Qigui Wang

Acidizing is widely used to stimulate hydrocarbon production, yet reservoir heterogeneity can substantially alter acid transport. In deep carbonate reservoirs, limestone and dolostone commonly coexist. Their markedly different acid–rock reaction rates, however, make the coupled dissolution mechanism poorly understood. This study investigates how mineral distribution and injection conditions affect acid dissolution and the competitive reactions between limestone and dolostone. Using a micro-continuum framework, we developed a pore-scale reactive-transport model based on the Darcy–Brinkman–Stokes equations and coupled mass balances for the fluid and mineral phases. The results show that dolostone does not merely act as a weakly reactive residual phase. Through flow obstruction, diversion, and interface-guided transport, it reconfigures the flow paths created by preferential limestone dissolution. At the same porosity increase, the normalized permeability, K/K0 differed by a factor of up to 2.77 among mineral configurations. For vertically arranged minerals, a dolostone fraction of 50% produced the highest porosity-to-permeability conversion efficiency through moderate flow obstruction and branch convergence. When the inlet acid concentration increased from 0.2 to 5 mol L-1, the peak limestone-to-dolostone reaction-rate ratio decreased from 2.84–5.97 to 1.78–3.32 under relatively convection-dominated conditions. Under strongly diffusion-dominated conditions, this ratio decreased from 2.5–4.0 to 1.3–2.7. These results indicate that greater acid availability shifts the competitive regime from preferential limestone reaction toward partially synchronous reactions of both phases. The Pe–Da regime determines whether differences in mineral reactivity are amplified into nonuniform dissolution. Meanwhile, mineral spatial configuration and abundance govern how efficiently newly generated pore space is converted into highly conductive flow pathways.

In this study, the Darcy–Brinkman–Stokes (DBS) model based on the theory of microscopic continuous media is used to model the pore-scale reaction transport in rocks. This reaction transport is solved discretely using a coupled Multiphysics-field simulation software to investigate the dissolution reactions and the evolution of porous media during carbon sequestration. The DBS model elucidates the inherent nonlinear coupling of mineral-dissolution processes, offering insights into the intricate relationship among the seepage, solute transport, and reaction-fluid chemistry. The findings indicate the progressive dissolution of soluble minerals with time to form new seepage channels, subsequently reducing the dissolution rate within the original seepage channels. Additionally, the increased salinity of the formation water decreases the solution pH, affecting the chemistry of the reservoir minerals. Conversely, increased reservoir temperature, pressure, and injection rate promote calcite dissolution. Furthermore, the augmented pressure differential promotes the expansion of the reaction zone toward the midstream, accelerating the dissolution and reaction processes of the calcite nodes. Overall, these findings offer a theoretical foundation for future carbon capture and storage technologies.

The storage of supercritical CO₂ in deep saline aquifers is essential for reducing carbon emissions, and the selection of an appropriate reservoir is a primary consideration for carbon sequestration. To investigate the impact of reservoir physical properties on the CO₂ storage capacity of saline aquifers, this study establishes a numerical simulation model of CO₂ storage in deep saline aquifers and utilizes the MRST toolbox to solve it by the finite volume method. The research thoroughly analyzes the influence of reservoir physical properties on the CO₂ migration process and CO₂ storage capacity of the saline aquifer layer. The results show that prolonged CO₂ injection involves a process of initially suppressing pressure and subsequently slowly diffusing it to the surroundings. Furthermore, the physical properties of the reservoir and the reservoir pressure significantly influence CO₂ burial in deep saline aquifers. Higher reservoir permeability and deeper burial depth result in enhanced CO₂ storage and faster CO₂ plume migration. However, the porosity and temperature of the reservoir have a negligible impact on CO₂ storage. Our research work provides a precise understanding of selecting suitable layers for CO₂ storage in deep saline aquifers, offering strong support for early predictions of carbon capture, utilization, and storage (CCUS).

The goal of this study was to compare the effects of three plants (ryegrass, chicory and cress) in floating bed systems on purification of sedimentation pond wastewater (low-concentration) and biogas slurry (high-concentration) from geese farm in winter. The results showed that the floating bed with ryegrass had better removal rates on chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) of low-concentration wastewater than other groups at 60 days (P<0.05), and the removal rates were 53.0%, 83.3% and 61.1% respectively. At 90 days, cress has the best performance on removing 5- day biochemical oxygen demand (BOD5) and turbidity (P<0.05), with a removal rate of 82.9% and 80.8%. The removal rates of BOD5, COD, TN and turbidity by ryegrass in highconcentration wastewater were significantly higher than other treatments (P<0.05), which were 84.0%, 70.2%, 56.2% and 82.1% respectively. However, ryegrass had better stem height, root length and plant biomass production compared with cress and chicory. In conclusion, ryegrass was an optimal floating plant for purification of geese wastewater in winter and the optimal treatment time was 60 days. The regress has strong adaption for fluctuate concentrations of pollutants and is suitable for treatment of livestock and poultry wastewater in practice.