Feasibility Study On Geothermal Dolomite Reservoir Reinjection With Surface Water In Tianjin, China

Reinjection is thought to be the most effective way to keep reservoir pressure and production capacity for the hydrothermal resources. This paper discusses geochemical responses of dolomite reservoir to lake water injection based on water-rock interactions experiments of Wumishan formation in Donglihu area, Tianjin. Results show that after reactions with dolomite，TDS of reacted water decreases indicating that precipitation happens, according to the calculation results of PHQREEC programme precipitation amount can be very limited. Geochemical analysis indicates that at the initial stage of reactions, plagioclase dissolves and releases the alkaline metals like K、Ca、Na, SiO2 and Al-bearing compositions, leading to oversaturation and precipitations of dolomite, calcite and K-feldspar. With the progress of reactions, part of the dolomite dissolves while calcite keeps precipitating at the later stage. Illite precipitates and its effects on reservoir structure depend on its shape．Based on the experimental data，it can be concluded that the dolomite reservoir will slightly be affected by reinjection of lake water, however, it's still a good way for sustainable development of geothermal resources．