Wan Tao, Ding Kun, Xiong Qiyong, Guo Jing
Faculty of Petroleum, China University of Petroleum (Beijing) at Karamay China
Xinjiang Oilfield Company, PetroChina China.
RSC Adv. 2024 Aug 27;14(37):27227-27240. doi: 10.1039/d4ra01239a. eCollection 2024 Aug 22.
The main purpose of this paper is to study the solubility of CO in oil and water phase under high temperature and pressure. Firstly, CO-crude oil PVT experiments were carried out to determine the physical parameters of the reservoir fluid in the study field in order to clarify the interaction mechanism of CO with the crude oil. Secondly, the solubility of CO in the reservoir fluid under different pores and the minimum mixed-phase pressure of the CO-crude oil system were calculated by the improved Peng-Robinson equation of state. In this paper, the effects of nano-pores limitation on CO solubility were studied. The results show that pressure increase is favorable to CO dissolution, the solubility increases with the increase of the oil-water ratio. CO solubility decreases with temperature increase. The greater the mineralization of formation water, the lower the CO solubility. Nanopore confinement causes the phase envelope to contract and the minimum mixed-phase pressure to decrease. When the pore radius is smaller, the restriction of the phase envelope is stronger. In this paper, the minimum mixing pressure of crude oil and carbon dioxide is reduced from 31.25 MPa at 50 nm to 21.25 MPa at 5 nm, thus it is beneficial for enhanced oil recovery (CO-EOR). Nanopore confinement favors CO to enhance shale oil recovery. The results of this study are critical to evaluate the effect of CO sequestration, solubility and phase behavior changes of CO in shale reservoirs with nano-pores.
本文的主要目的是研究高温高压下CO在油相和水相中的溶解度。首先，开展了CO - 原油PVT实验，以确定研究区域储层流体的物理参数，从而阐明CO与原油的相互作用机理。其次，采用改进的彭 - 罗宾逊状态方程计算了不同孔隙条件下CO在储层流体中的溶解度以及CO - 原油体系的最小混相压力。本文研究了纳米孔隙限制对CO溶解度的影响。结果表明，压力升高有利于CO溶解，溶解度随油水比的增加而增大。CO溶解度随温度升高而降低。地层水矿化度越高，CO溶解度越低。纳米孔隙限制导致相包络收缩，最小混相压力降低。当孔隙半径越小时，对相包络的限制越强。本文中，原油与二氧化碳的最小混相压力从50 nm时的31.25 MPa降至5 nm时的21.25 MPa，因此有利于提高采收率（CO - EOR）。纳米孔隙限制有利于CO提高页岩油采收率。本研究结果对于评估CO封存效果、CO在含纳米孔隙的页岩储层中的溶解度及相行为变化至关重要。
