Experimental and Numerical Evaluation of Carbonated Water Injection (CWI) for Improved Oil Recovery and CO2 Storage

Abstract

One of the well-known problems in CO2 enhanced oil recovery (EOR) processes is the poor sweep efficiency due to the high viscosity contrast between CO2 and the reservoir resident fluids (oil and brine). CO2-augmented waterflooding or carbonated water injection (CWI) could lessen this problem. As CO2 is dissolved in and transported by the flood water, CO2 is more evenly distributed within the reservoir thus improves the sweep efficiency. This is beneficial to watered-out oil reservoirs where high water saturations could adversely affect the performance of the conventional CO2 injections. CWI also provides a very safe method for storing large quantities of CO2 as a dissolved phase in oil reservoirs. This paper presents the results of our experimental and numerical investigations on the oil recovery and CO2 storage benefits of CWI in secondary and tertiary recovery modes through a series of coreflood experiments and detailed compositional simulation. The experiments were performed in a water-wet Clashach core with decane as well as restored North Sea reservoir core with stock tank crude oil and seawater at reservoir conditions. The experimental results demonstrate that CWI in both secondary and tertiary recovery modes can improve the oil recovery above the plain waterflooding. 45-51% of the injected CO2 was stored in the core at the end of the coreflood tests indicating the high potential of CWI not only for EOR but also as a CO2 storage injection strategy. Results of the corefloods were used to assess the capabilities and limitations of a commercial compositional flow simulator in modelling the CWI process. The simulation results show that diffusion should be taken into account to properly model the CWI process at the core scale. Using the commercially available reservoir simulators with the instantaneous equilibrium and complete mixing assumptions would lead to inaccurate evaluation of CWI process at this scale of interest.

Enhanced Wettability Modification and CO2 Solubility Effect by Carbonated Low Salinity Water Injection in Carbonate Reservoirs

“…In the 1960s, commercial applications of CWI in Oklahoma, Texas, and Kansas demonstrated that CWI resulted in increased water injectivity and oil recovery [2]. In more recent studies, the CWI phenomenon has been visualized in glass micromodels [1,3,4]. These studies confirmed oil swelling, oil viscosity reduction, and the generation of CO 2 -enriched gas during CWI.…”

“…These studies confirmed oil swelling, oil viscosity reduction, and the generation of CO 2 -enriched gas during CWI. Moreover, Sohrabi et al [1] and Kechut et al [4] have conducted coreflooding experiments to observe whether oil production is enhanced and performed numerical simulations.…”

Laboratory investigation of oil viscosity effect during carbonated water injection: Comparison of secondary and tertiary recovery

“…[12][13][14][15][16][17][18][19][20][21] The main mechanisms of oil recovery in CWI, as a result of transferring CO 2 from the aqueous phase to the oil phase, are oil swelling and viscosity reduction. [11,[26][27][28] Sohrabi et al implemented CWI experiments by using a high-pressure micro-model to clarify the mechanism of oil recovery at pore-scale level. [23][24][25] Martin observed nearly 12 % improvement in oil recovery with CWI and found a relation between carbonation level and oil recovery.…”

Application of CO2-Saturated Water Flooding as a Prospective Safe CO2 Storage Strategy

“…It has been shown that injection of CO 2 -saturated water in watered-out reservoirs is considerably attractive for safe permanent CO 2 storage [9]. A higher CO 2 retention factor was noticed when CO 2 -saturated water flooding was compared with a typical immiscible CO 2 flooding [10]. It has been reported that a relatively high percentage of the total volume of CO 2 injected (in the CO 2 -saturated water), about 46% was stored at the end of the tertiary CO 2 -saturated water flooding [11].…”