Patent RU-2745489-C1 (RU)
Title: Method for gas-cyclic injection of a mixture of carbon dioxide with associated petroleum gas under supercritical conditions into oil production well
Inventor: VOLKOV VLADIMIR ANATOLEVICH
IPC: E21B43/16
Filed: 2020-10-12
Granted: 2021-03-25
Abstract: FIELD: oil reserves. 
     SUBSTANCE: invention relates to methods for producing hard-to-recover oil reserves, including from low-permeability reservoirs. A method of gas-cyclic injection of a mixture of liquid carbon dioxide with associated petroleum gas under supercritical conditions into an oil production well is proposed, including the injection of two rims before and after injection of a mixture of carbon dioxide with APG into a production well. In this case, the injection of a mixture of carbon dioxide with APG is carried out under supercritical conditions, followed by a period of impregnation and initiation of oil production from the same production well. When implementing gas-cyclic injection, a mixture of carbon dioxide with associated petroleum gas is injected with a content of carbon dioxide and associated petroleum gas in the mixture of 75-95 vol.% and 5-25 vol.% correspondingly, under supercritical conditions: at the injection temperature at the wellhead T inj  and the injection pressure at the wellhead P inj , exceeding the critical temperature T crit  of the mixture and pressure P crit  of the mixture of carbon dioxide with associated petroleum gas. Before the injection of a mixture of carbon dioxide with associated petroleum gas, the first rim is injected into the well in a volume of 5-20 m 3  per meter of perforation of the treated reservoir, then a mixture of carbon dioxide with associated petroleum gas is injected under the above conditions and before the impregnation period, the second rim is injected in a volume of 5-20 m 3  per meter of perforation of the treated reservoir, after which the well is closed for the period of impregnation, followed by oil production from the same production well. Moreover, the number of injection cycles in the specified sequence into the production well is at least 1. The first rim contains wt%: the composition "Delta ASPGO" 70-80 and the composition "ML-super" 20-30. The second slug contains the composition "Delta ASPGO" 60-70, the composition "ML-super" 10-20, and a gas phase permeability regulator, at least one of the oil-soluble corrosion inhibitors - foaming agents from the class of imidazolines: aminoethylalkylimidazoline or hydroxyethylalkylimidazoline 10-30. The pressure of injection of a mixture of carbon dioxide with associated petroleum gas at the bottom of the well P bot.inj  is in the range of more than the pressure of the critical mixture of carbon dioxide with associated petroleum gas P crit  of the mixture and not more than the pressure P = 0.75 fr , where P fr  is the fracture pressure. It is preferable that the injection pressure at the bottomhole P bot.inj  exceeds not only the critical pressure of the P crit  mixture, but also the minimum miscibility pressure P mmp  of the mixture of carbon dioxide and associated petroleum gas with reservoir oil of a particular field. 
     EFFECT: technical result is to increase oil recovery while ensuring the utilization of associated gas. 
     2 cl, 1 tbl