Pore-Scale Experimental Investigation of the Effect of Supercritical CO₂ Injection Rate and Surface Wettability on Salt Precipitation

Injectivity is one of the most important factors to evaluate the feasibility of CO2 geological storage. Salt precipitation due to the mass of dry CO2 injected into a saline reservoir may cause a significant decrease in injectivity. However, the coupling effect of injection parameters and reservoir conditions on salt precipitation is not clear. Here, we conducted pore-scale visualization experiments to study the morphology and distribution of salt precipitation in porous structures and their effects on permeability reduction. The experimental results are achieved by controlling the supercritical CO2 injection rate and the surface wettability at the reservoir temperature and pressure. It is found that for hydrophilic and neutral porous surfaces, ex situ precipitation occurs and blocks the entirety of pore throats and bodies, which results in a significant reduction in permeability. Increasing the CO2 injection rate can suppress the capillary reflow and prevent the permeability reduction. For a hydrophobic porous surface, in situ precipitation occurs and occupies much smaller pore volume, which has a slight effect on permeability reduction compared to the hydrophilic samples at the same injection rate. Increasing the CO2 injection rate and dewetting the injection well and formation nearby reduce the possibility of salt accumulation, which has less effect on CO2 injectivity

Performance comparison of models that are trained with or without NetExpress score.

Spearman correlation metric is measured to test models performance on three negative selection experiment datasets. A) K562 cell line dataset. B) A549 cell line dataset. C) NB4 cell line dataset.</p

Pore-Scale Experimental Investigation of the Effect of Supercritical CO₂ Injection Rate and Surface Wettability on Salt Precipitation

Injectivity is one of the most important factors to evaluate the feasibility of CO2 geological storage. Salt precipitation due to the mass of dry CO2 injected into a saline reservoir may cause a significant decrease in injectivity. However, the coupling effect of injection parameters and reservoir conditions on salt precipitation is not clear. Here, we conducted pore-scale visualization experiments to study the morphology and distribution of salt precipitation in porous structures and their effects on permeability reduction. The experimental results are achieved by controlling the supercritical CO2 injection rate and the surface wettability at the reservoir temperature and pressure. It is found that for hydrophilic and neutral porous surfaces, ex situ precipitation occurs and blocks the entirety of pore throats and bodies, which results in a significant reduction in permeability. Increasing the CO2 injection rate can suppress the capillary reflow and prevent the permeability reduction. For a hydrophobic porous surface, in situ precipitation occurs and occupies much smaller pore volume, which has a slight effect on permeability reduction compared to the hydrophilic samples at the same injection rate. Increasing the CO2 injection rate and dewetting the injection well and formation nearby reduce the possibility of salt accumulation, which has less effect on CO2 injectivity

Pore-Scale Experimental Investigation of the Effect of Supercritical CO₂ Injection Rate and Surface Wettability on Salt Precipitation

Injectivity is one of the most important factors to evaluate the feasibility of CO2 geological storage. Salt precipitation due to the mass of dry CO2 injected into a saline reservoir may cause a significant decrease in injectivity. However, the coupling effect of injection parameters and reservoir conditions on salt precipitation is not clear. Here, we conducted pore-scale visualization experiments to study the morphology and distribution of salt precipitation in porous structures and their effects on permeability reduction. The experimental results are achieved by controlling the supercritical CO2 injection rate and the surface wettability at the reservoir temperature and pressure. It is found that for hydrophilic and neutral porous surfaces, ex situ precipitation occurs and blocks the entirety of pore throats and bodies, which results in a significant reduction in permeability. Increasing the CO2 injection rate can suppress the capillary reflow and prevent the permeability reduction. For a hydrophobic porous surface, in situ precipitation occurs and occupies much smaller pore volume, which has a slight effect on permeability reduction compared to the hydrophilic samples at the same injection rate. Increasing the CO2 injection rate and dewetting the injection well and formation nearby reduce the possibility of salt accumulation, which has less effect on CO2 injectivity

Pore-Scale Experimental Investigation of the Effect of Supercritical CO₂ Injection Rate and Surface Wettability on Salt Precipitation

Injectivity is one of the most important factors to evaluate the feasibility of CO2 geological storage. Salt precipitation due to the mass of dry CO2 injected into a saline reservoir may cause a significant decrease in injectivity. However, the coupling effect of injection parameters and reservoir conditions on salt precipitation is not clear. Here, we conducted pore-scale visualization experiments to study the morphology and distribution of salt precipitation in porous structures and their effects on permeability reduction. The experimental results are achieved by controlling the supercritical CO2 injection rate and the surface wettability at the reservoir temperature and pressure. It is found that for hydrophilic and neutral porous surfaces, ex situ precipitation occurs and blocks the entirety of pore throats and bodies, which results in a significant reduction in permeability. Increasing the CO2 injection rate can suppress the capillary reflow and prevent the permeability reduction. For a hydrophobic porous surface, in situ precipitation occurs and occupies much smaller pore volume, which has a slight effect on permeability reduction compared to the hydrophilic samples at the same injection rate. Increasing the CO2 injection rate and dewetting the injection well and formation nearby reduce the possibility of salt accumulation, which has less effect on CO2 injectivity

Pore-Scale Experimental Investigation of the Effect of Supercritical CO₂ Injection Rate and Surface Wettability on Salt Precipitation

Injectivity is one of the most important factors to evaluate the feasibility of CO2 geological storage. Salt precipitation due to the mass of dry CO2 injected into a saline reservoir may cause a significant decrease in injectivity. However, the coupling effect of injection parameters and reservoir conditions on salt precipitation is not clear. Here, we conducted pore-scale visualization experiments to study the morphology and distribution of salt precipitation in porous structures and their effects on permeability reduction. The experimental results are achieved by controlling the supercritical CO2 injection rate and the surface wettability at the reservoir temperature and pressure. It is found that for hydrophilic and neutral porous surfaces, ex situ precipitation occurs and blocks the entirety of pore throats and bodies, which results in a significant reduction in permeability. Increasing the CO2 injection rate can suppress the capillary reflow and prevent the permeability reduction. For a hydrophobic porous surface, in situ precipitation occurs and occupies much smaller pore volume, which has a slight effect on permeability reduction compared to the hydrophilic samples at the same injection rate. Increasing the CO2 injection rate and dewetting the injection well and formation nearby reduce the possibility of salt accumulation, which has less effect on CO2 injectivity

Schematic representation of the off-target specificity prediction model, AttnToMismatch_CNN.

Schematic representation of the off-target specificity prediction model, AttnToMismatch_CNN.</p

Feature importance study with input features perturbation method.

The feature importance of AttnToCrispr_CNN on-target efficiency prediction model, which is trained with Crispr-Cas9 dataset in A) K562 cell line B) A549 cell line and C) NB4 cell line. Each dimer is two contiguous nucleotide bases on the input sequence. D) The feature importance of AttnToMismatch_CNN off-target specificity prediction model, which is trained with Crispr-Cas9 dataset. Each dimer is a nucleotide base pair, with one from a sgRNA and its counterpart in the target DNA.</p

Comparison of models performances on Crispr-Cas12a (Crispr-Cpf1) dataset.

Spearman correlation, Pearson correlation, and mean squared error metrics (MSE) are compared.</p

Performances comparison of off-target specificity prediction models, including AUC-ROC and PR-AUC scores of AttnToMismatch_CNN, DeepCpf1, DeepCrispr, Random Forest, and Gradient Boosted trees models in 2 different scenarios.

A)-B) Crispr-Cas12a (Crispr-Cpf1). DeepCpf1 PR-AUC score is not provided in the previous study [33]. C)-F) Crispr-Cas9. C) and D) are the performances with the 5-fold cross-validation method. E) and F) are the performances by leaving three sgRNAs out as test dataset (leave-sgRNAs-out). In B), the PR-AUC of DeepCpf1 was not reported.</p