Aoxiang Zhang, Longyong Shu, Zhonggang Huo, Xin Song
The existing research on CH4 displacement by N2 mainly focuses on the gas injection displacement mechanism and the factors affecting displacement efficiency. And most of them are theoretical analyses at the model level or multifactor analyses at the simulation test level, while there are few targeted physical simulation tests and quantitative analyses. Given the above problems, the experiment system was used to study the gas migration evolution law and time-varying characteristics of CH4 displacement by N2 in coal under different injection pressures. The experimental results show that the whole process of CH4 displacement by N2 can be divided into three stages: stage I (original equilibrium stage); stage II (dynamic balance stage); stage III (new equilibrium stage). The concentration of CH4 and N2 presents an opposite variation trend, and the variation rate of CH4 and N2 increased first and then decreased. The breakthrough time was 50 minutes, 45 minutes, 35 minutes, 25 minutes, and 20 minutes, respectively, under different injection pressures. The displacement efficiency increased with the injection pressures, while the replacement ratio decreased with the injection pressures. The maximum flow rate of CH4 was 0.085 mL/min, 0.110 mL/min, 0.130 mL/min, 0.222 mL/min, and 0.273 mL/min, respectively, under different injection pressures. The accumulated production of CH4 was 3.59 mL, 3.91 mL, 4.39 mL, 5.58 mL, and 5.94 mL, respectively, under different injection pressures. The effective injection pressure range was 1.6~2 MPa. This research can provide a reference for the theoretical research of N2-ECBM-related technology in low permeability reservoirs and the selection of injection pressure in the field technology implementation.
{"title":"The Time-Varying Variation Characteristics of Methane during Nitrogen Injection Process: An Experimental Study on Bituminous Coals","authors":"Aoxiang Zhang, Longyong Shu, Zhonggang Huo, Xin Song","doi":"10.1155/2023/5075888","DOIUrl":"https://doi.org/10.1155/2023/5075888","url":null,"abstract":"The existing research on CH<sub>4</sub> displacement by N<sub>2</sub> mainly focuses on the gas injection displacement mechanism and the factors affecting displacement efficiency. And most of them are theoretical analyses at the model level or multifactor analyses at the simulation test level, while there are few targeted physical simulation tests and quantitative analyses. Given the above problems, the experiment system was used to study the gas migration evolution law and time-varying characteristics of CH<sub>4</sub> displacement by N<sub>2</sub> in coal under different injection pressures. The experimental results show that the whole process of CH<sub>4</sub> displacement by N<sub>2</sub> can be divided into three stages: stage I (original equilibrium stage); stage II (dynamic balance stage); stage III (new equilibrium stage). The concentration of CH<sub>4</sub> and N<sub>2</sub> presents an opposite variation trend, and the variation rate of CH<sub>4</sub> and N<sub>2</sub> increased first and then decreased. The breakthrough time was 50 minutes, 45 minutes, 35 minutes, 25 minutes, and 20 minutes, respectively, under different injection pressures. The displacement efficiency increased with the injection pressures, while the replacement ratio decreased with the injection pressures. The maximum flow rate of CH<sub>4</sub> was 0.085 mL/min, 0.110 mL/min, 0.130 mL/min, 0.222 mL/min, and 0.273 mL/min, respectively, under different injection pressures. The accumulated production of CH<sub>4</sub> was 3.59 mL, 3.91 mL, 4.39 mL, 5.58 mL, and 5.94 mL, respectively, under different injection pressures. The effective injection pressure range was 1.6~2 MPa. This research can provide a reference for the theoretical research of N<sub>2</sub>-ECBM-related technology in low permeability reservoirs and the selection of injection pressure in the field technology implementation.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"109 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138568225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhang Jiayu, Zhang Lili, Zhang Yaowen, Yao Yunsheng, Li Haoran, Dai Yiming, Wang Renlong, Hu Caixiong
Since the initial impoundment and commissioning of the Three Gorges Reservoir in June 2003, seismic activity surrounding the reservoir region has undergone substantial changes. Leveraging geological and hydrogeological data from the Three Gorges Reservoir area, this study statistically analyzes the historical water level and earthquake catalog within the reservoir. By examining the correlation between reservoir water levels and earthquake frequency, the relationship between seismicity along the Xiannvshan fault and water level is analyzed. Additionally, the ArcGIS software is employed to evaluate the spatial pattern of earthquake epicenters during the filling of the Three Gorges Reservoir, with the goal of elucidating the impact of water impoundment at the Three Gorges on the activity along the Xiannvshan fault. The results demonstrate the following. (1) There is a complex process of “continuous loading, permeation and saturation, rebound and rebalancing” in the crust of the reservoir head area during the impoundment of the Three Gorges Reservoir area, and the activity of the Xiannvshan fault is closely related to the reservoir water level. (2) At the 135 m impoundment stage, Xiannvshan fault activity is mainly affected by reservoir water level and is positively correlated with reservoir water level. At the 156 m impoundment stage, reservoir water load is still the main influencing factor of Xiannvshan fault activity, but the permeability of reservoir water is enhanced in this stage. (3) The earthquake epicenters near the northern section of the Xiannvshan fault are clustered during the 175 m experimental impoundment stage. During the continuous loading stage, the reservoir water load is still the main control factor of the Xiannvshan fault, and the seismic activity is significantly enhanced. From November 2010 to November 2013, during the permeation and saturation stage, the dominant factor of Xiannvshan fault activity changed from reservoir water load to reservoir water infiltration along the Xiannvshan fault. The period from 2013.11 to 2014.5 was a vertical rebound stage, and the infiltration effect of reservoir water had a more significant impact on Xiannvshan fault activities.
{"title":"Influence of the Three Gorges Reservoir Impoundment on Xiannvshan Fault Activity","authors":"Zhang Jiayu, Zhang Lili, Zhang Yaowen, Yao Yunsheng, Li Haoran, Dai Yiming, Wang Renlong, Hu Caixiong","doi":"10.1155/2023/6611611","DOIUrl":"https://doi.org/10.1155/2023/6611611","url":null,"abstract":"Since the initial impoundment and commissioning of the Three Gorges Reservoir in June 2003, seismic activity surrounding the reservoir region has undergone substantial changes. Leveraging geological and hydrogeological data from the Three Gorges Reservoir area, this study statistically analyzes the historical water level and earthquake catalog within the reservoir. By examining the correlation between reservoir water levels and earthquake frequency, the relationship between seismicity along the Xiannvshan fault and water level is analyzed. Additionally, the ArcGIS software is employed to evaluate the spatial pattern of earthquake epicenters during the filling of the Three Gorges Reservoir, with the goal of elucidating the impact of water impoundment at the Three Gorges on the activity along the Xiannvshan fault. The results demonstrate the following. (1) There is a complex process of “continuous loading, permeation and saturation, rebound and rebalancing” in the crust of the reservoir head area during the impoundment of the Three Gorges Reservoir area, and the activity of the Xiannvshan fault is closely related to the reservoir water level. (2) At the 135 m impoundment stage, Xiannvshan fault activity is mainly affected by reservoir water level and is positively correlated with reservoir water level. At the 156 m impoundment stage, reservoir water load is still the main influencing factor of Xiannvshan fault activity, but the permeability of reservoir water is enhanced in this stage. (3) The earthquake epicenters near the northern section of the Xiannvshan fault are clustered during the 175 m experimental impoundment stage. During the continuous loading stage, the reservoir water load is still the main control factor of the Xiannvshan fault, and the seismic activity is significantly enhanced. From November 2010 to November 2013, during the permeation and saturation stage, the dominant factor of Xiannvshan fault activity changed from reservoir water load to reservoir water infiltration along the Xiannvshan fault. The period from 2013.11 to 2014.5 was a vertical rebound stage, and the infiltration effect of reservoir water had a more significant impact on Xiannvshan fault activities.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"7 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138533950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The transient electromagnetic (TEM) method has long been applied in tunnel advanced prediction. However, it remains questionable to what extent a geologic anomaly body will influence the induced electromagnetic response in front of the heading face. The dilemma is partly because observed TEM data are frequently interpreted by empirical formulas or proportional relationships, and a quantitative measurement has not been established. In this paper, we strive to understand the TEM characteristics from a 3D finite-element time-domain (FETD) modeling aspect. The modeling algorithm is based on unstructured space meshing and unconditional stable time discretization, which ensures its accuracy and stability. The modeling algorithm is verified by a half-space model, in which the misfit of late-time channels that we are concerned with is generally below 1%. The algorithm has also been utilized to carry out the TEM response of tunnel models with different types of TEM devices. Through model studies, we find that both the traditional central-loop device and the recently developed weak-coupling opposing-coil device are feasible in tunnel advanced detection. Nevertheless, the latter type of device better distinguishes low-resistivity anomalies at 30 m ahead of the heading face with a relative difference (between models with and without the anomaly) of more than 1000% at certain time channels, compared with only a 10% difference of the central-loop device. Also, we conclude that the vertical electromagnetic field component should be recorded and interpreted together with the horizontal field to provide more convincing results.
{"title":"Feasibility of Tunnel TEM Advanced Prediction: A 3D Forward Modeling Study","authors":"Jiannan Fu, Xiaodong Yang, Guanqun Zhou, Xueliang Jin, Fuqin Zhai, Fanbin Meng, Yafei Wang","doi":"10.1155/2023/8486173","DOIUrl":"https://doi.org/10.1155/2023/8486173","url":null,"abstract":"The transient electromagnetic (TEM) method has long been applied in tunnel advanced prediction. However, it remains questionable to what extent a geologic anomaly body will influence the induced electromagnetic response in front of the heading face. The dilemma is partly because observed TEM data are frequently interpreted by empirical formulas or proportional relationships, and a quantitative measurement has not been established. In this paper, we strive to understand the TEM characteristics from a 3D finite-element time-domain (FETD) modeling aspect. The modeling algorithm is based on unstructured space meshing and unconditional stable time discretization, which ensures its accuracy and stability. The modeling algorithm is verified by a half-space model, in which the misfit of late-time channels that we are concerned with is generally below 1%. The algorithm has also been utilized to carry out the TEM response of tunnel models with different types of TEM devices. Through model studies, we find that both the traditional central-loop device and the recently developed weak-coupling opposing-coil device are feasible in tunnel advanced detection. Nevertheless, the latter type of device better distinguishes low-resistivity anomalies at 30 m ahead of the heading face with a relative difference (between models with and without the anomaly) of more than 1000% at certain time channels, compared with only a 10% difference of the central-loop device. Also, we conclude that the vertical electromagnetic field component should be recorded and interpreted together with the horizontal field to provide more convincing results.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"10 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138533973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Considering that karst caves, underground rivers, and dissolution fractures in shallow carbonate formation in the Sichuan Basin are extremely developed, leakage, failure and plugging difficulties are easy to occur in the drilling process. The TDEM was used to carry out the exploration of hidden karst geological bodies in well QM2, and the quasi-three-dimensional inversion based on lateral constrain was used to invert the TDEM data. Three NW trending anomalous bands were identified in the lower Triassic Jialingjiang Formation within the range of drilling, consisting of seven relatively low-resistivity anomalous zones. Under the guidance of TDEM quasi-three-dimensional inversion resistivity data, the low-resistivity karst development area is avoided, and the specific drilling location of well QM2 is determined. No karst cave and underground river were drilled in the later drilling process of well QM2, as well as no instability phenomenon occurred. It indicates that the TDEM detection results are consistent with the actual drilling, and the quasi-three-dimensional TDEM inversion interpretation data based on lateral constraints is reliable and can accurately detect the buried karst in the wellsite.
{"title":"Fine Detection and Analysis of Hidden Karst in Wellsite with Quasi-Three-Dimensional TDEM Based on Lateral Constraint","authors":"Bin Wu, Yunping Liao, Hongkai Chen, Lichuan Chen, Shicong Ren, Shihong Xiao, Yunjian Yang, Yong Yang, Haiyou Peng","doi":"10.1155/2023/2766524","DOIUrl":"https://doi.org/10.1155/2023/2766524","url":null,"abstract":"Considering that karst caves, underground rivers, and dissolution fractures in shallow carbonate formation in the Sichuan Basin are extremely developed, leakage, failure and plugging difficulties are easy to occur in the drilling process. The TDEM was used to carry out the exploration of hidden karst geological bodies in well QM2, and the quasi-three-dimensional inversion based on lateral constrain was used to invert the TDEM data. Three NW trending anomalous bands were identified in the lower Triassic Jialingjiang Formation within the range of drilling, consisting of seven relatively low-resistivity anomalous zones. Under the guidance of TDEM quasi-three-dimensional inversion resistivity data, the low-resistivity karst development area is avoided, and the specific drilling location of well QM2 is determined. No karst cave and underground river were drilled in the later drilling process of well QM2, as well as no instability phenomenon occurred. It indicates that the TDEM detection results are consistent with the actual drilling, and the quasi-three-dimensional TDEM inversion interpretation data based on lateral constraints is reliable and can accurately detect the buried karst in the wellsite.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"7 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138533937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Song Chol Kim, Song Guk Han, Yong Il Song, Jin Sim Kim, Myong Gun Hong
Stress sensitivity and the elastic outer boundary (EOB) condition have a great effect on the analysis of the characteristics of the fluid flow in a reservoir. When researchers analyzed the characteristics of the fluid flow, they have considered the stress sensitivity and the EOB condition separately but have not considered them simultaneously. Therefore, errors are inevitable during the analysis of well testing. The main object of this work is to present a well-testing model for stress-sensitivity dual-porosity reservoir (DPR) with EOB to improve the accuracy of the analysis of well-testing data. To this end, in this paper, we established a well-testing model for the DPR, considering the stress sensitivity and the EOB simultaneously, and presented its semianalytical solution. On the basis of the consideration of the EOB condition and stress sensitivity of permeability (SSP), a seepage model for the DPR with the EOB is built using the continuity equation, motion equation, state equation, and interporosity flow equation between matrix and fracture, which considers the stress sensitivity, wellbore storage, and skin. To solve this model, a nonlinear partial differential equation is changed into a linear form of a partial differential equation by introducing an effective well radius and applying Pedrosa’s transformation and perturbation transformation. Applying the Laplace transformation, an analytical solution in the Laplace space is obtained, and curves of pressure and pressure derivative (PPD) are drawn by numerically inverting them. The model is verified by comparing it with the EOB without consideration of SSP and using case data. The sensitivity of parameters on the curves of PPD is analyzed. This work may be significant for evaluating more accurately the parameters of wells and reservoirs using well testing.
{"title":"Well-Testing Model for Dual-Porosity Reservoir considering Stress-Sensitivity and Elastic Outer Boundary Condition","authors":"Song Chol Kim, Song Guk Han, Yong Il Song, Jin Sim Kim, Myong Gun Hong","doi":"10.1155/2023/4658604","DOIUrl":"https://doi.org/10.1155/2023/4658604","url":null,"abstract":"Stress sensitivity and the elastic outer boundary (EOB) condition have a great effect on the analysis of the characteristics of the fluid flow in a reservoir. When researchers analyzed the characteristics of the fluid flow, they have considered the stress sensitivity and the EOB condition separately but have not considered them simultaneously. Therefore, errors are inevitable during the analysis of well testing. The main object of this work is to present a well-testing model for stress-sensitivity dual-porosity reservoir (DPR) with EOB to improve the accuracy of the analysis of well-testing data. To this end, in this paper, we established a well-testing model for the DPR, considering the stress sensitivity and the EOB simultaneously, and presented its semianalytical solution. On the basis of the consideration of the EOB condition and stress sensitivity of permeability (SSP), a seepage model for the DPR with the EOB is built using the continuity equation, motion equation, state equation, and interporosity flow equation between matrix and fracture, which considers the stress sensitivity, wellbore storage, and skin. To solve this model, a nonlinear partial differential equation is changed into a linear form of a partial differential equation by introducing an effective well radius and applying Pedrosa’s transformation and perturbation transformation. Applying the Laplace transformation, an analytical solution in the Laplace space is obtained, and curves of pressure and pressure derivative (PPD) are drawn by numerically inverting them. The model is verified by comparing it with the EOB without consideration of SSP and using case data. The sensitivity of parameters on the curves of PPD is analyzed. This work may be significant for evaluating more accurately the parameters of wells and reservoirs using well testing.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"84 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138533960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Linchao Wang, Xin Liang, Xuyang Shi, Jianyong Han, Yang Chen, Wan Zhang
Dry hot rock geothermal resources by virtue of its wide distribution, large reserves, clean and low-carbon, stable, high utilization rate, and other characteristics have been widely used. The enhanced geothermal system (EGS) is the most efficient approach for harnessing and exploiting geothermal energy from hot, arid rock formations. To investigate the impact of varying parameters on heat recovery in EGS operations, we employed the COMSOL numerical simulation software to construct a seepage heat transfer model for fractured rock masses. Essential parameters and boundary conditions were established, followed by conducting numerical simulations. Through the numerical simulation results, the temporal and spatial changes of coupling effects among seepage field, stress field, and temperature field in fractured rock mass were analyzed. We investigated the impact of water injection temperature, injection-production pressure difference, injection flow rate, and initial reservoir temperature on the heat transfer process. The findings indicate that raising the water injection temperature and injection-production pressure difference can enhance the reservoir’s heat recovery capability. However, it may also accelerate thermal breakthrough and reduce the system’s operational lifespan. The higher injection flow rate can improve the heat recovery efficiency. However, too large injection flow can cause problems in other aspects of the reservoir; increasing reservoir temperature leads to higher production temperatures, which can potentially result in dynamic catastrophes. Therefore, while ensuring the heat recovery efficiency of the system, the operation life of the system can be extended by adjusting the water injection temperature in stages, setting a reasonable injection and production pressure difference, and selecting an appropriate injection flow rate, so as to achieve the purpose of EGS optimization.
{"title":"Heat Transfer Analysis of Enhanced Geothermal System Based on Heat-Fluid-Structure Coupling Model","authors":"Linchao Wang, Xin Liang, Xuyang Shi, Jianyong Han, Yang Chen, Wan Zhang","doi":"10.1155/2023/8840352","DOIUrl":"https://doi.org/10.1155/2023/8840352","url":null,"abstract":"Dry hot rock geothermal resources by virtue of its wide distribution, large reserves, clean and low-carbon, stable, high utilization rate, and other characteristics have been widely used. The enhanced geothermal system (EGS) is the most efficient approach for harnessing and exploiting geothermal energy from hot, arid rock formations. To investigate the impact of varying parameters on heat recovery in EGS operations, we employed the COMSOL numerical simulation software to construct a seepage heat transfer model for fractured rock masses. Essential parameters and boundary conditions were established, followed by conducting numerical simulations. Through the numerical simulation results, the temporal and spatial changes of coupling effects among seepage field, stress field, and temperature field in fractured rock mass were analyzed. We investigated the impact of water injection temperature, injection-production pressure difference, injection flow rate, and initial reservoir temperature on the heat transfer process. The findings indicate that raising the water injection temperature and injection-production pressure difference can enhance the reservoir’s heat recovery capability. However, it may also accelerate thermal breakthrough and reduce the system’s operational lifespan. The higher injection flow rate can improve the heat recovery efficiency. However, too large injection flow can cause problems in other aspects of the reservoir; increasing reservoir temperature leads to higher production temperatures, which can potentially result in dynamic catastrophes. Therefore, while ensuring the heat recovery efficiency of the system, the operation life of the system can be extended by adjusting the water injection temperature in stages, setting a reasonable injection and production pressure difference, and selecting an appropriate injection flow rate, so as to achieve the purpose of EGS optimization.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"11 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138533962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yilong Yuan, Wei Wang, Jiawei Tang, Qiang Guo, Yulong Liu
Cyclic injection hydraulic fracturing is a promising way for the geothermal energy exploitation by reactivating the fractures in geothermal reservoir. However, fracture initiation and growth induced by cyclic injection schemes have been inadequately studied for hot dry rock (HDR), and the cyclic injection fracturing optimized often by experience. For this reason, the initiation and propagation of hydraulic fractures in the HDR under different cyclic injection methods were determined by experiment research for hydraulic fracturing. The results show that the cyclic frequency and injection rate play different roles in the stimulation of HDR. The cyclic injection with low frequency-low pressure can create more branched fractures, forming a short but complex hydraulic fracture network. However, when high flow-high frequency injection method is subjected, the branch fractures formed are significantly reduced, but each branch fracture can be fully expanded. To fully exploit the advantages of different injection methods, a numerical model that contains a fracture network was established with PFC software, and an alternating cyclic injection scheme with synergistic control of the cyclic frequency and injection rate was proposed. The comparison results indicated that the alternating cyclic injection method can effectively improve the fracturing effect in the HDR. The stimulation area of the alternating cyclic injection method is about 2.3 times and 2.7 times that of the low flow-low frequency and high flow-high frequency injection methods, respectively. The method presented here can be adopted to optimize the fracture growth regime and provide a scientific basis for EGS hydraulic fracturing design.
{"title":"Fracture Initiation and Propagation in the Hot Dry Rock Subject to the Cyclic Injection Hydraulic Fracturing Treatment","authors":"Yilong Yuan, Wei Wang, Jiawei Tang, Qiang Guo, Yulong Liu","doi":"10.1155/2023/8859177","DOIUrl":"https://doi.org/10.1155/2023/8859177","url":null,"abstract":"Cyclic injection hydraulic fracturing is a promising way for the geothermal energy exploitation by reactivating the fractures in geothermal reservoir. However, fracture initiation and growth induced by cyclic injection schemes have been inadequately studied for hot dry rock (HDR), and the cyclic injection fracturing optimized often by experience. For this reason, the initiation and propagation of hydraulic fractures in the HDR under different cyclic injection methods were determined by experiment research for hydraulic fracturing. The results show that the cyclic frequency and injection rate play different roles in the stimulation of HDR. The cyclic injection with low frequency-low pressure can create more branched fractures, forming a short but complex hydraulic fracture network. However, when high flow-high frequency injection method is subjected, the branch fractures formed are significantly reduced, but each branch fracture can be fully expanded. To fully exploit the advantages of different injection methods, a numerical model that contains a fracture network was established with PFC software, and an alternating cyclic injection scheme with synergistic control of the cyclic frequency and injection rate was proposed. The comparison results indicated that the alternating cyclic injection method can effectively improve the fracturing effect in the HDR. The stimulation area of the alternating cyclic injection method is about 2.3 times and 2.7 times that of the low flow-low frequency and high flow-high frequency injection methods, respectively. The method presented here can be adopted to optimize the fracture growth regime and provide a scientific basis for EGS hydraulic fracturing design.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"59 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138533961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jie Gao, Hu Wang, Xiaojun Ding, Qingxiao Yuchi, Qiang Ren, Bo Ning, Junxiang Nan
The fluid flow behavior, generally referred to as seepage, could determine the hydrocarbon and brine movement behavior. Movable fluid property, as one of the vital parameters for seepage characteristic evaluation, was generally used for tight oil reservoirs’ fluid flow ability assessment. The nuclear magnetic resonance technique was used to experiment with movable fluid percentage and movable fluid porosity, which can provide a realistic assessment of the amount of fluid that can flow in the porous media. Other techniques were also used to analyze the main factors in regulating the differences in movable fluid parameters. However, the research about fluid flow behavior was generally based on traditional methods, while the seepage characteristics from the pore-scale view are still a myth. To promote this process, in this study, core samples obtained from the Chang 7 reservoir of the Triassic Yanchang Formation in the Longdong region of Ordos Basin, China, were tested. The results show that the average movable fluid percentage and average movable fluid porosity of the total 16 core samples are 36.01% and 2.77%, respectively. The movable fluid exists mainly in the midlarge pores with the corresponding relaxation time over 10 ms. distributions mainly present four typical patterns: (1) bimodal distribution with similar amplitudes of the two peaks (occupying 6.25%), (2) bimodal distribution with higher right peak and lower left peak (occupying 18.75%), (3) bimodal distribution with higher left peak and lower right peak (occupying 56.25%), and (4) unimodal distribution (occupying 18.75%). Pore structure heterogeneity is closely related to the movable fluid parameters; the movable fluid parameters exhibit a relatively good correlation with core throat radius as well as permeability. There is an obvious difference between the movable fluid parameters and the microscopic characteristic factors in tight oil reservoirs due to the difference in physical properties, clay mineral content, microcracks, and pore structure characteristics. This research has provided a new perspective for the movable fluid property evaluation, and the relevant results can give some advice for the oil field development.
{"title":"The Impact of Microscopic Pore Network Characteristics on Movable Fluid Properties in Tight Oil Reservoir","authors":"Jie Gao, Hu Wang, Xiaojun Ding, Qingxiao Yuchi, Qiang Ren, Bo Ning, Junxiang Nan","doi":"10.1155/2023/7464640","DOIUrl":"https://doi.org/10.1155/2023/7464640","url":null,"abstract":"The fluid flow behavior, generally referred to as seepage, could determine the hydrocarbon and brine movement behavior. Movable fluid property, as one of the vital parameters for seepage characteristic evaluation, was generally used for tight oil reservoirs’ fluid flow ability assessment. The nuclear magnetic resonance technique was used to experiment with movable fluid percentage and movable fluid porosity, which can provide a realistic assessment of the amount of fluid that can flow in the porous media. Other techniques were also used to analyze the main factors in regulating the differences in movable fluid parameters. However, the research about fluid flow behavior was generally based on traditional methods, while the seepage characteristics from the pore-scale view are still a myth. To promote this process, in this study, core samples obtained from the Chang 7 reservoir of the Triassic Yanchang Formation in the Longdong region of Ordos Basin, China, were tested. The results show that the average movable fluid percentage and average movable fluid porosity of the total 16 core samples are 36.01% and 2.77%, respectively. The movable fluid exists mainly in the midlarge pores with the corresponding <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M1\"> <msub> <mrow> <mi>T</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> </math> relaxation time over 10 ms. <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M2\"> <msub> <mrow> <mi>T</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> </math> distributions mainly present four typical patterns: (1) bimodal distribution with similar amplitudes of the two peaks (occupying 6.25%), (2) bimodal distribution with higher right peak and lower left peak (occupying 18.75%), (3) bimodal distribution with higher left peak and lower right peak (occupying 56.25%), and (4) unimodal distribution (occupying 18.75%). Pore structure heterogeneity is closely related to the movable fluid parameters; the movable fluid parameters exhibit a relatively good correlation with core throat radius as well as permeability. There is an obvious difference between the movable fluid parameters and the microscopic characteristic factors in tight oil reservoirs due to the difference in physical properties, clay mineral content, microcracks, and pore structure characteristics. This research has provided a new perspective for the movable fluid property evaluation, and the relevant results can give some advice for the oil field development.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"19 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134956685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yan Zhu, Ziteng Cui, Kun Li, Chaoqi Wang, Zhao Li, Xueyi Zhang, Zhi Dou
Adsorption reaction in unsaturated porous media is of great importance for soil and groundwater remediation. In this study, the influence of the Peclet number (Pe) and water saturation on adsorption behavior at liquid-liquid interfaces was quantitatively investigated. The pore-scale reactive transport in unsaturated porous media was directly simulated. The Navier-Stokes equations, the surface transfer and adsorption reaction equations, and the advection-diffusion equation (ADE) were coupled to obtain the flow and concentration fields. The results showed that water saturation had a significant influence on the complexity of the flow field. A nonmonotonic relationship was found between water saturation and the uniformity of the flow field. Peclet number had little influence on the maximum adsorption. On the other hand, the adsorption time showed a nearly linear relationship with the Peclet number and increased with increasing Peclet number. Additionally, a nonlinear relationship was found between water saturation and the maximum adsorption. As water saturation increased, the maximum adsorption tended to increase to a peak and then decrease. The peak of the maximum adsorption occurred at , , and the shortest adsorption time was observed at . However, the difference in adsorption times for saturations of 0.458 and 0.698 was not significant and was only about 20 PV difference.
非饱和多孔介质中的吸附反应对土壤和地下水的修复具有重要意义。在本研究中，定量研究了Peclet数(Pe)和水饱和度对液-液界面吸附行为的影响。直接模拟了非饱和多孔介质中孔隙尺度的反应输运过程。将Navier-Stokes方程、表面转移和吸附反应方程、平流扩散方程(ADE)耦合得到了流动场和浓度场。结果表明，含水饱和度对流场的复杂程度有显著影响。发现含水饱和度与流场均匀性之间存在非单调关系。Peclet数对最大吸附量影响不大。另一方面，吸附时间与Peclet数呈近似线性关系，并随着Peclet数的增加而增加。此外，含水饱和度与最大吸附量之间存在非线性关系。随着含水饱和度的增加，最大吸附量呈先增大后减小的趋势。最大吸附峰出现在Pe = 5, S w = 0.458, S w = 0.902时吸附时间最短。而饱和度0.458和0.698的吸附次数差异不显著，仅相差约20 PV。
{"title":"Influence of Water Saturation on Adsorption Behavior at Liquid-Liquid Interfaces in Unsaturated Porous Media","authors":"Yan Zhu, Ziteng Cui, Kun Li, Chaoqi Wang, Zhao Li, Xueyi Zhang, Zhi Dou","doi":"10.1155/2023/8155349","DOIUrl":"https://doi.org/10.1155/2023/8155349","url":null,"abstract":"Adsorption reaction in unsaturated porous media is of great importance for soil and groundwater remediation. In this study, the influence of the Peclet number (Pe) and water saturation on adsorption behavior at liquid-liquid interfaces was quantitatively investigated. The pore-scale reactive transport in unsaturated porous media was directly simulated. The Navier-Stokes equations, the surface transfer and adsorption reaction equations, and the advection-diffusion equation (ADE) were coupled to obtain the flow and concentration fields. The results showed that water saturation had a significant influence on the complexity of the flow field. A nonmonotonic relationship was found between water saturation and the uniformity of the flow field. Peclet number had little influence on the maximum adsorption. On the other hand, the adsorption time showed a nearly linear relationship with the Peclet number and increased with increasing Peclet number. Additionally, a nonlinear relationship was found between water saturation and the maximum adsorption. As water saturation increased, the maximum adsorption tended to increase to a peak and then decrease. The peak of the maximum adsorption occurred at <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M1\"> <mtext>Pe</mtext> <mo>=</mo> <mn>5</mn> </math> , <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M2\"> <msub> <mrow> <mi>S</mi> </mrow> <mrow> <mi>w</mi> </mrow> </msub> <mo>=</mo> <mn>0.458</mn> </math> , and the shortest adsorption time was observed at <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M3\"> <msub> <mrow> <mi>S</mi> </mrow> <mrow> <mi>w</mi> </mrow> </msub> <mo>=</mo> <mn>0.902</mn> </math> . However, the difference in adsorption times for saturations of 0.458 and 0.698 was not significant and was only about 20 PV difference.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":" 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135291153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhongquan Gao, Yunzhang Rao, Liang Shi, Xiaoming Zhang, Run Xiang
Ion-absorbed rare earth deposits react with the leaching agent during the in situ leaching process through ion exchange and hydration, which change the stability of ore agglomerates and even result in mining slopes or landslides. Indoor simulated column leaching assays were conducted on ion-absorbed rare earth deposit samples by using magnesium sulfate solution as the leaching solution. Surface zeta potential, double electric layer thickness, particle gradation, and pore structure were analyzed to measure the different concentrations and pHs of leaching solutions’ impact on the stability of ore agglomerates. Results show that the critical magnesium sulfate solution concentration and pH affecting the stability of deposit sample agglomerates are 3.5% and 4, respectively. The chemical replacement reaction between the leaching agent and rare earth ions occurs during column leaching when it reaches its zero-point potential at a pH of 3.5168. This breaks the balance between the van der Waals gravitational force and double-layer repulsion in clay particles and induces the disruption of agglomerates, which causes the difference in the pore radius ratio of the ore samples before and after column leaching. It is of great engineering guidance to solve the problems of slope instability and landslides that may occur in the ore body during the mining process of ionic rare earth ore.
{"title":"Investigation of the Impact of Leaching Agent Concentration and pH on the Stability of Agglomeration of Ion-Absorbed Rare Earth Deposits","authors":"Zhongquan Gao, Yunzhang Rao, Liang Shi, Xiaoming Zhang, Run Xiang","doi":"10.1155/2023/6333122","DOIUrl":"https://doi.org/10.1155/2023/6333122","url":null,"abstract":"Ion-absorbed rare earth deposits react with the leaching agent during the in situ leaching process through ion exchange and hydration, which change the stability of ore agglomerates and even result in mining slopes or landslides. Indoor simulated column leaching assays were conducted on ion-absorbed rare earth deposit samples by using magnesium sulfate solution as the leaching solution. Surface zeta potential, double electric layer thickness, particle gradation, and pore structure were analyzed to measure the different concentrations and pHs of leaching solutions’ impact on the stability of ore agglomerates. Results show that the critical magnesium sulfate solution concentration and pH affecting the stability of deposit sample agglomerates are 3.5% and 4, respectively. The chemical replacement reaction between the leaching agent and rare earth ions occurs during column leaching when it reaches its zero-point potential at a pH of 3.5168. This breaks the balance between the van der Waals gravitational force and double-layer repulsion in clay particles and induces the disruption of agglomerates, which causes the difference in the pore radius ratio of the ore samples before and after column leaching. It is of great engineering guidance to solve the problems of slope instability and landslides that may occur in the ore body during the mining process of ionic rare earth ore.","PeriodicalId":12512,"journal":{"name":"Geofluids","volume":"35 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134973623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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