Optimal selection method for foam acidizing fluid system

Abstract

The invention relates to a foam acidizing fluid system optimization method, which comprises the following steps: setting a plurality of first contrast ratios with different proportions of surfactant components and xanthan gum, respectively carrying out a foam half-life period test on the plurality of first contrast ratios, and optimizing a foam acidizing fluid system with good foam stability according to a foam half-life period test result. The optimal proportion of the xanthan gum is determined. And then carrying out acidification reaction based on the optimized foam acidizing fluid system, and finally optimizing the optimal components of the surfactant based on the acidification reaction result. A foam acidizing fluid system preferably selected according to the method is composed of 10 wt% of hydrochloric acid, 5 wt% of formic acid, 5 wt% of acetic acid, 1.5 wt% of DGME, 1.2 wt% of xanthan gum, 1.5 wt% of modified nanocrystallized disilicon, 1 wt% of HC-Y-02 and 0.5 wt% of an iron ion stabilizer, the foam acidizing fluid system has good stability, retarding performance and corrosion inhibition performance and is suitable for heat storage and yield increase of geothermal wells, mass-produced and low-price DGME is selected as a surface active agent, and the foam acidizing fluid system is suitable for being used for heat storage and yield increase of geothermal wells. The production cost of a foam acidizing fluid system is greatly reduced, and market popularization is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal storage development and relates to a method for optimizing a foam acidizing liquid system. Background Art

[0002] Acid fracturing technology is commonly used to increase thermal reservoir production. That is, acidizing fluid is used to chemically dissolve thermal reservoir rocks to increase the aperture and porosity of the fractures in the reservoir rocks, as well as the connectivity between the reservoir pores and fractures, thereby improving the reservoir permeability and achieving thermal reservoir production increase.

[0003] As a type of acidizing fluid, foamy acid is widely used in thermal reservoir production increase because it is in foamy form and has a buffering effect that can slow down the acid-rock reaction. It is also easy to flow back in the reservoir.

[0004] At present, foam acidizing fluid is mainly used in oil and gas wells. However, for geothermal wells, due to differences in rock composition, formation structure, ambient temperature, pressure, and geothermal fluid properties, the foam acidizing fluid used in oil and gas wells cannot be directly used in geothermal wells, otherwise it will cause irreversible damage to the reservoir.

[0005] However, the existing foam acidizing fluid system developed for geothermal well heat storage production increase has poor foam stability, and the surfactant used in its formula is independently synthesized and does not have the scale for mass production, which greatly increases the production cost of the foam acidizing fluid system and is not conducive to market promotion. Summary of the Invention

[0006] In view of this, the present invention provides a method for optimizing a foam acidizing system in order to solve the technical problems of poor foam stability, high production cost and disadvantageous market promotion of the foam acidizing liquid system in the prior art.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: A foam acidizing liquid system optimization method is used to optimize the foam acidizing liquid system, wherein the foam acidizing liquid system is composed of a compound acid solution, a surfactant, xanthan gum, 1.5 wt% modified nano-silica, 1 wt% HC-Y-02, and 0.5 wt% iron ion stabilizer, wherein the compound acid solution is composed of 10 wt% hydrochloric acid, 5 wt% formic acid, and 5 wt% acetic acid; The preferred method comprises the following steps: A plurality of first comparative ratios of the foam acidifying liquid system are prepared, wherein the plurality of first comparative ratios differ in that the ratios of the surfactant component and the xanthan gum in the foam acidifying liquid system are different; Based on a plurality of first comparative examples, a foam half-life test was conducted, and according to the foam half-life test results, the ratio of xanthan gum was optimized to be 1.2 wt %; An acidification reaction test was conducted on the foam acidification liquid system selected based on the foam half-life test, and a surfactant consisting of 1.5 wt% DGME was selected based on the results of the acidification reaction test.

[0008] Furthermore, the preferred method further comprises: The second comparative example and the third comparative example non-foaming acidizing fluid system were configured; The non-foaming acidizing liquid system of the second comparative example consists of 10 wt % hydrochloric acid, 5 wt % formic acid, 5 wt % acetic acid, 1 wt % corrosion inhibitor, and 0.5 wt % iron ion stabilizer; The third comparative example non-foaming acidizing fluid system consists of 20 wt % hydrochloric acid, 1 wt % corrosion inhibitor, and 0.5 wt % iron ion stabilizer; Based on a plurality of first comparative example foamed acidizing liquid systems and second comparative example non-foamed acidizing liquid systems, their apparent viscosity, density and surface tension, which are parameters characterizing their basic properties, were measured respectively.

[0009] Before conducting foam half-life tests based on multiple first comparative examples and optimizing the xanthan gum ratio of 1.2 wt% based on the foam half-life test results, it is also necessary to conduct a feasibility evaluation on the foam acidifying liquid systems of multiple first comparative examples, and the feasibility evaluation results are characterized by the dimensionless foam characteristic value.

[0010] Furthermore, the dimensionless foam characteristic value is measured by a foaming test, which includes the following steps: For each first comparative example, an equal amount of the unfoamed liquid acidifying solution was placed in a measuring cup and mixed with high-pressure gas for foaming. After the volume of the foamy acidifying liquid system stabilizes, read the reading of the measuring cup and record it. The reading of the measuring cup is the foaming volume; The ratio of the high-pressure gas volume to the foam volume is the dimensionless characteristic value of the foam.

[0011] Furthermore, the foam half-life test includes the following steps: Take equal amounts of multiple foam acidifying liquid systems of the first comparative example and add them to a measuring cup, and record the initial time T1; Obtain the time T2 when the volume of the foam acidifying liquid system in multiple measuring cups is reduced to half; The difference between time T2 and time T1 is the foam half-life.

[0012] Furthermore, the foaming test and the foam half-life test need to be repeated at set temperatures of 25°C, 70.6°C and 90°C, respectively, and the measuring cups required for the foaming test and the foam half-life test need to be preheated to the set temperature before the test.

[0013] Furthermore, the acidizing reaction test is carried out at a specific temperature, including an acid-rock reaction test, and includes the following steps: Select rock chips of equal particle size, clean them with deionized water, and then dry them; Take equal amounts of dried rock chips and place them in multiple beakers. Preheat the rock chips and beakers to a specific temperature. After the cuttings are fully preheated, equal amounts of the foam acidizing fluid system selected from the foam half-life test, the second comparative example, and the third comparative example of non-foaming acidizing fluid are added to the preheated beaker to allow the cuttings to fully react. The reacted cuttings were slowly cleaned with deionized water, and then dried in a drying oven, and the remaining The quality of rock cuttings; The cuttings mass loss rate and cuttings mass loss velocity were calculated based on the cuttings mass before and after reaction and the reaction time.

[0014] Furthermore, the acidification reaction test also includes a corrosion inhibition test, including the following steps: Selecting a plurality of metal sheets, washing the plurality of metal sheets and then drying the plurality of metal sheets, and weighing the pre-corrosion mass and the surface area of ​​the plurality of metal sheets respectively; A plurality of metal pieces are placed in a flask respectively, and the flask containing the metal pieces is preheated to a specific temperature and kept constant; Take equal amounts of the foam acidizing liquid system selected from the acid-rock reaction test and place them in flasks respectively, and connect them to condensers; After the foam acidifying liquid system has completely reacted with the metal sheet, stop heating and then stop passing the condensed water; The corroded metal sheet is taken out, washed and dried, and then the mass of the corroded metal sheet is weighed, the corrosion rate of the metal sheet is calculated, and the corrosion condition of the metal sheet is observed.

[0015] Furthermore, the specific temperature is 70.6°C.

[0016] The beneficial effects of the present invention are: A method for optimizing a foam acidizing liquid system comprises setting multiple first comparative examples, wherein the first comparative examples differ in the ratio of surfactant components and xanthan gum in the acidizing liquid system. During optimization, foam performance evaluation is first conducted based on the acidizing liquid systems of the multiple first comparative examples, and the optimal ratio of xanthan gum is determined based on the foam performance evaluation. Multiple second comparative examples are then set based on the acidizing liquid system optimized through stability testing results, wherein the multiple second comparative examples differ in the ratio of surfactant components. Acidification reaction tests are then conducted based on the multiple second comparative examples, and the surfactant component is optimized based on the results of the acidification reaction tests.

[0017] The acidizing fluid system obtained based on the above-mentioned preferred method consists of 10wt% hydrochloric acid, 5wt% formic acid, 5wt% acetic acid, 1.5wt% DGME, 1.2wt% xanthan gum, 1.5wt% modified nano dioxide, 1 wt% corrosion inhibitor, and 0.5%wt% iron ion stabilizer. It has been verified that the foam acidizing fluid system has good stability, slowness and corrosion inhibition, further improving the effective acidizing distance of the foam acidizing fluid system, effectively increasing the opening of the reservoir fracture, improving the reservoir permeability, and thus improving the acidizing transformation effect. Secondly, the surfactant used is a mass-produced product. Compared with the independently synthesized surfactant, it has good chemical stability and low price, which greatly reduces the production and manufacturing cost of the foam acidizing fluid, which is conducive to large-scale promotion and use.

[0018] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which: Figure 1 Schematic diagram of foam morphology of four foam acidizing liquid systems of the first comparative example 1-04, the first comparative example 2-04, the first comparative example 3-04, and the first comparative example 4-04 at the time of preparation completion in the embodiment of the present invention; Figure 2 1-04, 2-04, 3-04, 2-05, 3-10, 3-2, 3-3, 3-4, 3-10 for the first comparative example 1-04, 3-04, 3-05, 3-10 for the second comparative example 1-04, 3-04, 3-10 for the third comparative example 1-04, 3-10 for the first comparative example 1-04, Figure 3 1-01, 1-02, 1-03, and 1-04 in the embodiments of the present invention at 25° C., 70.6° C., and 90° C.; Figure 4 This is a schematic diagram of the corrosion of metal sheets in the first comparative example 1-04, the first comparative example 2-04, and the first comparative example 3-04. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below in conjunction with the drawings in the preferred embodiments of the present invention. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present invention, and should not be understood as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The embodiments of the present invention are described in detail below in conjunction with the drawings.

[0021] Based on the above-mentioned problems existing in the prior art, the present application provides a foam acidizing liquid system optimization method for optimizing the acidizing liquid system.

[0022] The preferred acidizing solution system of this embodiment is a foamy one, consisting of a composite acid solution, a surfactant, xanthan gum, 1.5 wt% modified nano-silica, 1 wt% HC-Y-02, and 0.5% wt% iron ion stabilizer. The composite acid solution is composed of 10 wt% hydrochloric acid, 5 wt% formic acid, and 5 wt% acetic acid.

[0023] As can be seen from the background technology, the foam acidizing fluid used in existing geothermal wells has poor foam stability, and the foam stability is mainly related to the surfactant component and the xanthan gum ratio. The present embodiment mainly optimizes the surfactant component and the xanthan gum ratio.

[0024] Specifically in this embodiment, the preferred method of the foam acidizing liquid system includes the following steps: S01: preparing a first comparative example of a plurality of acidifying liquid systems, wherein the difference between the first comparative examples is that the surfactant components and the xanthan gum ratios are different; Then, the second and third comparative examples of non-foaming acidifying liquid systems were prepared respectively.

[0025] The non-foaming acidifying liquid system of the second comparative example consists of 10 wt % hydrochloric acid, 5 wt % formic acid, 5 wt % acetic acid, 1 wt % HC-Y-02, and 0.5 wt % iron ion stabilizer.

[0026] The non-foaming acidizing liquid system of the fourth comparative example consists of 20 wt % hydrochloric acid, 1 wt % HC-Y-02, and 0.5 wt % iron ion stabilizer.

[0027] It should be noted that the foam acidizing liquid system of the first comparative example is in a foamy state. In order to further verify that the foam acidizing liquid system has good retarding and corrosion inhibition properties, the second and third comparative examples are set for comparison.

[0028] The components and proportions of the foamed acidizing liquid system of the first comparative example, the non-foamed acidizing liquid system of the second comparative example, and the non-foamed acidizing liquid system of the third comparative example are shown in Table 1: Table 1: Chemical composition of acidizing fluid system

[0029]

[0030] As shown in Table 1, the difference of a plurality of the first comparative examples foam acidizing fluid systems is that the xanthan gum proportioning is different from the surfactant component.First, by the different components of the acidizing fluid system surfactant, a plurality of the first comparative examples are divided into four groups. For ease of differentiation, they are named after the first comparative example 1, the first comparative example 2, the first comparative example 3 and the first comparative example 4. Then, the first comparative example of each group with the identical surfactant component is divided by the different proportioning of xanthan gum, and with the first comparative example 1 as an example, they are named after the first comparative example 1-01, the first comparative example 1-02, the first comparative example 1-03, the first comparative example 1-04. The naming methods of the remaining three groups are identical and will not be repeated herein.

[0031] S02: measuring basic properties of a plurality of first comparative example foamed acidizing fluid systems and second comparative example non-foamed acidizing fluid systems to compare differences in performance parameters between the foamed acidizing fluid systems and the non-foamed acidizing fluid systems.

[0032] Specifically, in this embodiment, the basic properties of the acidizing liquid system are characterized by apparent viscosity, density and surface tension, which are measured by test instruments. The specific measurement process is as follows.

[0033] 2.1. The apparent viscosity of the acidizing solution system is measured by a coaxial cylinder viscometer, which specifically includes the following steps: 1) Add the acidified liquid system into the outer cylinder of the cylinder viscometer, pull up the outer cylinder, and insert the inner cylinder into the acidified liquid system; 2) Start the cylinder viscometer and rotate it at a set speed of 100 r / min. Record the reading of the cylinder viscometer after it stabilizes. 3) Calculate the apparent viscosity of the acidizing liquid system based on the cylinder viscometer reading.

[0034] 2.2. The density of the acidizing fluid system is measured by a density meter. The measurement process is as follows: 1) Place the density meter sample cup on the weighing table, and then set the density meter reading to zero to remove the weight of the sample cup; 2) Slowly add the acidification liquid system to the sample cup to the cup mouth, cover the cup and press down, then wipe off the overflowed acidification liquid system; 3) Place the sample cup filled with the acidifying liquid system on the weighing table. The value displayed on the density meter is the density of the acidifying liquid system being measured.

[0035] 2.3. Surface tension is measured by a surface tension meter. The measurement process is as follows: 1) Calibrate the surface tension meter by immersing the platinum ring in a standard liquid (e.g., pure water), measuring its surface tension, and comparing it to the theoretical value (e.g., γ = 71.97 mN / m for pure water at 25°C). Adjust the instrument parameters to an error of <1%. 2) Turn on the surface tension meter and select the measurement mode (such as static surface tension or dynamic contact angle); 3) Foam acidification liquid sample preparation: Pour the liquid to be tested into a clean sample dish. The liquid level should be high enough to cover the platinum ring (usually ≥5 mm in depth). 4) Slowly raise the sample stage: Move the sample stage upward at a constant speed (e.g., 0.1-0.5 mm / s) until the platinum ring gradually separates from the liquid surface. The maximum tension value displayed on the surface tension meter is the surface tension value of the acidified liquid system being tested.

[0036] The above is a method for measuring the basic performance parameters of the acidizing fluid system. According to the above method, the apparent viscosity coefficient, density and surface tension of the acidizing fluid systems of the first comparative example and the third comparative example were measured respectively. The specific values ​​are shown in Table 2.

[0037] Table 2: Apparent viscosity, density and surface tension of acidizing fluid system:

[0038] Combining the data analysis of Table 1 and Table 2, it can be seen that the apparent viscosity of the first comparative example is significantly increased, and the density and surface tension are significantly reduced compared with the third comparative example, which proves that the acidizing liquid system formula of the first comparative example has the basic properties of foaming acid. S03: Conducting feasibility evaluation based on multiple foam acidizing fluid systems of the first comparative example; Here, the foam feasibility evaluation result is characterized by a dimensionless foam characteristic value, which is used to verify whether the foam acidizing liquid system prepared according to the formula and proportion of the foam acidizing liquid system of the first comparative example has foam characteristics.

[0039] To verify the feasibility and stability of the acidizing fluid system provided in this embodiment when used within the thermal storage temperature range, the dimensionless foam characteristic value needs to be obtained within the thermal storage temperature range when evaluating the feasibility of the foam acidizing fluid system.

[0040] As an example, the foam acidizing fluid system of this embodiment is mainly used for thermal reservoir production increase of medium-low temperature dolomite, and the thermal reservoir temperature range corresponding to medium-low temperature dolomite is 25℃-90℃. Therefore, the foam characteristic value dimensionless is obtained at 25℃, 70.6℃, and 90℃, making the obtained results more realistic and more convincing.

[0041] Specifically in this embodiment, the dimensionless foam characteristic value is measured by a foaming test, which includes the following steps: 1) For each first comparative example, take multiple equal amounts of the unfoamed liquid acidifying solution of the first comparative example and place them in a measuring cup, and mix them with high-pressure gas for foaming. The volume of high-pressure gas required for foaming is V1; Here, for each first comparative example, the number of the unfoamed liquid acidifying solution system and the measuring cups is 3, and the measuring cups need to be preheated before the test, and the preheating temperatures are 25° C., 70.6° C., and 90° C., respectively.

[0042] 2) After the foam volume of the foam acidifying liquid system is stable, read the reading of the measuring cup. The reading of the measuring cup is the foaming volume V2. For specific values, see Table 3; The ratio of the high-pressure gas volume V1 to the foaming volume V2 is the dimensionless foam characteristic value. For specific values, see Table 3.

[0043] Table 3: Dimensionless table of foam volume and foam characteristic values:

[0044] Here, for the production increase of medium- and low-temperature dolomite thermal reservoirs, the dimensionless value range of the foam characteristic value is 0.7-0.9. Referring to Table 3, the dimensionless foam characteristic values ​​of the acidizing fluid systems of the first comparative example at temperatures of 25°C, 70.6°C, and 90°C are all within the range of 0.7-0.9, indicating that the acidizing fluid system prepared according to the formulation of the first comparative example in this embodiment is feasible.

[0045] S04. Conducting a foam half-life test based on multiple foam acidifying liquid systems of the first comparative example, and optimizing the ratio of the xanthan gum to 1.2 wt % based on the foam half-life test results; Here, the foam half-life represents the foam stability of the foam acidifying liquid system. The larger the value, the better the foam stability.

[0046] Specifically in this embodiment, the foam half-life test includes the following steps: 1) Take equal amounts of multiple foam acidifying liquid systems of the first comparative example and place them in measuring cups respectively, and record the initial time T1; Here, the measuring cup needs to be preheated in a water bath before use. The preheating temperatures are 25°C, 70.6°C, and 90°C, respectively. The preheating temperatures are all within the medium and low temperature dolomite thermal storage temperature range.

[0047] 2) Obtain the time T2 when the volume of the foam acidifying liquid system in the multiple measuring cups is reduced to half; The difference between time T1 and time T2 is the foam half-life. The larger the difference, the better the foam half-life. For specific values, see Table 4.

[0048] Table 4: Foam half-life values:

[0049] See also Figure 3 , is the variation pattern of the liquid output volume over time at 25°C, 70.6°C and 90°C for the first comparative example 1-01, the first comparative example 1-02, the first comparative example 1-03 and the first comparative example 1-04, respectively, representing the foam half-life.

[0050] Combined with the values ​​in Table 1 and Table 4, and Figure 3 The curve was analyzed and the conclusion of the liquid volume was as follows: When the surfactant components are the same, the foam half-life gradually increases with the addition of xanthan gum, that is, the foam half-life values ​​of the acidified liquid systems corresponding to the first comparative example 1-04, the first comparative example 2-04, the first comparative example 3-04 and the first comparative example 4-04 are the largest, and the foam stability is the strongest. It is concluded that when the xanthan gum ratio is 1.2wt%, the foam stability of the acidified liquid system is optimal.

[0051] When the xanthan gum ratio is the same, the value of the foam half-life corresponding to the first comparative example 4 is quite different from that of the first comparative example 1, the first comparative example 2 and the first comparative example 3. The foam stability of the obtained acidified liquid system is poor. Therefore, the surfactant used in the acidified liquid system of the first comparative example 4 is not suitable for preparing a foamed acidified liquid system and is directly excluded.

[0052] Finally, based on the foam stability evaluation results, the foam stability of the acidified liquid systems of the first comparative example 1-04, the first comparative example 2-04 and the first comparative example 3-04 is optimal, and the corresponding xanthan gum ratio is 1.2wt%. It can be concluded that when the xanthan gum ratio is 1.2wt%, the foam stability of the acidified liquid system is the best.

[0053] S04: performing an acidification reaction test based on the acidification liquid system selected in step S03, and selecting, based on the results of the acidification reaction test, a surfactant composed of 1.5 wt % DGME.

[0054] Corresponding to this embodiment, the acidifying liquid systems selected in step S03 are the first comparative example 1-04, the first comparative example 2-04, and the first comparative example 3-04. The difference between them is that the components of the surfactant are different. It is intended to select the optimal formula of the surfactant by performing acidification reactions on the acidifying liquid systems with different surfactant components.

[0055] Specifically, in this embodiment, the acidizing reaction test includes an acid-rock reaction test and a corrosion inhibition test. The acid-rock reaction test is used to verify the retarding performance of the acidizing fluid system, while the corrosion inhibition test is used to verify the corrosiveness of the acidizing fluid system on metal products.

[0056] Here, the acid-rock reaction test and the corrosion inhibition test are both carried out at a specific temperature of 70.6°C. 70.6°C is within the thermal storage temperature range and is close to the actual operating conditions. Therefore, the test results obtained from the acid-rock reaction test and the corrosion inhibition test at this temperature are more realistic and convincing.

[0057] 4.1. Acid-rock reaction test. The specific test process is as follows: 1) Select dolomite cuttings of equal particle size, clean them with deionized water, and then dry them; 2) Take equal amounts of dried rock chips and place them in a beaker. Preheat the beaker and the rock chips to 70.6°C. 3) After the cuttings and the beaker are fully preheated, equal amounts of the acidizing liquid system selected in step S03 are added to the preheated beaker, and the heat storage temperature is kept constant to allow the cuttings and the acidizing liquid system to fully react; 4) Slowly clean the reacted rock chips with deionized water, then dry them in a drying oven, and weigh the mass of the remaining rock chips after drying; 5) Based on the cuttings mass before and after reaction, and the reaction time, calculate the cuttings mass change rate and cuttings mass change velocity. The specific values ​​are shown in Table 5.

[0058] Here, the cuttings mass change rate can characterize the dissolution of the cuttings by the acidizing fluid system, and the cuttings mass change rate can characterize the retarding property of the acidizing fluid system.

[0059] Table 5: Rock chip dissolution

[0060] It should be noted that, as shown in Table 5, when conducting the acid-rock reaction test, the acidizing fluid systems of the second comparative example and the third comparative example were specially introduced.

[0061] In order to intuitively show the change of cuttings mass in this test, a rectangular coordinate system is established with the names of the first comparative example 1-04, the first comparative example 2-04, the first comparative example 3-04, the second comparative example and the third comparative example as the horizontal axis and the cuttings mass change rate as the vertical axis. Figure 2 shown.

[0062] First, as shown in Table 5, the acid-rock reaction test results of the second comparative example and the third comparative example were compared to verify the effects of strong acid and weak acid on the acid-rock reaction. The results showed that weak acid has good retarding properties.

[0063] Then, as shown in Table 5 and Figure 2 As shown, by comparing the acid-rock reaction test results of the first comparative example 1-04, the first comparative example 2-04 and the first comparative example 3-04 with the second comparative example, it can be concluded that the foam acidizing fluid system has good retarding properties and is suitable for increasing the production of dolomite thermal reservoirs.

[0064] Finally, the acid-rock reaction test results of the first comparative example 1-04, the first comparative example 2-04 and the first comparative example 3-04 were compared with each other, and the values ​​were relatively close, indicating that the acidizing fluid systems corresponding to the first comparative example 1-04, the first comparative example 2-04 and the first comparative example 3-04 all have good retarding properties.

[0065] 4.2. Corrosion inhibition test, the test process includes the following steps: 1) Select multiple metal sheets, wash and dry them, and weigh the mass and surface area of ​​the metal sheets before corrosion; Here, the metal sheet selected is N80, which is a steel-grade metal material for oil well pipes. It is a standard test specimen with a length of 40 mm, a width of 13 mm, and a thickness of 2 mm.

[0066] 2) Place multiple metal pieces in a flask, preheat the flask containing the metal pieces to 70.6°C, and keep the temperature constant; Here, since the acidifying liquid system of this embodiment is in a foamy state, the foam will defoam over time, resulting in a decrease in volume. In this embodiment, a metal sheet is placed at the bottom of the flask in order to completely immerse the metal sheet in the acidifying liquid system so that the acidifying liquid system and the acidifying liquid can react completely.

[0067] 3) Add multiple foamed acidified liquids selected from the acid-rock reaction test into the flask and connect the condenser; after the foamed acidified liquids react completely with the metal sheet, stop heating and then stop passing the condensed water; 4) Take out the corroded metal sheet, wash and dry it, weigh the mass of the corroded metal sheet, calculate the corrosion rate of the metal sheet, and observe the corrosion of the metal sheet. The results are shown in Table 6 and Figure 4 As shown, Figure 4 These are the corrosion diagrams of the metal sheets by the foam acidizing liquid systems corresponding to the first comparative example 1-04, the first comparative example 2-04, and the first comparative example 3-04.

[0068] Table 6: Corrosion inhibition of metal sheets

[0069] Here, combined with Table 6 and Figure 4 Analysis shows that the acidizing liquid system of the first comparative example 1-04 has the lowest corrosion rate on metal, indicating that the acidizing liquid system corresponding to the first comparative example 1-04 has a good corrosion inhibition effect, and further it can be determined that the surfactant is preferably DGME.

[0070] Furthermore, if Figure 1 As shown, it is a schematic diagram of the foam morphology of the four groups of foam acidifying liquid systems of the first comparative example 1-04, the first comparative example 2-04, the first comparative example 3-04 and the first comparative example 4-04 at the time of preparation completion, Figure 1 It can be seen that the foam acidizing liquid system of the first comparative example 1-04 has relatively uniform foam size compared with the other three groups, further proving that the foam acidizing liquid system corresponding to the first comparative example 1-04 has the best performance and is the preferred foam acidizing liquid system.

[0071] The above is the preferred method for the foam acidizing liquid system of this embodiment. The foam acidizing liquid system preferably obtained based on the above method consists of 10wt% hydrochloric acid, 5wt% formic acid, 5wt% acetic acid, 1.5wt% DGME, 1.2wt% xanthan gum, 1.5wt% modified nano-silicon dioxide, 1wt% HC-Y-02, and 0.5% iron ion stabilizer.

[0072] It should be noted that the addition amount of each component in the foam acidizing liquid system of this embodiment is calculated based on the mass percentage of hydrochloric acid in the composite acid solution, in order to facilitate the calculation of the addition amount of other components.

[0073] Among them, DGME is the abbreviation of nonionic surfactant decaethylene glycol monododecyl ether, which is a nonionic surfactant dodecaethylene glycol monododecyl ether.

[0074] First, this embodiment uses DGME as a surfactant. Due to the non-ionic properties of DGME, it does not undergo charge adsorption with the metal surface, making the acidizing fluid system have good corrosion inhibition, thereby reducing corrosion to downhole tubing and tools, and greatly extending the service life of the equipment.

[0075] Secondly, since DGME is a mass-produced product, compared with independently synthesized surfactants, it has good chemical stability, low production cost and is easy to purchase, which greatly reduces the production cost of the foam acidizing liquid, which is conducive to the promotion and application of the foam acidizing liquid system of this embodiment on a large scale.

[0076] Xanthan gum is a bio-glue that combines thickening, suspending, emulsifying, and stabilizing properties. The foam acidifying solution system of this embodiment primarily utilizes its thickening properties to improve foam stability. In the preferred method, a foam half-life test was conducted on acidifying solution systems with different xanthan gum ratios. Based on the results of the foam half-life test, the optimal xanthan gum ratio was determined to be 1.2 wt%.

[0077] HC-Y-02 is a corrosion inhibitor, which is the commercial product code of the corrosion inhibitor. The corrosion inhibitor can significantly reduce the corrosion of foam acidizing fluid on metals such as iron, and protect acidizing equipment and downhole pipelines. The iron ion stabilizer works synergistically with HC-Y-02 to prevent Fe in the acid from Precipitation occurs under low pH conditions, thus avoiding clogging of reservoir pores and fissures.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for optimizing a foam acidizing liquid system, for optimizing a foam acidizing liquid system, characterized in that: The foam acidifying liquid system consists of a composite acid solution, a surfactant, xanthan gum, 1.5wt% modified nano-silica, 1wt% HC-Y-02, and 0.5wt% iron ion stabilizer, wherein the composite acid solution consists of 10wt% hydrochloric acid, 5wt% formic acid and 5wt% acetic acid; The preferred method comprises the following steps: preparing a plurality of first comparative ratios of the foam acidifying liquid system, wherein the plurality of first comparative ratios differ in that the ratios of the surfactant component and the xanthan gum in the foam acidifying liquid system are different; Based on the plurality of first comparative examples, foam half-life tests were respectively conducted, and according to the foam half-life test results, the ratio of the xanthan gum was optimized to be 1.2 wt %; The foam acidifying liquid system selected based on the foam half-life test was subjected to an acidification reaction test, and the surfactant was selected to consist of 1.5 wt % DGME based on the results of the acidification reaction test.

2. The method for optimizing the foam acidizing liquid system according to claim 1, wherein: The preferred method further comprises: The second comparative example and the third comparative example non-foaming acidizing fluid system were configured; The non-foaming acidizing liquid system of the second comparative example consists of 10 wt % hydrochloric acid, 5 wt % formic acid, 5 wt % acetic acid, 1 wt % corrosion inhibitor, and 0.5 wt % iron ion stabilizer; The non-foaming acidizing liquid system of the third comparative example consists of 20 wt % hydrochloric acid, 1 wt % corrosion inhibitor, and 0.5 wt % iron ion stabilizer; Based on a plurality of the first comparative example foamed acidizing liquid systems and the second comparative example non-foamed acidizing liquid systems, the parameters characterizing their basic properties, such as apparent viscosity, density and surface tension, were measured respectively.

3. The method for optimizing the foam acidizing liquid system according to claim 2, wherein: Before the step of conducting foam half-life tests based on multiple first comparative examples and optimizing the xanthan gum ratio to be 1.2 wt% based on the foam half-life test results, it is also necessary to conduct a feasibility evaluation on the foam acidifying liquid systems of multiple first comparative examples, and the feasibility evaluation results are characterized by a dimensionless foam characteristic value.

4. The method for optimizing the foam acidizing liquid system according to claim 3, wherein: The dimensionless foam characteristic value is measured by a foaming test, which includes the following steps: For each of the first comparative examples, an equal amount of the unfoamed liquid acidifying solution was placed in a measuring cup, and mixed with high-pressure gas for foaming. After the volume of the foamy acidifying liquid system stabilizes, read the reading of the measuring cup and record it. The reading of the measuring cup is the foaming volume; The ratio of the high-pressure gas volume to the foaming volume is the dimensionless foam characteristic value.

5. The method for optimizing the foam acidizing liquid system according to claim 4, wherein: The foam half-life test comprises the following steps: Taking equal amounts of the foam acidifying liquid systems of the first comparative example respectively, adding them to a measuring cup, and recording the initial time T1; Obtaining the time T2 when the volume of the foam acidifying liquid system in the plurality of measuring cups is reduced to half; The difference between the time T2 and the time T1 is the foam half-life.

6. The method for optimizing the foam acidizing liquid system according to claim 5, wherein: The foaming test and the foam half-life test need to be repeated at set temperatures of 25°C, 70.6°C and 90°C, respectively. The measuring cups required for the foaming test and the foam half-life test need to be preheated to the set temperature before the test.

7. The method for optimizing the foam acidizing liquid system according to claim 4, wherein: The acidizing reaction test is carried out at a specific temperature, including an acid-rock reaction test, and includes the following steps: Selecting rock chips of equal particle size, washing the rock chips with deionized water, and then drying the rock chips; Taking equal amounts of the dried rock chips and placing them in a plurality of beakers, and preheating the rock chips and the beakers to the specific temperature; After the rock cuttings are fully preheated, equal amounts of the foamed acidizing fluid system selected from the foam half-life test, the non-foamed acidizing fluid systems of the second comparative example, and the third comparative example are added to the preheated beaker to allow the rock cuttings to fully react; The rock chips after the reaction were slowly washed with deionized water, and then placed in a drying oven for drying, and the mass of the rock chips remaining after drying was weighed; The cuttings mass loss rate and cuttings mass loss velocity are calculated based on the cuttings mass before the reaction, the cuttings mass after the reaction, and the reaction time.

8. The method for optimizing the foam acidizing liquid system according to claim 7, wherein: The acidification reaction test also includes a corrosion inhibition test, which includes the following steps: Selecting a plurality of metal sheets, washing the plurality of metal sheets and then drying the plurality of metal sheets, and weighing the pre-corrosion mass and the surface area of ​​the plurality of metal sheets respectively; placing a plurality of the metal sheets in a flask respectively, and preheating the flask containing the metal sheets to the specific temperature and maintaining the temperature constant; Equal amounts of the foam acidizing liquid system selected from the acid-rock reaction test were placed in the flasks, and connected to a condenser; After the foam acidifying liquid system has completely reacted with the metal sheet, heating is stopped, and then the flow of condensed water is stopped; The corroded metal sheet is taken out, washed and dried, and then the mass of the corroded metal sheet is weighed, the corrosion rate of the metal sheet is calculated, and the corrosion condition of the metal sheet is observed.

9. The method for optimizing the foam acidizing liquid system according to claim 8, wherein: The specific temperature is 70.6°C.

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