RU2021495C1 - Method for development of oil field - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: method consists in injection of aqueous solution of ammonium salt through injection wells, heating of solution in formation and oil recovery through producing wells. Ammonium salt is used in form of ammonium carbonate. Aqueous solution of ammonium carbonate is injected in form of fringe amounting to 0.2-0.4 of pore space, and forced by water. EFFECT: higher oil recovery. 1 tbl

Description

 The alleged invention relates to the oil industry and may find application in the development of deposits using chemical agents.

 A known method of developing an oil field, which consists in pumping carbonated water through injection wells and producing oil through production wells.

 The disadvantage of this method is the need for a source of carbon dioxide, the additional costs associated with its delivery to the field and dissolution in water in special installations.

The closest to the invention in technical essence and the achieved result is a method of developing an oil field, which consists in pumping through an injection well aqueous solutions of ammonium salts, such as ammonium sulfite and bisulfite, in concentrations of 0.01-1.0 mol / l (1-10 % ethyl p-p in water) at temperatures up to 50 ^{° C,} heating the solution in the reservoir to a temperature 50-140 ^{° C} due to natural warming or heating medium pumping rim required for decomposition of the ammonium salt to gaseous agents and extracting oil through Suitable well.

 The disadvantage of this method is the high corrosivity of the reagents, their scarcity and high cost.

 The aim of the invention is to increase oil recovery.

 This goal is achieved by the fact that in the method of developing an oil field, including the injection through injection wells of 1.0-10.0% aqueous solution of ammonium salt, heating the solution in the reservoir and oil production through production wells, ammonium carbonate is pumped as ammonium in the form of a rim as ammonium salt the size of 0.2-0.4 threshold volume, followed by pushing it with water.

 Specification

 Ammonium carbonate (ammonium carbonate) - GOST 3770-75.

 Ammonium carbonate - colorless crystals. Finds application in medicine, baking, dyeing fabrics.

 SUMMARY OF THE INVENTION

NH

+ NH₄HCO₃

NH

+ CO

+ H₂O При разложении 1 молекулы карбоната аммония образуется 2 молекулы аммиака и 1 молекула двуокиси углерода, т.е. из 1 т карбоната аммония образуется 466 м³ аммиака и 233 м³ двуокиси углерода. Образующиеся при разложении карбоната аммония аммиак и двуокись углерода растворяются в воде и нефти. Исходя из того, что растворимость аммиака в воде значительно превышает его растворимость в нефти, а растворимость двуокиси углерода в воде ниже, чем в нефти, в системе будет происходить перераспределение газов: аммиак будет в основном растворяться в воде, а двуокись углерода - в нефти. При этом в водной фазе будут происходить ионные процессы, которые отражают следующие уравнения:
H₂O

H⁺ + OH^-;
NH₃ + CO₂ + H₂O

NH $\genfrac{}{}{0ex}{}{\text{+}}{\text{4}}$ + HCO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$ ;
NH₃ + HCO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$

NH₂COO^_ + H₂O ;
NH₃ + HCO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$

NH $\genfrac{}{}{0ex}{}{\text{+}}{\text{4}}$ + CO $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ ^-;
Из уравнений видно, что в водной фазе будут присутствовать ионы аммония, образующие с гидроксил-ионом гидрат окиси аммония NH₄OH и ионы карбоновой кислоты СО₃ ^2-.Ammonium carbonate (NH _{4) 2} CO ₃ starts to decompose already at room temperature and at 60 ° ^C the reaction proceeds rapidly:
(NH ₄ ) ₂ CO ₃

NH

+ NH ₄ HCO ₃

NH

+ CO

+ H ₂ O Upon decomposition of 1 molecule of ammonium carbonate, 2 molecules of ammonia and 1 molecule of carbon dioxide are formed, i.e. 466 m ^{3 of} ammonia and 233 m ^{3 of} carbon dioxide are formed from 1 ton of ammonium carbonate. Ammonia and carbon dioxide formed during the decomposition of ammonium carbonate dissolve in water and oil. Based on the fact that the solubility of ammonia in water significantly exceeds its solubility in oil, and the solubility of carbon dioxide in water is lower than in oil, redistribution of gases will occur in the system: ammonia will mainly dissolve in water, and carbon dioxide in oil. In this case, ionic processes will occur in the aqueous phase, which reflect the following equations:
H ₂ O

H ⁺ + OH ^- ;
NH ₃ + CO ₂ + H ₂ O

NH $\genfrac{}{}{0ex}{}{\text{+}}{\text{4}}$ + HCO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$ ;
NH ₃ + HCO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$

NH ₂ COO ^_ + H ₂ O;
NH ₃ + HCO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$

NH $\genfrac{}{}{0ex}{}{\text{+}}{\text{4}}$ + CO $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ ^- ;
From the equations it is seen that in the aqueous phase there will be ammonium ions forming with a hydroxyl ion ammonium oxide hydrate NH ₄ OH and ions of carboxylic acid CO ₃ ^2- .

Thus, summing up what has been said regarding the processes occurring with ammonium carbonate in its aqueous solutions during heating, we can draw the following conclusion: due to its thermal decomposition, both ammonia and carbon dioxide soluble in the aqueous and oil phases, as well as ammonium ions will be present in the formation. NH ₄ ⁺ and carboxylic acids CO ₃ ^2- in the aqueous phase.

 For this reason, a carbon dioxide exposure mechanism and a mechanism similar to alkaline water flooding will operate in the reservoir.

Upon contact of ammonium oxide hydrate with oil, the interfacial tension at the interface of the oil-solution NH ₄ OH decreases, which ultimately leads to the emulsification of oil in the formation zone affected by the impact. The formation of an oil-in-water emulsion helps to increase reservoir coverage. The interaction of the NH ₄ OH solution with the rock leads to an improvement in its wettability, which also positively affects the increase in oil recovery.

 The interaction of carbon dioxide with formation fluids is accompanied by intense mass transfer as a result of a multi-contact process and a change in the physical properties of the fluids (density, viscosity, volumes, interfacial tension).

 Under certain conditions, depending on the composition of the oil, temperature and pressure, carbon dioxide is capable of unlimited mixing with oil. In addition, there is a better washing of the oil film from the surface of the rock, while the surface tension at the interface with water decreases and the wettability of the rock increases.

 An aqueous solution of carbon dioxide reacts with carbonate rocks and dissolves them. This increases the permeability of the reservoir and increases the absorbed ability of the injection wells.

 The combination of two mechanisms: exposure to carbon dioxide and a process similar to alkaline flooding, will determine the effectiveness of the use of ammonium carbonate as a chemical that contributes to enhanced oil recovery.

 The proposed method is as follows.

 Under surface conditions, an aqueous solution of ammonium carbonate (1-10%) is prepared. The concentration of the solution and the volume of the rim is determined by preliminary laboratory experiments on reservoir models, based on the optimal regime in terms of oil displacement. A rim of ammonium carbonate is pumped into the formation, which is then pushed with water.

 Examples of specific performance.

 Displacement experiments were carried out on a tubular reservoir model, which is a stainless steel coil with an inner diameter of 6.3 mm and a length of 10 m, equipped with a shut-off valve at the inlet and a fine adjustment valve at the outlet of the formation. The reservoir model was filled with quartz sand with a grain size of 0.2-0.3 mm.

The pore volume was 190 cm ³ ; porosity 30%, permeability 15 darcy.

Several experiments were performed on the displacement of oil deposits Anastasevskaya Dneprovsko-Donetsk cavity at a temperature of 95 ^{° C} and a pressure of 30 MPa.

 1) Oil displacement by rims equal to 0.1; 0.2; 0.4; 0.5 pore volume of the reservoir, 5% aqueous solution of ammonium carbonate.

 During the displacement process, the rim of the ammonium carbonate solution was pushed with water with a volume of 2 pore volumes of the formation.

2) Oil displacement by rim to 0.5 pore volume of the reservoir, 5% aqueous solution of ammonium sulfite (NH ₄ ) ₂ SO ₃ . During the displacement process, the rim of the ammonium sulfite solution was pushed with water up to 2 pore volumes of the formation.

 The results are presented in the table.

 From the table it follows that the method according to examples 2-4, allows to increase oil production from the reservoir in comparison with the prototype (example 6). Control examples show that flooding without ammonium salts (example 1) leads to very low oil recovery, and an increased rim size of ammonium salts (example 5) practically does not lead to an increase in oil recovery.

 The application of the proposed method will significantly increase oil recovery.

Claims (1)

 METHOD FOR DEVELOPMENT OF OIL DEPOSIT, including the injection of 1-10% aqueous solution of ammonium salt through injection wells, heating of the solution in the formation and oil production through production wells, characterized in that, in order to increase oil recovery, ammonium carbonate is injected into in the form of a rim of 0.2 - 0.4 pore volume, followed by pushing it with water.

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