RU2272789C2 - Method of protecting oil-field equipment and pipelines against corrosion - Google Patents

Abstract

FIELD: oil and gas production and corrosion protection.

SUBSTANCE: invention relates to protection of oil-field equipment and pipelines operated under conditions when oil formations are microbiologically infected. In particular, when oxygen-containing fresh water with demulsifier is continuously supplied to waste water disposal system, the latter is subjected to a single treatment with bactericidal reagent acidified with weak hydrochloric acid solution containing corrosion inhibitor, after which oxygen dissolved in fresh water is completely removed.

EFFECT: prohibited favorable conditions in waste water disposal system for vital activity of bacteria and prevented corrosion of equipment.

1 dwg

Description

The invention relates to the field of corrosion protection of metal equipment and pipelines, mainly in systems for wastewater utilization of fields when they are returned to oil reservoirs by suppressing active microbiological activity and gradually suppressing the process of saturation of productive reservoirs with hydrogen sulfide, which significantly changes the development of oil fields at a late stage their operation.

It is known that sulfate-reducing bacteria and hydrocarbon-oxidizing bacteria, which usually enter the oil reservoir and the oil production system when injecting water from ground sources in order to maintain reservoir pressure, have a significant impact on the corrosion process and other negative technological effects during the exploitation of oil fields (1, 2).

A known method of corrosion protection of pipelines and equipment in the oil production system, in which to suppress the vital activity of bacteria used chemical reagents, bactericides (1, 2, 3, 4, 5, 6, 7). However, in conditions of disposal of sewage from fisheries, this method is ineffective. Firstly, the destruction of existing bacteria takes a large number of expensive chemicals. Secondly, after a single destruction of the microbial population operating here, it is quickly restored with the help of a large number of inactive bacteria in the oil reservoirs.

Thirdly, bacteria actively operating in the wastewater disposal system effectively shield themselves from the effects of bactericidal chemicals with the help of special low-permeable polysaccharide films with which they cover themselves. In addition, oxygen-containing fresh water is introduced into the wastewater for the demulsification process with demulsifiers, which contributes to the active life of hydrocarbon-oxidizing bacteria, which serves as the main food for sulfate-reducing bacteria.

The situation is further complicated by the fact that sulfate-reducing bacteria and hydrocarbon-oxidizing bacteria enter an active state, mainly in the wastewater disposal system because the most suitable conditions exist for their active development: weakly mineralized environment, the presence of traces of oxygen (0.5-1 , 0 mg / l), as well as the main factor - the metal surface, which is necessary for these bacteria to firmly attach to it and obtain the ions of iron they need during their life. As a result, a large community of sulfate-reducing and hydrocarbon-oxidizing bacteria, which saturates the wastewater pumped into the oil reservoir with hydrogen sulfide and inactive bacteria, forms an especially active, adhesive on the metal surface of pipes and tanks. These two components sharply worsen the process of demulsification, cause severe corrosion of all metal equipment and ultimately affect the process of oil recovery.

A known method of corrosion protection of oil production equipment and pipelines by introducing a chemical reagent-bactericide in the oil production system (SU 865833, C 02 F 1/50, 09/23/81).

According to the known method, to prevent the growth of sulfite-reducing bacteria, 6-methyl-7 (propen-1-yl-1) -2,4-dioxabicyclo (3.4) nonane is used as a reagent, which is introduced in an amount of 5-25 mg / l.

According to the known method, oxygen is not removed from the water, which contributes to the active activity of bacteria.

The present invention is the search and creation of such a method, which would exclude the appearance in the wastewater disposal system favorable conditions for the active life of bacteria.

The problem is solved in that in the method of corrosion protection of oil-producing equipment and pipelines, including the introduction of a chemical reagent-bactericide, according to the invention, first in the process of continuously introducing oxygen-containing water with a demulsifier into the sewage disposal system of a oil field, the system is treated once with a chemical reagent, a bactericide, acidified with a weak a solution of hydrochloric acid with a corrosion inhibitor, after which the oxygen dissolved in it is completely removed from fresh water. Removal of oxygen from fresh water is carried out using active radicals, in a way developed by the Institute of Nuclear Physics at Moscow State University.

The invention is illustrated by examples of the method and the scheme of operation of the wastewater disposal system, which is integrated into the overall oil production system of each field.

The drawing shows a diagram of the development of a typical oil field.

Most oil fields are developed according to the generally accepted unified technology. From the very beginning of operation, a reservoir pressure maintenance system is put in place, in order to compensate for the falling reservoir pressure, the estimated amount of fresh water 2 containing harmful bacteria for the field - sulfate-reducing and symbiotic hydrocarbon-oxidizing bacteria, is fed into the reservoir of the oil field 1. After the commissioning of the wastewater disposal system 3, in which oxygen dissolved in water is present, a vigorous process of bacterial activity and reproduction begins, with the gradual saturation of the oil extracted from the formation with hydrogen sulfide and an additional amount of these bacteria. This is confirmed by the practice of exploitation of oil fields of the Ural-Volga region and Western Siberia (5, 6).

As a result of bacterial activity, first from 150 to 350 mg / l of hydrogen sulfide appears in the wastewater disposal system, and then in the oil reservoir and oil gathering pipeline system.

In addition to hydrogen sulfide, after passing through oil dehydration unit 4, a large amount of iron sulfide precipitate enters the wastewater, which in contact with metals causes very strong local corrosion of all ferrous metals in the oil production system, and also clogs the most permeable porous channels of the oil reservoir, which reduces it oil recovery. In addition, iron sulfide is constantly formed near bacteria fixed on the metal and actively functioning biocenoses. As a result, the rate of local corrosion of the metal at its contact with sulfide increases sharply, and the sulfide precipitate further isolates the bacterial community from the effects of bactericides and corrosion inhibitors.

After analyzing the situation, the authors found a simple and reliable method of suppressing the activity of the most dangerous bacteria in an active state.

The essence of the proposed method is as follows.

In the process of continuous introduction of oxygen-containing fresh water with demulsifiers into the wastewater disposal system to suppress the vital activity of active forms of sulfate-reducing and hydrocarbon-oxidizing bacteria, their communities are first destroyed by a single treatment with an increased concentration of chemical reagent-biocide. If there is a precipitate of iron sulfide on top of the bacteria, it is removed by dissolving with a weak hydrochloric acid solution with corrosion inhibitors. Then dissolved oxygen is removed from fresh water. Thus, the activity of sulfate-reducing and hydrocarbon-oxidizing bacteria is blocked, which stops the process of saturation of the medium with hydrogen sulfide. Already available in the oil reservoir, hydrogen sulfide is constantly consumed and carried away from the extracted oil, until its amount after a certain time is reduced to a minimum. As a result, the conditions for the additional development of oil fields at a late stage of operation are significantly improved.

From available sources of information, the authors did not identify methods with similar characteristics.

The proposed method is feasible in the conditions of oil fields. This does not require unique equipment or special inaccessible components.

Information sources

1. Belyaeva S.S., Rozanova E.P. and others J. "Microbiology", 1990, No. 6, p.105.

2. Andreiuk K.I. and others. Microbial corrosion and its pathogens. Kiev, Naukova Dumka, 1980, p. 180.

3. Gonik A.A. Corrosion of oil production equipment and measures to prevent it. M .: Nedra, 1976, p. 178.

4. Rubenchik L.I. Sulfate-reducing bacteria. M .: Publishing. USSR Academy of Sciences, 1947, p. 94.

5. Waver V.I. J. "Corrosion and protection of metals", M.: VNIIOENG, 1983, No. 2, p.5.

6. Nedoboeva V.O. RNTS "Oilfield business", 1980, No. 4, p.3.

7. Rezyapova IB Sulfate-reducing bacteria in the development of oil fields. Ufa, Gilem, 1997, p. 51.

Claims (1)

A method of corrosion protection of oil-producing equipment and pipelines, which includes introducing a chemical agent-bactericide into the oil production system, characterized in that first, during the process of constant input of oxygen-containing fresh water with a demulsifier into the wastewater disposal system of oil fields, it is treated once with a chemical agent-bactericide, acidified with a weak solution hydrochloric acid with a corrosion inhibitor, after which the oxygen dissolved in it is completely removed from fresh water.