当前位置：
X-MOL 学术
›
Ore Geol. Rev.
›
论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
The effect of hydrothermal fluids on Ordovician carbonate rocks, southern Ordos Basin, China
Ore Geology Reviews ( IF 3.3 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.oregeorev.2020.103803 Bo Jiu , Wenhui Huang , Yuan Li
Ore Geology Reviews ( IF 3.3 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.oregeorev.2020.103803 Bo Jiu , Wenhui Huang , Yuan Li
|
Abstract Hydrothermal processes have an important influence on the spatial distribution and formation of carbonate reservoirs, and play a critical role in certain deep reservoirs where hydrothermal fluid-rock interaction may result in permeability creation due to carbonate dissolution or permeability destruction due to the deposition of cementing minerals. This study analyzed certain hydrothermal indicator minerals (quartz, celestite, multi-stage calcareous fillings) in carbonate rocks from the Ordovician Majiagou Formation, southern Ordos Basin, China. The petrological and geochemical characteristics of these indicator minerals imply that the Majiagou Formation was affected by two metasomatic events related to the Hercynian–Indosinian and Yanshanian orogenies and linked to magmatic-hydrothermal fluids derived from basaltic melts. Most of the δCe and δEu values obtained from matrix dolomite samples were lower than one, but U/Th and V/C ratios showed positive anomalies. The δ13C and δ18O values of the matrix dolomite were concentrated between −12.8‰ and −6.0‰, whereas δ13C showed a bipolar distribution at the same depth. Elemental geochemistry results showed that the Ordovician carbonate rocks were subjected to freshwater leaching followed by evaporation and widespread hydrothermal dissolution successively. As a result of the multi-episodic hydrothermal activity that affected the southern Ordos Basin and the path of migration channel, a parental magmatic-hydrothermal fluid (fluid 1) that had been generated during the underplating of the southern North China Craton by Mesozoic alkaline basalt melts, separated into two types of fluids with different chemical properties: an acidic, hydrocarbon-bearing fluid (fluid 2a) mixed with Cambrian oil and gas and a weakly to moderately alkaline brine (fluid 2b), not in contact with hydrocarbons. Both fluids 2a and 2b then interacted with the Ordovician carbonate rocks with fluid 2a having undergone hydrothermal sulfate reduction with SO42- in the layers in which gypsum was developed, and convection of fluid 2a having resulted in brine formation. The reaction products of H2S and CO2 together with organic acid co-dissolved carbonate minerals in the Ordovician strata played a major role in the formation of a high porosity reservoir. Conversely, owing to the progressive reduction of temperature and solubility during fluid ascent, fluid 2b precipitated quartz-calcite fillings in the residual pore spaces, resulting in the localized destruction of the original reservoir permeability. In summary, this study analyzed the petrological and geochemical characteristics of 60 carbonate rock drill core samples, established the likely formation mechanism of fluids 2a and 2b, and determined the effects of these hydrothermal fluids on the Ordovician Majiagou Formation carbonate reservoir.
更新日期：2020-11-01
京公网安备 11010802027423号