RU2060354C1 - System of closed circulating water supply in operation of oil and gas well - Google Patents

Abstract

FIELD: oil/gas production. SUBSTANCE: system of closed circulating water supply includes closed loop of industrial sewage waters comprising units of productive and injection wells, unit of sewage water collection, unit of solid separation and water clarification, and unit of cleaned up water. The system is additionally provided with units for concentrating and utilizing mineralized waters. Cleaned up water is obtained from units of concentration and secondary treatment. EFFECT: water of high quality. 3 dwg

Description

 The invention relates to the oil and gas industry and can be used in the development of oil and gas fields.

Known technological schemes by which these processes are carried out, which include a system of production wells, a system for collecting sewage (produced, associated, industrial) water, a system for cleaning water from pollution, a system of injection wells [1]
The disadvantage of such a water use system is that the valuable hydro-mineral raw materials obtained along with oil and gas are again pumped into the absorbing layers. In addition, since the extraction and re-injection of wastewater does not resolve their desalination, there remains the danger of highly mineralized water getting into surface water bodies, soils, underground freshwater sources, which leads to salinization and poisoning.

In this regard, a closed-circuit water supply system, taken as a prototype, including a closed loop of industrial wastewater containing production and injection wells, a sewage collection unit, a solid phase separation and clarification unit, and a purified water unit, as well as a chemical one, is more rational. treatment of injected effluents [2]
However, this system only provides for the treatment of wastewater from suspended particles and partly from organic impurities, and deeper treatment, disposal of water and its waste are not provided.

 The purpose of the invention is to increase the efficiency of utilization of formation and associated waters with the possibility of simultaneously improving the processes of secondary production of hydrocarbon and mineral raw materials.

 This goal is achieved by the fact that the closed-loop water supply system, including a closed loop of industrial wastewater, containing production and injection wells, a wastewater collection unit, a solid phase separation and clarification unit and a purified water unit, is additionally equipped with concentration units, primary and secondary of processing and utilization of mineralized water communicated by its outlets with a contour of industrial wastewater and a block of purified and demineralized water received in the unit ah concentration and recycling.

 The salient features of the inventive closed-loop water supply system is that it is additionally equipped with units for concentrating, primary and secondary processing and utilization of mineralized water, communicated by their outlets with a production wastewater circuit and a purified and demineralized water unit obtained in concentration and secondary processing units.

 The inventive step of the claimed invention is not in doubt, since the essential distinguishing features of the invention, together with the known ones, will allow to achieve the purpose of the invention and be unenviable for specialists in this field.

 The invention is industrially applicable, as it can be used in industry, in particular, in the gas and oil industry in the extraction and processing of formation water.

 In FIG. 1-3 presents the proposed closed water system for production and injection wells in the development of oil and gas fields.

 The system consists of a block of injection and production wells (BNES), a block for collecting wastewater (produced, associated, produced) (BSPV), a block for separating solid phase and clarification of water (BOSV), a block for concentrating mineralized water (BKMV), and a block for primary processing of mineralized water (BPPMV), mineral water recycling units (BVPMV) and purified and demineralized water (BOOV) blocks.

 The technological process of closed circulating water supply in the development of oil and gas fields is as follows. The water-hydrocarbon (gas, gas condensate, oil) produced through production wells enters the production waste water collection unit (BSPW), where the hydrocarbon components are separated from the water, and the purified mineralized water is supplied to the solid phase separation unit (BOSV), in which mechanical impurities are released from the water and, if necessary, precipitation of calcium, magnesium and other multivalent ions takes place.

Purified from the solid phase, clarified water enters the mineralized water concentration unit (BCMW), in which, by evaporation, freezing, electrodialysis, reverse osmosis or other means, an excess of fresh water is extracted from the solution and the salts dissolved in it are concentrated (for example, NaCl, CaCl ₂ ) and other chemical components (e.g. iodine, bromine, cesium, etc.).

Desalted water is discharged into a block of purified and demineralized water (BOOV), and the remaining brine enters the block of primary mineralized water treatment, in which one of the selected methods (chemical deposition, extraction, ion exchange, electrochemical treatment, etc.) is the primary processing of water in chemical products for various purposes. The latter in its original form or after secondary processing (BVPMV ₁ , BVPMV ₂ blocks, etc.) are used either for their intended purpose, namely in oil and gas production processes as additives to water injected into the formation, or for other purposes in other technological processes. The purified and demineralized water obtained in the secondary processing processes is discharged into the BOOV unit and subsequently can be used both for injection into the reservoir and for technical purposes or discharged into the natural circuit.

 The operability of the proposed system can be illustrated by the example of integrated utilization of formation and associated waters of the Voi-Vozhsky oil field (Fig. 2).

 The oil-water mixture coming from the system (block) of production wells (BNES) is collected in the BSPV block, where it is separated into oil and water by known methods, after which the latter is pumped to the block for separating the solid phase and water clarification (BOSV).

Let us take the volumes of water entering the WWTP unit in 100 thousand m ³ / g with an average mineralization of 135 g / l and salt content, g / l: NaCl 88.5; CaCl ₂ 36.0; MgCl ₂ 10.5.

и магния

, которые совместно с имеющимися в воде нерастворимыми примесями и загрязнениями методами отстоя, фильтрации и другими удаляются из нее. В результате поступающая на следующий передел (блок БКМВ) минерализованная вода оказывается обогащенной только хлоридом натрия. В блоке БКМВ одним из выбранных методов (выпаривание, вымораживание, электродиализ и др.) происходит дальнейшее концентрирование хлорида натрия до его содержания 310-320 г/л, а избыточная обессоленная и очищенная вода поступает в блок БООВ. Полученный в результате обезвоживания рассол NaCl подается на первичную обработку в блок БППМВ, представляющий собой систему ртутных, диафрагменных или мембранных электролизеров.In the BOSV block, by adding certain reagents (for example, alkali) to the incoming water, calcium compounds precipitate

and magnesium

which, together with the insoluble impurities and contaminants present in the water, are removed from it by sludge, filtration and others. As a result, the mineralized water entering the next redistribution (BKMV block) is enriched only with sodium chloride. In the BCMV unit, one of the selected methods (evaporation, freezing, electrodialysis, etc.) further concentrates the sodium chloride to its content of 310-320 g / l, and excess desalinated and purified water enters the BOOV unit. The NaCl brine obtained as a result of dehydration is fed for primary processing to the BPPMV unit, which is a system of mercury, diaphragm, or membrane electrolyzers.

Under the action of an electric current, various electrochemical reactions occur in mineralized water entering the electrolysers, as a result of which new chemical products are formed. Since in this case an aqueous solution of sodium chloride is subjected to electrical action, the result of the electrochemical treatment of water is the production of alkali (sodium hydroxide NaOH) chlorine (Cl ₂ ) and hydrogen (H ₂ ), which can then be converted into other chemical units in secondary processing units target products.

Sodium hydroxide can be obtained both in the form of a solution, and in the form of granular solid material (block BVPMV ₂ ):
during the combustion of chlorine and hydrogen, hydrogen chloride (Cl ₂ + H ₂ 2HCl) is formed, the dissolution of which in water leads to hydrochloric acid (block BVPMV ₂ );
when chlorine and alkali react, a new chemical product is formed (Cl ₂ + + 2NaOH NaCl + NaClO + H ₂ O) sodium hypochlorite, NaClO (BVPMV block ₃ );
when magnesium hydroxide and calcium hydroxide interact with chlorine, calcium and magnesium hypochlorites Ca (ClO) ₂ , Mg (ClO) ₂ (BVPMV block ₄ ), etc. are formed.

The possibilities for further disposal of products of primary and secondary treatment of produced water can be very diverse. Firstly, this is the direct use of chemical reagents in the processes of oil displacement from the reservoir by pumping alkaline solutions into the injection well system. An essential feature of alkaline water flooding is that the interaction of alkali with acidic components of oil leads to the formation of surface-active substances (surfactants) directly in the formation, which is accompanied by a decrease in interfacial tension at the oil-alkali interface, an improvement in the wetting angle and the formation of highly viscous emulsions at the front of oil displacement with an alkali solution. All this leads to an improvement in the conditions of oil displacement in the reservoir, and, as a consequence, an increase in oil recovery. Secondly, during the flooding of production facilities, the bottom-hole zone of injection wells over time is silted with mechanical impurities and products of recrystallization of mineralized water injected into the reservoir. As a result of this, injection wells gradually reduce their injectivity until it is completely lost. In these cases, in order to restore the injectivity of injection wells, acid treatment of the bottom-hole zone is carried out by pumping saline solutions into the wells (HCl solution). Thirdly, water flooding in some cases leads to their bactericidal contamination, in order to exclude which the injected water is treated with chlorine or another bactericide, for example, NaClO, Ca (ClO) ₂ , etc.

 As can be seen from the foregoing, the proposed water supply system not only provides for the possibility of pumping certain water into injection wells, but also expands these possibilities by using the products of the utilization of produced water directly from the field for the preparation of alkaline, acid and bactericidal solutions, thereby increasing the economic (increase oil recovery) and technological (acid and bactericidal injection) efficiency of the water supply system.

 The chemical reagents obtained in the processes of complex processing can be used as independent target products in other industries. For example, acids and alkalis, chlorine and hydrogen are widely used in organic and inorganic synthesis, chemical technology and other fields, sodium and calcium hypochlorites are used in the pulp and paper industry as effective bleaches, for wastewater disinfection, etc.

 In this regard, the products of the treatment of produced water can be considered as commodity delivered to consumers at wholesale or contractual prices. Assessment of the economic efficiency of the production of processed products from their sale shows the following.

Voi-Vozhsky produced water produced in the amount of about 100 thousand m ³ / g contains in its composition g / l: NaCl 88.5; CaCl ₂ 36.0; MgCl ₂ 10.5. Complex processing of the entire volume of these waters allows to obtain, t / g: NaOH up to 8500; Cl ₂ 7600; ₂₃₀₀ H; Ca (ClO) ₂ 2500; NaClO 5600; HCl 6500.

 The payback period of such a production is 1-2 years, which indicates the high profitability and efficiency of integrated water treatment as a production.

 From the foregoing, it seems obvious that various options for implementing the proposed circulating water supply scheme are possible. So, when discharging wastewater, a system is usually used, including a block of production wells (BES), waste water collection (BSPV), a block of injection wells (BPS), and injection is carried out according to the BES-BSPV-1-BNS schemes (Fig. 2) or AB -1-A (Fig. 3).

 The well-known system of waterflooding, including a block of production wells (BES), the collection of industrial wastewater (BSPV), water purification from pollution (BOSV) and a block of injection wells, is carried out according to the BES-BSPV-BOSV-2-BNS scheme (Fig. 2) or ABC-2-A (FIG. 3).

 The proposed recycled water supply system additionally contains a mineralized water concentration unit (BKMV), as a result of which a significant part of the produced water is desalted and enters the recycled water supply system.

 In this case, the process of waterflooding occurs according to the scheme BES-BSPV-BOSV-BKMV-3-BNS (Fig. 2) or A-B-C-D-3-A (Fig. 3).

If water recycling system involves further processing of the primary water (BPPMV) and secondary (BPPMV _1), then flooding processes carried out according to schemes (BES-BSPV-BOSV-BKMV _{BPPMV-1-BPPMV} -6-3 and LBP (Fig. 2) or A-B-C-D-E-F-6-3-A (Fig. 3).

 If necessary, alkaline flooding, it is carried out according to the schemes BOOV-13-9-BNS (Fig. 2) or N-13-19-A (Fig. 3), while the alkaline reagent is obtained according to the scheme A-B-C-D-E -F-13 (Fig. 3), and purified and demineralized water according to schemes A-B-C-D-3-H and A-B-C-D-E-F-6-N (Fig. 3).

 Water flooding with the simultaneous restoration of injectivity of injection wells is carried out according to the schemes BOOV-12-19-BNS (Fig. 2) or P-12-19-A (Fig. 3). In this case, hydrochloric acid is obtained according to the combined schemes A-B-C-D-E-4-G and A-B-C-D-E-18-G (Fig. 3), and desalted water according to the above scheme.

 Bactericidal flooding is carried out according to the schemes BOOV-15-19-BNS (Fig. 2) or N-15-19-A (Fig. 3), and the bactericidal is obtained according to the combined schemes A-B-C-D-E-18-14 -K-16 and ABC-D-E-F-K-16 (Fig. 3).

For more complete utilization of the products of treatment and treatment of produced water, technological processes for obtaining target chemical products, for example, CaMg (OH) ₂ according to the scheme A-B-C-22-21 (Fig. 3) and CaMg, can be provided within the framework of the proposed reverse water supply system (ClO ₂ ) according to the combined schemes ABC-22-L-20 and ABC-D-E-18-L-20 (Fig. 3).

 The proposed water recycling scheme does not exclude deeper formation water treatment. Removing the microcomponents contained in them (iodine, bromine, lithium, cesium, etc.), it is possible to significantly increase the profitability of waterflooding and reverse water supply processes.

Thus, the proposed closed water recycling system for the operation of oil and gas wells provides:
partial or complete desalination of produced and associated waters and their purification from pollution;
integrated processing of produced water with the release of targeted chemical products for various purposes;
additional selection of hydrocarbon feedstock by improving the conditions for their displacement by water;
additional selection of hydromineral raw materials due to leaching of rocks with desalinated or acidified water,
stabilization of water during alkalization, acidification or bactericidal treatment;
stable rate of water injection due to the elimination of siltation zones,
prevention of pollution of surface and underground water bodies with highly saline waters due to their demineralization.

 The proposed system fully fits into any technological scheme for the development of oil and gas fields, providing high economic, technological and environmental efficiency of water recycling and well operation processes.

Claims (1)

 Closed-loop water supply system for the operation of oil and gas wells, including a closed loop of industrial wastewater containing blocks of production and injection wells, a wastewater collection unit, a solid phase separation and clarification unit and a purified water unit, characterized in that it is equipped with concentration units , primary and secondary processing and disposal of mineralized water, communicated by their outputs to the industrial wastewater circuit and the purified water unit obtained in Okahim concentration and recycling.

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