Wells – Processes – Nuclear energy or radioactivity for treating
Patent
1985-03-11
1987-01-27
Suchfield, George A.
Wells
Processes
Nuclear energy or radioactivity for treating
166307, 166312, 166902, E21B 2100, E21B 4102, E21B 4327
Patent
active
046388613
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
The invention relates to the oil recovery, and more specifically, it deals with methods for treating the bottom-hole formation zone.
STATE OF THE ART
Known in the art are methods for suppressing sulfate-reducing bacteria in flooded oil-bearing beds by using chemical reagents which are fed to the bottom-hole zone with water.
The general disadvantage of the known methods resides in that it is not possible to achieve complete suppression of the activity of sulfate-reducing bacteria, hydrocarbon-oxidizing and other microorganisms since during the period when a bactericidal substance is in the bottom-hole zone microorganisms adjust themselves to bactericidal reagents so that different types of bactericidal substances should be alternately used. These methods give inadequate oil recovery rate and high content of bacterial slime and biomass.
In addition, these known methods are difficult in realization, they require expenses for low-capacity production facilities for producing bactericidal substances and for creating specific-action additives having an effect with respect to sulfate-reducing bacteria; the substances used should comply with requirements as to solubility or colloidal dispersibility in aqueous media, compatibility with mineralized water; they should have a low solidification point, low toxicity, etc. Such chemical reagents should be continuously fed to formations, they cannot reduce the content of hydrogen sulfide in the injected water, nor can they reduce the formation of iron sulfides and bacterial slime on the bottom-hole walls.
It is known to treat the bottom-hole zone of a formation being worked by feeding a bactericidal agent to the bottom-hole zone (cf. USSR Inventor's Certificate No. 976039, Cl. E 21B 43/22, 1981).
This method cannot, however, increase the oil recovery rate since the bottom-hole zone is clogged with a biomass consisting of anaerobic and aerobic microorganisms and with sulfides.
SUMMARY OF THE INVENTION
The invention is based on the problem of providing a method for treating the bottom-hole formation zone which can ensure the suppression of aerobic and anaerobic microorganisms and improve permeability of the formation by lowering sulfate reduction and formation biomass of microorganisms and bacterial slime on the bottom-hole zone walls.
This problem is solved by that in a method for treating the bottom-hole zone of a formation being worked, comprising feeding a bactericidal agent to the bottom-hole zone, according to the invention, the bactericidal agent comprises gamma-radiation with a dose of at least 150 krad, the pressure in the bottom-hole zone being maintained within the range from 2 to 50 MPa during the irradiation.
Owing to application of gamma-radiation with a dose of at least 150 krad, suppression (inactivation) of sulfate-reducing, hydrocarbon-oxidizing and other kinds of anaerobic and aerobic microorganisms is ensured which, in turn, makes it possible to reduce corrosion of the equipment, lower hydrogen sulfide content in the bottom-hole zone and oil being recovered and improve the intake rate of injection wells. Maintaining pressure within the range from 2 to 50 MPa during irradiation of the bottom-hole zone inactivates sulfate-reducing bacteria, hydrocarbon-oxidizing and other microorganisms (including ferrobacteria) which are present in the bottom-hole zone fluids thereby lowering the amount of hydrogen sulfide being formed, hence the amount of iron sulfides and bacterial slime. The reduction of the amount of bacterial slime, hydrogen sulfide and iron sulfide results in the maintenance and improvement of permeability of the formation, improvement of oil quality and reduction of corrosion of oil recovery equipment.
In order to intensify the process of suppression of anaerobic and aerobic microorganisms, the bottom-hole zone is preferably treated at regular intervals with a chemical bactericidal agent during the exposure to gamma-radiation.
The combined action of bactericidal agent, pressure and gamma-radiation can provide for lowering the
REFERENCES:
patent: 2769921 (1956-11-01), Nahin et al.
patent: 3489218 (1970-01-01), Means
Moskovsky Institut Neftekhimicheskoi i Gazovoi Promyshlennosti
Suchfield George A.
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