In-situ stress is a key reservoir parameter to evaluate reservoir permeability,hydraulic fractures,coal seam deformation and coalbed methane(CBM)recovery.With limited CBM test wells in the Zhengzhuang field,southeast ...In-situ stress is a key reservoir parameter to evaluate reservoir permeability,hydraulic fractures,coal seam deformation and coalbed methane(CBM)recovery.With limited CBM test wells in the Zhengzhuang field,southeast of the Qinshui basin,North China,the in-situ stress data is inadequate for CBM exploration and development.It is necessary to find a method to predicate in-situ stress through other exploration data such as geophysical well loggings.In this study,we provide a new well-logging databased model to predicate the in-situ stress based on 17 sets of well test data and comprehensive logging data.As a distinguished characteristic of this model,different structural compartmentalization of CBM reservoirs was considered.A regional adaptive residual strain index was introduced to the model.Based on the model,the in-situ stress distribution in the Zhengzhuang field were evaluated systematically,and the influences of in-situ stress on permeability and the propagation of hydro-fractures were discussed.Results indicate that the magnitude of the maximum(S_(Hmax),14.19e45.40 MPa)and minimum horizontal stresses(Shmin,10.62e28.38 MPa)and the gravitational stress(Sv,9.58e30.82 MPa)all show positive correlations with burial depths.The in-situ stress fields in the study area are characterized by 1)SHmax>Sv>Shmin in shallow layers(<700 m),indicating a dominant strike-slip faulting stress regime;2)Sv z S_(Hmax)>S_(hmin)and S_(Hmax)>Sv>S_(hmin)in the depth of 700e1050 m,suggesting a transformed regime;and 3)S_(Hmax)>Sv>S_(hmin)in deep layers(>1050 m),indicating a strike-slip faulting stress regime.The S_(Hmax)in the study area is orientated by NE-SW,with a trend of 40e49.Resulted from the change of the in-situ stress regimes from shallow(500 m)to deep layers(~1000 m),the reservoir permeability variation shows a typical increase followed by decrease.The presence of natural fractures significantly affect the propagation pattern of hydraulic fractures,and the length difference between the major and branch fractures increases with increasing stress anisotropy in the Zhengzhuang field.展开更多
CCUS (carbon capture, utilization, and storage) technology is regarded as a bottom method to achieve carbon neutrality globally. CO_(2) storage in deep coal reservoirs serves as a feasible selection for CCUS, and its ...CCUS (carbon capture, utilization, and storage) technology is regarded as a bottom method to achieve carbon neutrality globally. CO_(2) storage in deep coal reservoirs serves as a feasible selection for CCUS, and its storage potential can be attributed to the CO_(2) adsorption capacity of the coal. In this paper, a series of CO_(2) adsorption isotherm experiments were performed at different pressures and temperatures in sub-bituminous coal from the southern Junggar Basin (reservoir temperature ∼25.9°C and pressure ∼3.91 MPa). In addition, the high-pressure CO_(2) adsorption characteristics of the southern Junggar Basin coal were characterized using a supercritical D-R adsorption model. Finally, the CO_(2) storage capacities in sub-bituminous coal under the in situ reservoir temperature and pressure were analyzed. Results indicated that the excess adsorption capacities increase gradually with increasing injection pressure before reaching an asymptotic maximum magnitude of ∼34.55 cm3/g. The supercritical D-R adsorption model is suitable for characterizing the excess/absolute CO_(2) adsorption capacity, as shown by the high correlation coefficients > 0.99. The CO_(2) adsorption capacity increases with declining temperature, indicating a negative effect of temperature on CO_(2) geological sequestration. By analyzing the statistical relationships of the D-R adsorption fitting parameters with the reservoir temperature, a CO_(2) adsorption capacity evolution model was established, which can be further used for predicting CO_(2) sequestration potential at in situ reservoir conditions. CO_(2) adsorption capacity slowly increases before reaching the critical CO_(2) density, following a rapid decrease at depths greater than ∼800 m in the southern Junngar Basin. The research results presented in this paper can provide guidance for evaluating CO_(2) storage potential in deep coal seams.展开更多
基金We acknowledge financial support from the National Natural Science Foundation of China(4183042741872123)the National Major Research Programfor Science and Technology in China(2016ZX05043-001).
文摘In-situ stress is a key reservoir parameter to evaluate reservoir permeability,hydraulic fractures,coal seam deformation and coalbed methane(CBM)recovery.With limited CBM test wells in the Zhengzhuang field,southeast of the Qinshui basin,North China,the in-situ stress data is inadequate for CBM exploration and development.It is necessary to find a method to predicate in-situ stress through other exploration data such as geophysical well loggings.In this study,we provide a new well-logging databased model to predicate the in-situ stress based on 17 sets of well test data and comprehensive logging data.As a distinguished characteristic of this model,different structural compartmentalization of CBM reservoirs was considered.A regional adaptive residual strain index was introduced to the model.Based on the model,the in-situ stress distribution in the Zhengzhuang field were evaluated systematically,and the influences of in-situ stress on permeability and the propagation of hydro-fractures were discussed.Results indicate that the magnitude of the maximum(S_(Hmax),14.19e45.40 MPa)and minimum horizontal stresses(Shmin,10.62e28.38 MPa)and the gravitational stress(Sv,9.58e30.82 MPa)all show positive correlations with burial depths.The in-situ stress fields in the study area are characterized by 1)SHmax>Sv>Shmin in shallow layers(<700 m),indicating a dominant strike-slip faulting stress regime;2)Sv z S_(Hmax)>S_(hmin)and S_(Hmax)>Sv>S_(hmin)in the depth of 700e1050 m,suggesting a transformed regime;and 3)S_(Hmax)>Sv>S_(hmin)in deep layers(>1050 m),indicating a strike-slip faulting stress regime.The S_(Hmax)in the study area is orientated by NE-SW,with a trend of 40e49.Resulted from the change of the in-situ stress regimes from shallow(500 m)to deep layers(~1000 m),the reservoir permeability variation shows a typical increase followed by decrease.The presence of natural fractures significantly affect the propagation pattern of hydraulic fractures,and the length difference between the major and branch fractures increases with increasing stress anisotropy in the Zhengzhuang field.
基金the National Natural Science Foundation of China(Grant Nos.42141012,41972168,and 42030810)the Peng Cheng Shang Xue Education Fund of CUMT Education Development Foundation(No.PCSX202204)+1 种基金the Fundamental Research Funds for the Central Universities(No.2020ZDPYZD01)aa project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘CCUS (carbon capture, utilization, and storage) technology is regarded as a bottom method to achieve carbon neutrality globally. CO_(2) storage in deep coal reservoirs serves as a feasible selection for CCUS, and its storage potential can be attributed to the CO_(2) adsorption capacity of the coal. In this paper, a series of CO_(2) adsorption isotherm experiments were performed at different pressures and temperatures in sub-bituminous coal from the southern Junggar Basin (reservoir temperature ∼25.9°C and pressure ∼3.91 MPa). In addition, the high-pressure CO_(2) adsorption characteristics of the southern Junggar Basin coal were characterized using a supercritical D-R adsorption model. Finally, the CO_(2) storage capacities in sub-bituminous coal under the in situ reservoir temperature and pressure were analyzed. Results indicated that the excess adsorption capacities increase gradually with increasing injection pressure before reaching an asymptotic maximum magnitude of ∼34.55 cm3/g. The supercritical D-R adsorption model is suitable for characterizing the excess/absolute CO_(2) adsorption capacity, as shown by the high correlation coefficients > 0.99. The CO_(2) adsorption capacity increases with declining temperature, indicating a negative effect of temperature on CO_(2) geological sequestration. By analyzing the statistical relationships of the D-R adsorption fitting parameters with the reservoir temperature, a CO_(2) adsorption capacity evolution model was established, which can be further used for predicting CO_(2) sequestration potential at in situ reservoir conditions. CO_(2) adsorption capacity slowly increases before reaching the critical CO_(2) density, following a rapid decrease at depths greater than ∼800 m in the southern Junngar Basin. The research results presented in this paper can provide guidance for evaluating CO_(2) storage potential in deep coal seams.
