Subcritical CO2 effects on kaolinite fines transport in porous limestone media

Abstract

Carbonate reservoirs account for 60% share in global oil reserves, and CO 2-EOR process is employed in these carbonate fields for effective oil recovery and retention as well. Recent research reports that fines 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 fines existence in certain carbonate formations will cause severe damage to permeability and well productivity. This paper reports the single-phase flow of subcritical CO 2 in porous limestone rock core containing kaolinite clay fines. Fines are natural reservoir minerals (example, quartz) and clay particles such as kaolinite, illite, feldspar, smectite, and montmorillonite. But, this paper explores this CO 2-clay fines behavior in limestone rock as a function of kaolinite. So, two sets of core flood 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 fines in the internal pore chambers of the core. After that, the CO 2 under subcritical condition has been injected into the porous limestone core for fines mobilization 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 coefficient and enthalpy was noted for increasing gas saturation and time. Concentration of fines 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 CO 2 effects on kaolinite clay fines behavior and its impact on oil recovery in carbonate fields.

Permeability Damage and Supercritical Fluid Storage in the Cauvery Basin Neyveli Lignite Bed Containing Kaolinite Deposits during Alternative Injection of Brine and CO2

“…Furthermore, CO 2 injection in coal seams generates high ins-situ stress and high swelling rates, which ultimately decrease the permeability to a great extent, as this phenomenon was observed and reported in Kushiro low rank coals from Kushiro coal basin, Japan (Anggara et al 2016). It should be noted that beyond brine injection, the CO 2 injection and transport in porous rocks has savaging effects on nes migration and porous rock permeability (Mahalingam et al 2019). For example, Xie et al (2017) reported nes migration during CO 2 injection through experimental investigation as a function of surface forces.…”

“…20. It should be noted that water and CO 2 injection in porous rocks lead to suspension transport and eventually, the particles being captured in the rock grain and contributing to permeability damage or decline, where the reservoir uid transport is deteriorated and arduous or almost impossible for surface recovery (Kanimozhi et al 2020;Mahalingam et al 2019;Bedrikovetsky and Caruso 2014). It can be seen from this gure that there is a gradual decline in the lignite core permeability and permeability stabilization occurred in between the injection period.…”

“…Generally, nes straining, plugging, and internal cake formation in the porous rocks decrease the permeability and restrict the uid movement, and also, pressure drop across the reservoir rocks is the rst stage of evidence of nes intrusion and permeability decline (Yang et al 2019;Vaz et al 2017;Sacramento et al 2015;Bedrikovetsky et al 2001). Mahalingam et al (2019), and Kanimozhi et al (2019a), have reported that the pressure curve in the Fig. 19 is a standard pattern during nes migration in the porous rocks under brine and CO 2 ow.…”

“…Brine-CO 2 interactions during CO 2 storage in deep coal seams lead to chemical precipitation and clay and inorganic mineral alterations (Wang et al 2016). Also, the presence of kaolinite clay in the porous rocks can trap CO 2 by mineral trapping mechanism (Mahalingam et al 2019). Table 5 presents the CO 2 retention data in the lignite core during WAG injection and these data were obtained from the hysteresis modelling.…”

“…Concurrently, the CBM reservoirs with clay mineral deposits are highly susceptible to reservoir formation damage due to nes (inorganic minerals) and coal nes (tiny fragment from broken coal matrix) migration under hydrodynamic and thermodynamic forces Guo et al 2018;Huang et al 2018;Zhao et al 2018;Zhao et al 2016;Valentim et al 2016;Han et al 2015;Bai et al 2015;Guo et al 2015;Zeinijahromi et al 2012;Seidle 2011). Actually, kaolinite clay minerals are located in several sedimentary formations, especially in sandstone and carboniferous rocks, and moreover, kaolinite occurs through dissolution of feldspar at extreme temperature and geochemical alterations (Mahalingam et al 2019;Kanimozhi et al 2019a). Figure 1 presents the kaolinite nes behaviour in lignite seam during the external uid invasion.…”