CN102020981B - Temperature-resistant, salt-resistant and low-tension foam flooding agent and preparation method thereof - Google Patents

Abstract

The invention relates to a temperature-resistant, salt-resistant and low-tension foam flooding agent and a preparation method thereof. The temperature-resistant, salt-resistant and low-tension foam flooding agent is prepared by continuously stirring alkanolamide, bipolar surfactant and water at 40-60DEG C until the alkanolamide, the bipolar surfactant and the water are completely dissolved. The temperature-resistant, salt-resistant and low-tension foam flooding agent provided by the invention is suitable for tertiary recovery under the conditions that the temperature is 50-120DEG C and the mineralization is 0-100000ppm. Compared with other common foam agents in the prior art, the oil-water interfacial tension is reduced from 10<-2>mN.m<-1> to 10<-3>mN.m<-1>; and compared with common interfacial active agents in the prior art, the half foam life period at 50DEG C is increased from 15 minutes to more than 40minutes, and the recovery ratio of an indoor model is increased by more than 15%.

Description

A temperature-resistant salt-resistant low-tension foam oil displacement agent and preparation method thereof

technical field

The invention belongs to the field of oil field chemistry and relates to a chemical oil displacement agent for tertiary oil recovery, in particular to a tertiary oil recovery system which can be used in the late stage of high water-cut development of conventional oil reservoirs and high-temperature and high-salt oil reservoirs for one-time and greatly enhanced recovery.

Background of the invention

At present, more than 30 of the world's largest oil fields have entered the late stage of exploitation, and the use of technical means to further increase the recovery rate, that is, tertiary oil recovery has been recognized as an inevitable technical measure.

Existing studies have shown that capillary effect and reservoir heterogeneity are the main contradictions restricting the low recovery rate of crude oil in the process of primary and secondary oil recovery. The capillary effect makes it difficult for crude oil to be effectively driven when it stays in blind channels and small pores, while the heterogeneity of the reservoir leads to low sweep coefficient of the displacement system, so that the crude oil in the low-permeability zone cannot be driven.

Gas flooding is one of the most rapidly developed tertiary oil recovery technologies in recent years. Alkanes, carbon dioxide, nitrogen, and even air can be used as displacing agents for gas flooding. However, due to the low density, low viscosity and high fluidity of the gas, compared with water flooding, it is more affected by the heterogeneity of the reservoir, and it is very prone to fingering, which cannot reach the low permeability area, so that the EOR The effect is limited.

By adding surfactants, the gas is displaced in the form of foam fluid, and the increase of foam fluid apparent viscosity reduces the flow velocity in the high-permeability layer, increases the sweep coefficient, and improves the recovery factor. And because the foam agent itself is a surfactant and has interfacial activity, if it can reduce the oil/water interfacial tension to an ultra-low level and significantly increase the capillary number, it will be able to exert a better effect and greatly increase the recovery factor at one time.

The characteristics of the foam fluid determine that the foam can selectively block high-permeability channels, reduce the carrying capacity of high-permeability areas without destroying low-permeability areas, and also have oil/water selectivity, blocking water flow without blocking oil In addition, it is not difficult to realize the optimization of the temperature-resistant and salt-resistant properties of the foaming agent. Therefore, in the absence of a breakthrough in the development of temperature-resistant and salt-resistant polymers, the foam undoubtedly has an incomparable role in plugging and profile control. application potential. Especially for the development of high-temperature and high-salt reservoirs, it is of great significance.

The enrichment behavior of surfactants at the gas/water and oil/water interfaces is determined by the molecular structure, but the structure-activity relationship and mechanism are different, and are affected by environmental factors, including gas phase composition, oil phase composition, temperature, salinity , additives and other factors, so it is a difficult problem to optimize foam stability and oil-water interfacial activity at the same time, and low-tension foam systems with good foam stability and high oil-water interface activity are very scarce.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention provides a temperature-resistant, salt-resistant, low-tension foam oil displacement agent and a preparation method thereof.

The invention not only has excellent foam stability, strong plugging and profile control ability, but also has strong interfacial activity, can reduce the crude oil/water interfacial tension to an ultra-low level, and has a remarkable effect of enhancing the recovery factor.

Technical scheme of the present invention is as follows:

A temperature-resistant salt-resistant low-tension foam oil displacement agent, the composition of raw materials by mass is as follows:

40-55 parts of alkanolamide, 10-50 parts of bipolar surfactant, and 100-200 parts of water. in,

Described alkanolamide is coconut oil alkanolamide, fatty acid monoethanolamide or coconut oil diethanolamine, wherein preferred coconut oil alkanolamide;

The bipolar base surfactant is alkyl dicarboxyethyl imidazoline, alkyl alcohol polyoxyethylene ether sulfate, alkylphenol polyoxyethylene ether sulfate, sulfobetaine, carboxybetaine Or dialkyl diphenyl ether sulfonates, among which sulfobetaine is preferred.

Preferably, a temperature-resistant salt-resistant low-tension foam oil displacement agent, the composition of the raw materials by mass is as follows:

40-50 parts of alkanolamide, 20-30 parts of bipolar surfactant, and 100-160 parts of water.

Further preferably, a temperature-resistant salt-resistant low-tension foam oil displacement agent, the composition of the raw materials by mass is as follows:

Coconut oil alkanolamide 42 parts, sulfobetaine 28 parts, water 130 parts.

The above-mentioned alkanolamides and bipolar-based surfactants are all selected from prior art products, which are available in the market. in,

Preferably, the coconut oil alkanolamide is prepared as follows: in the synthesis reactor, quantitatively add coconut oil, the temperature is controlled at 60-100°C, and the mass ratio of coconut oil to diethanolamine is 2.0-1.0:1 to the reactor Add diethanolamine to the mixture, stir evenly, add 0.3-1% KOH of the total mass of reactants, raise the temperature to 100-150° C. and react for 4-6 hours.

The preparation method of the above-mentioned temperature-resistant and salt-resistant low-tension foam oil displacement agent of the present invention, the steps are as follows:

Add the above-mentioned alkanolamide and bipolar surfactant into water, and keep stirring at 40-60°C until completely dissolved to obtain the product.

Preferably, a method for preparing a temperature-resistant and salt-resistant low-tension foam oil displacement agent, the above-mentioned alkanolamide and bipolar surfactant are added to 1/3 to 1/2 of the total amount of water, and at 40-60°C Stir continuously until it is completely dissolved, then add the remaining amount of water, stir evenly, and the product is ready.

The application of the temperature-resistant, salt-resistant and low-tension foam oil displacement agent of the present invention is used for tertiary oil recovery under the condition of temperature 50-120°C and salinity 0-100,000ppm. When applied, the product of the present invention is formulated to a concentration of 0.05-0.3wt% and injected downhole, mixed with air or nitrogen at the bottom of the well to generate foam, and then enters the formation. Compared with other commonly used foam agents in the prior art, the oil-water interfacial tension is reduced from 10 ^-2 mN.m ^-1 to 10 ^-3 mN.m ^-1 , compared with the commonly used surfactants in the prior art, at 50°C The half-life of foam is increased from 15 minutes to more than 40 minutes, and the recovery rate of the indoor model is increased by more than 15%. The temperature-resistant, salt-resistant, low-tension foam oil displacement agent of the invention is suitable for a total concentration of calcium and magnesium ions of 0-1,000ppm.

The temperature-resistant, salt-resistant and low-tension foaming agent of the present invention has the following excellent effects:

1. The low-tension foaming agent of the present invention adopts alkanolamides with weak polar head anchoring effect, so that the surfactant molecules are arranged in a "lying down" pattern on the foam liquid film, and the network structure formed by the interlacing of hydrophobic chains is used The interfacial film stabilizes the foam liquid film, thus maintaining high foam stability from normal to elevated temperatures.

2. The low-tension foaming agent of the present invention is compounded with a bipolar-based surfactant with high interfacial efficiency and an alkanolamide with high interfacial density to obtain high interfacial effectiveness and reduce the interfacial tension of crude oil and water to ultra-low .

3. The low-tension foaming agent of the present invention is compounded with a bipolar-based surfactant with good salt resistance, so that the system can withstand higher salinity, and the salinity can be used to further modulate the surface active agent at the oil-water interface. Adsorption, higher interfacial activity at high salinity.

Detailed ways

The present invention will be further described below in conjunction with the examples, but not limited thereto.

Example 1:

A temperature-resistant salt-resistant low-tension foam oil displacement agent, the composition of raw materials by mass is as follows:

Coconut oleic acid diethanolamide 42 parts, sulfobetaine 28 parts, water 130 parts. Wherein, coconut oleic acid diethanolamide is prepared by the following method:

In a 1000L synthetic reaction kettle, add 366 kilograms of coconut oil, add 234 kilograms of diethanolamine while stirring in the above-mentioned synthetic reaction kettle, keep the temperature at 80°C, stir 15g of potassium hydroxide, heat up to 120°C for 5 hours, Get coconut oleic acid diethanolamide.

In parts by mass, take 42 parts of the above-mentioned coconut oleic acid diethanolamide, add 28 parts of sulfobetaine, add 50 parts of water, stir at 50°C until completely dissolved, then add 80 parts of water, and stir evenly to obtain a low-tension foam The oil displacing agent is labeled LIF-1.

Example 2:

A temperature-resistant salt-resistant low-tension foam oil displacement agent, the composition of raw materials by mass is as follows:

49 parts of coconut oleic acid diethanolamide, 21 parts of alkyl alcohol polyoxyethylene ether sulfate, 150 parts of water. Wherein, coconut oleic acid diethanolamide is made according to embodiment 1, and alkyl alcohol polyoxyethylene ether sulfate is the product of Taiyuan Fakai Company, and the model is AE3S.

In parts by mass, take 49 parts of coconut oleic acid diethanolamide, add 21 parts of alkyl alcohol polyoxyethylene ether sulfate, add 50 parts of water, stir at 50°C until completely dissolved, then add 100 parts of water, stir evenly, That is, the low-tension foam oil displacement agent is obtained, and the label is LIF-2.

Example 3: Foam stability and plugging profile control test

The foam agent is prepared as an aqueous solution with a concentration of 0.3%, and the foam is generated by the air flow method. The temperature of the foam generator is controlled at 50°C. The foam volume is measured as a function of time to obtain a foam decay curve, and the time when the foam volume decays to half of the initial volume is taken. is the half-life of the foam, marked as t _1/2 . Foam stability is directly proportional to half-life.

Use 80-200 mesh quartz sand to fill a 55cm simulated core tube with a core pore volume of 32% and a permeability of 1.5 Darcy. After being saturated with water, inject aqueous solution and N ₂ at speeds of 10ml/min and 160ml/min respectively, and measure The pressure at the inlet and outlet of the core pipe is obtained by initial pressure difference ΔP _initial = P _inlet - P _outlet , and then injecting 0.3% foam agent aqueous solution and N ₂ at the same speed, and the pressure difference ΔP _foam = P _inlet - P _outlet , The resistance factor δ= _ΔPfoam / _ΔPinitial is calculated. During the measurement, the whole process is at a temperature of T=120°C. The blocking capacity of the foam is directly proportional to the resistance factor.

The comparison foam agent α-olefin sulfonate, product code AOS, was purchased from the market and produced by Xi'an Nanfeng Chemical Co., Ltd. The surfactant petroleum sulfonate PS-1 used for comparison was purchased from the market and produced by Zhongsheng International Petrochemical Group Co., Ltd. in Shengli Oilfield.

The experimental results are as follows:

Embodiment 4: the interfacial activity of foaming agent

Adjust the TEXAS-500 spinning drop interfacial tensiometer to 50°C, and measure the interfacial tension between 0.3% foaming agent and comparative sample solution and the crude oil in the Shengtuo area of Shengli Oilfield according to the national standard SY/T5370-1999 method, and record the lowest interfacial tension as γmin. For the water phase, the formation water in the Shengtuo block of Shengli Oilfield was used. The foaming agent solution concentration is 0.3%.

The experimental results are as follows:

Example 5: Effect of Foam System on Enhanced Oil Recovery

Use 80-200 mesh quartz sand to fill a 55cm simulated core tube with a core pore volume of 28-34% and a permeability of 1.0-1.8 Darcy. After being saturated with water, it is saturated with Shengtuo crude oil from Shengli Oilfield and aged at 80°C for 48 hours. Finally, use 80°C hot water to displace until the water content of the produced fluid reaches 98%, then inject 80°C hot water and N ₂ at speeds of 10ml/min and 160ml/min to displace 5PV, and then inject 10ml/min and 160ml/min Inject 0.5% foaming agent aqueous solution and N ₂ at 80°C at a high speed, and displace until the water content of the produced fluid is 98%. The process was maintained at 80°C throughout the test.

The test results are as follows:

Claims (7)

1. A temperature-resistant and salt-resistant low-tension foam oil displacement agent is characterized in that the mass parts of raw materials are composed as follows: 40-55 parts of alkanolamide, 10-50 parts of bipolar-based surfactant, 100-200 parts of water; among them, Described alkanolamide is coconut oil alkanolamide, is to make as follows: In the synthesis reaction kettle, add coconut oil quantitatively, the temperature is controlled at 60-100°C, add diethanolamine into the reaction kettle according to the mass ratio of coconut oil and diethanolamine at 2.0-1.0:1, stir evenly, and add 0.3 -1wt% KOH, heated to 100-150°C for 4-6 hours; The bipolar-based surfactant is alkyl dicarboxyethyl imidazoline, alkyl alcohol polyoxyethylene ether sulfate, alkylphenol polyoxyethylene ether sulfate, sulfobetaine or dialkyldiphenyl ether sulfonate. 2. oil displacing agent as claimed in claim 1, is characterized in that raw material mass part is formed as follows: 40-50 parts of alkanolamide, 20-30 parts of bipolar surfactant, and 100-160 parts of water. 3. The oil-displacing agent according to claim 1 or 2, characterized in that said bipolar surfactant is sulfobetaine. 4. oil displacing agent as claimed in claim 1, is characterized in that, raw material mass part is composed as follows: Coconut oil alkanolamide 42 parts, sulfobetaine 28 parts, water 130 parts. 5. The preparation method of the oil-displacing agent described in any one of claims 1 to 4, the steps are as follows: adding the above-mentioned alkanolamide and bipolar surfactant into water, stirring continuously at 40-60°C until completely dissolved , that is. 6. the preparation method of the described oil displacement agent of any one of claim 1～4, wherein above-mentioned alkanolamide, bipolar surfactant are joined in the water of 1/3～1/2 total amount, in 40- Stir continuously at 60°C until it is completely dissolved, then add the rest of the water, stir evenly, and the product is ready. 7. The application of the oil displacement agent according to any one of claims 1 to 4, which is used for tertiary oil recovery at a temperature of 50-120° C. and a salinity of 0-100,000 ppm. the