Influence of pore seepage and mineralogical characteristics on the evolution of CO₂ transport in the Huaziping area

The Ordos Basin is an important energy and chemical base in China, with a large number of low-cost, high-concentration coal chemical CO₂ sources and low-permeability reservoir storage space suitable for CO₂ storage, making it an ideal candidate for CCUS technology demonstration. However, there are still many challenges to achieve efficient CO₂-EOR and effective storage in low-permeability reservoirs. In this paper, we take the Haziping reservoir of the Yanchang Formation in the Ordos Basin as the target layer for geological storage, and find that the original porosity, permeability and initial mineral fraction have different levels of influence on the evolution of CO₂ transport and reservoir water chemistry changes through numerical simulations. As CO₂ is injected, the original minerals begin to undergo hydrogeochemical reactions and some of the minerals begin to dissolve, with the dissolved amounts of minerals ranked from largest to smallest: chlorite, feldspar-like, kaolinite. Mineral precipitation amounts were ranked as follows: iron dolomite, sodium montmorillonite, calcite, magnesite, illite, quartz. By analysing whether the precipitated minerals can be stabilised as carbon fixing minerals in the reservoir, the final determination of the carbon fixing mineral combination in the target reservoir is iron dolomite+magnesite. The presence of carbon fixing minerals in the target reservoir is indicative of geological storage, and it was found that iron dolomite could be used as a mineral tracer for the presence of CO₂ in the geological storage process.