Laboratory Investigation of CO2 Flooding

Abstract

Carbon dioxide (CO2) flooding is an efficacious method of EOR and it is a very complicated process, involving phase behavior. To master the performance of CO2 flooding and provide accurate data for designing oil development, a comprehensive investigation of CO2 flooding phase behavior and mechanism based on laboratory study was conducted. In order to get representative fluid samples of a reservoir, it was necessary that the right operation of mixing the separator oil and gas samples to match the bubble point pressure be carried out. The result from PVT experiments shows that for a certain reservoir, through a slight manipulation of the measured PVT properties including bubble point pressure, volume factor, swelling factor, solubility of CO2 and viscosity, it is possible to obtain regression curves, which can be used to estimated the PVT behavior for any hydrocarbon fluid-CO2 mixture of this reservoir. The result of slim tubule tests indicates that it is more appropriate to determine the minimum miscibility pressure of the reservoir fluid-CO2 mixture by the position of inflexion on the curve of oil recovery with flooding pressure than by reaching a special oil recovery point. Introduction Carbon dioxide flooding is an effective enhanced oil recovery process. It appeared in 1930's and had a great development in 1970's. Over 30 years' production practice, CO2 flooding has become the leading enhanced oil recovery technique for light and medium oils1–4. It can prolong the production lives of light or medium oil fields nearing depletion under waterflood by 15 to 20 years, and may recover 15% to 25% of the original oil in place1. CO2 flooding process involves very complicated phase behavior, which depends on the temperature, pressure and fluids properties of a certain reservoir. Many factors have been found contributing to the oil recovery in CO2 flooding. These mainly include5–11:low interface tensions;viscosity reduction;oil swelling;formation permeability improvement;solution gas flooding;density change of oil and water. R.K Srivastava et al6 took a laboratory study of Weyburn CO2 miscible flooding. From the PVT data generated from the three Weyburn reservoir fluid-CO2 mixtures it was showed that viscosity reduction and oil swelling by CO2 contributed to oil recovery. The viscosity showed an almost linear decrease with CO2 concentration. A slight manipulation of the measured PVT properties of the mixtures made it possible to obtain single property curves for the three Weyburn oils. This feature can be used to estimate the PVT behaviour for any Weyburn oil from the reservoir.

A Review of CO2-Enhanced Oil Recovery with a Simulated Sensitivity Analysis

“…However, according to Jarrell et al [24], adequate purity in the injecting CO2 (90%-98%) is required, particularly for miscible oil recovery. In addition to the swelling factor, oil viscosity reduction caused by the injecting CO2 is also favourable for oil recovery, and according to Yongmao et al [59] and Srivastava et al [60], injection of CO2 into an oil reservoir may cause oil viscosity in the reservoir to be reduced by around 10%-70%, significantly enhancing oil productivity. Importantly, Azzolina and co-workers' [61] statistical analysis of 31 CO2-EOR candidates clearly shows the dominant role of the injecting CO2 volume on oil production enhancement.…”

A data analysis of immiscible carbon dioxide injection applications for enhanced oil recovery based on an updated database

“…One of the most widely applied, and highly advantageous and productive enhanced oil recovery (EOR) methods is carbon dioxide injection. CO 2 can be injected into the reservoir as a miscible solvent, or an immiscible fluid [1][2][3]. The choice of whether the CO 2 should be miscible or immiscible is based on many factors mainly the reservoir fluid properties, including oil viscosity, molecular weight (MW), API gravity, and composition, and reservoir rock properties, including pay zone depth, thickness, and mineralogy.…”

Enhanced oil recovery by alkaline-surfactant-alternated-gas/CO2 flooding

“…Currently, alkaline-surfactant-polymer (ASP) is considered as the most promising chemical EOR method having the ability to improve the microscopic sweep as well as the macroscopic displacement efficiencies. Among the gas EOR methods, CO 2 flooding is the leading EOR technique for light and medium crude oil (Yongmao et al 2004;Gogoi 2013). Notwithstanding the successful application of CO 2 EOR in many laboratory-scale and field-scale tests, CO 2 cannot recover all of the oil in the formation because its low density and viscosity gives rise to a number of mobility and conformance issues (Enick and Olsen 2012;Farajzadeh et al 2012;Talebian et al 2013;Yang Zhang et al 2015).…”