Offshore high-temperature-resistant thick oil emulsification and viscosity reduction system and preparation method thereof

Abstract

The preparation method comprises the following steps: at normal temperature and normal pressure, firstly adding an anionic surfactant, a cationic surfactant and water into a compounding kettle in proportion, fully stirring until the materials are dissolved, then adding alkali into the compounding kettle, controlling the temperature at 60 DEG C, and stirring until the materials are uniform single-phase liquid. The offshore high-temperature-resistant thick oil emulsification viscosity-reduction oil displacement system can tolerate the use environment of 300 DEG C, can tolerate formation water with the total mineralization degree smaller than or equal to 10000 mg / L, and does not damage the formation. After the thick oil emulsification viscosity-reduction oil displacement system with the mass concentration of 1% is used for high-temperature treatment for 12 h at the temperature of 300 DEG C, the interfacial tension of the thick oil-oil displacement system can be reduced to 10 <-2 > mN / m level, and the steam oil displacement efficiency is improved by 15% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy oil development, and particularly relates to an offshore high-temperature resistant heavy oil emulsification and viscosity reduction system and a preparation method thereof. Background Art

[0002] Heavy oil development faces three key challenges, commonly referred to as "difficulty in startup," "difficulty in migration," and "difficulty in sweep," which directly impact recovery efficiency and effectiveness. These challenges stem primarily from heavy oil's high viscosity, low fluidity, and reservoir heterogeneity, posing significant challenges to traditional recovery techniques. Optimizing injection strategies and employing chemical and thermal recovery techniques can effectively improve recovery efficiency. Steam injection is widely used in offshore heavy oil development, but with continued development, production becomes increasingly challenging. Steam injection alone is becoming less effective, and steam energy consumption and costs are high. Emulsified viscosity reduction flooding, however, is a low-cost and simple process, attracting the attention of many experts and researchers. High-temperature emulsified viscosity reducers emulsify the crude oil, reducing interfacial tension and viscosity, thereby improving oil-water fluidity and interaction. High-temperature flooding agents, on the other hand, alter the wettability of the rock surface, reducing the adhesion of crude oil to the pore surfaces and facilitating its displacement.

[0003] By introducing a high-temperature resistant emulsified viscosity-reducing flooding agent and combining it with steam flooding, the fluidity of heavy oil can be effectively improved, thereby increasing flooding efficiency. Using a high-temperature resistant emulsified viscosity-reducing flooding agent to enhance steam flooding efficiency offers advantages such as low cost, minimal process complexity, and rapid results, providing technical support for the efficient development of heavy oil.

[0004] The existing heavy oil emulsification viscosity reduction system has the following disadvantages:

[0005] 1. The temperature resistance has not yet reached 300℃.

[0006] 2. The emulsion is unstable and can only last for 6 hours. Summary of the Invention

[0007] The present invention is proposed to solve the problems of high crude oil viscosity and poor seepage capacity faced by offshore heavy oil steam injection development in the prior art, and its purpose is to provide an offshore high-temperature resistant heavy oil emulsification and viscosity reduction system and a preparation method thereof.

[0008] The present invention is achieved through the following technical solutions:

[0009] An offshore high-temperature resistant heavy oil emulsification and viscosity reduction system, the heavy oil emulsification and viscosity reduction flooding system includes components and the mass percentage of each component is:

[0010] Anionic surfactant 0.5% to 1%;

[0011] Cationic surfactant 0.5% to 1%;

[0012] Alkali 0.1%;

[0013] Water balance.

[0014] In the above technical solution, the anionic surfactant is C 12-18 Fatty alcohol polyoxyethylene (5) ether, C 12-18 Fatty alcohol polyoxyethylene (7) ether, C 12-18 Any one or more of fatty alcohol polyoxyethylene (9) ether, sodium nonylphenol polyoxyethylene ether (5) carboxylate, sodium nonylphenol polyoxyethylene ether (7) carboxylate, sodium nonylphenol polyoxyethylene ether (9) carboxylate, isomeric sodium tridecanol polyoxyethylene ether (5) carboxylate, isomeric sodium tridecanol polyoxyethylene ether (7) carboxylate or isomeric sodium tridecanol polyoxyethylene ether (9) carboxylate.

[0015] In the above technical solution, the cationic surfactant is a gemini quaternary ammonium salt.

[0016] In the above technical solution, the alkali is any one of sodium hydroxide or calcium hydroxide.

[0017] A method for preparing an offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system comprises the following steps: at room temperature and pressure, firstly adding anionic surfactant, cationic surfactant and water in proportion to a compounding kettle, fully stirring until dissolved, then adding alkali to the compounding kettle, controlling the temperature at 60°C, and stirring until a uniform single-phase liquid is obtained, thereby obtaining the offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system.

[0018] The beneficial effects of the present invention are:

[0019] The present invention provides an offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system and a preparation method thereof, and improves the offshore heavy oil thermal recovery development effect by conducting research on oil displacement agent-assisted steam thermal recovery technology. The polyoxyethylene ether carboxylate surfactant selected by the present invention has the advantages of both anionic and non-ionic surfactants. Its anionic group imparts good temperature resistance, making it exhibit relatively stable performance under high temperature environment; while the non-ionic part enhances the emulsification performance, which helps to form a stable oil-water emulsion. The present invention compounds the polyoxyethylene ether carboxylate surfactant with a cationic surfactant, which can change the interfacial properties, enhance the stability and rigidity of the interfacial film, and more effectively reduce the interfacial tension. The heavy oil emulsification and viscosity reduction flooding system of the present invention is formed by using anionic surfactants, cationic surfactants, alkali, etc. through a specific product process, can withstand an operating environment of 300°C, can withstand formation water with a total salinity of less than or equal to 10,000 mg / L, and does not damage the formation; using a 1% concentration of the heavy oil emulsification and viscosity reduction flooding system, after high-temperature treatment at 300°C for 12 hours, the interfacial tension of the heavy oil-flooding system can be reduced to 10-2 mN / m level, improving steam flooding efficiency by more than 15%. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below through specific implementation methods.

[0021] Example 1

[0022] An offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system, comprising the following components and the mass percentage of each component:

[0023]

[0024] Among them, the mass ratio of anion and cation is 5:1.

[0025] A method for preparing an offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system, specifically comprising:

[0026] At room temperature and pressure, first add anionic surfactant (isomeric tridecanol polyoxyethylene ether-7 carboxylate sodium), cationic surfactant (gemini quaternary ammonium salt) and water into the compounding kettle, stir thoroughly until dissolved, then add alkali (sodium hydroxide) into the compounding kettle, control the temperature at 60°C, and stir until a uniform single-phase liquid is obtained to obtain the offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system.

[0027] Example 2

[0028] An offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system, comprising the following components and the mass percentage of each component:

[0029]

[0030] Among them, the mass ratio of anion and cation is 3:1.

[0031] An offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system, specifically comprising:

[0032] At room temperature and pressure, first add anionic surfactant (straight-chain fatty alcohol polyoxyethylene ether carboxylate sodium), cationic surfactant (gemini quaternary ammonium salt) and water into the compounding kettle, stir thoroughly until dissolved, then add alkali (sodium hydroxide) into the compounding kettle, control the temperature at 60°C, and stir until a uniform single-phase liquid is obtained to obtain the offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system.

[0033] The products obtained in Examples 1 and 2 were prepared into a mass concentration of 1% for performance testing:

[0034] 1. Determination of temperature resistance of heavy oil emulsification viscosity reduction flooding system solution

[0035] A composite system of anionic surfactant and cationic surfactant was prepared according to the proportion of the corresponding embodiment, and 0.1% sodium hydroxide was added dropwise to adjust the pH. The mixture was poured into a high-temperature and high-pressure aging kettle. The temperature of the high-temperature and high-pressure aging kettle was set to 300° C. and the high-temperature treatment time was 12 h. The heavy oil emulsified viscosity-reducing flooding agent solution after high-temperature treatment was poured into a glass container and the color of the solution was observed.

[0036] 2. Determination of interfacial tension of heavy oil emulsification and viscosity reduction flooding system

[0037] A composite system of anionic surfactants and cationic surfactants was prepared in a high-temperature, high-pressure aging kettle according to the proportions of the corresponding examples. 0.1% sodium hydroxide was added to adjust the pH. The pH value of the mixed solution was measured. The heavy oil emulsification viscosity reduction flooding system solution before and after high-temperature treatment was placed in a spinning drop interfacial tension meter at a speed of 5000 r / min, and the oil-water interfacial tension was measured at 60°C.

[0038] 3. Determination of solution viscosity reduction by emulsification of heavy oil flooding system

[0039] The measurement method is as follows: Use an IKA me-vi viscometer. Turn on the power switch and wait for the instrument's self-test to complete. Based on the viscosity range of the emulsified heavy oil solution, select a VOL-SP-6.7 spindle and set the speed to 10 rpm. Turn the lift knob to slowly lower the viscometer, gradually immersing the spindle in the liquid being measured until the mark on the spindle is level with the liquid surface. Press the measurement button to begin measuring and display the viscosity value. Wait for the value to stabilize before recording the result.

[0040] 4. Steam flooding efficiency determination

[0041] The measurement method is as follows: fill a sand filling pipe with consistent formation permeability (2000mD), use 300℃ steam to displace the water content of the output fluid to 95%, then inject 0.5PV of heavy oil emulsification viscosity reduction flooding system, and inject steam to displace the water content of the output fluid to 95%.

[0042] The experimental results are shown in Table 1 below:

[0043] Table 1

[0044]

[0045]

[0046] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. An offshore high-temperature resistant heavy oil emulsification and viscosity reduction system, characterized by: The heavy oil emulsification viscosity reduction flooding system includes the following components and their mass percentages:

2. The offshore high temperature resistant heavy oil emulsification and viscosity reduction system according to claim 1, characterized in that: The anionic surfactant is C 12-18 Fatty alcohol polyoxyethylene (5) ether, C 12-18 Fatty alcohol polyoxyethylene (7) ether, C 12-18 Any one or more of fatty alcohol polyoxyethylene (9) ether, sodium nonylphenol polyoxyethylene ether (5) carboxylate, sodium nonylphenol polyoxyethylene ether (7) carboxylate, sodium nonylphenol polyoxyethylene ether (9) carboxylate, isomeric sodium tridecanol polyoxyethylene ether (5) carboxylate, isomeric sodium tridecanol polyoxyethylene ether (7) carboxylate or isomeric sodium tridecanol polyoxyethylene ether (9) carboxylate.

3. The offshore high temperature resistant heavy oil emulsification and viscosity reduction system according to claim 1, characterized in that: The cationic surfactant is a gemini quaternary ammonium salt.

4. The offshore high temperature resistant heavy oil emulsification and viscosity reduction system according to claim 1, characterized in that: The alkali is any one of sodium hydroxide or calcium hydroxide.

5. A method for preparing the offshore high-temperature resistant heavy oil emulsification and viscosity reduction system according to any one of claims 1 to 4, characterized in that: The preparation method specifically comprises the following steps: at room temperature and pressure, firstly, adding anionic surfactant, cationic surfactant and water in proportion to a compounding kettle, fully stirring until dissolved, then adding alkali to the compounding kettle, controlling the temperature at 60°C, and stirring until a uniform single-phase liquid is obtained, thereby obtaining an offshore high-temperature resistant heavy oil emulsification and viscosity reduction flooding system.

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