Coreflooding Studies to Investigate the Potential of Carbonated Water Injection as an Injection Strategy for Improved Oil Recovery and CO2 Storage

Abstract

Carbonated water injection (CWI) is a CO 2 -augmented water injection strategy that leads to increased oil recovery with added advantage of safe storage of CO 2 in oil reservoirs. In CWI, CO 2 is used efficiently (compared to conventional CO 2 injection) and hence it is particularly attractive for reservoirs with limited access to large quantities of CO 2 , e.g. offshore reservoirs or reservoirs far from large sources of CO 2 . We present the results of a series of CWI coreflood experiments using water-wet and mixed-wet Clashach sandstone cores and a reservoir core with light oil (n-decane), refined viscous oil and a stock-tank crude oil. The experiments were carried out to assess the performance of CWI and to quantify the level of additional oil recovery and CO 2 storage under various experimental conditions. We show that the ultimate oil recovery by CWI is higher than the conventional water flooding in both secondary and tertiary recovery methods. Oil swelling as a result of CO 2 diffusion into the oil and the subsequent oil viscosity reduction and coalescence of the isolated oil ganglia are amongst the main mechanisms of oil recovery by CWI that were observed through the visualisation experiments in high-pressure glass micromodels. There was also evidence of a change in the rock wettability that could also influence the oil recovery. The coreflood test results also reveal that the CWI performance is influenced by oil viscosity, core wettability and the brine salinity. Higher oil recovery was obtained with the mixed-wet core than the water-wet core, with light oil than with the viscous oil and low salinity carbonated brine than high-salinity carbonated brine. At the end of the flooding period, an encouraging amount of the injected CO 2 was stored in the brine and the remaining oil in the form of stable dissolved CO 2 . The experimental results clearly demonstrate the potential of CWI for improving oil recovery as compared with the conventional water flooding (secondary recovery) or as a water-based EOR (enhanced oil recovery) method for watered out reservoirs.

Carbonated water injection revisited

“…At Texas A&M University, CWI method was tested on limestone cores. At Heriot Watt University in Scotland, researchers visualised CWI process through a transparent glass model (Sohrabi et al, 2012). The test pressure was 2000 psi.…”

“…It was reported that at 2,000 psi and 100 F, the solubility of CO 2 was 165 scf/stbbrine (Sohrabi et al, 2012). It was reported that at 2,000 psi and 100 F, the solubility of CO 2 was 165 scf/stbbrine (Sohrabi et al, 2012).…”

“…Compared with CO 2 injection, CWI requires much less CO 2 supply (Sohrabi et al, 2012). CWI is to inject water saturated with CO 2 into reservoirs.…”

The influence of spreading coefficient on carbonated water alternating gas injection in a heavy crude oil

“…To produce the trapped oil phase enhanced oil recovery (EOR) techniques are suggested and applied [1,2]. In this regard, extensive laboratory studies and field applications of water alternating gas injection (WAGI), cyclic injection of carbonated water (CW) and CO 2 , carbon dioxide-EOR processes to investigate the potential of carbonated water injection as an injection method for improved oil recovery and CO 2 storage have been performed [3][4][5][6][7][8]. Storing carbon dioxide underground is being considered as a promising sequestration technology for mitigating greenhouse gas emissions [9][10][11].…”

Suggesting a numerical pressure-decay method for determining CO2 diffusion coefficient in water

“…This is so important that many of the previous papers worked on this issue somehow. Strategies such as carbonated water injection [13][14][15], ex situ dissolution approach [16,17], static mixer [18], injecting brine on top of the injected CO 2 [19], hydraulic fractures in the injection wells [20] and using horizontal injection wells in the absence of chase brine injection [20] are some examples. Here, we focus on determining CO 2 diffusion coefficient (DC) using an experimental model.…”