The analysis of changes in the chemical composition of seawater during the injection into the anhydrous granitoid reservoir of the White Tiger deposit, in which the cracks are partially filled with minerals that are active to cation exchange (calcite and lomontite), has been analyzed. It is shown that these minerals interact with injected seawater, as a result of which Mg2+ seawater is absorbed by minerals to release equivalent amounts of Ca2+ into the solution, which leads to precipitation of anhydrite in the reservoir cavities, and in more surface conditions: in the producing wells and surface equipment - calcite . According to the quantitative change in the composition of the injected seawater, which showed a sharp increase in the Ca2+ ion in the associated water (5 times), with a simultaneous decrease in the Mg2+ content (10 times) and the SO42- ion (5 times) and using the equations chemical reactions, was carried out analytical calculation of the amount of salts that may fall as a result of flooding. This calculation showed that 2.9 g of CaSO4 and 0.05 g of CaCO3 can be deposited fr om each liter of injected water. Considering the scale of waterflooding, which cannot be less than 100 tons / day for profitable extraction, the amount of salt deposited will be 295 kg / day, with most of the salts represented by anhydrite, will be deposited in reservoir conditions. The calculation of the decrease in reservoir permeability due to sulphate scaling, carried out using the converted Kozeny – Karman formula, showed a possible decrease in reservoir permeability by 8.3 %. The transition of drilling to ever greater depths (more than 4000 m), wh ere the rocks almost everywhere contain lomontite (lomontite stage of metamorphism), requires to take into account the phenomena of cation exchange between injected water and rock in the predictions of scaling.
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