Geochemical and Mineralogical Alteration of Sandstone in West Kazakhstan Reservoir after the Injection of CO2

Abstract:

Geological interactions between sequestered CO₂ and surrounding environments with brine and rocks during the CO₂ injection in depleted oil reservoirs can change their natural physical properties, significantly influencing the safety and effectiveness of the sequestration procedure. The main purpose of this study was to characterize such interaction-caused mineralogical alterations in the oil reservoir of Western Kazakhstan and to identify their influence on the flow parameters of reservoir rocks. The potential change of reservoir rocks and formation of brine and supercritical CO₂ were investigated under the reservoir temperature and pressure conditions. Geochemical Equilibrium model, PHREEQC, was applied to the simulation of brine-rock-CO₂ interactions at high pressure and high temperature (30-70°C). As a potential reservoir which will be investigated for the CO₂ injection, Kalamkas field, one of West Kazakhstan’s reservoirs, was chosen. Kalamkas is located onshore of Western Kazakhstan: Its reservoir temperature is ranged in 38-43°C, and lithology consists of sandstones, siltstones, and clays. The reservoir is marked by substantial heterogeneity distribution of permeability throughout the reservoir area indicating the possibility of early breakthrough and low sweep effectiveness of lower permeability layers. The high-water salinity also could affect polymer stability. Acidic fluid potentially created after the sequestration of CO₂ might affect the dissolution of carbonate minerals (calcite, dolomite, etc.), which is an essential mechanism for the creation of secondary pores and the start of formation of dissolution pathways increasing the permeability of rocks. The geological procedure increasing the CO₂ storage space and flow of CO₂ was investigated and identified in the simulated reservoir modeling.

This study was supported by the Research Grant of Nazarbayev University (NLA Contract No. 284-2019//012-2019 and 091019CRP2106).