Figure - available from: Carbonates and Evaporites
This content is subject to copyright. Terms and conditions apply.
Cross section of Wumishan formation showing the difference of mud leakage with interpreted petrography on a NW–SE section
Source publication
To characterize the polyphase palaeokarst development of Wumishan formation in Jizhong depression, the data of outcrops, cores, thin sections, SEM, core plugs, drilling relief and leakage, and carbon isotope have been analyzed in this paper. The results reveal that the polyphase palaeokarst was petrography controlled of microbial dolostone and grai...
Similar publications
Epigenetic karstic systems in carbonate rocks commonly result from progressive dissolution by acidic meteoric waters over thousands to millions of years. The generation of secondary porosity and permeability improvement due to dissolution in carbonate reservoirs of geofluids (e.g., groundwater, hydrocarbons, and CO2) can profoundly impact reservoir...
The basal hadrosauroid Tethyshadros insularis from the uppermost Cretaceous of NE Italy lived on an island of the European archipelago in the Tethys Ocean. The tail of this dinosaur presents several apomorphic traits respect to the tails of other coeval hadrosauroids of the archipelago and of hadrosauroids in general. The estimated total length of...
The epigenetic karstic systems in carbonate units are the result of the dissolution of rocks by meteoric waters during the geological time. It is important to generate secondary porosity and permeability in carbonate reservoirs and aquifers. The topic investigated in this study are the structural discontinuities, such as vertical fractures, horizon...
High resolution multibeam bathymetry along the carbonate-dominated passive margins of the Florida and Yucatan platforms in the eastern Gulf of Mexico (the Gulf) reveals steep-walled canyons, sinkholes, and wave cut benches in present day water depths of more than 500 m. Subaqueous marine processes are inadequate to explain these features that are t...
Cet article présente dans une première partie le bassin versant de la Cèze avec une description lithologique des terrains pour aboutir à un modèle chronologique dans le but de mieux comprendre les conséquences sur l’écoulement des eaux. À travers les coupes géologiques et la représentation en trois dimensions de la zone d’étude, on observe une évol...
Citations
... A series of deep faults controlling the development of the Jizhong Depression due to crustal extension [27][28][29]. These longterm active faults were formed in the middle and late stages of the Yanshanian Movement [5,30] and were more active in the early stage of the Himalayan Movement. Among them, the NE-trending Niudong Fault and the EWtrending Niunan Fault cut into the crystalline basement, with horizontal fault length of 3.2 km and 2.5 km, and vertical fault depth of 7 km and 1.1 km, respectively [31]. ...
Medium-low temperature geothermal resources in the Wumishan Formation, which is the geothermal reservoir, are local enrichment resources in Xiong’an New Area, North China. In this study, 35 water samples were collected from the bedrock of Taihang Mountains and Wumishan Formation in Xiong’an New Area and display the chemical compositions of water samples as well as the stable isotope compositions for hydrogen, oxygen, carbon, sulfur, and strontium. Hydrogeochemical characteristics and isotope compositions of water samples are analyzed to understand the origin and circulation processes of these geothermal fluids. Our results of cold groundwaters in the bedrock of Taihang Mountain indicate a more open oxidation environment, and the HCO3-Ca·Mg-type groundwater also indicates a prevailing carbonate dissolution condition. The deep geothermal fluids in the Wumishan Formation beneath Xiong’an New Area indicate a closed reduction condition, and their hydrochemical types are mainly Cl·HCO3-Na type. The diagram of hydrogen vs. oxygen isotope indicates that the recharge for the deep geothermal fluids in the Wumishan Formation of Xiong’an New Area is mainly from atmospheric precipitation. The high δ13C values (-3.4‰−-4.9‰) are notably controlled by the eluviation of the carbonate rock layers. The δ34S values vary from 18.02‰ to 27.01‰; the relatively high values indicate the eluviation of sedimentary rock layers. The high 87Sr/86Sr ratios (0.70806−0.71270) and the high Sr2+ concentrations (0.69−2.92 mg/L) suggest that the Sr in the deep geothermal fluids originates from the eluviation of both silicates and carbonates. According to the multimineral equilibrium diagram, chalcedony is saturated at the measured temperature of geothermal wells; therefore, we chose chalcedony as a geothermal thermometer for the calculation of the reservoir temperature of the Wumishan Formation, and the results vary from 68.63 to 89.10°C. Our study identifies the geothermal type of the deep medium-low temperature hydrothermal systems and also recognizes their water-rock interaction processes. We get a comprehensive understanding that the geothermal resources in the Wumishan Formation beneath Xiong’an New Area is convection-conduction type, for which potential of geothermal development and utilization is enormous.
Fractures provide pore spaces for the preservation and migration of hydrocarbons and control the quality of dolomitic reservoirs. Textures caused by sedimentary and tectonic processes control the mechanical properties of dolostones and the development and distribution of fractures in them. An understanding of the influence of textures present in dolostones in the development of fractures is crucial. Therefore, massive micritic, brecciated, columnar stromatolitic, and siliceous dolostones and laminites present in the early Mesoproterozoic Wumishan Formation (between ca. 1.5 Ga and ca. 1.45 Ga) in the Jizhong Depression with varying internal textures were analyzed based on observations of outcrops, core, and microstructures to determine their influence on reservoir quality. The development characteristics of fractures in the dolostones were investigated, and their petrophysical properties were measured. Uniaxial and triaxial compression tests were utilized to explore the impacts of textures on the distribution patterns of fracture in the dolostones. The fracture density, porosity, and permeability are 5.4/m, 1.55%, and 17.10 mD in the homogeneous and massive micritic dolostone, with fracture oriented parallel or at an acute angle to the maximum principal stress direction. The fracture density, porosity, and permeability, respectively, are characterized by averages of 8.9/m, 6.39%, and 106.68 mD, and are significantly better in the brecciated dolostones, and the fractures develop along the preexisting weakly cemented planes between the brecciated textures. The fracture density of the siliceous dolostone is 9.8/m, and its porosity and permeability are 2.74% and 29.68 mD. The extension of high-angle fractures is usually restrained by the low-angle bedding fractures, and intensive microcracks are developed in the siliceous textures. The occurrence of algal laminae in dolostones increases the proportion of low-angle fractures; these fractures can extend along the maximum principal stress direction and rupture along the weak algal laminae. The fracture density and petrophysical properties of columnar stromatolitic dolostones (7.4/m, 4.39%, and 87.75 mD) are better than those of laminites (4.3/m, 1.21%, and 14.57 mD). Therefore, the formative environment of textures in dolostones controls the quality of the reservoirs in the Wumishan Formation. The reservoirs in brecciated dolostones that are located in structural highs and fracture zones and columnar stromatolitic dolostones deposited in high-energy intertidal to upper subtidal zones have the highest reservoir quality. The quality of the reservoirs in siliceous banded dolostones deposited in mid-energy intertidal zones is average, and that of massive micritic dolostones and laminites deposited in low-energy lower-subtidal zones is poor.
