CO2 Storage in Low Permeable Carbonate Reservoirs: Permeability and Interfacial Tension (IFT) Changes During CO2 Injection in an Iranian Carbonate Reservoir

Abstract

The lack of fundamental experimental studies on low permeable carbonate reservoirs for CO2 sequestration purposes is essential for further application of CO2 sequestration as a highly-anticipated CO2 mitigation method in deep saline aquifers, specifically those with low permeabilities. The core samples were taken from a carbonate reservoir in Iran and the brine composition was based on that of the same formation. The objective of this study is to investigate permeability alteration during CO2 sequestration in the aquifers of a low permeable Iranian carbonate reservoir. Various parameters have been investigated. The effects of different parameters such as injection pressure, confining pressure, and temperature on permeability alteration of the cores was investigated. Moreover, the interfacial tension (IFT) of CO2/brine was also determined at pressures and temperatures up to 7 MPa and 100 °C, respectively. The experimental results showed CO2 solubility and rock dissolution to be the governing mechanism when CO2 was injected into carbonate cores. The permeability measurements showed that permeability increases by increasing injection pressure and decreases by increasing confining pressure and temperature. The IFT measurement results showed that the IFT decreases significantly when there is an increase in pressure and temperature.

Review on Experimental Investigation into Formation Damage during Geologic Carbon Sequestration: Advances and Outlook

“…92 It is crucial to analyze for both economic viability and appropriate storage. According to an experiment conducted by Karaei et al, 20 there is significant formation damage when confining or injection pressure and temperature change in carbonate aquifers with a lowpermeability formation in the Iranian formation. The experiment involved three different fluids: brine water, seawater, and freshwater.…”

“…On the other hand, other studies have indicated that permeability will be reduced, while others have stated that permeability will be increased during the sequestration of CO 2 . These reports showed the critically significant challenges during CO 2 injection, which need addressing and attention for future projects.…”

“…48,49 Similarly, Shao et al reported that the permeability could decrease when the precipitation size is nearly equal to the size of the pore throats in the porous system of the formation. 29 According to studies by Karaei et al, 20 Al-Ameri et al, 50 and Dawson et al, 51 the injection of CO 2 into reservoir formation dissolves rock minerals by in situ weak and strong acids. However, reactive rock minerals, like magnesium and calcium, have also been observed to interact and react with CO 2 to generate carbonate precipitations.…”

“…According to studies by Karaei et al, Al-Ameri et al., and Dawson et al, the injection of CO 2 into reservoir formation dissolves rock minerals by in situ weak and strong acids. However, reactive rock minerals, like magnesium and calcium, have also been observed to interact and react with CO 2 to generate carbonate precipitations. , Furthermore, carbonate precipitations have been witnessed during high and low pH measurements. ,, Different kinds of literature presented CO 2 sequestration in geological formations through solubility mechanisms. Their results have reported that solubility mechanisms are significantly affected by the temperature and pressure of injected CO 2 and the salinity of the formation reservoir. − …”

“…56−62 On the other hand, other studies have indicated that permeability will be reduced, while others have stated that permeability will be increased during the sequestration of CO 2 . 20 These reports showed the critically significant challenges during CO 2 injection, which need addressing and attention for future projects. Some of the challenges presented with these reports were geo-mechanical and geochemical, such as dissolution and precipitations 63−68 of reactive minerals that can change the injectivity of CO 2 and block pores during precipitation, consequently reducing the permeability of the formation.…”