Integrated PVT and Coreflooding Studies of Carbonated Water Injection in Tight Oil Reservoirs: A Case Study

Abstract

Carbonated water injection (CWI) is a modified CO2 flooding technique for enhanced oil recovery, which takes advantage of both CO2 flooding and water injection and has attracted much attention recently. However, the dedicated research so far has focused heavily on conventional reservoirs. The objective of this research is to investigate the performance of CWI in a tight oil reservoir. First, a set of well-designed multiple contact tests were conducted to simulate the dynamic mass transfer process of fresh carbonated water (CW) to live crude oil. In each test, CW was brought into contact with live crude oil in a high-temperature and high-pressure PVT cell. Pressure changes during the test were observed and recorded. After equilibrium, all the transferred CW was taken out of the cell and the swelled oil proceeded to the next contact. The volumes of water and liberated gas were measured. Then, the oil swelling factor could be calculated, which would verify the existence of the moving interface between CW and live crude oil. It was observed that the system pressure built up immediately after CW was mixed with live crude oil in the PVT cell. For the first contact, the equilibrium pressure increased by 6.46 MPa, and the equilibrium pressure increased by 2.16 MPa at the last contact. This result indicates a strong interaction between CW and live crude oil, which is beneficial to maintain reservoir pressure. Because a large amount of CO2 from CW was transferred to the live crude oil, the swelling factor of 1.26 was obtained at the end of the tests. The diffusion of CO2 into the live crude oil also leads to subsequent oil viscosity reduction. In addition, a series of coreflood experiments under real reservoir conditions were carried out to evaluate the performance of CWI for improving oil recovery in core samples from a tight sandstone reservoir. Coreflood results showed that both secondary and tertiary CWI recovered additional oil compared to water flooding. Finally, a significant amount of CO2 was stored in the cores. Our experimental results clearly indicate the potential of CWI for improving oil recovery and CO2 storage capacity in tight oil reservoirs.

Carbonated Water Injection for Enhanced Oil Recovery and CO2 Geosequestration in Different CO2 Repositories: A Review of Physicochemical Processes and Recent Advances

“…54 Conversely, the utilization of half-saturated CW lowered the ultimate oil recovery from tight sandstone samples by 7.4% and 3.8% for secondary and tertiary CWI processes, respectively. 55 Research has also revealed that the oil recovery efficiency of CWI is comparatively higher in light to moderately light crude oils than in heavy crude oils. The solubility of CO 2 in different crude oil types supports this claim (Figure 3).…”

Quantitative Analysis of Natural Gas Diffusion Characteristics in Tight Oil Reservoirs Based on Experimental and Numerical Simulation Methods

“…At the present stage, the method of gas injection mainly includes gas flooding and huff-n-puff, while both have their own mechanism for oil recovery. Diffusion is one of the important mechanisms of gas injection development, and the gas diffusion coefficient is the most important parameter to measure the diffusion ability of gas. − When there is a concentration difference between two or more substances in a system, the substance will spontaneously transfer mass until the system reaches equilibrium, which is the diffusion process. − The diffusion coefficient refers to the amount of gas passing through a unit area per unit of time when the concentration gradient is one unit. The diffusion coefficient can be divided into self-diffusion coefficient, mutual diffusion coefficient, and restricted diffusion coefficient.…”

Tight oil reservoir production characteristics developed by CO2 huff ‘n’ puff under well pattern conditions

“…An effective supply of reservoir energy is the key to improving the production performance of tight oil reservoirs (Kang et al 2020;Wei et al 2021). Water and gas are the most studied injectants for reservoir energy supplementation (Wu et al 2020;Zou et al 2019). Compared with water, the gas viscosity is lower and easier to inject (Zhou et al 2020).…”