An evaluation method for deep acidizing retarding fluid in acid-sensitive sandstone reservoir matrix

Abstract

The present invention provides an evaluation method for deep acidizing retarding fluid in acid-sensitive sandstone reservoir matrix, obtains information and parameters affecting acidized rock minerals; establishes a model for the change of acidizing and acid etching quality of core over time; establishes the relationship between the change of single minerals and content of rocks over time; establishes an acid-rock reaction rate formula for key single mineral components of rocks in acidizing fluid; comprehensively compares and analyzes deep acidizing retarding fluid in acid-sensitive sandstone reservoir matrix, and evaluates its applicability. The present invention can provide a targeted basis for the selection and proportioning of retarding acidizing fluid, and can effectively improve the acidizing success rate, so as to solve the problem of low operation success rate of existing acidizing measures and provide an evaluation method for deep acidizing retarding fluid in acid-sensitive sandstone reservoir matrix.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield drilling and development, and more specifically to an evaluation method for deep acidizing retarding fluid of an acid-sensitive sandstone reservoir matrix. Background Art

[0002] During the drilling and development of oil fields, the reservoir will be damaged to varying degrees, which often occurs during the drilling and completion process or the actual development and production process. If necessary, appropriate deep acidizing operations can be taken to effectively eliminate damage in the near-wellbore area and restore or improve reservoir recovery.

[0003] Acid-sensitive sandstone reservoirs contain many acidifiable rock minerals. After the reservoir matrix reacts with acid, it is easy to form secondary precipitation or dispersed migration of particles, causing the permeability to decrease. When the existing acid is used for acid-rock reaction slowing treatment, it is easy to cause clay expansion and migration, and high-valent ions to form precipitation, which provides limited effect on the design of acidification and plugging removal of reservoir matrix.

[0004] Due to the complex acid-rock reaction mechanism of sandstone reservoirs, many influencing factors and many correlations in the causes of damage, the acid-rock acidizing reaction rate in the near-wellbore area is faster and the acidizing distance is shorter, which seriously affects the success rate and efficiency of acidizing measures. Summary of the invention

[0005] The present invention overcomes the shortcomings of the prior art. The existing acidizing measures have the problem of low success rate. An evaluation method for deep acidizing slow-rate fluid in acid-sensitive sandstone reservoir matrix is ​​provided. The evaluation method can provide a targeted basis for the selection and proportioning of slow-rate acidizing fluid, thereby effectively improving the acidizing success rate.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] An evaluation method for deep acidizing retarding fluid in acid-sensitive sandstone reservoir matrix is ​​carried out according to the following steps:

[0008] Step 1, obtaining key formation rock mineral information and parameters that affect acidization of acid-sensitive sandstone reservoirs: The method for obtaining key formation rock mineral information and parameters that affect acidization of acid-sensitive sandstone reservoirs is as follows: observing the surface morphology characteristics of fresh cross-sections of rock minerals through a scanning electron microscope, combining the XRD whole-rock analysis of core samples and their rock and mineral composition characteristics, to obtain key formation rock mineral information and parameters that affect acid-rock reaction of acid-sensitive sandstone reservoirs;

[0009] Step 2, establish a model of the time-varying acid etching rate of the core by the acidizing fluid under the formation temperature and pressure: Experiments were conducted on the cores of the same batch of lithology and slow-rate acid under the conditions of simulating reservoir temperature and pressure in a high-temperature and high-pressure rotating disk instrument. The calculation formula of the core etching rate obtained through the experimental data is:

[0010]

[0011] Where: i is the value of the same time interval, μ i is the core acid erosion mass percentage at the i-th time point, m0 is the initial mass of the dried core before the acid etching experiment, and m i is the mass of the dry core after the acid etching experiment at time point i;

[0012] At the same time, the core acid etching experiment of soil acid under the same concentration condition was carried out. According to the core experimental data, the core acid etching rate of soil acid at the same time interval was calculated to be μ i，土 :

[0013]

[0014] Where: i is the value of the same time interval, μ i，土 is the core acid erosion mass percentage at the i-th time point, m 0土 is the initial mass of the dried core before the acid etching experiment, m i土 is the mass of the dry core after the acid etching experiment at time point i;

[0015] Step 3, establish the relationship between the single mineral and its content of the rock and the change of acid etching time: take the measured core and the acid solution after the acid etching rate of the slow acid solution at the i-th time, and use ICP quantitative analysis to determine the HF acid ion concentration after the acid etching rate at the i-th time point as C HF，i , measure the change curve of its HF acid ion concentration at time point i.

[0016] Take the measured core and the rock sample after the slow acid solution has been etched at the i-th time, use X-ray diffractometer to qualitatively and quantitatively analyze the rock mineral composition Dn and the corresponding content Ki of the acid-sensitive sandstone reservoir, and establish the relationship between the change of single rock mineral and its content with the acidizing and etching time:

[0017]

[0018] Where: Dn is a single rock mineral component, μ Dn，i is the acid-etched mass percentage of a single rock mineral Dn at the i-th time point, K0 is the initial mass percentage of a single rock mineral Dn, K i is the mass percentage of a single rock mineral Dn at the i-th time point;

[0019] At the same time, the rock samples after core acid etching with soil acid (reference acid) under the same concentration conditions were carried out, and the mineral composition of the acid-sensitive sandstone reservoir was qualitatively and quantitatively analyzed by X-ray diffractometer. n土 And the corresponding content K i,土 , establish the relationship between the change of single rock mineral and its content with acid etching time as μ Dn，i土 :

[0020]

[0021] Where: Dn is a single rock mineral component, μ Dn，i土 is the acid-etched mass percentage of a single rock mineral Dn at the i-th time point, K 0土 is the initial mass percentage of a single rock mineral Dn, K i土 is the mass percentage of a single rock mineral Dn at the i-th time point;

[0022] Step 4: Establish the acid-rock reaction rate formula of key rock single mineral components in acidizing solution: According to the acid-rock reaction model and the experimental acid-rock reaction kinetic equation, the reaction rate formula is:

[0023]

[0024] Where: R Dn，i is the acid-rock reaction rate of a single rock mineral Dn at time i, μ Dn，i-1 is the acid corrosion mass percentage of a single rock mineral at the i-1th time point, -F is the reaction rate constant of a single rock mineral, C HF，i is the HF acid concentration after the acid etching experiment at time point i, t i ,t i-1 Respectively represent the time corresponding to the i-th and i-1-th time points;

[0025] At the same time, the reaction rate formula of the rock sample after core acid etching with soil acid under the same concentration condition, that is, the reference acid, is R Dn，i土 :

[0026]

[0027] Where: R Dn，i土 is the acid-rock reaction rate of a single rock mineral Dn at time i, μ Dn，i-1土 is the acid corrosion mass percentage of a single rock mineral at the i-1th time point, -F is the reaction rate constant of a single rock mineral, C HF，i土 is the HF acid concentration after the acid etching experiment at time point i, t i土 ,t i-1土 Respectively represent the time corresponding to the i-th and i-1-th time points;

[0028] Step 5: Comprehensively compare and analyze the deep acidizing slow-moving fluid in the acid-sensitive sandstone reservoir matrix to evaluate its applicability: Step ①: The hydrogen ion concentration of the slow-moving acid before acidizing and etching is C H,0 The acid hydrogen ion concentration of the final slow acid solution of acid etching is C H,终Concentration change: the applicability is evaluated by the ratio of the hydrogen ion concentration before and after acidizing and etching. When sufficient acid is added, the effect of the acidizing and etching rate is scored with this value, so that the applicability of the acidizing retarder can be intuitively evaluated as a whole during the comprehensive evaluation.

[0029] η=C H,终 / C H,0

[0030] Step ②, when the acidification and etching rate reaches the maximum value, compare the total time i used by the slow acid 总，缓速酸 With soil acid 总，土酸 Relationship of total time used: When sufficient amount of acid is added, the ratio of the total time used by the retarder acid to the total time used by the soil acid is scored with this value, so that the applicability of the acidification retarder can be intuitively evaluated as a whole during the comprehensive evaluation:

[0031] θ=i 总，缓速酸 / i 总，土酸

[0032] The time division and comparison are carried out by using the range of theta ratio change, which can intuitively evaluate the applicability of the acidification slow-down fluid.

[0033] When sufficient acid is added, the core etching rate μ i Core acid erosion rate μ i，土 The ratio relationship β is described by this value:

[0034] β=μ i / μ i，土

[0035] The best mineral composition D for slow acid etching of single rock sensitive minerals n The ratio of the content change with acidizing and etching time to the acidizing and etching rate of the overall core γ:

[0036] γ=μ Dn，i / μ i

[0037] According to the above-mentioned SEM test occurrence analysis results, the acid-rock reaction rate of each rock mineral in the slow acidizing solution will change with the reaction time. Dn，i Reaction rate with mud acid R Dn，i土 The ratio of 2:1 to 2:1 is used to facilitate the comprehensive evaluation and intuitively evaluate the applicability of the acidification retarder:

[0038] Φ=R Dn，i / R Dn，i土

[0039] R Dn，iThe smaller the change and the slower the change trend, the better the slowing effect of the acid-rock reaction is, and the purpose of deep acidification can be achieved.

[0040] In step 1, the surface morphology characteristics of the fresh section of the rock mineral include pore throat structure characteristics, intergranular fracture filling minerals and filling forms.

[0041] In step 5, when the evaluation parameters meet the following conditions: 0.8≤η≤1, θ≥3, γ≤1, Φ≤1, it means that the retarding applicability of the acid-rock reaction of the retarding acid is better than that of the soil acid, and can achieve the purpose of deep acidizing; otherwise, it means that the retarding applicability of the acid-rock reaction of the retarding acid is poor.

[0042] In the actual acid etching experiment, the ranges of parameters θ and β are as follows:

[0043] When 0<θ i ≤1, 0≤β i ≤0.25;

[0044] When 1<θ i ≤2, 0.25<β i ≤0.50;

[0045] When 2<θ i ≤3, 0.50<β i ≤0.75;

[0046] When 3<θ i When 0.75<β i ≤1;

[0047] Among them, θ i and β i are the values ​​of θ and β at time i respectively.

[0048] The beneficial effects of the present invention are as follows: the evaluation method of the acidizing retarder of the present invention can evaluate the applicability of the acidizing retarder for rock minerals, and then the acidizing retarder can be selected in a targeted manner according to the evaluation results, thereby ensuring the acidizing effect and effectively improving the success rate of the acidizing operation measures; and the problem of low success rate of existing acidizing operation measures is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is an evaluation flow chart of the deep acidizing slow-rate fluid for the acid-sensitive sandstone reservoir matrix of the present invention. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below through specific embodiments.

[0051] An evaluation method for deep acidizing retarding fluid in acid-sensitive sandstone reservoir matrix is ​​carried out according to the following steps:

[0052] The key formation rock mineral information and parameters that affect the acidification of acid-sensitive sandstone reservoirs are obtained, specifically: cut off the fresh section of the same core, put it into the coating instrument and spray the conductive coating material; after the spraying is completed, fix the rock block sprayed with the conductive coating material on the sample stage of the electron microscope, and the electron microscope room is automatically closed and then evacuated; after evacuation, by adjusting the position angle and magnification of the scanning electron microscope, observe the surface morphology characteristics of the fresh section of the rock mineral: pore throat structure characteristics, intergranular fracture filling minerals and filling forms.

[0053] After obtaining the above rock mineral information and parameters, combined with the XRD whole rock analysis of the core sample and its rock mineral composition characteristics, the specific process is as follows: Sample pretreatment: Wash the oil-bearing rock sample to below the fourth level of fluorescence. After washing, place the sample in an electric drying oven at ≤60°C and dry it, then cool it to room temperature; after cooling, place the crushed rock sample in an agate mortar and grind it until the total particle size is less than 40μm, and use the back pressure method to make a close-fitting measurement test piece: use a sample spoon to put the prepared powder sample into the sample frame, and press it vertically and evenly to form it; after the measurement test piece is made, the sample X-ray diffraction data is compared with the standard X-ray diffraction data of the mineral through an X-ray diffractometer, and a qualitative analysis is performed to accurately identify the mineral types in the sample; ④ Measure the intensity of the selected diffraction peaks of clay minerals and various non-clay minerals on the diffraction spectrum, compare it with the intensity of the standard X-ray diffraction spectrum peak, calculate the formula to obtain the relative percentage of each mineral, and obtain the key formation rock mineral information and parameters that affect the acid-rock reaction of the acid-sensitive sandstone reservoir. Specific examples of specific rock mineral information and parameters are as follows:

[0054] Table 1 shows the information of non-clay minerals.

[0055]

[0056] Table 2 shows the clay mineral information

[0057]

[0058] After obtaining specific rock mineral information and parameters, a model of the time-varying acid etching mass of the core by the acidizing fluid under formation temperature and pressure was established. Specifically, before the test, the core was selected and dried at 105°C for 2 hours and then cooled, and its mass was weighed as m0; the core was fixed in a high-temperature and high-pressure rotating disk instrument to simulate the reservoir temperature and pressure conditions and a slow acid solution or soil acid solution of the same concentration was injected for acid etching experiment. The experiment was stopped after 30 minutes, and the kettle was disassembled after the experiment to obtain the core after the experiment; the core mass m after drying during the experimental time period was tested i , i is the core mass after 30 minutes in the same time period; through the above corrosion inhibition experiment process, the data is processed to obtain the core acid corrosion rate μ i Calculation formula:

[0059]

[0060] Where: i is the value taken at the same time interval (30min), μ i is the core acid erosion mass percentage at the i-th time point, m0 is the initial mass of the dried core before the acid etching experiment, and m i is the mass of the dry core after the acid etching experiment at the i-th time point.

[0061] Establish the relationship between the change of single minerals and their contents in rocks with the acidification and etching time, specifically: use a plastic beaker to extract 20mL of the residual acid solution after the above-mentioned acid etching experiment reaction to carry out the ICP ion test experiment, specifically: ① take the acid solution after the acid etching rate of the above-mentioned core and slow acid solution at the i-th time, filter it through a 0.45μm microporous filter membrane, dilute it to 10 times with the slow acid solution, and test the working curve of the HF standard solution containing a known concentration (at least 2 concentration points); ② After the working curve test of the HF standard solution is completed, high-purity argon gas is ionized into plasma in an inductively coupled high-frequency magnetic field, bombarding the atomized sample to be tested, so that the element transitions and emits a spectrum; ③ According to the intensity of the characteristic spectral line of the spectrum, the concentration of F element after the acid etching rate at the i-th time point is quantitatively calculated, which is C H,i At the same time, the hydrogen ion concentration of the slow acid solution before acid etching is C H,0 The acid hydrogen ion concentration of the final slow acid solution of acid etching is C H,终 Changes in concentration;

[0062] Take about 5g of the core and the rock sample after the acid etching rate of slow acid solution at the i-th time, and use X-ray diffractometer to qualitatively and quantitatively analyze the mineral composition of the acid-sensitive sandstone reservoir rock. For example, one of the mineral components is quartz Dn, and its corresponding content Ki is measured. Before participating in the acidification reaction, the mass of the single mineral quartz is m0·K0, and after the reaction for i time, the mass of the single mineral quartz is m i ·K i Therefore, the relationship between the content of quartz in a single rock mineral and the acid etching time is established as follows:

[0063]

[0064] Where: Dn is a single rock mineral component, μ Dn，i is the acid-etched mass percentage of a single rock mineral Dn at the i-th time point, K0 is the initial mass percentage of a single rock mineral Dn, K i is the mass percentage of a single rock mineral Dn at the i-th time point.

[0065] The acid-rock reaction rate formula of key rock single mineral components in acidizing solution is established. Specifically, according to the Freundlich-ARRR mechanism model and the experimental acid-rock reaction kinetic equation, the corresponding reaction rate formula is:

[0066]

[0067] Where: R Dn，i is the acid-rock reaction rate of a single rock mineral at time point i, μ Dn，i-1 is the acid corrosion mass percentage of a single rock mineral at the i-1th time point, -F is the reaction rate constant of a single rock mineral, C HF is the HF acid concentration after the acid etching experiment at time point i, t i ,t i-1 Represent the time corresponding to the i-th and i-1-th time points respectively.

[0068] A comprehensive comparative analysis of deep acidizing retarding fluids in acid-sensitive sandstone reservoir matrix was conducted to evaluate the applicability, specifically:

[0069] The hydrogen ion concentration of the slow acid solution before acid etching is C H,0 The acid hydrogen ion concentration of the final slow acid solution of acid etching is C H,终 Concentration change: the applicability is evaluated by the ratio of the hydrogen ion concentration before and after acidizing and etching. When sufficient acid is added, the effect of the acidizing and etching rate is scored with this value, so that the applicability of the acidizing retarder can be intuitively evaluated as a whole during the comprehensive evaluation.

[0070] η=C H,终 / C H,0

[0071] When the acidizing and etching rate reaches the maximum value, the total time i used by the slow acid 总，缓速酸 With soil acid 总，土酸 The total time used is the ratio of the total time used by the slow acid to the total time used by the soil acid when the amount of acid added is sufficient. This value is used to score the effect, so that the applicability of the acidizing slow liquid can be intuitively evaluated as a whole during the comprehensive evaluation:

[0072] θ=i 总，缓速酸 / i 总，土酸

[0073] The time division and comparison are carried out by using the θ ratio variation range to intuitively evaluate the applicability of the acidizing slow fluid. When sufficient acid is added, the core etching rate μ of the slow acid is i Core acid erosion rate μ i，土 The ratio relationship β is described by this value:

[0074] β=μi / μ i，土

[0075] The best mineral composition D for slow acid etching of single rock sensitive minerals n The ratio of the content change with acidizing and etching time to the acidizing and etching rate of the whole core γ;

[0076] γ=μ Dn，i / μ i

[0077] According to the above-mentioned SEM test occurrence analysis results, the acid-rock reaction rate of each rock mineral in the slow acidizing solution will change with the reaction time. Dn，i Reaction rate with mud acid R Dn，i土 The ratio of , so that the applicability of the acidification retarder can be intuitively evaluated as a whole during the comprehensive evaluation:

[0078] Φ=R Dn，i / R Dn，i土

[0079] R Dn，i The smaller the change, the slower the change trend, indicating that the slowing effect of the acid-rock reaction is better, and the purpose of deep acidification can be achieved;

[0080] In order to better illustrate the applicability of the acidizing retarder, the items evaluated by the above evaluation parameters are compared with the parameters of the acid soil acid:

[0081] When the evaluation parameters meet the following conditions, it means that the slowing applicability of the acid-rock reaction of the slowing acid is good and can achieve the purpose of deep acidizing; otherwise, it means that the slowing applicability of the acid-rock reaction of the slowing acid is poor:

[0082] 0.8≤η≤1,θ≥3,γ≤1,Φ≤1;

[0083] And in the actual acid etching experiment, the ranges of parameters θ and β are as follows:

[0084] When 0<θ i ≤1, 0≤β i ≤0.25;

[0085] When 1<θ i ≤2, 0.25<β i ≤0.50;

[0086] When 2<θ i ≤3, 0.50<β i ≤0.75;

[0087] When 3<θ iWhen 0.75<β i ≤1;

[0088] Among them, θ i and β i are the values ​​of θ and β at time i respectively.

[0089] The evaluation method of deep acidizing retarder in acid-sensitive sandstone reservoir matrix can evaluate the applicability of acidizing retarder according to rock minerals, and then can select acidizing retarder in a targeted manner according to the evaluation results, thereby ensuring the acidizing effect and effectively improving the success rate of acidizing operation measures; through experimental simulation and experimental core testing, the calculation accuracy is high and the determination of relevant parameters is relatively easy; the problem of low success rate of existing acidizing operations is solved.

[0090] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for evaluating deep acidizing retarding fluid for acid-sensitive sandstone reservoir matrix, characterized by: Follow the steps below: Step 1, obtaining key formation rock mineral information and parameters that affect acidization of acid-sensitive sandstone reservoirs: The method for obtaining key formation rock mineral information and parameters that affect acidization of acid-sensitive sandstone reservoirs is as follows: observing the surface morphology characteristics of fresh cross-sections of rock minerals through a scanning electron microscope, combining the XRD whole-rock analysis of core samples and their rock and mineral composition characteristics, to obtain key formation rock mineral information and parameters that affect acid-rock reaction of acid-sensitive sandstone reservoirs; Step 2, establish a model of the time-varying acid etching rate of the core by the acidizing fluid under the formation temperature and pressure: Experiments were conducted on the cores of the same batch of lithology and slow-rate acid under the conditions of simulating reservoir temperature and pressure in a high-temperature and high-pressure rotating disk instrument. The calculation formula of the core etching rate obtained through the experimental data is: Where: i is the value of the same time interval, μ i is the core acid erosion mass percentage at the i-th time point, m0 is the initial mass of the dried core before the acid etching experiment, and m i is the mass of the dry core after the acid etching experiment at time point i; At the same time, the core acid etching experiment of soil acid under the same concentration condition was carried out. According to the core experimental data, the core acid etching rate of soil acid at the same time interval was calculated to be μ i，土 : Where: i is the value of the same time interval, μ i，土 is the core acid erosion mass percentage at the i-th time point, m 0土 is the initial mass of the dried core before the acid etching experiment, m i土 is the mass of the dry core after the acid etching experiment at time point i; Step 3, establish the relationship between the single mineral and its content of the rock and the change of acid etching time: take the measured core and the acid solution after the acid etching rate of the slow acid solution at the i-th time, and use ICP quantitative analysis to determine the HF acid ion concentration after the acid etching rate at the i-th time point as C HF，i , measure the change curve of HF acid ion concentration at time point i; Take the measured core and the rock sample after the slow acid solution has been etched at the i-th time, use X-ray diffractometer to qualitatively and quantitatively analyze the rock mineral composition Dn and the corresponding content Ki of the acid-sensitive sandstone reservoir, and establish the relationship between the change of single rock mineral and its content with the acidizing and etching time: Where: Dn is a single rock mineral component, μ Dn，i is the acid-etched mass percentage of a single rock mineral Dn at the i-th time point, K0 is the initial mass percentage of a single rock mineral Dn, K i is the mass percentage of a single rock mineral Dn at the i-th time point; At the same time, the rock samples after the core acid etching with soil acid under the same concentration conditions were carried out, and the soil acid was used as the reference acid. The X-ray diffractometer was used to qualitatively and quantitatively analyze the mineral composition of the acid-sensitive sandstone reservoir. n土 And the corresponding content K i,土 , establish the relationship between the change of single rock mineral and its content with acid etching time as μ Dn，i土 : Where: Dn is a single rock mineral component, μ Dn，i土 is the acid-etched mass percentage of a single rock mineral Dn at the i-th time point, K 0土 is the initial mass percentage of a single rock mineral Dn, K i土 is the mass percentage of a single rock mineral Dn at the i-th time point; Step 4: Establish the acid-rock reaction rate formula of key rock single mineral components in acidizing solution: According to the acid-rock reaction model and the experimental acid-rock reaction kinetic equation, the reaction rate formula is: Where: R Dn，i is the acid-rock reaction rate of a single rock mineral Dn at time i, μ Dn，i-1 is the acid corrosion mass percentage of a single rock mineral at the i-1th time point, -F is the reaction rate constant of a single rock mineral, C HF，i is the HF acid concentration after the acid etching experiment at time point i, t i ,t i-1 Respectively represent the time corresponding to the i-th and i-1-th time points; At the same time, the reaction rate formula of the rock sample after core acid etching with soil acid under the same concentration condition, that is, the reference acid, is R Dn，i土 : Where: R Dn，i土 is the acid-rock reaction rate of a single rock mineral Dn at time i, μ Dn，i-1土 is the acid corrosion mass percentage of a single rock mineral at the i-1th time point, -F is the reaction rate constant of a single rock mineral, C HF，i土 is the HF acid concentration after the acid etching experiment at time point i, t i土 ,t i-1土 Respectively represent the time corresponding to the i-th and i-1-th time points; Step 5: Comprehensively compare and analyze the deep acidizing slow-moving fluid in the acid-sensitive sandstone reservoir matrix to evaluate its applicability: Step ①: The hydrogen ion concentration of the slow-moving acid before acidizing and etching is C H,0 The acid hydrogen ion concentration of the final slow acid solution of acid etching is C H,终 Concentration change: the applicability is evaluated by the ratio of the hydrogen ion concentration before and after acidizing and etching. When sufficient acid is added, the effect of the acidizing and etching rate is scored with this value, so that the applicability of the acidizing retarder can be intuitively evaluated as a whole during the comprehensive evaluation. η=C H,终 / C H,0 Step ②, when the acidification and etching rate reaches the maximum value, compare the total time i used by the slow acid 总 , 缓速酸 With soil acid 总 , 土酸 Relationship of total time used: When sufficient amount of acid is added, the ratio of the total time used by the retarder acid to the total time used by the soil acid is scored with this value, so that the applicability of the acidification retarder can be intuitively evaluated as a whole during the comprehensive evaluation: θ=i 总，缓速酸 / i 总，土酸 The time division and comparison are carried out by using the range of theta ratio change, which can intuitively evaluate the applicability of the acidification slow-down fluid. When sufficient acid is added, the core etching rate μ i Core acid erosion rate μ i，土 The ratio relationship β is described by this value: β=μ i / m i，土 The best mineral composition D for slow acid etching of single rock sensitive minerals n The ratio of the content change with acidizing and etching time to the acidizing and etching rate of the overall core γ: c = m Dn，i / m i According to the above-mentioned SEM test occurrence analysis results, the acid-rock reaction rate of each rock mineral in the slow acidizing solution will change with the reaction time. Dn，i Reaction rate with mud acid R Dn，i土 The ratio of 2:1 to 2:1 is used to facilitate the comprehensive evaluation and intuitively evaluate the applicability of the acidification retarder: Φ=R Dn，i / R Dn，i土 R Dn，i The smaller the change and the slower the change trend, the better the slowing effect of the acid-rock reaction is, and the purpose of deep acidification can be achieved.

2. The method for evaluating an acid-sensitive sandstone reservoir matrix deep acidizing slow fluid according to claim 1, characterized in that: In step 1, the surface morphology characteristics of the fresh section of the rock mineral include pore throat structure characteristics, intergranular fracture filling minerals and filling forms.

3. The method for evaluating an acid-sensitive sandstone reservoir matrix deep acidizing slow fluid according to claim 1, characterized in that: In step 5, when the evaluation parameters meet the following conditions: 0.8≤η≤1, θ≥3, γ≤1, Φ≤1, it means that the retarding applicability of the acid-rock reaction of the retarding acid is better than that of the soil acid, and can achieve the purpose of deep acidizing; otherwise, it means that the retarding applicability of the acid-rock reaction of the retarding acid is poor.

4. The method for evaluating a deep acidizing slow-rate fluid for an acid-sensitive sandstone reservoir matrix according to claim 1, characterized in that: In the actual acid etching experiment, the ranges of parameters θ and β are as follows: When 0<θ i ≤1, 0≤β i ≤0.25; When 1<θ i ≤2, 0.25<β i ≤0.50; When 2<θ i ≤3, 0.50<β i ≤0.75; When 3<θ i When 0.75<β i ≤1; Among them, θ i and β i are the values ​​of θ and β at time i respectively.

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