A 100,000 t/year demonstration project for carbon dioxide (CO 2 ) capture and storage in the deep saline formations of the Ordos Basin, China, has been successfully completed. Field observations suggested that the injectivity increased nearly tenfold after CO 2 injection commenced without substantial pressure build-up. In order to evaluate whether this unique phenomenon could be attributed to geochemical changes, reactive transport modeling was conducted to investigate CO 2 -water-rock interactions and changes in porosity and permeability induced by CO 2 injection. The results indicated that using porosity-permeability relationships that include tortuosity, grain size, and percolation porosity, other than typical Kozeny-Carman porosity-permeability relationship, it is possible to explain the considerable injectivity increase as a consequence of mineral dissolution. These models might be justified in terms of selective dissolution along flow paths and by dissolution or migration of plugging fines. In terms of geochemical changes, dolomite dissolution is the largest source of porosity increase. Formation physical properties such as temperature, pressure, and brine salinity were found to have modest effects on mineral dissolution and precipitation. Results from this study could have practical implications for a successful CO 2 injection and enhanced oil/gas/geothermal production in low-permeability formations, potentially providing a new basis for screening of storage sites and reservoirs.
CO2 geological storage is considered as an important measure to reduce anthropogenic CO2 emissions to the atmosphere for addressing climate change. The key prerequisite for long-term CO2 geological storage is the sealing capacity of caprock. This study investigates the evolution of sealing capacity of caprock induced by geochemical reactions among CO2, water and caprock using TOUGHREACT code based on the Heshanggou Formation mudstone at the Shenhua Carbon Capture and Storage (CCS) demonstration site of China. The results show that the self-sealing phenomenon occurs in the lower part of the caprock dominated by the precipitation of dawsonite, magnesite, siderite, Ca-smectite and illite. While the self-dissolution occurs in the upper part of caprock mainly due to the dissolution of kaolinite, K-feldspar, chlorite and Ca-smectite. Sensitivity analyses indicate that the precipitation of dawsonite, magnesite, siderite is highly advantageous leading to self-sealing of caprock, with albite and chlorite dissolution providing Na+, Mg2+ and Fe2+. The dissolution of K-feldspar dominates illite precipitation by providing required K+, and albite affects Ca-smectite precipitation. The self-sealing and self-dissolution of caprock are enhanced significantly with increasing temperature, while the effect of salinity on caprock sealing capacity is negligible perhaps due to the low salinity level of formation water.
The Shenhua CO 2 capture and sequestration (CCS) project has achieved its goal of injecting 100,000 tons/year CO 2 into the saline aquifers of the Ordos Basin. This study analyzes the geochemical interactions between CO 2 , formation fluid, and host rock of the major formations in the Ordos Basin, assesses the CO 2 trapping capabilities, and predicts the final mineral forms of injected CO 2 . Reactive transport simulations are performed using a 2D radial model, which represents a homogeneous formation. The results show that 80% of injected CO 2 remains as free supercritical gas in each formation after injection, while most of CO 2 is sequestrated in different carbonate mineral assemblages after 10,000 years. The CO 2 mineral trapping capacities of the Shiqianfeng and Shihezi formations are smaller than the Liujiagou formation. Calcite, dawsonite, and siderite are stable CO 2 trapping minerals, while dolomite, ankerite, and magnesite are not. The increase in porosity and permeability of the three formations in the first 100 years agrees with the observation from the Shenhua CCS Project. Also the decrease in porosity and permeability after 100 years shows agreement with other modelling studies using the similar methods. These results are useful for the evaluation of the geochemical process in long-term CO 2 geological storage.
A wellbore and a combined reservoir system are essential for the management of subsurface fluid resources and the geological storage of CO 2 . But the interaction between wellbore and reservoir flow is often neglected in studies of the combined system. A 2D radial model, considering the interaction of wellbore and reservoir flow was developed to investigate its impact on CO 2 geological sequestration. The mass, energy and momentum equations for the wellbore and reservoir were solved using T2Well/ECO2N. The gas flow rate of the reservoir and wellbore are predicted, and the impact of interaction between wellbore and reservoir flow on the CO 2 plume distribution and evolution was investigated. Furthermore, the influence of the CO 2 injection rate, reservoir properties and salinity on the distribution of wellbore and reservoir flow was also explored. Interaction between the wellbore and reservoir flows determines the distribution of the reservoir gas flow rate which combined with layer thickness and porosity controls the horizontal distribution and evolution of the CO 2 plume. The CO 2 wellhead injection rate and reservoir properties (including lateral transmissivity, permeability) are vital factors influencing wellbore and reservoir flows. However, reservoir salinity has little effect on the interaction between the wellbore flow and the reservoir flow, but increased reservoir salinity can accelerate the horizontal migration of CO 2 . The results of this study may help to change the widely held opinion that the distribution of the injected CO 2 among the individual layers is simply proportional to their transmissivity, and thereby enhance our understanding of CO 2 evolution beneath the surface and provide theoretical support for safe and potential geological storage of CO 2 . List of symbols KThe index for components, k = 1 (H 2 O), 2 (salt), 3 (CO 2 ), and 4 (energy) M kThe accumulation terms of the components and energy k, kg m -3 q k Source/sink terms for mass or energy components, kg m -3 s -1 F k The mass or energy transport terms along the borehole due to an advective process, W m -1 X k b Mass fraction of component k in fluid phase b,The Darcy's velocity in phase b, m s -1 AThe well cross-sectional area, m 2 z Distance along-wellbore coordinate (can be vertical, inclined, or horizontal), m U bThe internal energy of phase b per unit mass, J kg -1The momentum of phase b per unit mass, J kg -1 k Thermal conductivity, W K -1 m -1 h bThe specific enthalpy of phase b, J kg -1 gGravitational acceleration constant, m s -2 hThe angle of inclination of the wellbore, dimensionlessThe wellbore heat loss/gain per unit length of wellbore, kg m -3 s -1 T Temperature, C, K TTime, s C 0The profile parameter (or distribution coefficient), dimensionless u d Drift velocity, m s -1 q mThe density of the gas-liquid mixture, kg m -3 u mThe mixture velocity (velocity of the mixture mass center), m s -1 q m * The profile-adjusted average density, kg m -3 u inThe flow in mass flow rate of wellbore block, kg s -1 u outThe flow out mass ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.