Work

Effects of CO2 Flooding for Brine Extraction on the Pore Structure of Brine Reservoirs with Different Lithologies

Year: 2026

Type: article

Abstract: The deep brine reservoirs in the Jianshishan area of the Qaidam Basin are abundant in strategic mineral resources. Traditional extraction methods suffer from insufficient reservoir energy and low recovery efficiency, while CO2 flooding technology offers a new solution integrating brine development and CO2 sequestration. However, the reservoir comprises three typical lithologies (calcareous mudstone, laminated mudstone, and massive sandstone) with distinct mineral compositions and structural characteristics and the mechanisms by which CO2–brine–reservoir reactions affect their pore structures remain unclear. This study conducted laboratory simulation experiments combined with multiple analytical techniques to investigate the evolutionary characteristics of the three lithologies under CO2 action. The results show that (1) calcareous mudstone has the strongest dissolution effect, with porosity increasing from 6.25% to 9.29% (an increase of 48.6%) and permeability increasing from 0.0012 mD to 0.0511 mD (an increase of 41.6 times); (2) laminated mudstone shows a trend of “first improvement, then deterioration”, with porosity initially rising to 11.84% and then slightly decreasing, and permeability decreasing from 0.0042 mD to 0.0036 mD; and (3) massive sandstone has stable mineral composition, with porosity increasing from 10.74% to 11.63% (an increase of 8.3%) and permeability fluctuating slightly between 0.0028 and 0.0032 mD. This study reveals that lithological mineral composition and structural characteristics are core factors controlling pore structure evolution, providing theoretical and experimental support for optimizing differentiated CO2 flooding schemes for deep brine reservoirs.

Source: Processes

DOI: 10.3390/pr14030486