Investigating the formation mechanisms of carbonate geothermal reservoirs is of theoretical and practical significance for summarizing the formation pattern of geothermal resources and further guiding their effective ...Investigating the formation mechanisms of carbonate geothermal reservoirs is of theoretical and practical significance for summarizing the formation pattern of geothermal resources and further guiding their effective exploitation.The Beijing-Tianjin-Hebei Plain(BTHP),predominantly located within the Jizhong Depression and Cangxian Uplift in the Bohai Bay Basin,serves as the primary region for geothermal exploitation and utilization in China.More than 1500 geothermal wells have been drilled therein,with water temperature at the wellhead ranging from 55 to 110°C,single-well flow rate ranging between 80 and 120 m^(3)/h,and cumulative heating area exceeding 100×10^(6)m^(3).However,the exploration and research in the region remain limited overall.As per the previous geothermal and petroleum exploration results and the latest geothermal drilling data,this study comprehensively evaluated the geothermal resources of karst geothermal reservoirs.The results show that two suites of carbonate karst reservoirs,namely the Jxw Formation and the Ordovician strata,have primarily developed in the BTHP,and their formation and evolution can be divided into four stages:the Mesoproterozoic-Early Paleozoic stage with carbonate sedimentation and the development of interlayer karst,the Late Paleozoic stage with the development of direct sedimentary cover,the Mesozoic stage with compressional uplifting and development of buried hill karst,and the Cenozoic stage with regional cover deposition and the modification and finalization of karst geothermal reservoirs.Accordingly,the porosity evolution history of the geothermal reservoirs is composed of three stages,namely a significant decrease followed by a minor increase,a gradual decline,and then a small fluctuation from increase to decrease before slowly rising again.The karstification in geothermal reservoirs can be summarized into quasi-syngenetic karstification,epigenetic karstification,and burial karstification,which can be subdivided into seven subcategories.The carbonate geothermal reservoirs in the study area boast total geothermal resources of 53.821×10^(9)GJ,or 184.155×10^(9)t of standard coal equivalent(tce),and the annual exploitable geothermal resources in the urban area can heat an area of(400‒500)×10^(6)m^(3),indicating great potential of geothermal exploitation.展开更多
As typical carbonate geothermal reservoirs with low porosity in northern China,the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration.The Jixianian System comprises the Gaoy...As typical carbonate geothermal reservoirs with low porosity in northern China,the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration.The Jixianian System comprises the Gaoyuzhuang,Yangzhuang,Wumishan,Hongshuizhuang,and Tieling formations.The characteristics,formation periods,and controlling factors of reservoir tectonic fractures have been determined based on analyses of outcrops,cores,thin sections,and image logs.The results show that unfilled fractures account for over 87% and most tectonic fractures are high-angle shear fractures with angles concentrated at 40°to 70°and the fracture porosity increases linearly with an increased fracture aperture.Within the same tectonic setting and stress field,the lithology and layer thickness are the dominant factors governing the development of tectonic fractures,which are the most developed in dolomites and thin layers.Tectonic fractures were most likely formed in regions near faults or areas with larger stress gradients.The tectonic fractures in the carbonate geothermal reservoirs are roughly divided into four sets:NNW-SSE and NNE-SSW oriented‘X’-conjugated shear fractures formed from the Paleozoic to the pre-Yanshanian Movement;NE-SW-oriented shear fractures,formed in episode B of the Yanshanian Movement,occurred at the Early Cretaceous;nearly E-W-oriented tensional fractures formed in the late Yanshanian Movement at the Late Cretaceous to Paleogene,and NEE-SW-oriented shear fractures formed during the Himalayan movement.展开更多
文摘Investigating the formation mechanisms of carbonate geothermal reservoirs is of theoretical and practical significance for summarizing the formation pattern of geothermal resources and further guiding their effective exploitation.The Beijing-Tianjin-Hebei Plain(BTHP),predominantly located within the Jizhong Depression and Cangxian Uplift in the Bohai Bay Basin,serves as the primary region for geothermal exploitation and utilization in China.More than 1500 geothermal wells have been drilled therein,with water temperature at the wellhead ranging from 55 to 110°C,single-well flow rate ranging between 80 and 120 m^(3)/h,and cumulative heating area exceeding 100×10^(6)m^(3).However,the exploration and research in the region remain limited overall.As per the previous geothermal and petroleum exploration results and the latest geothermal drilling data,this study comprehensively evaluated the geothermal resources of karst geothermal reservoirs.The results show that two suites of carbonate karst reservoirs,namely the Jxw Formation and the Ordovician strata,have primarily developed in the BTHP,and their formation and evolution can be divided into four stages:the Mesoproterozoic-Early Paleozoic stage with carbonate sedimentation and the development of interlayer karst,the Late Paleozoic stage with the development of direct sedimentary cover,the Mesozoic stage with compressional uplifting and development of buried hill karst,and the Cenozoic stage with regional cover deposition and the modification and finalization of karst geothermal reservoirs.Accordingly,the porosity evolution history of the geothermal reservoirs is composed of three stages,namely a significant decrease followed by a minor increase,a gradual decline,and then a small fluctuation from increase to decrease before slowly rising again.The karstification in geothermal reservoirs can be summarized into quasi-syngenetic karstification,epigenetic karstification,and burial karstification,which can be subdivided into seven subcategories.The carbonate geothermal reservoirs in the study area boast total geothermal resources of 53.821×10^(9)GJ,or 184.155×10^(9)t of standard coal equivalent(tce),and the annual exploitable geothermal resources in the urban area can heat an area of(400‒500)×10^(6)m^(3),indicating great potential of geothermal exploitation.
基金funded by the National Key Research and Development Program of China(Grant No.2019YFB1504101)the Natural Science Foundation of Hebei Province,China(Grant No.D2021504041)。
文摘As typical carbonate geothermal reservoirs with low porosity in northern China,the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration.The Jixianian System comprises the Gaoyuzhuang,Yangzhuang,Wumishan,Hongshuizhuang,and Tieling formations.The characteristics,formation periods,and controlling factors of reservoir tectonic fractures have been determined based on analyses of outcrops,cores,thin sections,and image logs.The results show that unfilled fractures account for over 87% and most tectonic fractures are high-angle shear fractures with angles concentrated at 40°to 70°and the fracture porosity increases linearly with an increased fracture aperture.Within the same tectonic setting and stress field,the lithology and layer thickness are the dominant factors governing the development of tectonic fractures,which are the most developed in dolomites and thin layers.Tectonic fractures were most likely formed in regions near faults or areas with larger stress gradients.The tectonic fractures in the carbonate geothermal reservoirs are roughly divided into four sets:NNW-SSE and NNE-SSW oriented‘X’-conjugated shear fractures formed from the Paleozoic to the pre-Yanshanian Movement;NE-SW-oriented shear fractures,formed in episode B of the Yanshanian Movement,occurred at the Early Cretaceous;nearly E-W-oriented tensional fractures formed in the late Yanshanian Movement at the Late Cretaceous to Paleogene,and NEE-SW-oriented shear fractures formed during the Himalayan movement.
