CN102559168A - Acid-sensitive variable-viscosity mixed surfactant - Google Patents

Abstract

The invention provides an acid-sensitive viscous mixed surfactant, which is formed by mixing a sulfonate gemini surfactant and an alkyl glycoside nonionic surfactant at a mass ratio of 1:4 to 4:1. The viscosity of the mixed system is high, but after adding acid to the system, the viscosity drops rapidly. The acid-containing acid-sensitive mixed surfactant system causes the viscosity of the solution to increase through the consumption of acid. It has the characteristics of automatically finding low-permeability intervals during oil reservoir acidification, and has the function of self-steering, which can realize uniform acidification and obtain Good acidifying effect. Acid-containing acid-sensitive mixed surfactants have high viscosity after acidification, but when they contact with crude oil or hydrocarbons, they will automatically reduce their viscosity. The viscosity is close to that of water, and the flowback is easy.

Description

A kind of acid-sensitive viscous mixed surfactant

Technical field:

The invention relates to an acid-sensitive viscous mixed surfactant, specifically, the viscosity of the acid-sensitive viscous mixed surfactant system increases with the decrease of the acid liquid concentration, has a self-steering function, and can be used for acidification Self-steering agent.

Background technique:

Acidizing is one of the enhanced oil recovery (EOR) methods, and an effective technical measure for increasing production of oil and gas wells and injection wells. Its principle is to recover or improve the permeability of formation pores and fractures through the dissolution and dissolution of acid liquid on rock cement or formation pores and blockages in fractures. Acidizing can be divided into pickling, matrix acidizing and acid fracturing (also called acid fracturing) according to different processes. Pickling is to inject a small amount of acid liquid into the wellbore to remove acid-soluble particles, drill cuttings and scale in the wellbore holes, and to dredge the perforation holes. Matrix acidizing is to inject acid into the formation below the rock fracture pressure, relying on the dissolution of acid liquid to restore or improve the permeability of the oil layer in a large area near the wellbore. Acid fracturing is to inject acid into the formation at a pressure higher than the fracture pressure of the rock, forming fractures in the formation, and forming fractures with high conductivity through the uneven dissolution of the fracture wall by the acid liquid. Acidizing construction uses construction vehicles such as cement trucks and pump trucks to inject acidic aqueous solutions (such as hydrochloric acid, hydrofluoric acid , organic acids ) into the formation . The injected acid solution will dissolve formation rock or cement , thereby increasing formation permeability, making oil and gas production and displacement water injection more convenient.

Due to the heterogeneity of the formation, the injected fresh acid first enters the interval of least resistance and high permeability, where the acid dissolves carbonate or sandstone minerals and creates high conductivity Channels, so that these intervals have higher injection capacity, the final result is that most of the acid liquid flows into the same interval, while other target intervals do not enter the acid, and it is impossible to get acidized. Therefore, acid diversion is required to ensure that the entire formation is acidified in order to achieve uniform permeability. The role of the diverting agent is to balance the flow of acid fluid so that formations with different permeability can be acidified. According to the mechanism of action, acidification steering technology can be divided into mechanical steering and chemical steering.

Mechanical steering mainly includes packer steering and particle steering, but the mechanical technology is cumbersome and requires on-site installation and equipment, which is time-consuming and expensive, and its effectiveness is affected by the roundness and smoothness of the holes and the number of perforations; particle steering uses The steering agent is also difficult to discharge, which is easy to cause formation damage.

The acidification methods of chemical steering include oil-soluble resin suspension, self-steering of polymers, self-steering of surfactants, and foam steering.

After the oil-soluble resin suspension is injected, it sticks on the well wall, and the crude oil is extracted from the formation to dissolve it and flow back out. The advantage is that the resin can be deformed, the temperature resistance is also good, and the plugging effect is good, but the price is expensive, and it is commonly used abroad. Soluble solids that match the size of the pore throats are used. However, in China, firstly, the analysis of pore throat data is rarely done during design, and secondly, it is difficult to find industrialized materials with known particle sizes, so the effect has been poor.

Polymer diverting agents are composed of acid-soluble polymers or acid-soluble polymers and cross-linking agents to increase the viscosity of acid liquids. This type of diverting agent has a higher viscosity when the pH value is low, and the viscosity increases when the pH value increases. drop, or under the action of a depolymerizing agent to ensure complete disintegration of the crosslinks. Acid fluids are less viscous and easier to remove from the formation. However, polymers remaining in the interval will impair the permeability of the reservoir, thus reducing the effectiveness of acidizing treatment. According to the systematic analysis of the flowback fluid, during the acidizing treatment, 30% to 45% of the injected polymers are recovered in the flowback stage of the oil well, and quite a lot of polymers remain in the formation. In order to increase the effectiveness of the removal operation, a series of measures have been tried, but with little success.

The self-steering of surfactants mainly uses viscoelastic surfactants. When the viscoelastic surfactants are self-steering and the acid penetrates into carbonate rocks, the acid concentration will continue to decrease as the acid-rock reaction proceeds, and the pH of the solution will decrease. And the concentration of CaCl ₂ , MgCl ₂ increases, the appearance of salt and the increase of pH value make the long rod-shaped micelles in the viscoelastic fluid transform into intertwined worm-like micelles, and the high-viscosity fluid acts as a temporary Barrier function, diverting the fluid to the remaining low-permeability treatment layer. After the treatment, the acid barrier based on viscoelastic surfactants will automatically break when it encounters hydrocarbons or pre (post) treatment fluids in the reservoir . The viscoelastic surfactants used in the report mainly include betaine type (Zheng Yunchuan, Zhao Liqiang, Liu Pingli. Study on viscosifying acidification liquid with erucamide propyl betaine[J]. Oilfield Chemistry, 2005, 4:302-306) and quaternary ammonium Salt type (Bernhard Lungwitz. Diversion and clean upstudies of viscoelastic surfactant-based self-diverting acid [C]. SPE 86504: 9-11) two categories.

Foam turning acidizing is to fully mix the acid liquid with foaming agent and nitrogen in the surface foam generator, form stable foam and then inject it into the well to increase the productivity of the formation. Because the gas in foam acid can help drainage, foam acid acidification is especially suitable for reservoir reconstruction with low pressure and low permeability that is difficult to drain. Tapping the potential of old wells and increasing production of low-pressure wells can also effectively solve the problem of difficult drainage and water-sensitive reservoirs. layer and other special well operations.

In the above-mentioned application of chemical self-steering, surfactants have the best self-steering effect on site, but the viscoelastic surfactant used has a high concentration, generally greater than 4%, so the cost is high, and its application is limited.

Invention content:

The purpose of the present invention is to provide an acid-sensitive viscous mixed surfactant by utilizing the characteristic that the solution viscosity of the mixed surfactant system changes with the change of the acid concentration.

In order to achieve the above technical objectives, the present invention proposes the following technical solutions.

The acid-sensitive viscous mixed surfactant is composed of a sulfonate gemini surfactant and an alkyl glycoside nonionic surfactant in a mass ratio of 4:1 to 1:4, wherein,

The structural formula of sulfonate gemini surfactant is as follows:

In the formula, n=2, 4, 6, 8,

Hydrophobic R group is:

The molecular weight of the sulfonate gemini surfactant is 642-726.

The structural formula of the alkyl glycoside nonionic surfactant is as follows:

In the formula, m=8～16, n=1.2～1.8,

The molecular weight of the alkyl glycoside nonionic surfactant is 304.6-550.4.

Sulfonate gemini surfactants have good chemical stability, temperature resistance and salt resistance, high activity and critical micelle concentration is 1-2 orders of magnitude lower than conventional single-chain surfactants (Zhao Xiutai et al. Effect of interfacial tension and foaming performance of sulfonate-type gemini surfactants [J]. Journal of Petroleum (Petroleum Processing), 2011, Volume 27, Issue 2).

Alkyl Polyglycoside (APG) is a new type of non-ionic surfactant synthesized from renewable resources, natural fatty alcohols and glucose. It is a compound with an amphiphilic structure that does not dissociate into an ionic state in water. APG has four outstanding advantages: (1) low surface tension, can be compounded with various surfactants, and has the characteristics of synergistic effect; (2) low toxicity, little irritation to the skin; (3) complete biodegradation, in line with Environmental protection concept; (4) It is a renewable resource, which can solve various disadvantages caused by the oil crisis. Therefore, APG is known as a world-class green surfactant in the 21st century.

The mass ratio of the sulfonate gemini surfactant to the alkyl glycoside nonionic surfactant in the mixed surfactant system is 4:1-1:4. When the total mass concentration of surfactants in the mixed surfactant system is 2%, the viscosity of the system is high; while slowly adding hydrochloric acid to the system, the viscosity of the system decreases. Add hydrochloric acid with a mass concentration of 5% to a mixed surfactant system with a mass concentration of 2%, and then add calcium carbonate therein. As the reaction progresses, the concentration of the acid solution decreases and the viscosity of the system increases.

The beneficial effect of the invention is that the acid-containing acid-sensitive viscous mixed surfactant has the characteristic that the viscosity increases with the decrease of the acid liquid concentration, and can be used as an acid liquid diverting agent for oil reservoir acidification. In the initial stage of acidification, fresh acid liquid enters the high-permeability section. As the acid-rock reaction proceeds, the concentration of acid liquid decreases and the viscosity of the system increases. The reaction speed between acid liquid and rock is bound to slow down. large, so that the follow-up fresh acid solution enters the layer with relatively low permeability, and the viscosity of the system increases after the acid-rock reaction, which makes the follow-up acid solution enter other low-permeability layers. Therefore, the use of an acid-containing acid-sensitive viscous mixed surfactant system can obtain an acidification effect with uniform permeability.

Detailed ways:

The present invention is further illustrated below by way of examples.

Embodiment 1: According to the mass ratio of sulfonate gemini surfactant and alkyl glycoside nonionic surfactant is 4: 1, 3: 1, 2: 1, 1: 1, 1: 2, 1: 3 and 1 : 4 prepare the mixed surfactant system that the total mass concentration of surfactant is 2% respectively, then add the anhydrous calcium chloride that mass concentration is 2% respectively in each system, measure different shear rates under the condition of 60 ℃ Viscosity, the results are shown in Table 1. Under the mass ratio of 1:4～4:1, the mixed surfactant has higher viscosity, and the viscosity is far greater than the viscosity of a single surfactant solution, and when the mass ratio is 2:1, the viscosity of the mixed surfactant Best for thickening.

Table 1 Viscosity of acid-sensitive mixed surfactant system

Embodiment 2: preparation hydrochloric acid mass concentration is respectively the mass ratio of sulfonate gemini surfactant and alkyl glycoside nonionic surfactant of 1%, 0.5%, 0.1%, 0.05%, 0.01%, 0.005% and 0% It is a 2: 1 mixed surfactant solution system, the total surfactant mass concentration of the system is 1.5%, and then anhydrous calcium chloride with a mass concentration of 2% is added to each system, and measured at 60°C Viscosities at different shear rates are shown in Table 2. The viscosity of the mixed surfactant system increases with the decrease of acid mass concentration.

The influence of table 2 acid concentration on the viscosity of acid-sensitive mixed surfactant system

Embodiment 3: preparation mass concentration is 1.5%, the mass ratio of sulfonate gemini surfactant and alkyl glycoside nonionic surfactant is the mixed surfactant solution system of 2: 1 and mass concentration is 2% anhydrous Calcium chloride solution, the viscosity of the solution system is very large, then add the volume ratio of 3% kerosene, the viscosity of the solution system obviously decreases after stirring, then add the volume ratio of 3% kerosene, the solution system viscosity is close to the viscosity of water.

Embodiment 4: preparation acidifying acid solution, wherein containing the hydrochloric acid that mass concentration is 5%, mass concentration is 2.0%, the mass ratio of sulfonate gemini surfactant and alkyl glycoside nonionic surfactant is 2: 1 Mixed surfactant solution system, anhydrous calcium chloride with a mass concentration of 2% and octynyl alcohol with a mass concentration of 0.2%; inject the acidified acid solution into the rock core with a large permeability difference, with the acid rock reaction As the process progresses, the injection pressure gradually increases. After the reaction is completed, the core is taken out, and a small section of the inlet section that is in contact with the acid solution is cut off. Observed under a microscope, it is found that the pore size is basically uniform.

Compared with the prior art, the present invention has the following advantages:

(1) The viscosity of the acid-sensitive mixed surfactant system provided by the invention is very sensitive to changes in acid concentration, and the viscosity of the system significantly increases with the reduction of acid concentration;

(2) The acid-sensitive mixed surfactant system provided by the present invention can be used as the self-steering agent of the acid liquid during acidification, and has the function of automatically finding low-permeability layers;

(3) The fresh acid-sensitive mixed surfactant system containing acid has low viscosity and is easy to inject;

(4) The acid-sensitive mixed surfactant system provided by the present invention has a higher viscosity after acidification, and will automatically reduce the viscosity when it contacts with crude oil or hydrocarbons, the viscosity is close to that of water, and the flowback is easy;

(5) The use concentration of the acid-sensitive mixed surfactant system provided by the invention is lower than that of the reported viscoelastic surfactant diverting agent, which creates favorable conditions for its popularization and application.

Claims (2)

1. acid sensitivity mixed surfactant that becomes sticky; It is characterized in that mixing in 1: 4～4: 1 by mass ratio by sulphonate Gemini surfactant and APG nonionogenic tenside; The molecular weight of described sulphonate Gemini surfactant is 642～726, and its structural formula is following:

Wherein, n=2,4,6,8,

Hydrophobic group R group is:

The molecular weight of described APG nonionogenic tenside is 304.6～550.4, and its structural formula is following:

Wherein, m=8～16, n=1.2～1.8.

2. acid sensitivity according to claim 1 become sticky mixed surfactant during as acidifying acid solution from diversion agent.