METHOD FOR DEVELOPMENT OF CARBONATE RESERVOIR BY PERIODIC ACID TREATMENT Russian patent published in 2016 - IPC E21B43/27 

FIELD: oil and gas industry.

SUBSTANCE: method for development of carbonate reservoir by periodic acid treatment involves drilling horizontal wells, running on pipe string to horizontal part of shafts of pumps, separation of horizontal shaft into sections by packers depending on permeability, acid treatment through filters with different density of perforation, withdrawal of production well. In horizontal hole, which is open, three pipe strings are lowered with diameter of not more than 2.5 inches. At roof of productive formation in production string packer for three strings is installed. On first column in centre of each section of horizontal shaft is arranged one pump, wherein every next pump from end of horizontal shaft to its beginning is selected to allow fluid flow rate of not less than sum of fluid yields of previous pumps. To second and third pipe strings are attached throughout length of horizontal shaft series-connected filters, in which perforation density at every said section is different. Perforation density N_n at second pipe string of each n-th section of filters is made according to ratio of N_n=N_min·k_max/k_n, holes/m, where k_max is maximum permeability along horizontal shaft, m², k_n is permeability of n-th section of collector, m², N_min is density of perforation holes of filters at second pipe string opposite collector with maximum permeability, holes/m. Perforation density M_n at third pipe string of each n-th section of filters is calculated by formula M_n=M_min·k_n/k_min, holes/m, where k_min is minimum permeability along horizontal shaft, m², M_min is density of perforation holes of filters at third string opposite collector with minimum permeability, holes/m. At stopped pumps acid is fed into second pipe string with filters, flushed by process water in volume not less than that of pipe string, through which acid is injected, after reaction of acid with rock reaction products are extracted through same pipe until oil appears, then pump brought into operation in horizontal shaft. If oil flow rate drops by more than 50 % of oil flow rate after acid treatment, process of acid treatment is repeated, wherein volume of service water for pressing of acid is selected at least 2 volumes of service water compared to used in previous treatment cycle. When water cut of well rises to 80-98 % through third string with filters at stopped pumps is pumped into formation water with fine particles radius 0.1-0.4 of pore mean radius of collector r_u, defined by relationship m, where m is mean porosity of collector, unit fractions, k is weighted average permeability along horizontal shaft, m². Pumping of water with fine particles is performed for 3-10 days with rate close to maximum well injection capacity.

EFFECT: increasing oil recovery of carbonate reservoir.

1 cl, 1 dwg, 2 ex