CN107474811B

CN107474811B - Micro-foam acid liquid and preparation method thereof

Info

Publication number: CN107474811B
Application number: CN201710877063.9A
Authority: CN
Inventors: 蒋建方; 林梅钦; 许晓; 廉静怡; 黄勇; 熊婷; 仇晓丽
Original assignee: China University of Petroleum Beijing
Current assignee: China University of Petroleum Beijing
Priority date: 2017-09-25
Filing date: 2017-09-25
Publication date: 2020-03-27
Anticipated expiration: 2037-09-25
Also published as: CN107474811A

Abstract

The invention belongs to the technical field of foamed acid, and discloses a micro-foamed acid solution and a composition and a preparation method of a compound foaming agent thereof, wherein the micro-foamed acid solution comprises 10-25% of HCl (hydrochloric acid) + 0.36% of SDJR-2 (compound foaming agent) + 0.24% of SBW-101 (foam stabilizer) + 0.2% of FS3802 (thickening agent) and water by mass fraction; the water is used for complementing to 100 percent; the compound foaming agent SDJR-2 consists of 55.56 mass percent of FBM-5-2 foaming agent and 44.44 mass percent of AK-304 foaming agent. The micro-bubble acid liquid has good foaming, foam stabilizing, viscosity maintaining, acid rock reaction slowing, temperature resistance, salt resistance, oil resistance, sand carrying and other properties; observing the microstructure and the size of the micro-foam acid liquid by an optical microscope to meet the size requirement of the micro-foam; experimental evaluation shows that the micro-foam acid liquid is a novel acid liquid system with excellent performance and has wide application prospect.

Description

Micro-foam acid liquid and preparation method thereof

Technical Field

The invention belongs to the technical field of foamed acid, and particularly relates to a micro-foamed acid liquid, a composition of a compound foaming agent and a preparation method of the micro-foamed acid liquid.

Background

After twenty-first century, many oil fields at home and abroad are developed for decades and already enter the middle and later stages of development, and new development problems appear, such as a high permeability layer is fully developed, and a lower permeability layer is seriously underdeveloped or even hardly developed due to poor physical property and weak flow capacity compared with an adjacent low permeability layer, so that interlayer contradiction is further increased, the water content of oil field exploitation is higher and higher, reaches more than 98%, and the comprehensive development level is reduced. Some profile control temporary plugging measures are implemented, wherein the foam acid can effectively plug a high-permeability layer and force the acid liquid to enter a low-permeability layer for acidification treatment because the foam liquid of the foam acid has the characteristics of high apparent viscosity, large seam plugging and large pore plugging but small pore low permeability; in addition, the foam acid has the characteristics of being stable when meeting water and defoaming when meeting oil, so that the foam acid blocks a high-water layer and easily enters an oil-containing low-permeability layer, and the aims of profile control, blocking and uniform acidification are fulfilled. Some oil fields have insufficient natural stratum energy and low stratum pressure coefficient, and working fluid after operation is difficult to return quickly, stays in the stratum, causes damage, causes secondary pollution and reduces the operation effect. For example, in the Changqing oil field, the pressure coefficient of the original stratum is generally between 0.72 and 0.86. The foam liquid comprises the foam acid, so that the density is low, the expansibility is good, the flowback capability of the operation fluid is improved, the flowback rate of the working fluid is improved, and meanwhile, the high viscosity of the foam acid further enables stratum migration particles to return out of the stratum along with the flowback liquid, so that the damages such as blockage, liquid blockage and the like are reduced, and the measure effect is improved. After the oil field is developed for years, the bottom pressure of the oil well is low, and similar problems exist after treatment, and the foam liquid can play a unique role due to the particularity of the foam liquid. Most oil and gas fields in China have the characteristics of small formation pore, low permeability and poor fluid fluidity, squeezed fluid enters an oil layer and is easy to cause formation damage such as emulsion blockage, wax blockage, clay expansion blockage and the like, pressure conduction is slow during flowback, the liquid supply capacity is insufficient, the oil and gas layers are damaged for many times, and the success rate and the validity period of measures are greatly reduced. The effect of the conventional acidification technology on the stratum is obviously reduced, and the efficient development of the oil field is restricted. But the foam acid can not only quickly generate acid-rock reaction and increase the porosity of the stratum, but also increase the backflow force of the acid-rock reaction residual acid by depending on the expansion energy of gas and low liquid column pressure, thereby effectively reducing the secondary damage of acidification and further improving the acidification effect. Meanwhile, compared with other types of acid liquid, the foam acid has large foam mass, less water content and high viscosity, so that the reaction speed of the acid with operation equipment and underground operation production strings can be effectively reduced, the corrosion to metal and the damage of products thereof to stratums are reduced, and the low reaction speed and corrosion rate have more special effects on high-temperature deep wells. Besides normal optimization and optimal application of a conventional oil-gas field, the foamed acid is particularly suitable for repeated acidification of low-pressure, low-permeability and heterogeneous formations, carbonate rock bottom water layers, water-sensitive formations and old wells, and has special effects, application prospects and effects in the fields.

Summarizing and analyzing the application of the foamed acid and other types of acid liquid in mines in the operation and production processes of oil and gas fields and experimental research on action mechanisms, comprehensively, the foamed acid has the characteristics of low content, easy flowback, low damage and the like compared with the conventional acid liquid, can well realize diversion and diversion of the acid liquid for a heterogeneous reservoir stratum, and is a very ideal acid liquid system for yield increase transformation of low-pressure, low-permeability, heterogeneous and high-water-content oil and gas reservoirs. Summarizing, the foam acids have the following specific advantages:

(1) high gas-liquid ratio, low density, low liquid column pressure, high expansion energy and high back-flow capacity.

(2) High viscosity and low filter loss.

(3) The pipe flow friction resistance is small.

(4) The acid rock reaction speed is slow, and the retarding effect is good.

(5) The capability of carrying solid particles is strong.

(6) The liquid drainage speed is high, the oil testing period is short, and the damage to a reservoir is small.

Of course, also due to the nature of the foam acid itself, the foam acid also finds some problems in its application, mainly expressed in:

(1) the foam is easy to gather, the strength is low, the structure is easy to break, and the stability is poor.

(2) The compressive plugging strength is low, and the plugging steering failure is easily caused.

(3) The operation of the foam acid requires a foam generating device and a compression device, the construction equipment cost is high, and the working procedure is relatively complex.

(4) And the method is limited for deep wells, high pressure wells and the like.

In summary, the problems of the prior art are as follows: the foam is easy to gather, the strength is low, the structure is easy to break, and the stability is poor; the compressive plugging strength is low, so that the plugging steering failure is easily caused; the operation of the foam acid requires a foam generating device and compression equipment, the construction equipment cost is high, and the working procedure is relatively complex; and the method is limited for deep wells, high pressure wells and the like.

Disclosure of Invention

Aiming at the problems and the defects of the prior foam acid technology, the invention provides a composition of a micro-foam acid liquid and a preparation method thereof.

The invention is realized in such a way that the micro-foaming acid liquid consists of 10 to 25 mass percent of hydrochloric acid, 0.36 mass percent of compound foaming agent, 0.24 mass percent of foam stabilizer, 0.2 mass percent of thickening agent and water; the water is used for complementing to 100 percent.

Another object of the present invention is to provide a method for preparing the micro-foaming acid solution, wherein the method for preparing the micro-foaming acid solution comprises the following steps:

step one, 61.1g of analytical hydrochloric acid with the mass fraction of 36% is measured by a measuring cylinder and poured into a 1000ml beaker filled with 32.1g of deionized water to prepare an HCl solution with the mass fraction of about 20%. Preparing other hydrochloric acid solutions with the mass fractions by the same method;

weighing 0.22g of thickener white powder by using an electronic balance, adding the thickener white powder into an HCl solution beaker with the mass fraction of 20%, and stirring by using a high-speed stirrer at the stirring speed of 3000r/min until the thickener is uniformly dispersed; waiting for 2 hours to ensure that the thickening agent is fully swelled in the acid liquor, and sealing the beaker by using a plastic film to reduce the volatilization of the hydrochloric acid;

measuring 9.9g of pipette from the standard compound foaming agent solution into a HCl solution beaker with the mass fraction of 20%; a pipette measures 6.6g of the standard foam stabilizer solution into a beaker of HCl solution with the mass fraction of 20%; stirring 100ml of liquid in a 1000ml beaker by a high-speed stirrer at a stirring speed of 3000r/min until milky uniformly dispersed micro-foaming acid liquid is formed, and finishing the preparation of the micro-foaming acid liquid.

The invention also aims to provide a compound foaming agent for preparing the micro-foam acid solution, wherein the compound foaming agent consists of 55.56% of foaming agent and 44.44% of foaming agent in mass fraction.

The invention also aims to provide a preparation method of the compound foaming agent, which comprises the following steps:

firstly, measuring 55.56g to a 200ml measuring cylinder from a standard foaming agent solution bottle by using a pipette;

secondly, 44.44g of the solution is metered by a pipette from a standard foaming agent bottle and added into a 200ml measuring cylinder added with 55.56g of the foaming agent;

and thirdly, rapidly stirring the mixture by using a glass rod until the mixture is uniform to form 100g of standard compound foaming agent.

Another object of the present invention is to provide a foamed acid prepared from the micro-foamed acid solution.

Another object of the present invention is to provide an oil well using the micro foaming acid liquid.

The invention has the advantages and positive effects that: the micro-bubble acid liquid has the characteristics and the sizes of micro-bubbles, such as low density, expansibility, deformability, high expansion energy, acid rock reaction slowness and the like, besides the common properties of the conventional foam acid, such as low density, expansibility, deformability, high expansion energy, acid rock reaction slowness and the like, because the micro-bubble acid liquid has a core, two layers and three films (the core is a core, gas is positioned in the middle of spherical micro-bubbles, a gas core is a gas core, the two layers 1 are gas core outer wrapping films, the viscosity of aqueous solution is high, a high viscosity water layer is formed, the two layers 2 are transition layers formed by polymer high molecules and surface active agents in mass fraction, the transition layers are transition layers, the three films 1 are positioned at the outer side of the gas core, the gas core is tightly wrapped, the interfacial tension between gas and liquid is reduced, the surface tension is reduced, the high viscosity water layer is kept all the time, the high viscosity is fixed film, the three films 3 are films which are formed by aggregating the polymer and the surface active agents, the, compared with the conventional foam acid, the foam acid has higher pressure resistance, better dispersibility, low friction resistance, sand carrying capacity, temperature resistance, salt resistance and oil resistance, is a novel acid liquid system with excellent performance, has self-foaming characteristic in the production practice of oil and gas fields, does not need a special foaming device in mines, and can form micro-foam liquid by using pump circulation; because of the structural characteristics of 'one core, two layers and three films', a supercharging device is not needed, and construction equipment and working procedures can be greatly simplified; the process targets of plugging, turning, quick flowback, slow reaction and the like in the acidification process can be realized by depending on the foam property; meanwhile, the liquid amount in the application is small, the discharge assisting speed is high, the carrying capacity is high, and the formation damage can be obviously reduced; the countless micro-bubbles are distributed in the body phase, so that the high-pressure micro-bubble. Therefore, the micro-foaming acid liquid has wide application prospect.

The volume of the micro-foam acid liquid generally increases along with the increase of the mass fraction of the foaming agent, but the volume of the micro-foam is larger when the mass fraction is larger, and the volume of the micro-foam is basically not changed when the mass fraction is increased to a certain degree; as the mass fraction of blowing agent increases, not all microfoam stability increases and half-life lengthens; some have a large foaming volume and a short half-life, and some have a small foaming volume but a long half-life. Optimization is needed to obtain the foaming agent with larger foaming volume and longer half-life period and the mass fraction thereof. Through optimization, the compound foaming agent SDJR-2 is formed and consists of 55.56% of FBM-5-2+ 44.44% of AK-304 (FBM-5-2 is an amphoteric surfactant and is produced by Xinxiang Fubang science and technology limited company; AK-304 is potassium lauroyl glycinate and is an anionic surfactant and is produced by Dandongkang fine chemical engineering limited company), has good foaming volume and half life (565ml and 73min), and the using mass fraction of the compound foaming agent is 0.36%.

Through experimental comparison of evaluation of the foaming stabilization effect of the foaming agent under different mass fractions of two foam stabilizers SBW-101 with better foam stabilization performance and dodecanol, the fact that the volume change of the micro-foaming acid liquid is not large after the foam stabilizer is added is found, but the foam stabilization time is obviously prolonged (138 min); however, the foam stabilizing time does not always increase with the increase of the mass fraction of the foam stabilizer, and the foam stabilizing time is basically stabilized at 130min after reaching a certain mass. The obtained foam stabilizer after optimization is SBW-101 (a nonionic surfactant which is widely applied in recent years and is produced by Xinxiang Fubang science and technology Limited company), and the using mass fraction of the foam stabilizer is 0.24%.

The viscosity of the micro-foam acid liquid can be effectively increased by adding a proper amount of thickening agent, the stability of the micro-foam is increased, and the flow resistance of the micro-foam acid liquid at a high speed is obviously reduced under the action of a linear polymer structure. The impact of the thickener on the foaming and foam stabilization of the microfoam acid was evaluated in a systematic study. As the mass fraction of the thickener increases, the volume of the micro-foam rises in a wave shape; the stability of the foam also increases with increasing mass fraction of thickener. When the mass fraction of the thickener FS3802 (a thickener for polyacrylamide acids, which can be crosslinked under a strongly acidic condition and is produced by Beijing Schitao technology development Co., Ltd.) is 0.25%, the foam volume increase range is maximal, 565ml, and the foam stability increase range is also maximal, and the half-life period is 173 min. Preferably, the thickening agent is FS3802 with the mass fraction of 0.2%.

The half-life of the microfoam acid system decreases with increasing temperature, i.e., an increase in temperature decreases the stability of the microfoam acid system. The temperature is increased to make the thermal movement of gas molecules aggravated, and simultaneously the liquid film is accelerated to evaporate and become thin, so that the strength of the bubble film is reduced, and the stability of the micro-foam acid system is reduced. But the experiments show that the micro-foam acid system can also keep better stability at high temperature and can meet the field requirements due to the special structure 'one core, two layers and three films'. The apparent viscosity of the microcellular acid solution decreases with increasing temperature, which aggravates molecular thermal motion, but can still be maintained at a higher level due to the high surface tension of the microcellular foaming agent and the use of the thickener. The apparent viscosity at 90 ℃ can be maintained at 35 mPas or more. The microfoam acid has better salt pollution resistance, and the influence on the stability of a high-salinity microfoam acid system can be reduced by adding the salt swelling agent. The addition of kerosene showed characteristics different from those when Na salt was added, and had a large effect on the foaming volume, because oil is a defoaming agent. However, the micro-foaming acid not only has the foaming agent, the foam stabilizer and the thickening agent, but also has better surface interfacial tension property, so that the influence of the oil on the micro-foaming acid is far lower than that of the conventional foaming acid. The experimental result shows that when 15% of kerosene is added, the foam quality of the micro-foam acid is kept at about 80%, the half-life period is about 120min, and the micro-foam acid has strong oil pollution resistance and completely meets the application requirement of a mine site.

Drawings

Fig. 1 is a flow chart of a preparation method of a micro-foaming acid solution provided by an embodiment of the invention.

FIG. 2 is a flow chart of a preparation method of the compound foaming agent provided by the embodiment of the invention.

Fig. 3 is a photograph of an end face of a micro-foaming acid solution provided by an embodiment of the present invention.

FIG. 4 is a schematic diagram of the effect of different shear rates on the apparent viscosity of a micro-foaming acid system under a compound foaming agent provided by the embodiment of the invention.

FIG. 5 shows the influence of temperature on the apparent viscosity of a micro-foaming acid solution system of a compound foaming agent (170 s)^-1) Schematic representation.

FIG. 6 shows the effect of temperature on the apparent viscosity of a micro-foaming acid solution system of a compound foaming agent (511 s)^-1) Schematic representation.

Fig. 7 is a schematic view of an acid liquid foam structure of an eyepiece micro-foam with a magnification of 200 times provided by an embodiment of the invention.

Fig. 8 is a schematic view of a 200-fold magnification objective micro-foaming acid liquid foam structure provided in an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

On the basis of fully researching and comparing the properties of the foam acid and other acid liquids and understanding of mechanisms causing the differences, the invention starts to consider which method can be adopted to form a new acid liquid, which not only has some excellent characteristics of foam, such as high viscosity, high energy, low gravity, acid rock reaction slowing, and the like, but also has most characteristics of conventional acid liquids, such as water solubility, acid reaction, compatibility with acidification additives, and the like. Through analyzing the parameters and regular characteristics of the anionic surfactant, the cationic surfactant, the amphoteric surfactant and the nonionic surfactant which are evaluated in China and have good application effect, the purposive re-evaluation is considered to be preferable, and the foam acid with the micro-bubble structure can be formed. In practice, on the basis of the guidance idea and the understanding of the foaming and foam stabilizing mechanism of the surfactant, a micro-foam acid solution with excellent performance is formed through a series of experiments, evaluations and optimizations indoors, and the micro-foam acid solution has the following technical advantages: (1) self-foaming: automatic generation, no need of special foaming device, indoor stirring and field pump circulation. (2) The construction and process equipment is simplified: compared with the conventional foam acid operation, a pressurizing device is not needed. (3) The acidification process target can be realized: can be blocked, can be turned, can be quickly discharged, can be slowly reacted, etc. (4) Low damage: less liquid amount, fast discharge and strong carrying capacity. (5) For low pressure formations: the construction pressure is favorably established and the quick flow-back is realized. (6) Can be used for deep wells: countless microbubbles are distributed in the body phase, and have small elasticity and slight compressibility.

The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.

The micro-foaming acid solution provided by the embodiment of the invention consists of 10-25% of HCl (hydrochloric acid), 0.36% of SDJR-2 (compound foaming agent), 0.24% of SBW-101 (foam stabilizer), 0.2% of FS3802 (thickener) and water by mass percentage; the water is used for complementing to 100 percent.

As shown in fig. 1, the method for preparing a micro-foaming acid solution (taking 100ml of micro-foaming acid solution as an example) provided by the embodiment of the present invention includes the following steps:

s101: preparing acid liquor with different mass fractions: 61.1g of 36% by mass of analytical hydrochloric acid are weighed out in a measuring cylinder and poured into a 1000ml beaker with 32.1g of deionized water to give an approximately 20% by mass HCl solution. Other mass fractions of hydrochloric acid solutions were prepared using the same method.

S102: preparation of amino acid: weighing 0.22g of thickening agent FS3802 (white powder) by using an electronic balance, slowly adding the thickening agent FS3802 into an HCl solution beaker with the mass fraction of 20%, and stirring the mixture by using a high-speed stirrer at a stirring speed of 3000r/min until the thickening agent is uniformly dispersed; and waiting for 2h to ensure that the thickening agent is fully swelled in the acid liquor, and sealing the beaker by using a plastic film during the process to reduce the volatilization of the hydrochloric acid.

S103: preparing micro-foaming acid liquid: 9.9g of standard compound foaming agent SDJR-2 solution was weighed into a beaker with 20% by mass HCl solution by pipette. 6.6g of the standard foam stabilizer SBW-101 solution is weighed by a pipette into a beaker with a mass fraction of 20% HCl solution. Stirring 100g of liquid in a 1000ml beaker by using a high-speed stirrer at a stirring speed of 3000r/min until milky uniformly dispersed micro-foaming acid liquid is formed, and finishing the preparation of the micro-foaming acid liquid.

The compound foaming agent consists of 55.56 percent of FBM-5-2 (foaming agent) and 44.44 percent of AK-304 (foaming agent) in percentage by mass.

As shown in fig. 2, the preparation method of the compound foaming agent provided by the embodiment of the invention comprises the following steps:

s201: 55.56g are pipetted from a bottle of a standard blowing agent FBM-5-2 solution into a 100ml measuring cylinder.

S202: 44.44g were pipetted from a standard foaming agent AK-304 bottle into a 100ml measuring cylinder.

S203: and (3) rapidly stirring the mixture by using a glass rod until the mixture is uniform to form 100g of standard compound foaming agent SDJR-2.

The application principle of the present invention is further illustrated by the following experiments.

1 micro-foaming acid liquor laboratory formula optimization

1.1 Experimental reagents and instruments

The main experimental reagents comprise five foaming agents (FBM-5-1, FBM-5-2, AK-MES, sodium cocoyl sarcosinate (AK-303) and potassium lauroyl glycinate (AK-304)), two foam stabilizers (SBW-101 and dodecanol), a compound foaming agent SDJR-2, a thickening agent for acid (FS3802), analytical hydrochloric acid, calcium carbonate, sodium chloride, deionized water and the like, wherein the foaming agents comprise 55.56% of FBM-5-2 and 44.44% of AK-304. Wherein FBM-5-1 and FBM-5-2 are nonionic surfactants, SBW-101 is a diionic surfactant, the effective content of which is 40%, and the surfactant is produced by Xinxiang Fubang technology Co. AK-MES, AK-303 and AK-304 are anionic surfactants, dodecanol is a nonionic surfactant, the effective content of all the surfactants is 40%, and the surfactant is produced by Dandongkang fine chemical Co. FS3802 is a thickener for polyacrylamide acids, white powder, produced by beijing shitao technologies development ltd. Analytical grade HCl, CaCO₃Chemical reagents such as NaCl, etc. are purchased from Beijing, modern Oriental Fine Chemicals Co., Ltd, and deionized water is purchased from ChinaProvided by the basic chemical laboratory of oil university.

The main experimental instruments are the HAAKE-RS600 type rheometer, available from the German HAAKE company, the PL2002 type electronic balance available from Metler-Toriledo instruments, Inc., Shanghai, the SHB-IIIAB type circulating water vacuum pump available from ST France, the BX-41 type optical microscope available from Olympus, Japan, and high-speed electronic mixers, timers, beakers, measuring cylinders, volumetric flasks, pipettes, etc.

1.2 results of the experiment

1.2.1 preference for Single blowing agent

At normal temperature (25 ℃ C.) and normal pressure, FBM-5-1, FBM-5-2, AK-MES, AK-303 and AK-304 were tested for the foam volume and half-life at mass fractions of 0.04%, 0.08%, 0.12%, 0.16%, 0.2%, 0.24%, 0.28%, 0.32%, 0.36%, 0.4%, 0.48% and 0.6%, respectively, and the results of the measurements are shown in Table 1.

TABLE 1 foaming Capacity test of five foaming agents

As can be seen from Table 1, FBM-5-1 and FBM-5-2 have better foaming ability, although the foaming volume is not the maximum, the half-life period is obviously larger than that of three foaming agents of AK-MES, AK-303 and K-304, and the properties of the foam are relatively stable. AK-303 and AK-304 have relatively strong foaming ability, but have short half-life and unstable foam properties. AK-MES has weak foaming ability, stability and half-life. Comparing foaming and foam stabilizing capability comprehensively, when the FBM-5-2 mass fraction reaches 0.32%, the foam volume is 460ml, and the half-life period is 71min, which is relatively best.

1.2.2 optimization of Compound foaming agent

0.12 percent, 0.16 percent, 0.2 percent and 0.24 percent of FBM-5-2 and 0.12 percent, 0.16 percent and 0.2 percent of AK-303 and AK-304 are compounded respectively, and then the performance test of the compounded foaming agent is carried out according to the same method in the performance test experiment of a single foaming agent to obtain the foaming volume and the half-life period of the compounded foaming agent, and the results are shown in tables 2 and 3.

TABLE 2 Properties of FBM-5-2 compounded with AK-303

TABLE 3 Performance of FBM-5-2 compounded with AK-304

When the mass fraction of FBM-5-2 is 0.16%, the mass fraction of AK-304 is 0.2%; and when the mass fraction of FBM-5-2 is 0.2 percent and the mass fraction of AK-304 is 0.16 percent, the foaming capacity is strongest, and the maximum foaming volume is about 565 ml. When the mass fraction of FBM-5-2 is 0.2 percent, the mass fraction of AK-304 is 0.16 percent; and when the mass fraction of FBM-5-2 is 0.24 percent and the mass fraction of AK-304 is 0.12 percent, the stability of the system is best. The comprehensive comparison shows that the foaming and foam stabilizing effects are relatively good when 0.2 percent FBM-5-2 and 0.16 percent AK-304 are compounded, the volume of the generated foam is 565ml, and the half-life period is 73 min.

The compound foaming agent is named as SDJR-2 and consists of 0.2 percent of FBM-5-2 and 0.16 percent of AK-304, and a standard compound foaming agent solution is prepared according to a standard foaming agent solution method. The preparation method of the compound foaming agent comprises the following steps:

① A55.56 g to 100ml measuring cylinder was pipetted from a standard blowing agent FBM-5-2 solution bottle.

② A44.44 g aliquot was pipetted from a standard foaming agent AK-304 bottle into a 100ml graduated cylinder.

③ was stirred rapidly with a glass rod until homogeneous to form 100g of standard compounded blowing agent SDJR-2.

1.2.3 preference for foam stabilizers

Foaming volume and half life are respectively tested when 0.04%, 0.08%, 0.12%, 0.16% and 0.2% of foam stabilizer SBW-101 and dodecanol are added into a 0.36% SDJR-2 system of the compound foaming agent at normal temperature (25 ℃) and normal pressure, and the results are shown in tables 4 to 7.

TABLE 4 foam volume of foam stabilizer SBW-101 added to blowing agent

TABLE 5 foam stabilizing Properties of foam stabilizers SBW-101 added to blowing agent

TABLE 6 foam volume of foam stabilizer dodecanol added to the blowing agent

TABLE 7 foam stabilizing Properties of the foam stabilizer dodecanol added to the blowing agent

By comparing the test results of the two foam stabilizers, the foam stabilizer SBW-101 is found to have better foam stabilizing effect than dodecanol. Therefore, the foam stabilizer is preferably SBW-101, and the mass fraction of the foam stabilizer used in combination with the compound foaming agent system is preferably 0.24%.

1.2.4 thickener mass fraction is preferred

At normal temperature and pressure, 0.24% of SBW-101 is added into a 0.36% SDJR-2 system of the compound foaming agent, then 0.05%, 0.1%, 0.15%, 0.175%, 0.2%, 0.25% and 0.3% of thickening agent FS3802 are added, and after the mixture is stirred to generate foam, the foam volume and half life are respectively measured, and the results are shown in Table 8.

TABLE 8 foam stabilization Performance of thickeners in Compound foamer systems

The foam volume shows a wave ascending trend along with the increase of the mass fraction of the thickening agent FS3802, and the stability of the foam is increased along with the increase of the mass fraction of the thickening agent FS 3802. In a compound foaming agent system, when the mass fraction of the thickening agent FS3802 is 0.2%, the foam volume reaches the maximum, and the foam stability increase amplitude is large. Therefore, the mass fraction of the thickening agent FS3802 is selected to be 0.2%, the foam volume of the micro-foam system is 610ml, and the half-life period is 71 min.

(5) Through laboratory formula optimization, the formula of the microfoam base fluid is as follows: 0.36 percent of SDJR-2, 0.24 percent of SBW-101 and 0.2 percent of FS3802, wherein the compound foaming agent consists of a foaming agent FBM-5-2 and a foaming agent AK-304 according to the mass percent of 5: 4.

1.3 formula composition of micro-foaming acid liquid

1.3.1 formulation composition

According to comprehensive evaluation of a single foaming agent, a compound foaming agent, a foam stabilizer and a thickening agent on foaming volume, size, stable state and half-life period under different mass fractions, the compound foaming agent SDJR-2 with relatively excellent performance is preferably selected, wherein the mass fraction of the compound foaming agent SDJR-2 is 0.36%, the mass fraction of the foam stabilizer SBW-101 is 0.24%, the mass fraction of the foam stabilizer FS3802 is 0.2%. According to the general use range of hydrochloric acid in an oil-gas field and a mine field, 10-25% of a micro-foam acid solution formula system is formed: 10% -25% of HCl + 0.36% of SDJR-2+ 0.24% of SBW-101+ 0.2% of FS 3802.

1.4.2 foam acid form

According to the preferred micro-foaming acid liquid formula composition, the micro-foaming acid liquid shown in figure 3 is formed according to the preparation method and steps of the micro-foaming acid liquid.

2 factors influencing apparent viscosity of micro-foam acid liquid system

2.1 Experimental part

2.1.1 Experimental reagents and instruments

The main reagents and apparatus were the same as described in 1.2.1.

2.1.2 Experimental methods

In the experiment, HAAKE RS600 type rheometer produced by Germany HAAKE company is adopted to carry out the influence of different foaming agent systems, different shear rates and different temperatures on the viscosity of the micro-foam acid liquid.

2.2 Experimental results and analysis

2.2.1 shear Rate Effect on the apparent viscosity of the micro-foam acid System

Taking a micro-foam acid liquid system (20% HCl + 0.36% SDJR-2+ 0.24% SBW-101+ 0.2% FS3802) of a compound foaming agent as an experimental object, and respectively measuring the shear rate to be 170s by using a HAAKE RS600 type rheometer^-1And 511s^-1The apparent viscosity of the micro-foaming acid solution and the change thereof at room temperature (25 ℃) within 2h are shown in figure 4.

As can be seen from FIG. 4, when the shear rate is 170s^-1When the micro-foaming acid solution system is used, the apparent viscosity of the micro-foaming acid solution system is about 43 mPas, and is slightly reduced within 2h, but the change is not greatly shown, and the micro-foaming acid solution system has better shear stability. When the shear rate is increased to 511s^-1When the micro-foaming acid liquid system is used, the apparent viscosity is reduced to about 36 mPas, and is slightly reduced within 2h, but the change is not large, the micro-foaming acid liquid system is basically maintained to be more than 33 mPas, and the micro-foaming acid liquid system also shows better shear resistance stability; shear rate is 170s^-1Increase to 511s^-1In the case of the microcellular acid liquid system, the apparent viscosity is reduced, but not much, by about 7 mPas, and the apparent viscosity of the system is stabilized within a specific range with time. Namely, the micro-foaming acid liquid of the compound foaming agent system has good shear stability; increasing the shear rate decreases the apparent viscosity of the micro-foaming acid solution, increases fluidity, but has little effect on stability.

2.2.2 Effect of experiment temperature on apparent viscosity of micro-foam acid liquid system

Taking a micro-foam acid liquid system of a compound foaming agent as an experimental object, and respectively measuring the shear rate to be 170s by using a HAAKE RS600 type rheometer^-1And 511s^-1The apparent viscosity of the micro-foaming acid solution was changed at 25 deg.C, 60 deg.C, and 90 deg.C, and the results are shown in FIG. 5 and FIG. 6.

As can be seen from FIG. 5, at a shear rate of 170s^-1The apparent viscosity at 25 ℃ is about 43 mPas, and even if the shear is carried out for 2 hours, the apparent viscosity is not greatly reduced, and the better stability is shown; the apparent viscosity at 60 ℃ is about 34 mPas, the apparent viscosity during 2h shearing is basically stable, and the reduction is small; apparent viscosity at 90 ℃ at initial stage30 mPas, and the fluctuation is obvious, the apparent viscosity is slowly reduced in the fluctuation along with the shearing, and after 2 hours, the apparent viscosity is stabilized at 19 mPas, which shows that the apparent viscosity of the micro-foam acid liquid system at 90 ℃ is obviously influenced by the stability.

As can be seen from FIG. 6, at a shear rate of 511s^-1When the temperature is 25 ℃ and 60 ℃, the apparent viscosity of the micro-foaming acid liquid system is stabilized near a value, and slightly decreases within 2 hours, but the decrease range is not large, which shows that the influence on the apparent viscosity at a certain temperature is not large; after the temperature is increased, the apparent viscosity shows a descending trend, but the relative stability of the apparent viscosity can still be maintained under isothermal condition; however, when the temperature is 90 ℃, the apparent viscosity of the micro-foaming acid liquid system is changed greatly and shows a trend of decreasing obviously all the time, but the apparent viscosity begins to be stable after shearing for 70min and is basically maintained at about 12 mPas. It can be seen that at the same temperature the stability of the microfoam acid liquid system starts to deteriorate at 90 c, while at 60 c and 25 c it shows better stability. As a result, in the micro-foaming acid liquid system of the compound foaming agent, the higher the temperature is, the lower the apparent viscosity of the system is, and the higher the fluidity is.

Acid rock reaction characteristic of 3 micro-foaming acid liquid

3.1 Experimental reagents and instruments

The main reagents and apparatus were the same as described in 1.2.1.

3.2 Experimental methods

And (3) carrying out a reaction rate experiment of the micro-foaming acid liquid and the calcium carbonate powder according to an acid rock reaction kinetics experiment determination method. The acid rock reaction characteristic experiment of the micro-foaming acid solution comprises three steps of preparation, reaction and drying.

3.3 data processing and retardance of micro-foaming acid solutions

The acid rock kinetic equation can be expressed as:

J＝KC^m

in the formula: j-acid rock reaction speed, g/min;

c-hydrochloric acid mass fraction,%;

m is the reaction stage number, and represents the influence of the concentration of reactants on the reaction speed;

k-reaction rate constant, g-1. min^-1And characterizing the reaction speed of different acid rocks.

Taking the logarithm of the two ends of the above formula, it can be written as:

lgJ＝lgK+mlgC

knowing the reaction speeds under different acid concentrations, drawing by using lgJ and lgC to obtain a straight line, wherein the slope of the straight line is m, and the intercept is lgK, so that the reaction order number m and the reaction rate constant K can be obtained, and an acid rock reaction kinetic equation can be obtained.

According to the Allen Arrielills theory, the law of the reaction rate constant with temperature can be expressed by the following equation:

in the formula: k-reaction rate constant, g^-1·min^-1；

k₀Frequency factor, g^-1·min^-1；

E_a-activation energy of reaction, J/mol;

r-gas constant, 8.314J/(mol. K);

T-Absolute temperature, K.

In the experiment, under the condition of keeping the initial concentration of the acid liquor in the microcellular acid unchanged, the reaction temperature is changed, the reaction speed at different temperatures can be obtained, then a relation graph of lgJ-1/T is made, and the frequency factor k can be obtained₀And activation energy of reaction E_aThe value of (c). The intercept and slope of the line are respectively the frequency factor k₀And activation energy of reaction E_aThe value of (c).

The single foaming agent micro-vesicular acid systems with acid concentrations of 10%, 15%, 20% and 25% were used as experimental subjects, and were reacted with the same mass of calcium carbonate, respectively, and the reaction rates at the respective acid concentrations were calculated from the corrosion amounts of calcium carbonate after different reaction times, as shown in table 9. It can be seen that the first 10min of the reaction is the time period with the fastest reaction speed, and the longer the reaction time, the lower the reaction speed. The hydrochloric acid participating in the reaction is less after 20min, the reaction is almost completed after half an hour, and the corrosion amount is not changed any more.

TABLE 9 reaction rates of hydrochloric acid at different mass fractions

lgC and lgJ were obtained from the reaction rates at different acid concentrations, and a graph of the acid rock reaction rate and the acid concentration was obtained, and the results are shown in Table 10.

TABLE 10 reaction rates for different acid concentrations

The slope of the straight line, i.e., the value of the reaction order m, is 1.1217, and the intercept, i.e., the value of lgK, is 0.7626, the reaction rate constant is 5.790g^-1·min^-1. The reaction kinetic equation of the micro-foaming acid liquid and the carbonate rock is as follows:

J＝5.790C^0.7626

by obtaining the reaction rates at different temperatures at 10% acid concentration, 1/T and lgJ were obtained, and the relationship between the reaction rate and the temperature was obtained, and the results are shown in Table 11.

TABLE 11 reaction rates at different temperatures

According to the experimental results, the slope of the line after linear regression was-1228.54 and the intercept was 4.4510. The reaction kinetic parameters at varying temperatures can be found:

reaction activation energy: e_a＝1228.54J·mol^-1

Frequency factor: k is a radical of₀＝4.4510g-1·min^-1

The equation for the reaction kinetics at varying temperatures is:

compared with the reaction of the conventional ketocarbonate hydrochloride rock, the reaction rate constant and the reaction series of the micro-foaming acid liquid system are obviously smaller than those of the conventional hydrochloric acid, and the slowness of the micro-foaming acid liquid system is reflected.

4 micro-foaming acid liquid system performance

4.1 basic properties of the microcellular acid foams

The conventional performance of microfoam is primarily to evaluate the basic properties of the microfoam, such as half-life, bubble volume, etc., to determine the stability of the microfoam. The volume and half-life of the microfoam formulations of the single blowing agent system at different stirring times are shown in table 12.

TABLE 12 conventional performance parameters for microfoam

Therefore, the volume of the foam liquid is basically maintained unchanged with the continuous stirring of the micro-foam acid liquid, but the half-life period of the micro-foam acid is obviously increased, the volume of a single foam is more tiny, the half-life period is increased, and meanwhile, the stability of the micro-bubbles is improved.

4.2 micro-morphology of micro-foaming acid liquid

The size, the shape and the even distribution of the foam are observed by a microscope to judge the foaming of the foam and the micro-shape of the micro-foam acid. For observation of foam, microbubbles were smeared evenly onto the slide and then covered gently with a cover slip. The observation results of the micro-foam acid system of the compound foaming agent under a 10-fold ocular lens and a 20-fold objective lens are shown in fig. 7 and 8.

Therefore, the micro-foam acid is round, the interior of the micro-foam acid is an air core, the exterior of the micro-foam acid is wrapped by a layer of liquid film, the shell is formed by an inner surface active agent film and an outer surface active agent film which sandwich a tackifying water layer, the radius of the shell is larger, and some of the shell can even reach half of the radius of the whole foam, so that the foam has very good stability and is not easy to break. The statistical results of the microfoam size in fig. 8 show that the diameter of the microfoam ranges mainly from 10 μm to 100 μm, the smallest point observable by the human eye is 50 μm, and a part of the microfoam is visible by the human eye, whereas the conventional foam is typically from micrometer to centimeter, and the majority is visible by the human eye. The foam size and the form of the micro-foam acid liquid show that the foam acid is the micro-foam acid.

4.4 evaluation of anti-pollution Properties

(1) Salt contamination resistance

Adding Na with different mass fractions into a micro-foaming acid liquid system⁺The foaming properties and stability of the foam system were observed. Table 13 shows that after adding sodium salts with different mass fractions, the volume of the microfoam decreases with the increase of the salt content, and even if the mineralization is increased to 100000ppm, the volume retention rate of the microfoam acid solution is still over 90%; but the half-life period of the micro-foaming acid liquid is slightly influenced by the mineralization degree, when the mineralization degree of the sodium salt reaches 40000ppm, the half-life period of the micro-foaming acid liquid is obviously reduced to 87min, the mineralization degree of the sodium salt is further increased, and the half-life period of the micro-foaming acid liquid is gently reduced. In general, the salt contamination resistance of the microbubble acid is better, but the stability needs to be improved. In field application, it is preferable to add an anti-salt swelling agent to reduce the influence on the stability of the micro-bubble acid system.

TABLE 13 foam characteristics at different mass fractions Na +)

(2) Evaluation of oil stain resistance

And evaluating the foaming performance and stability of the system after adding kerosene into the micro-foaming acid liquid system. As can be seen from table 14, after kerosene with different mass fractions was added, the volume and half-life period of the microcellular acid solution were both reduced, but defoaming was not significant, and even if kerosene with a mass fraction of 15% was added, the foam mass of the microcellular acid solution was still about 80% and the half-life period was about 120 min. Therefore, the micro-foaming acid liquid has better oil pollution resistance.

TABLE 14 foam characteristics at different kerosene contents

4.5 evaluation of Sand carrying Properties

Adding 20-40 mesh quartz sand into the micro-foaming acid liquid system, and observing the falling of the quartz sand in the micro-foaming acid liquid and the falling of the foam liquid level at different time. Within the first 30s, the sand hardly drops and is suspended in the micro-foaming acid liquid, and the foam liquid level is hardly sunken; after 60s, the liquid level is slightly concave, but the change is not obvious; after 90s, the liquid level is sunken obviously, and the quartz sand begins to settle. The result shows that the micro-foam acid liquid has better sand carrying performance.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. The micro-foaming acid liquid is characterized by comprising 10-25% of HCl, 0.36% of SDJR-2, 0.24% of SBW-101 and 0.2% of FS3802 in percentage by mass; SDJR-2, consisting of 0.2% FBM-5-2+ 0.16% AK-304.