that CO_2 first formed diffusion channels in the oil phase, and then preferentially passed through the diffusion channels to the rock surface. CO_2 formed hydrogen bonds on the surface and generated adsorption.
引文
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[2] LIU Bing,SHI Junqin,WANG Muhan,et al.Reduction in interfacial tension of water-oil interface by supercritical CO2 in enhanced oil recovery processes studied with molecular dynamics simulation[J].The Journal of Supercritical Fluids,2016,111:171-178.
[3] HELALEH A H,ALIZADEH M.Performance prediction model of miscible surfactant-CO2 displacement in porous media using support vector machine regression with parameters selected by ant colony optimization[J].Journal of Natural Gas Science and Engineering,2016,30:388-404.
[4] 孙艳阁.表面活性剂多元复配低张力泡沫驱油体系的分子设计及应用性能研究[D].济南:山东大学,2016. SUN Yange.Molecular design and performance study of foam flooding systems with ultralow interfacial tension formed from multiple surfactant mixtures[D].Jinan:Shandong University,2016.
[5] 徐军.3-(N,N-二甲基十二烷基胺)-2-羟基-丙基磺酸溶液性质、模拟及应用研究[D].济南:山东大学,2007. XU Jun.Investigation into properties and behaviors of 3-(n,n-dimethyldodeecylammonio)-2-hydroxypropopanesulfonte[D].Jinan:Shandong University,2007.
[6] 梁向东,银建中.实验与MD模拟探究基于LS-45的超临界CO2微乳液结构[J].应用科技,2017,44(4):70-74. LIANG Xiangdong,YIN Jianzhong. Study on micro-structure of scCO2 microemulsion with LS-45 by experiment and molecular dynamics simulation method[J].Applied Science and Techno-logy,2017,44(4):70-74.
[7] 乔贵民.表面活性剂改变亲油岩石润湿性的分子模拟研究[D].青岛:中国石油大学(华东),2012. QIAO Guimin.Molecular simulation of wettability alteration of oil-wet rock using surfactants[D].Qingdao:China University of Petroleum (East China),2012.
[8] 牟雷.纳米尺度下液体的流动机理研究进展[J].断块油气田,2017,24(5):666-669. MU Lei.Advances in nanoscale liquid flow mechanisms[J].Fault-block Oil & Gas Field,2017,24(5):666-669.
[9] 蒲万芬,季晓靖,金发扬,等.表面活性剂与油相动态界面张力影响因素研究[J].化学研究与应用,2015,27(11):1655-1659. PU Wanfen,JI Xiaojing,JIN Fayang,et al.Study on dynamic interfacial tension of surfactants with oil phase[J].Chemical Research and Application,2015,27(11):1655-1659.
[10] 郭宇.耐温抗盐型复合表面活性剂驱油体系的合成及应用[J].断块油气田,2018,25(2):258-261. GUO Yu.Synthesis and application of oil displacement system of temperature-resistant and salt-resistant high-efficiency composite surfactant[J].Fault-block Oil & Gas Field,2018,25(2):258-261.
[11] 吴伟.特高温中低渗透油藏乳液表面活性剂驱提高采收率技术[J].油气地质与采收率,2018,25(2):72-76,82. WU Wei.Enhanced oil recovery technology of emulsion-surfactant flooding for extra-high temperature and mid-low permeability reservoirs[J].Petroleum Geology and Recovery Efficiency,2018,25(2):72-76,82.
[12] 倪军,王成俊,高怡文.特低渗油藏表面活性剂驱潜力评价新模型[J].特种油气藏,2018,25(1):68-72. NI Jun,WANG Chengjun,GAO Yiwen.A new evaluation model for the surfactant flooding potential in ultra-low permeability reservoir[J].Special Oil and Gas Reservoirs,2018,25(1):68-72.
[13] 王磊.超临界二氧化碳剥蚀原油机理的分子模拟研究[D].青岛:中国石油大学(华东),2014. WANG Lei.Molecular simulation of oil detachment and erosion mechanism by supercritical carbon dioxide[D].Qingdao:China University of Petroleum (East China),2014.