CO2 fracturing is an important measure to realize the implementation of the “carbon neutralization” policy characterized by carbon recycling. Conventional fracturing equipments is difficult to meet the technical requirements of CO2 fracturing, so it is necessary to promote the promotion and application of this technology through the research and development of core equipment. In combination with the technical characteristics and the special nature of CO2, The core equipment with completely independent intellectual property rights – CO2 closed sand-mixing device and N2 pressurization device have been developed successfully, which solved the problems of CO2 closed sand-mixing and displacement & fluid supply”.With the steady progress of the “dual carbon policy”, the core equipment for large-scale CO2 fracturing with large sand volume and sand ratio needs to be developed urgently. This article introduces the development direction of the core equipment from two aspects: closed continuous sand mixing technology and CO2 gasification pressurization technology. The successful development of these two core technologies will greatly promote the industrial application of CO2 fracturing technology in the future.
CO2 injection into subsurface reservoirs for storage engineering is the most important means to reduce greenhouse gases. To satisfy the huge carbon-neutral target, injection and storage engineering exploration is needed for tight reservoirs beyond aquifers or abandoned reservoirs. Later, China carried out an exploration and research project on CO2-ECBM and CO2-EOR demonstration projects in tight reservoirs for the applicability, reliability and coordination of different monitoring technologies. This paper relies on the CO2-ECBM project for a passive monitoring technique of the TS634 well in ShiZhuang City, Shanxi Province, China. The monitoring adopted the three-component grid monitor system with the long-time continuous acquisition, and applied the passive seismic tomography algorithm, and obtained the energy perturbation during reservoir injection. The results integrated the target coal seam configuration, porosity, and permeability distribution of the layer before injection, which well represents the energy distribution and fractures probability distribution caused by fluid perturbation during the injection process. After that, comparing the results of the multi-period processing can illustrate the fluid transport trend and inter-well interconnection direction, and it is consistent with the production well verification. For the first CO2-ECBM demonstration project in China, the passive seismic monitoring technology is used to complete the fluid transport trend analysis with the passive seismic tomography technology as the core, and better presentation results are obtained at a certain scale, which initially verifies the effectiveness of the passive seismic monitoring technology for the ECBM carbon storage project. This study lays a foundation for the development of domestic carbon storage geophysical monitoring technology, and is more likely to improve the accuracy of comprehensive research on multi-dimensional and multi-domain monitoring technology.
CO2 as cushion gas of underground natural gas storage can not only effectively save the initial capital investment, but also slow down the greenhouse effect and realize the geological burial of CO2. It has important strategic significance and social value for the development and construction of underground natural gas storage. Based on a large number of literature research at home and abroad, this paper summarizes and combs the differences in physical properties between carbon dioxide and natural gas, the mixing mechanism of carbon dioxide as cushion gas and natural gas in natural gas underground storage, the influence of multiple rounds of injection and production in the operation of natural gas underground storage and the influence on the capacity and stability of gas storage under fluid solid coupling, so as to provide reference for the implementation of CO2 as cushion gas in natural gas underground storage. In addition, it also puts forward the deficiency of theoretical understanding of cushion gas in CO2 as natural gas underground storage, including: ①High-speed non Darcy seepage of gas, the movement law of displacement phase front and the distribution characteristics of mixing zone under the action of alternating load; ②The accuracy of three-dimensional three-phase oil, gas and water injection production dynamic multi physical field coupling model is improved; ③For geological activities in the early stage of natural disasters, which may lead to gas leakage, specific measures shall be taken to deal with emergencies; ④The geological conditions of gas storage construction are more complex, and its development is more difficult. In addition, the mathematical model of injection production operation evaluation in the whole life cycle of natural gas underground storage operation is established.
The decrease of pipe wall temperature caused by CO2 drainage is the direct cause of the tough-brittle transformation of long distance pipeline materials. In this paper, the experimental research scheme of CO2 pipeline small hole leakage is designed, and the corresponding experimental equipment is set up to measure the temperature of the pipe wall after CO2 drainage. The variation rule of pipe wall temperature in leakage area under different parameters is studied. The experimental data obtained have guiding significance for the safety evaluation and design of pipeline
Underground hydrogen storage (UHS) is an effective means to solve large-scale energy storage. The depleted gas reservoirs can be used as the potential targets for UHS due to its huge storage space, good sealing ability, and the existing facilities. CO2 can be injected as the cushion gas to reduce the loss of hydrogen and achieve carbon sequestration. This work proposes a novel analytical method to calculate the hydrogen storage capacity in depleted gas reservoirs using CO2 as cushion gas considering hydrogen storage safety and gas (e.g., CO2, H2, CH4) dissolution in formation water. The multi-components (H2-CO2-CH4-H2O) material balance equations are further developed by considering the edge/bottom water and gas dissolution in water as well as caprock breakthrough and fault instability. The maximum operating pressure of UHS is determined by calculating the caprock-breakthrough pressure and the fault-instability pressure. The proposed method has been applied to evaluate the UHS capacity of a depleted gas reservoir in the Sichuan Basin of China. The maximum pressure threshold of formation is determined to be 42M. The hydrogen storage capacity under different CO2 cushion gas volume conditions is calculated. The study compares with the model without considering dissolution, and the influence of sensitive factors such as temperature and pressure on hydrogen storage capacity is analyzed.
The sustainable deterioration of the climate caused by continuous global warming poses a serious threat to human survival. Carbon Capture Utilization and Storage (CCUS) is a potential and effective technology to alleviate global warming. CO2 pipeline transportation is an economical and safety way to connect other parts in the CCUS system. It is essential to understand the characteristics of CO2 release and hazards and these are essential to the design and arrangement of pipeline. Existent CO2 pipeline release experimental studies lack of repeatable verification tests, especially those seriously affected by the environment, CO2 far-field diffusion research, for example. It is necessary to guarantee the same initial conditions between different repetitive tests. In this paper, the equal density principle for CO2 pipeline release tests was summed up based on thermal process before release operation. A computational model to calculate the charging mass and phase state of CO2 to achieve a specific initial pressure and temperature inside pipeline for release test was established, using MTLAB software. The Span-Wagner (SW) equation of state was applied to calculate the thermodynamic properties of CO2. The initial pressure, initial temperature, and inventory in authors’ previous studies are presented. By comparing the experimental data and the calculated results, the model has good predictive ability. Larger CO2 mass for the injection operation is the result of lower initial temperature or greater initial pressure. The numerical model provides convenience to improve accuracy for CO2 release tests.
Carbon capture, utilization and storage (CCUS) has become a key technology in the process of promoting low-carbon development, where the safe transport-ation of high-pressure pipelines is crucial. In order to study the discharge characteristics of CO2 pipelines, a large-scale experimental pipe with a length of 258 m and an inner diameter of 233 mm was developed to simulate the real leakage scenario as much as possible. The jet morphology generated during the rupture of the pipeline under different leakage sizes (15mm, 50mm, 100mm, 233mm) was photographed from the side of the discharge port with a high-frequency camera, and it was found that there were different degrees of under-expanded jet areas near the leakage outlet in the initial stage of leakage, which gradually developed and formed visible clouds, but there were obvious differences in their development scale and duration. In this paper, we analyzed the theoretical structure of the jet. And we extracted key features such as leak duration and jet length by analyzing the morphology of jets under different calibers. So as to propose the correlation between the morphology of the jet and cracks. When a leakage accident occurs, the scale of the crack can be quickly and accurately estimated from the leakage morphological characteristics of the periphery of the accident, and the degree of the accident can be judged, which provides a basis for the formulation of the early warning plan.
Carbon neutralization is gaining increasing attention in various countries, and the risk of leakage is inevitable in the transport of captured CO2 to storage. High pressure Carbon Dioxide (CO2) pipeline transport is an important component of the Carbon Capture Utilization and Storage (CCUS) chain. Hence, accurate estimation of the leak caliber is an important component in determining the risk level when leakage happens. Carbon dioxide leaks are hazardous accidents, and accidental releases from pipeline transportation can lead to catastrophic damage. To ensure safety in the process of pipeline transportation, it is necessary to understand the impact of different leak sizes on the risk range after the occurrence of a pipeline failure. In this paper, a proposed model for estimation of pipe leak caliber based on back analysis through experimental and numerical studies. First establishes that the danger of CO2 leakage from supercritical phase transport using a large pipe experiment (258 m long, internal diameter is 233 mm). Then a two-stage Computational Fluid Dynamics (CFD) model to predict different caliber supercritical phase CO2 leakage ranges was proposed, and the CFD model was validated by experimental data. The error between numerical simulation values and experimental results is within 5%. The numerical model calculated the leakage ranges at different calibers, back analysis of the CO2 concentration data, a model capable of predicting leakage caliber by leakage range is proposed. When a leakage accident of a pipe occurs, the leakage caliber is confirmed by this model, which provides a new method for determining the time of appearance of leakage.
The coupled reaction-extraction-crystallization process for CO2 mineralization is a essential technology for CCUS. The thermal regeneration of organic amine hydrochlorides is a crucial technique to facilitate the industrialization of this process. In this study, DFT was used to calculate the geometry, charge distribution, infrared spectrum and solvation free energy of TOAHCl in different solvents. MD was used to examine the thermal dissociation of TOAHCl in non-polar solvents and calculate the RDF, MSD and diffusion coefficient during the dissociation. Through DFT and MD, effect of solvent on the thermal dissociation of TOAHCl was investigated. DFT calculations is consistent with experimental results. MD results show solvents can disperse reactants and products, enhance mass transfer.
The treatment of CaCl2 waste liquid has become a common technical problem in the soda industry, and there is still no good solution. Meanwhile, the global is under intense pressure from drastic climate change, and CO2 emission reduction is urgent. If the two waste are utilized, it will have multiple benefits, but there is little research on it. In this work, a novel route for comprehensively utilizing the flue gas CO2 of power plant and the CaCl2 waste liquid of ammonia-alkali plant was developed, in which CaCl2 solution and flue gas CO2 were transformed into CaCO3 products based on an absorption−mineralization process using water-soluble amines. The technical feasibility with six amines was fully verified, and to further obtain the larger particle size CaCO3 that facilitates industrial filtration, the effects of different operating conditions were investigated. Results showed that ethanolamine (MEA) is the optimal amine, with the mineralization rate is 97.2%. The CaCO3 with the larger particle size is of 20-30 μm under the optimal condition.