Subcritical CO2 effects on kaolinite fines transport in porous limestone media

Carbonate reservoirs account for 60% share in global oil reserves, and CO2-EOR process is employed in these carbonate felds for efective oil recovery and retention as well. Recent research reports that fnes migration may lead to reservoir formation damage in oil bearing limestone and dolomite rocks. Although carbonate reservoirs are poor in clay minerals, some mass of clay fnes existence in certain carbonate formations will cause severe damage to permeability and well productivity. This paper reports the single-phase fow of subcritical CO2 in porous limestone rock core containing kaolinite clay fnes. Fines

are natural reservoir minerals (example, quartz) and clay particles such as kaolinite, illite, feldspar, smectite, and montmoril- lonite. But, this paper explores this CO2-clay fnes behavior in limestone rock as a function of kaolinite. So, two sets of core food experiments were performed in the rock temperatures 120 °C and 160 °C. Initially, kaolinite clay has been injected into the limestone core in the form of suspension and then dried for hours in order to retain the solid fnes in the internal pore chambers of the core. After that, the CO2 under subcritical condition has been injected into the porous limestone core for fnes obilization and injected gas recovery. The major observations that are reported from the experimental tests are there is an increase in gas saturation for increasing injection time. Steady rise of heat transfer coefcient and enthalpy was noted
for increasing gas saturation and time. Concentration of fnes linearly soars with respect to elevating PVI and permeability declines for rising time. Pressure in the limestone core shows abnormal and nonlinear variation. Finally, gas discharge rate declines for increasing injection time. Experimental data are tested against the statistical model (regression), and the outcome indicated good agreement. Overall, this paper has successfully established the CO2 efects on kaolinite clay fnes behavior
and its impact on oil recovery in carbonate felds.