致密砾岩油藏超临界CO_(2)吞吐开发可行性

Feasibility of Supercritical CO_(2) Huff⁃Puff Development of Tight Conglomerate Reservoirs

CO_(2)吞吐开发具有溶解、抽提、混相等独特的机理优势,超临界CO_(2)具有更优异的注入性、穿透性和轻质组分抽提性。为进一步认识超临界CO_(2)吞吐在致密砾岩油藏开发中提高采收率的可行性,基于超临界CO_(2)—原油相互作用实验、超临界CO_(2)原油抽提实验、超临界CO_(2)吞吐物理模拟实验等手段,揭示吞吐过程中原油性质变化与增产机理,确定了不同注入参数下的采收率。结果显示:超临界CO_(2)能有效补充地层能量,降低原油黏度和密度,抽提原油轻质和中质组分,改善原油流动性;注入0.50 PV超临界CO_(2)可提高采收率22.16%,随着超临界CO_(2)注入量的增加,采收率上升,超临界CO_(2)换油率下降;4轮次吞吐相较于单次吞吐,可提高采收率20.00%~24.00%;焖井时间120 min时采收率为22.16%,焖井时间240 min后采收率变化不大;实验结果揭示了致密砾岩油藏衰竭式开发后超临界CO_(2)吞吐提高采收率的可行性,对致密砾岩油藏开发具有指导意义。

CO_(2) huffpuff development has unique mechanisms such as dissolution,extraction and miscibility and supercritical CO_(2) has better injectivity,penetrability and extraction of light components.In order to further understand the feasibility of supercritical CO_(2) huffpuff in enhancing oil recovery of tight conglomerate,based on supercritical CO_(2) crude oil interaction,supercritical CO_(2) crude oil extraction experiment and supercritical CO_(2) huffpuff indoor physical simulation,oil property changes and stimulation mechanism during huffpuff process were revealed,and the recovery factors obtained with different injection parameters were determined.The results show that supercritical CO_(2) can effectively supplement formation energy,reduce viscosity and density of crude oil,and improve mobility of crude oil.The recovery factor was improved by 22.16% after injecting 0.50 PV of supercritical CO_(2);with the increase of supercritical CO_(2) injection rate,the recovery factor increased but the replacement ratio decreased.Compared with the single round stimulation,the recovery efficiency of the fourround huffpuff can be increased by 20%~24%.The recovery factor was 22.16%after soaking for 120 minutes,but changed little after soaking for 240 minutes.The findings demonstrate that it is feasible to enhance the recovery by implementing supercritical CO_(2) huffpuff development after depletion development in tight conglomerate reservoirs,which provides a reference to the development of tight conglomerate reservoirs.