METHOD FOR OPTIMIZING WATER INJECTION INTO INJECTION WELLS AT INITIAL STAGE OF THEIR OPERATION Russian patent published in 2023 - IPC E21B43/20 

FIELD: development of hydrocarbon deposits.

SUBSTANCE: method has been declared for optimizing the injection of water into injection wells at the initial stage of work, including taking a sample of the reservoir rock and determining its mineral composition, and sampling formation water from a well in reservoir conditions with determining its composition in reservoir conditions. Next, the stability of the injection water is checked under conditions that meet all possible injection modes at reservoir temperatures and pressures in the range from the initial reservoir pressure to the pressure corresponding to hydraulic fracturing, and in case of instability, the amount and composition of precipitation, as well as the rate of precipitation, is determined. The stability of the “reservoir water - reservoir rock” system under conditions that meet all possible injection modes at reservoir temperatures and pressures in the range from the initial reservoir pressure to the pressure corresponding to hydraulic fracturing is checked, and, in case of instability, the amount and composition of precipitation, as well as the rate their loss, are determined. The stability of the “injection water - formation water - reservoir rock” system with various proportions of injection water and reservoir water under conditions that meet all possible injection modes at reservoir temperatures and pressures in the range from the initial reservoir pressure to the pressure corresponding to hydraulic fracturing is checked, and, in case of instability, the amount and composition of precipitation, as well as the rate their loss, are determined. The pore size distribution for a reservoir rock sample is determined and the distribution of fluid flow velocity in pores of different sizes in the sample is determined under various conditions corresponding to all possible injection modes at reservoir temperatures and pressures in the range from the initial reservoir pressure to the pressure corresponding to hydraulic fracturing. For each mode, the distribution of formation water displacement rate is constructed. Based on the specific composition of formation water, injection water, precipitation rates, as well as the distribution of fluid flow rates in pores of different sizes in the sample, a water injection mode and composition of the injection water are selected that minimizes the amount of sediment per unit volume of rock. The injection water is prepared to ensure the selected composition, the selected injection pressures are set, and the prepared water is pumped into the injection well.

EFFECT: minimizing the risk of reducing the permeability of rocks near injection wells and, accordingly, the risk of blocking injection wells during the injection of water into injection wells at the initial stage of their operation by selecting the optimal composition of the injected water and the injection mode.

15 cl, 1 dwg, 6 tbl