Abstract
The Jizhong Depression is located in the western Bohai Bay Basin, eastern China. The deep strata are mainly composed of carbonate buried hill, and the shallow strata are a mainly siliciclastic deposition. In the present work, the Na-K-Mg triangle diagram and geothermometers were used to investigate the geochemical characteristics of shallow groundwater and reservoir temperature features of three geothermal reservoirs in the depression, including the Ordovician, the Cambrian, and the Precambrian Wumishan Formation. The results showed that the geothermal water in the depression could be divided into three groups: group I, Cl· HCO 3 -Na type; group II, Cl-Na type; and group III, Cl-Na·Ca type. By using the Na-K-Mg triangle diagram, group II and group III geothermal water samples were identified as the partially equilibrated water, whose temperature of the geothermal reservoir can be calculated based on the cation geothermometers. The ranges of the calculated temperature of the shallow strata and the deep strata are 91~146°C and 147~176°C, respectively. It has the good results obtained with some cation geothermometers in a geothermal system hosted in carbonate rocks like the studied area. The analysis workflow and calculation data obtained in this work contribute to the evaluation of the temperature field and the exploration and development of the geothermal resources in the Bohai Bay Basin.
Highlights
Many countries around the world are engaging in research on new energy, especially on renewable energy, in order to gradually reduce their nation’s dependence on traditional fossil fuels
It is shown that there has been a rapid development in geothermal utilization in the past few years and the installed capacity of geothermal power generation will increase by 1 GWe per year in the 6 and 7 years [1]
Using the Na-K-Mg triangle diagram, Zheng et al [23] consider that the cation geothermometer can estimate the water samples in the Guanzhong Basin; the calculation results were similar; and after studying the silica equilibrium with selected geothermal water samples, the results show that chalcedony has a better fit than quartz, which inferred that chalcedony controls the silica concentration in the deep reservoir
Summary
Many countries around the world are engaging in research on new energy, especially on renewable energy, in order to gradually reduce their nation’s dependence on traditional fossil fuels. There are roughly 82 countries (regions) making use of geothermal energy directly and 26 countries (regions) using geothermal energy for power generation. It is shown that there has been a rapid development in geothermal utilization in the past few years and the installed capacity of geothermal power generation will increase by 1 GWe per year in the 6 and 7 years [1]. With most of the oilfields in eastern China entering the middle and late stages of development, the difficulty of oil and gas exploitation gradually increases, and the proportion (water content) and the total amount of water in the produced fluid are increasing. The reservoirs in these oilfields are no longer oil but water. More and more wells have been abandoned in these oilfields when the petroleum reservoir was depleted without economic feasibility.
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