CN103468235A - Chemical assistant for thermal recovery of thick oil and application thereof - Google Patents

Abstract

The invention discloses a chemical assistant for thermal recovery of thick oil. The chemical assistant is prepared from the following components in percentage by mass: 0.5-10% of alkaline material, 0.05-5% of surfactant, 0.5-10% of alcohol and 75-98.95% of water through mixing and stirring. When the chemical assistant provided by the invention is added under the condition of steam injection in the thermal recovery of thick oil, the viscosity of the thick oil can be greatly reduced, the viscosity reduction rate reaches up to 98%, the fluidity of the thick oil can be improved effectively, and the yield of the thick oil reservoir is improved, and furthermore, the chemical assistant can be widely used in the field of development of thermal recovery thick oil reservoir.

Description

A chemical additive for thermal recovery of heavy oil and its application

technical field

The invention relates to the field of heavy oil and super heavy oil reservoir development, in particular to a chemical agent for heavy oil and super heavy oil reservoir development.

Background technique

The world's oil consumption is increasing year by year, but the recoverable oil reserves are decreasing year by year, especially the reserves of easy-to-recover thin oil are getting less and less, the world's energy crisis is becoming more and more severe, and many countries have raised the issue of oil to the level of national security. Altitude, especially in our country, there is a more realistic and urgent demand for the exploitation of heavy oil. With the increasing difficulty of heavy oil production and thicker oil, ordinary steam huff and puff and steam flooding can no longer meet the needs of heavy oil production. People urgently need a newer and better extraction method to meet the urgent needs of heavy oil extraction.

At present, thermal oil recovery is the main method to reduce the viscosity of heavy oil by heating underground oil reservoirs. The required thermal energy is generated at the surface and injected into the reservoir in the form of steam, hot water or gas. The most common heavy oil recovery technologies at home and abroad are thermal recovery technologies such as steam huff and puff, steam flooding and steam assisted gravity drainage (SAGD). Although the application of these thermal recovery technologies has a high recovery rate, the energy utilization rate is very low. In addition, there is another technology of enhanced oil recovery (EOR), which mainly adds surfactants to the alkaline solution to reduce the interfacial tension of oil and water and change the wettability of reservoir rocks, and ultimately enhance the recovery. However, the temperature resistance of these chemical agents is usually lower than 80°C. Therefore, the exploitation of high-viscosity crude oil is limited.

Therefore, for heavy oil reservoirs, it is necessary to enhance oil recovery at high temperature, mainly through chemical methods in steam applications to further enhance oil recovery and reduce energy consumption and cost of heavy oil recovery.

Contents of the invention

In view of the deficiencies of the existing technology and the needs of industry development, the purpose of the present invention is to provide a steam thermal oil recovery process, thereby increasing the recovery rate of heavy oil and reducing energy consumption and cost in heavy oil recovery. Chemical agents for the development of heavy oil and super heavy oil reservoirs.

In order to achieve the above object, the present invention adopts the following technical solutions to realize:

A chemical auxiliary agent for thermal recovery of heavy oil. According to the mass fraction, the chemical auxiliary agent consists of 0.5-10% alkaline substance, 0.05-5% surfactant, 0.5-10% alcohol and 75% ~98.95% water mixed and stirred.

The basic substance is at least one of amine, ammonia, alkali metal hydroxide, alkali metal carbonate, alkali metal bicarbonate or ammonium carbonate.

The surfactant is at least one of nonionic surfactants, anionic surfactants and cationic surfactants.

Described nonionic surfactant is alkyl, aryl, or alkylaryl; Alkyl, aryl, alkylaryl polymer; Polyether polyol; Alkoxy carbonyl hydrazine compound; N-tris(hydroxymethyl)methylglycine; trimethylglycine; ammonia oxide; alkylphosphine oxide; sulfinyl; amino carboxylate or sulfonate; polyol ester; polyoxyethylene sorbitol; sarcosine hydrochloride; acetylene glycol nonionic surfactant; polyoxyethylene alkanolamide; at least one of alkyl imidazoline, alkyl polyglucoside, fatty alcohol .

Described anionic surfactant is alkyl sulfate ester salt, sulfosuccinate, sulfonic carboxylate, alkylnaphthalene sulfonate, alkenyl sulfonate, fatty acid sulfonate, polycarboxylate , at least one of phosphonocarboxylate and thiosulfate.

The cationic surfactant is at least one of quaternary ammonium salt, amine salt, imidazolinium salt, betaine and pyridine derivative.

The alcohol is at least one of saturated monohydric alcohol, aromatic monohydric alcohol and polyhydric alcohol, and the number of carbon atoms in the alcohol is 4-9.

Another object of the present invention is to provide the application of the above-mentioned heavy oil recovery aid, which is to use the above-mentioned prepared recovery aid for heavy oil recovery.

The technical solution of the present invention is to increase the crude oil output by reducing the oil-water interfacial tension, changing the wettability of the rock matrix of the heavy oil reservoir, improving the fluidity of the heavy oil, reducing the viscosity of the heavy oil and increasing its fluidity , increasing the volume of the steam chamber leads to a decrease in the density of the well, shortening the production cycle, and can also reduce the amount of residual oil after the entire production cycle in the production process, and finally increase the recovery of heavy oil. For the SAGD process, the recovery factor is related to the oil drainage rate, which is controlled by the characteristics of the multiphase flow (heavy oil and hot water) in the porous media. When the droplet size is comparable to the pore size, the emulsion will hinder the oil drainage rate. One way to avoid this problem is to make the microemulsion droplet size smaller (20 nm) than the pore size of heavy oil reservoirs. The microemulsion phase can be in equilibrium with the organic phase, the aqueous phase, or both. Due to its low viscosity, it is beneficial for enhanced oil recovery or steam-assisted gravity drainage recovery.

The main factors affecting the recovery of heavy oil at high temperature are the wettability of the rock matrix and the interfacial tension between the organic phase and the aqueous phase. Accordingly, the present invention has been described with the aim of improving the wettability of the rock matrix and reducing the interfacial tension between the organic and aqueous phases.

In the technique of producing heavy oil, steam is injected into the underground reservoir to heat the reservoir, thus improving the fluidity and production effect of at least a small part of the oil and gas in the reservoir, and forming a steam chamber in the reservoir. There is a continuous stream of steam condensing at the boundary of the steam chamber. Heat will increase the temperature, thereby reducing the viscosity of the heavy oil in the reservoir. Next, chemical additives are injected into the injection well, and these chemical additives reach the steam chamber periodically or continuously.

When selecting chemical additives, the high temperature during steam extraction must be considered. During steam huff and puff extraction, the maximum temperature near the wellbore can reach 350°C, and the temperature can drop to 85-100°C after a period of extraction. Therefore, the thermal stability of chemical additives can be extended to a certain extent when using the steam stimulation process. On the one hand, chemical additives are very stable at temperatures above 200°C.

During SAGD production, although the temperature varies with the properties of crude oil and reservoir, the maximum temperature can be as high as 350°C. Since thermal strain is determined by both temperature and residence time, the residence time of applied chemicals in different temperature regions in the reservoir has a great influence on the choice of chemical additives.

In addition, chemical additives generally have a higher vapor pressure, which facilitates the injection of chemical additives into the reservoir. Additives that are thermally stable and have a sufficiently high vapor pressure are compatible with the steam here. In cases where the additive has a low vapor pressure and is incompatible with the vapor, the chemical can be injected as a liquid, aerosol or suspension.

In the technical solution of the present invention, an alkaline substance is used as one of the raw materials, and the alkaline substance can increase the pH value of the steam and the reservoir, and the increase of the pH value will promote the release of the natural surfactant in the heavy oil. These surfactants reduce the oil-water interfacial tension. Furthermore, a decrease in the viscoelasticity of the oil–water interface was observed at higher pH values due to the release of natural surfactants. Surfactant provided by the present invention can change the wettability of rock matrix, generally the vapor pressure of nonionic surfactant is higher than ionic surfactant, when nonionic surfactant is used in conjunction with ethanol, oil-water interface The tension can be close to zero. In this case, microemulsions can be formed. The ionic surfactants include: ionic surfactants are produced when alkaline substances react with acids in the steam stimulation process. Alkalines and acids can be alternately injected into the reservoir. Considering that low-molecular-weight alcohols such as methanol, ethanol, propanol, butanol, pentanol, etc. have higher water solubility, they have a larger distribution in the aqueous phase. Therefore, the present invention adopts alcohols with 4 to 9 carbon atoms, and the alcohols with medium chain length have very little solubility in the water phase, and they tend to be distributed in the interface phase and the oil phase. In the interfacial phase, the -OH group of the alcohol faces the water phase, while the alkyl group faces the oil phase.

The above-mentioned chemical additives can be injected into the reservoir in any order, together with the steam, or separately with the steam. The chemical additives can be mixed before steam injection, or the additives can be injected together with the steam. In some cases, it may be desirable to inject the additive-containing steam before or after the single steam injection.

To sum up, the beneficial effects of the present invention are: the addition of the chemical additives provided by the present invention can greatly reduce the viscosity of the heavy oil, and the viscosity reduction rate can reach more than 98%, which can effectively improve the fluidity of the heavy oil and increase the viscosity of the heavy oil. Reservoir recovery factor, the invention can be widely used in the development field of thermal exploitation of heavy oil reservoirs.

Detailed ways

Below by specific embodiment, the present invention is described in detail:

Example 1

A chemical auxiliary agent for thermal recovery of heavy oil. According to the mass fraction, the chemical auxiliary agent is composed of alkaline substance A, surfactant B, alcohol C and water.

specific:

Component A is a mixture of ammonium bicarbonate, ammonium carbonate and sodium carbonate.

Component B is a mixture of anionic surfactant sodium alkylbenzene sulfonate and nonionic surfactant alkylaryl polyethoxyethylene sodium sulfonate;

Component C is n-butanol;

The molar ratio of heavy oil to chemical additives in an oilfield is 0.5:1. Mix the above-mentioned component A, component B, component C and water and stir evenly to obtain a chemical agent for heavy oil heating, wherein the mass percentage of component A is 5%, and the mass percentage of component B The percentage composition is 0.5%, the mass percentage composition of component C is 1.5%, all the other are water.

Example 2

A chemical auxiliary agent for thermal recovery of heavy oil. According to the mass fraction, the chemical auxiliary agent is composed of alkaline substance A, surfactant B, alcohol C and water.

specific:

Component A is a mixture of sodium bicarbonate and sodium carbonate.

Component B is a mixture of anionic surfactant sodium lauryl ether sulfate and nonionic surfactant dodecyl trimethylglycine;

Component C is n-pentanol.

The molar ratio of heavy oil to chemical additives in an oilfield is 0.5:1. Mix the above-mentioned component A, component B, component C and water and stir evenly to obtain a chemical agent for heavy oil heating, wherein the mass fraction of component A is 4%, and the mass percentage of component B is The content is 0.3%, the mass percentage composition of component C is 1.5%, and the balance is water.

Example 1-2 Using the steam flooding experimental device to evaluate the prepared thermal recovery chemical additives, take degassed heavy oil in an oil field (reservoir temperature is 50°C) as an example, its viscosity is 19870mPa·s, design 250°C for steam flooding According to the scheme, a constant-rate oil displacement experiment is carried out indoors at a rate of 0.5mL/min (water equivalent), until the water content of the produced fluid is higher than 99.5%. ℃ steam flooding + synergistic chemical agent prepared in Example 1-2 to carry out steam flooding experiments, the two oil displacement efficiencies before and after were 78.34%, 90.25%, 88.38%, respectively, and the oil displacement efficiency increased by 11.91% and 10.04% respectively.

Example 3

A chemical auxiliary agent for thermal recovery of heavy oil. According to the mass fraction, the chemical auxiliary agent is composed of alkaline substance A, surfactant B, alcohol C and water.

specific:

Component A is a mixture of ammonium carbonate and ammonium bicarbonate.

Component B is a mixture of anionic surfactant sodium alkylbenzenesulfonate and nonionic surfactant polyoxyethylene alkanolamide;

Component C is n-hexanol.

The molar ratio of heavy oil to chemical additives in an oilfield is 0.5:1. Mix the above component A, component B, component C and water and stir evenly to get the chemical agent for heavy oil heating, wherein the mass fraction of component A is 10%, and the mass percentage of component B The content is 0.5%, the mass percentage composition of component C is 2.5%, and the balance is water.

Thick oil with a viscosity of 19870mPa·s (50°C) and the above-mentioned chemical additives are put into a high-pressure reactor at a molar ratio of 0.5:1, mixed and heated to 300°C, and after 24 hours, wait for the temperature to drop to room temperature and react from high pressure The oil sample was taken out of the kettle to measure the viscosity to be 350 mPa·s, and the viscosity reduction rate reached 98.23%.

The application of the heavy oil production aid is to use the prepared production aid for the production of heavy oil reservoirs. Heavy oil thermal recovery chemical additive is a process method with the advantages of simple manufacturing process, no need for special equipment, quick effect, simple construction and convenient operation.

Claims (9)

1. A chemical auxiliary agent for thermal recovery of heavy oil, characterized in that: according to the mass fraction, the chemical auxiliary agent consists of 0.5-10% alkaline substance, 0.05-5% surfactant, 0.5-5% It is made by mixing 10% alcohol and 75~98.95% water. 2. A chemical additive for heavy oil thermal recovery according to claim 1, characterized in that: the basic substance is amine, ammonia, basic metal hydroxide, basic metal carbonate , alkali metal bicarbonate or at least one of ammonium carbonate. 3. A kind of chemical auxiliary agent for thermal recovery of heavy oil according to claim 1, characterized in that: said surfactant is one of nonionic surfactant, anionic surfactant and cationic surfactant at least one. 4. A kind of chemical assistant for heavy oil thermal recovery according to claim 3, is characterized in that: described nonionic surfactant is alkyl, aryl or alkyl aryl; Aryl, alkylaryl polymers; polyether polyols; alkoxycarbonylhydrazine compounds; alkylaryl polyethoxy ethers; N-tris(hydroxymethyl)methylglycine; trimethylglycine; Ammonium oxides; Alkylphosphine oxides; Sulfinyl compounds; Amino carboxylates or sulfonates; Polyol esters; Polyoxyethylene sorbitol; Sarcosine hydrochloride; Acetylene glycol nonionic surfactants ; Polyoxyethylene alkanolamide; At least one of alkyl imidazoline, alkyl polyglucoside, fatty alcohol. 5. A chemical auxiliary agent for heavy oil thermal recovery according to claim 3, characterized in that: said anionic surfactant is alkyl sulfate, sulfosuccinate, sulfonic acid At least one of carboxylates, alkylnaphthalene sulfonates, alkenyl sulfonates, fatty acid sulfonates, polycarboxylates, phosphonocarboxylates, and thiosulfates. 6. A kind of chemical additive for heavy oil thermal recovery according to claim 3, it is characterized in that: described cationic surfactant is derived from quaternary ammonium salt, amine salt, imidazoline salt, betaine, pyridine at least one of the 7. A chemical auxiliary agent for heavy oil thermal recovery according to claim 1, characterized in that: said alcohol is at least one of saturated monohydric alcohol, aromatic monohydric alcohol and polyhydric alcohol. 8. A chemical additive for thermal recovery of heavy oil according to claim 7, characterized in that: the alcohol has 4-9 carbon atoms. 9. A heavy oil production aid as claimed in claim 1, its application is: the above-mentioned prepared production aid is used for heavy oil production.