CN108949133B

CN108949133B - Foam flooding system and preparation method thereof

Info

Publication number: CN108949133B
Application number: CN201710359258.4A
Authority: CN
Inventors: 许关利; 吕成远; 赵淑霞; 王锐; 周国华; 王欣; 孙爱军; 卢刚
Original assignee: China Petroleum and Chemical Corp; Sinopec Exploration and Production Research Institute
Current assignee: China Petroleum and Chemical Corp; Sinopec Exploration and Production Research Institute
Priority date: 2017-05-19
Filing date: 2017-05-19
Publication date: 2020-12-11
Anticipated expiration: 2037-05-19
Also published as: CN108949133A

Abstract

The invention belongs to the field of oil exploitation, and relates to a foam flooding system and a preparation method thereof. The foam flooding system comprises a liquid phase and a gas phase, wherein the liquid phase is an aqueous solution containing a foaming agent and a stabilizing agent, the pH value of the aqueous solution is more than or equal to 10, the foaming agent is a cationic surfactant and a nonionic surfactant, and the stabilizing agent is selected from fatty alcohol ether phosphate and/or alkylphenol ether phosphate. Compared with the conventional foam system which adopts cation and anion active agents as foaming agents, the foam flooding system has the advantages of simple preparation method, no higher requirements on water quality and the like, and high stability.

Description

Foam flooding system and preparation method thereof

Technical Field

The invention belongs to the field of oil exploitation, and relates to a foam flooding system and a preparation method thereof.

Background

The foam is a dispersion system formed by dispersing a large amount of gas in a small amount of liquid, belongs to a complex fluid, has different viscoelasticity from simple fluids such as water, air and the like, can show elasticity under the action of smaller stress, can show plasticity under the action of larger stress and can flow under the action of larger stress. The viscosity of the foam is generally much greater than that of the liquid phase and the viscosity of the foam fluid decreases with increasing shear rate, a property that makes it particularly suitable as an enhanced oil recovery displacement fluid. Foam technology has been applied in foam drilling and foam drainage, while the initial objective in flooding is to use the permeability characteristics of foam in porous media to control the gas mobility during gas flooding, and although there are some problems, foam does do so and is used in gas and water flooding enhanced oil recovery practices. Gas flooding uses foam as an aid to control gas mobility, while water flooding uses foam as a displacement medium.

In addition, as well as the application of foam in other industrial processes, the oil displacement technology also requires the stability of foam, and one of the central problems in the current foam technology research is to optimally design a formula system of the foam with the aim of improving the stability of the foam.

The foam formulation mainly contains surfactant and other auxiliary agents (such as polymer, nano particles and the like). Wherein, the surfactant can be adsorbed on a gas-liquid interface to reduce the interfacial tension, thereby improving the foamability and the stability; the auxiliary agent has the functions of improving the stability of the foam, such as increasing the viscosity of a liquid phase by using a water-soluble polymer (polyacrylamide, polyvinyl alcohol, polyvinylpyrrolidone, xanthan gum, etc.), and reducing the diffusion rate of liquid discharge and gas, thereby improving the stability of the foam.

The surfactant is various, the stability of foams generated by different surfactants is greatly different, and at present, anionic surfactants are mainly used as foaming agents in laboratories and mines, and anionic surfactants and nonionic surfactants are mixed as foaming agents. CN104762078A discloses a multifunctional air foam flooding system, and the adopted foaming agent is fatty alcohol polyoxyethylene ether sodium sulfate, which is an anionic surfactant. CN104745168A discloses a high temperature resistant low tension foam system, the foaming agent used is a mixture of anionic surfactant (fatty acid salt or alkyl benzene sulfonate) and amphoteric surfactant (betaine type). CN105315982A discloses a three-phase foam system for oil displacement, wherein the foaming agent is a nonylphenol polyoxyethylene ether nonionic surfactant and a sodium dodecyl benzene sulfonate anionic surfactant, and the foam stabilizer is a polymer cross-linked gel system or nanoparticles. CN103834379A proposes a wormlike micelle foam flooding system, which consists of a betaine amphoteric surfactant and an alkyl sulfate anionic surfactant. The efficient foam compound oil displacement system for tertiary oil recovery disclosed in CN1032544884A is prepared by compounding alpha-olefin sodium sulfonate serving as a main surfactant with other anionic surfactants, amphoteric surfactants and anionic-nonionic surfactants, and can reduce the oil-water interfacial tension and has good compatibility with high-salinity water. The reinforced foam flooding system disclosed by CN102977872A uses a mixture of an anionic surfactant and a nonionic surfactant as a foaming agent, and obtains the reinforced foam flooding system by utilizing various associations and weak interactions between water-soluble polymers and the foaming agent.

Currently, although anionic and nonionic surfactants have good foaming properties, the generated foam has poor stability, and thus the use of water-soluble polymers or nanoparticles is required to improve the stability. Water soluble polymers can increase the viscosity of the liquid phase in a foam system, but higher liquid phase viscosities can reduce foaming properties. The nano particles are particles with surfaces subjected to hydrophobic modification treatment, and the existing particles are low in yield and high in price and are not suitable for application in the petroleum industry. CN104152128A proposes a stable and oil-resistant foam system formed by mixing anionic and cationic surfactants, wherein the foam system is composed of two anionic surfactants and one cationic surfactant, and the preparation method comprises mixing the anionic surfactant, the cationic surfactant, the polymer, the inorganic salt and the like into an aqueous solution and then foaming the aqueous solution. However, the requirement of directly mixing the anionic and cationic surfactants is severe, and the requirements on concentration, mixing sequence, water quality composition and the like are particularly high, otherwise, precipitation is easy to occur.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a foam flooding system with simple composition and high stability and a preparation method of the foam flooding system.

According to a first aspect of the invention, the invention provides a foam flooding system, which comprises a liquid phase and a gas phase, wherein the liquid phase is an aqueous solution containing a foaming agent and a stabilizing agent, the pH value of the aqueous solution is more than or equal to 10, the foaming agent is a cationic surfactant and a nonionic surfactant, and the stabilizing agent is selected from fatty alcohol ether phosphate and/or alkylphenol ether phosphate.

According to a second aspect of the present invention, the present invention provides a preparation method of the foam flooding system, which comprises the following steps:

1) dissolving the foaming agent in water, and adjusting the pH value to be more than or equal to 10 to obtain a foaming agent aqueous solution;

2) mixing the foaming agent aqueous solution with an air source, and foaming to obtain a foaming solution;

3) and mixing the foaming liquid with the aqueous solution of the stabilizer and foaming to prepare the foam flooding system.

Compared with the conventional foam system which adopts cation and anion surfactants (hereinafter also referred to as surface active agents) as foaming agents, the foam flooding system has the advantages of simple preparation method, no higher requirements on water quality and the like, high stability (for example, the half-life period is more than 90 min) due to the existence of the specific stabilizer, and can be used for tertiary oil recovery and improving the oil recovery rate. In addition, in the preparation method, a two-step method of firstly using the cationic surfactant and the nonionic surfactant as foaming agents to prepare foam and then adding the foam stabilizer with opposite charges (anions) is adopted, so that a foam system with good stability is prepared by utilizing the strong electrostatic interaction of the anionic surfactant and the cationic surfactant, and the problem of direct mixing and precipitation of the anionic surfactant and the cationic surfactant is avoided.

Drawings

FIG. 1 is a flow diagram of an on-line preparation of the foam flooding system, according to one embodiment.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In the present invention, the cationic surfactant may be selected from quaternary ammonium salt type cationic surfactants well known in the art, such as alkyl trimethylammonium salt type, dialkyl dimethylammonium salt type, and the like. Preferably, the cationic surfactant is selected from at least one of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride and octadecyltrimethylammonium bromide.

In the present invention, the nonionic surfactant may be selected from at least one of fatty alcohol polyoxyethylene ether surfactants (AEO) and alkylphenol polyoxyethylene ether surfactants (APEO) well known in the art. The nonionic surfactant is commercially available, and is selected from surfactants having a trade designation MOA-20, MOA-35, O-30, SOPE-20, etc., and produced by Haian petrochemical plant of Jiangsu province.

In the present invention, the stabilizer is selected from fatty alcohol ether phosphate esters and/or alkylphenol ether phosphate esters (hereinafter also collectively referred to as "phosphate-based surfactants"). The phosphate ester surfactant is divided into monoester and diester, wherein the monoester is at least one of the compounds shown in formula 1 and formula 3, and the diester is at least one of the compounds shown in formula 2 and formula 4.

In the formulas 1-4, R is respectively selected from alkyl or aralkyl (the carbon number is usually 8-18); in the formulas 3 to 4, n is usually 3 to 20.

Preferably, the fatty alcohol ether phosphate is at least one selected from fatty alcohol polyoxyethylene ether phosphate, and the alkylphenol ether phosphate is at least one selected from alkylphenol polyoxyethylene ether phosphate. Namely, the foam stabilizer is at least one selected from the group consisting of compounds represented by formula 3 and formula 4. The compounds represented by the formulas 3 and 4 can be prepared by the following method: fatty alcohol or alkyl phenol and ethylene oxide are polymerized and then phosphorylated, and the adopted phosphorylation agent can be selected from phosphorus pentoxide, phosphorus trichloride, polyphosphoric acid and the like.

In addition, the stabilizer is also commercially available, for example, from commercial products such as MOA-3P, MOA-9P, TXP-4 and TXP-10, which are produced by Haian petrochemical plants of Jiangsu province.

The content of each component in the liquid phase is not particularly limited, as long as the stability of the foam flooding system meets the use requirement. Generally, the concentration of the cationic surfactant is 0.2-5 wt%, the concentration of the nonionic surfactant is 0.1-1 wt%, and the molar ratio of the cationic surfactant to the foam stabilizer is 5: 1-1: 5, based on the total weight of the liquid phase.

Preferably, the concentration of the cationic surfactant is 0.5-3 wt%, the concentration of the nonionic surfactant is 0.1-0.5 wt%, and the molar ratio of the cationic surfactant to the foam stabilizer is 5: 1-1: 5, based on the total weight of the liquid phase.

More preferably, the molar ratio of the cationic surfactant to the foam stabilizer is 3: 1-1: 3.

In the foam flooding system, the pH of the liquid phase can be NaOH or NaHCO₃And regulating with alkaline pH regulator.

In the foam flooding system, the gas phase is preferably air, nitrogen or carbon dioxide.

In the step 2), a high-concentration stabilizer aqueous solution is preferably mixed with the foaming liquid and foamed, and specifically, the concentration of the stabilizer aqueous solution is 20 to 50 wt%.

In the present invention, the preparation process may be carried out continuously, and preferably, the steps 2) to 3) include the following schemes: the aqueous solution of the foaming agent and the gas source are respectively fed into a first foaming device (foam generator) to be mixed and foamed, and then the obtained foaming liquid and the aqueous solution of the stabilizer are fed into a second foaming device to be mixed and foamed.

According to a specific embodiment, the preparation process of the foam flooding system is shown in figure 1: preparing a mixed solution of a cationic surfactant and a nonionic surfactant according to the designed concentration, and adjusting the pH of the solution to be more than or equal to 10 by using sodium hydroxide to obtain a foaming agent aqueous solution (also called as a foaming agent solution); the frother solution is then injected into the first bubbler by means of a metering pump, while being mixed and frothed in the first bubbler with a gas from a gas source (air, nitrogen or carbon dioxide) controlled by a gas flow meter: the foaming agent solution and gas are mixed by a first foaming device to form uniform foam, and then the uniform foam is mixed with an aqueous solution (also called as a foam stabilizer solution) of a foam stabilizer from another metering pump to enter a second foaming device for further mixing and foaming, so that the foam flooding system is prepared.

According to the method of the invention, the ratio of the volume flow of the gas to the frother solution is preferably 3: 1 to 20: 1. The first and second foam generators may be a cavity structure filled with porous medium, such as the structure described in CN 201236686Y.

The method can prepare the foam flooding system with high stability and no special requirement on water quality (such as common clear water), and the specific reason is that the solution of the fatty alcohol ether phosphate and the alkylphenol phosphate is acidic, and phosphate molecules are uncharged (namely, belong to nonionic type) under the acidic condition; after being mixed with alkaline (pH is more than or equal to 10) foaming agent aqueous solution containing cationic surfactant, acidic and alkaline neutralization reaction is carried out, active hydrogen on phosphate molecules is neutralized by hydroxide radicals, and thus the phosphate molecules have negative charge anion characteristics; on the gas-liquid interface of the foam, phosphate ester surfactant molecules with negative charges and cationic surfactant molecules with positive charges (such as quaternary ammonium salt surfactant) generate stronger electrostatic interaction to attract, so that the arrangement of the surfactant molecules on the interface is more compact, and simultaneously, after the anionic surfactant and the cationic surfactant are mutually associated, respective hydrophilic groups of the original surfactant molecules are concentrated at the middle part of the associated molecule, so that the contact space of the hydrophilic groups and water molecules is obviously reduced, namely, the hydrophilicity of the surfactant molecules in the interface layer is reduced, the interface film of the foam system has good water-resistant dilution capability, and the stability of the foam system can be greatly improved.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples, a foam flooding system was prepared by the foam on-line preparation method shown in fig. 1.

The stability of the foam was evaluated using a foam scanning analyzer (FoamScan): and introducing the prepared foam flooding system into a sample container of a foam scanner, injecting 150mL of foam, starting to record the change of the volume of the foam along with time, and calculating the half-life period to represent the stability of the foam, wherein the more the half-life period is longer when the instrument is at a constant temperature of 45 ℃, the better the stability of the foam is.

Example 1

Preparing a foaming agent aqueous solution (pH of the solution is adjusted to 11 by NaOH) according to the concentration of octadecyl trimethyl ammonium chloride of 1 weight percent and the concentration of fatty alcohol polyoxyethylene ether MOA-20 of 0.5 weight percent in the liquid phase, and preparing an aqueous solution of fatty alcohol phosphate ester MOA-3P foaming agent of 30 weight percent by adjusting the molar ratio of the cationic surfactant to the stabilizer to be 1: 1. And (2) taking nitrogen as a gas source, setting the volume flow ratio of the nitrogen to the foaming agent aqueous solution to be 10: 1, preparing uniform foam, adding the aqueous solution of the foam stabilizer, mixing and foaming to prepare a foam flooding system, injecting the foam system into a foam scanner, and testing the half-life period of the foam to be 118 minutes.

Example 2

Preparing a foaming agent aqueous solution (pH of the solution is adjusted to be 12 by NaOH) according to the concentration of hexadecyl trimethyl ammonium chloride in the liquid phase being 2 wt% and the concentration of fatty alcohol-polyoxyethylene ether MOA-30 in the liquid phase being 0.5 wt%, and preparing an aliphatic alcohol phosphate ester MOA-3P foaming agent aqueous solution with the concentration of 30 wt% by adjusting the molar ratio of the cationic surfactant to the stabilizer to be 1: 1. And (2) taking nitrogen as a gas source, setting the volume flow ratio of the nitrogen to the foaming agent aqueous solution to be 8: 1, preparing uniform foam, adding the aqueous solution of the foam stabilizer, mixing and foaming to prepare a foam oil displacement system, injecting the foam system into a foam scanner, and testing the half-life period of the foam to be 95 minutes.

Example 3

Preparing the foaming agent aqueous solution according to the concentration of octadecyl trimethyl ammonium chloride of 3 weight percent and the concentration of fatty alcohol polyoxyethylene ether MOA-20 of 1 weight percent in the liquid phase (regulating the pH of the solution to be 11 by NaOH), and preparing the fatty alcohol phosphate ester MOA-9P foaming agent aqueous solution with the concentration of 30 weight percent by making the molar ratio of the cationic surfactant to the stabilizer be 4: 5. And (2) taking nitrogen as a gas source, setting the volume flow ratio of the nitrogen to the foaming agent aqueous solution to be 10: 1, preparing uniform foam, adding the aqueous solution of the foam stabilizer, mixing and foaming to prepare a foam flooding system, injecting the foam system into a foam scanner, and testing the half-life period of the foam to be 134 minutes.

Example 4

Preparing a foaming agent aqueous solution (pH of the solution is adjusted to 11 by NaOH) according to the concentration of octadecyl trimethyl ammonium chloride of 1 weight percent and the concentration of fatty alcohol polyoxyethylene ether MOA-35 of 0.5 weight percent in the liquid phase, and preparing an aqueous solution of fatty alcohol phosphate ester MOA-3P foam stabilizer of 30 weight percent by adjusting the molar ratio of the cationic surfactant to the stabilizer to be 1.5: 1. And taking nitrogen as a source, setting the volume flow ratio of the nitrogen to the foaming agent aqueous solution to be 5: 1, preparing uniform foam, adding the aqueous solution of the foam stabilizer, mixing and foaming to prepare a foam flooding system, injecting the foam system into a foam scanner, and testing the half-life period of the foam to be 102 minutes.

Example 5

Preparing a foaming agent aqueous solution (pH of the solution is adjusted to be 12 by NaOH) according to the concentration of tetradecyltrimethylammonium chloride in the liquid phase being 3 weight percent and the concentration of fatty alcohol-polyoxyethylene ether MOA-20 being 0.5 weight percent, and preparing a fatty alcohol phosphate ester MOA-3P foaming agent solution with the concentration of 30 weight percent by adjusting the molar ratio of the cationic surfactant to the stabilizer to be 1: 1. And (2) taking air as an air source, setting the volume flow ratio of the air to the foaming agent aqueous solution to be 10: 1, preparing uniform foam, adding the aqueous solution of the foam stabilizer, mixing and foaming to prepare a foam flooding system, injecting the foam system into a foam scanner, and testing the half-life period of the foam to be 96 minutes.

Comparative example 1

A foam flooding system was prepared as in example 1 except that no foam stabilizer solution was added, the stability of the foam so prepared was poor and the half-life of the test foam was 42 minutes.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the illustrated embodiments.

Claims

1. The foam flooding system is characterized by comprising a liquid phase and a gas phase, wherein the liquid phase is an aqueous solution containing a foaming agent and a stabilizer, the pH value of the aqueous solution is more than or equal to 10, the foaming agent is a cationic surfactant and a nonionic surfactant, the cationic surfactant is a quaternary ammonium salt type surfactant, the nonionic surfactant is at least one selected from fatty alcohol polyoxyethylene ether surfactants and alkylphenol polyoxyethylene ether surfactants, and the stabilizer is selected from fatty alcohol ether phosphate and/or alkylphenol ether phosphate.

2. The foam flooding system of claim 1, wherein the concentration of the cationic surfactant is 0.5-3 wt%, the concentration of the nonionic surfactant is 0.1-0.5 wt%, and the molar ratio of the cationic surfactant to the stabilizer is 5: 1-1: 5, based on the total weight of the liquid phase.

3. The foam flooding system of claim 1 or 2, wherein the quaternary ammonium salt surfactant is selected from at least one of dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, and octadecyl trimethyl ammonium bromide.

4. The foam flooding system of claim 1 or claim 2, wherein the fatty alcohol ether phosphate is selected from at least one of fatty alcohol polyoxyethylene ether phosphate, and the alkylphenol ether phosphate is selected from at least one of alkylphenol polyoxyethylene ether phosphate.

5. The foam flooding system of claim 1, wherein the gas phase is selected from air, nitrogen, or carbon dioxide.

6. A method of preparing the foam flooding system of any one of claims 1 to 5, characterized in that the preparation method comprises the steps of:

2) mixing the foaming agent aqueous solution with gas, and foaming to obtain a foaming solution;

7. The method according to claim 6, wherein the concentration of the aqueous solution of the stabilizer is 20 to 50% by weight.

8. The production method according to claim 6 or 7, wherein the steps 2) to 3) comprise the following procedures: respectively feeding the foaming agent aqueous solution and gas into a first foaming device for mixing and foaming, and then feeding the obtained foaming liquid and the stabilizing agent aqueous solution into a second foaming device for mixing and foaming.

9. The preparation method according to claim 8, wherein the volume ratio of the gas to the flow rate of the foaming agent aqueous solution is 3: 1 to 20: 1.