Laboratory Measurements on Changes in Carbonate Rock Properties due to CO2-Saturated Water Injection

Abstract

Carbon dioxide enhanced oil recovery (CO 2 -EOR) is gaining attention as a technique for reducing environmental impact and enhancing crude oil recovery. The injected CO 2 reaches supercritical states at certain temperature and pressure conditions to be miscible with crude oil. Then, miscible CO 2 -oil mixture has lower viscosity and higher mobility than oil alone, leading to increased oil recovery rate. However, carbonate minerals are known to dissolve when CO 2 is injected into reservoirs; therefore, it is important to evaluate how properties of rocks in a carbonate rock reservoir are affected by CO 2 -EOR. In this study, CO 2 -rich water was injected on carbonate rock samples mainly collected from Middle Eastern oil field and laboratory measurements including SEM image, liquid chromatography analysis, NMR T2 relaxation time and elastic wave velocity measurement, were conducted. The dissolution states of carbonate minerals were investigated by SEM images. Furthermore, liquid chromatography analysis was applied to CO 2 -rich water flooded through the samples to detect the amount of dissolved carbonate minerals. The porosity increase estimated from the chromatography analysis could be 0.6% or higher at 100 pore volumes (PV) injection. On the other hands, it was observed that samples became shorter as injection increased. The sample shortening may be caused by mechanical compaction associated with pressure loading test. The corresponding porosity reduction due to the sample shortening was estimated; magnitude of the average value of four sample is comparable to porosity increase due to chemical dissolution. Elastic wave velocity measurements showed P-wave velocity decreased in all the samples, as the amount of CO 2 -rich water increased; P-wave velocity increase at 100 PV was 2 -10 %. S-wave velocity decrease was also observed to be 2 -4% in the most of samples. Moreover, intensity reduction of small size pore was observed by NMR T2 relaxation time analysis. Thus, it was confirmed that effects of CO 2 -rich water injection on reservoir rock properties cannot be negligible.

Hybrid Carbonated Engineered Water as EOR Solution for Oil-Wet Carbonate Formation

“…In carbonate-rockand sulfate-rich aqueous systems, the potential of the surface is determined by the activity of these ions because they can either dissolve or deposit on the rock surface, influencing the surface potential [52]. The ICP-MS study was vital in discerning the rock dissolution process during flooding [53]. ICP analysis of injection and produced brine from CF-1 and CF-2 are presented in graphical form in Figures 12-17 water because its salinity is nearly one-fourth of that of the formation water.…”

Carbonated water injection: an efficient EOR approach. A review of fundamentals and prospects

“…Several experimental studies have been performed to examine the changes in the rock petro-physical properties by the injection of CO 2-saturated water (Sayegh et al 1990). Kono et al (2014) conducted experimental studies to show how the carbonated water can change the carbonate rock properties in the reservoirs of Middle East, through core flooding at reservoir conditions, measuring porosities and permeabilities. The carbonate mineral dissolution studies were conducted on scanning electron microscope (SEM) and liquid chromatography also.…”

Carbonated Smart Water Injection for Optimized Oil Recovery in Chalk at High Temperature

“…The evolution of solution gas from the heavy oil caused by CO2 dissolution is also considered one of the mechanisms for oil recovery by injecting CW [9]. The reaction between rock and CW resulting in rock dissolution and increase permeability by creating new a path to mobilize oil might also help to increase oil recovery [10].…”