At present,there is a growing demand for safe and low-pollution rock-breaking technology.The rock breaking technology of supercritical CO_(2)thermal fracturing has many advantages,such as no dust noise,no explosion,hi...At present,there is a growing demand for safe and low-pollution rock-breaking technology.The rock breaking technology of supercritical CO_(2)thermal fracturing has many advantages,such as no dust noise,no explosion,high efficiency,controllable shock wave and so on.Fully considering the combustion rate of energetic materials,heat and mass transfer,CO_(2)phase change and transient nonlinear flow process,a multi-field coupled numerical model of rock breaking by supercritical CO_(2)thermal fracturing was established based on the existing experiments.The influence factors of CO_(2)thermal fracturing process were studied to provide theoretical guidance for site construction parameters optimization.The numerical simulation results were in good agreement with the experimental observation results.The results showed that the maximum temperature of CO_(2)and the growth rate of CO_(2)pressure during the fracturing process would decrease accordingly with the increase of CO_(2)initial pressure.But the change in CO_(2)peak pressure wasn't significant.Appropriately increasing the heat source power could improve the heating and pressurization rate of CO_(2)and accelerate the damage rate of rock.The relevant results were of great importance for promoting the application of rock breaking by supercritical CO_(2)thermal fracturing technology.展开更多
CO_(2) dry fracturing is a promising alternative method to water fracturing in tight gas reservoirs,especially in water-scarce areas such as the Loess Plateau.The CO_(2) flowback efficiency is a critical factor that a...CO_(2) dry fracturing is a promising alternative method to water fracturing in tight gas reservoirs,especially in water-scarce areas such as the Loess Plateau.The CO_(2) flowback efficiency is a critical factor that affects the final gas production effect.However,there have been few studies focusing on the flowback characteristics after CO_(2) dry fracturing.In this study,an extensive core-to-field scale study was conducted to investigate CO_(2) flowback characteristics and CH_(4) production behavior.Firstly,to investigate the impact of core properties and production conditions on CO_(2) flowback,a series of laboratory experiments at the core scale were conducted.Then,the key factors affecting the flowback were analyzed using the grey correlation method based on field data.Finally,taking the construction parameters of Well S60 as an example,a dual-permeability model was used to characterize the different seepage fields in the matrix and fracture for tight gas reservoirs.The production parameters after CO_(2) dry fracturing were then optimized.Experimental results demonstrate that CO_(2) dry fracturing is more effective than slickwater fracturing,with a 9.2%increase in CH_(4) recovery.The increase in core permeability plays a positive role in improving CH_(4) production and CO_(2) flowback.The soaking process is mainly affected by CO_(2) diffusion,and the soaking time should be controlled within 12 h.Increasing the flowback pressure gradient results in a significant increase in both CH_(4) recovery and CO_(2) flowback efficiency.While,an increase in CO_(2) injection is not conducive to CH_(4) production and CO_(2) flowback.Based on the experimental and field data,the important factors affecting flowback and production were comprehensively and effectively discussed.The results show that permeability is the most important factor,followed by porosity and effective thickness.Considering flowback efficiency and the influence of proppant reflux,the injection volume should be the minimum volume that meets the requirements for generating fractures.The soaking time should be short which is 1 day in this study,and the optimal bottom hole flowback pressure should be set at 10 MPa.This study aims to improve the understanding of CO_(2) dry fracturing in tight gas reservoirs and provide valuable insights for optimizing the process parameters.展开更多
基金financially supported by National Key R&D Program-Sino US intergovernmental Cooperation Project(No.2023YFE0120500)Science and Technology Program of the Ministry of Housing and Urban-Rural Development of the People's Republic of China(No.2021-K-087)+1 种基金the Surface Project of the Natural Science Foundation of Jiangsu Province,China(No.BK20201313)the State Key Laboratory Open Fund Project of China(No.HKLBEF202004)。
文摘At present,there is a growing demand for safe and low-pollution rock-breaking technology.The rock breaking technology of supercritical CO_(2)thermal fracturing has many advantages,such as no dust noise,no explosion,high efficiency,controllable shock wave and so on.Fully considering the combustion rate of energetic materials,heat and mass transfer,CO_(2)phase change and transient nonlinear flow process,a multi-field coupled numerical model of rock breaking by supercritical CO_(2)thermal fracturing was established based on the existing experiments.The influence factors of CO_(2)thermal fracturing process were studied to provide theoretical guidance for site construction parameters optimization.The numerical simulation results were in good agreement with the experimental observation results.The results showed that the maximum temperature of CO_(2)and the growth rate of CO_(2)pressure during the fracturing process would decrease accordingly with the increase of CO_(2)initial pressure.But the change in CO_(2)peak pressure wasn't significant.Appropriately increasing the heat source power could improve the heating and pressurization rate of CO_(2)and accelerate the damage rate of rock.The relevant results were of great importance for promoting the application of rock breaking by supercritical CO_(2)thermal fracturing technology.
基金support from the National Natural Science Foundation of China(No.51904324,No.51974348)the Prospective Basic Major Science and Technology Projects for the 14th Five Year Plan(No.2021DJ2202).
文摘CO_(2) dry fracturing is a promising alternative method to water fracturing in tight gas reservoirs,especially in water-scarce areas such as the Loess Plateau.The CO_(2) flowback efficiency is a critical factor that affects the final gas production effect.However,there have been few studies focusing on the flowback characteristics after CO_(2) dry fracturing.In this study,an extensive core-to-field scale study was conducted to investigate CO_(2) flowback characteristics and CH_(4) production behavior.Firstly,to investigate the impact of core properties and production conditions on CO_(2) flowback,a series of laboratory experiments at the core scale were conducted.Then,the key factors affecting the flowback were analyzed using the grey correlation method based on field data.Finally,taking the construction parameters of Well S60 as an example,a dual-permeability model was used to characterize the different seepage fields in the matrix and fracture for tight gas reservoirs.The production parameters after CO_(2) dry fracturing were then optimized.Experimental results demonstrate that CO_(2) dry fracturing is more effective than slickwater fracturing,with a 9.2%increase in CH_(4) recovery.The increase in core permeability plays a positive role in improving CH_(4) production and CO_(2) flowback.The soaking process is mainly affected by CO_(2) diffusion,and the soaking time should be controlled within 12 h.Increasing the flowback pressure gradient results in a significant increase in both CH_(4) recovery and CO_(2) flowback efficiency.While,an increase in CO_(2) injection is not conducive to CH_(4) production and CO_(2) flowback.Based on the experimental and field data,the important factors affecting flowback and production were comprehensively and effectively discussed.The results show that permeability is the most important factor,followed by porosity and effective thickness.Considering flowback efficiency and the influence of proppant reflux,the injection volume should be the minimum volume that meets the requirements for generating fractures.The soaking time should be short which is 1 day in this study,and the optimal bottom hole flowback pressure should be set at 10 MPa.This study aims to improve the understanding of CO_(2) dry fracturing in tight gas reservoirs and provide valuable insights for optimizing the process parameters.
