Return Permeability and Critical Velocity Testing: Formation Damage in CO2 Storage Projects

Abstract

Abstract CO2 Geological Sequestration (GS) is by far the most tangible and practical solution when compared with the other options, such as wind and solar, in the race to reach net zero global goals. GS includes depleted oil and gas reservoirs, in different minerologies, being sandstones, carbonates and dolomite the most common ones. One key parameter for subsurface CO2 storage is well injectivity. Change in well injectivity is a well-known problem in CO2 injection wells, either in enhanced oil recovery or sequestration projects (Grigg and Svec 2003). The well injectivity might change due to precipitation of sulfate and carbonate scales, which are the reaction products between CO2/ rock/brine. This change depends on petrophysical properties, such as pore throat and pore body sizes, minerology, which impacts wettability. It is an interesting problem that the industry needs to take more into consideration to be able to store CO2 in the levels needed to achieve the global temperature goals. The risk for solid precipitation and for water blockage is present. The primary objective of this paper is to quantify the reduction on permeability and changes in pore throat distribution, due to CO2 interaction with the rock. A core flood study was conducted using core plugs with a range of minerologies including sandstone, carbonate, and dolomite. Cores were saturated with 35K NaCl brine and effluent samples were collected, and the concentrations of calcium, potassium, magnesium, aluminum, sulfate, iron, and silicon ions were measured by Inductively Coupled Plasma (ICP) and Ion Chromatography (IC). CO2 was injected under supercritical conditions at a pressure of 3000 psi, and at 250°F at 8 different injection flow rate for 7 days. After the test, return permeability, pore throat distribution, NMR, and precipitated material collected after the tests will be analyzed using XRD and XRF. The air and water permeability (Kair and Kw) will be measured before and after the test to evaluate the changes in per permeability.