Deep penetrating cleaning slow acid acidification method

Abstract

The present invention discloses a deep-penetrating clean slow-speed acid acidification plugging removal method, which specifically relates to the field of plugging removal, including the step of performing a preliminary assessment of the application environment before configuring the acid solution, the preliminary assessment including formation characteristics and environmental parameters; the formation characteristics including the assessment of the downhole porosity and permeability; the environmental parameters including the assessment of the downhole temperature and pressure; establishing conditions one and two based on the preliminary assessment, and if condition one or condition two is determined to be abnormal, entering the comprehensive assessment step. By real-time monitoring of formation porosity, permeability, temperature, pressure and other data, the composition ratio of the pre-acid, main acid and displacement fluid is dynamically adjusted to meet the needs of different formation conditions; this method can increase the probability that the acid solution can effectively penetrate into the deep blockage area, while avoiding overreaction and waste of resources, thereby improving the plugging removal efficiency and construction adaptability.

Description

Technical Field

[0001] The present invention relates to the technical field of plugging removal, and more particularly to a deep-penetrating cleaning slow-rate acid acidification plugging removal method. Background Art

[0002] The reference document CN117777974A discloses a deep penetrating clean slow acid unblocking agent and an acid unblocking method, and CN115873572A also discloses a deep penetrating clean slow acid unblocking agent and an acid unblocking method; both achieve the purpose of unblocking oil and water wells in oil fields through the combined action of pre-acid, main acid and displacement fluid;

[0003] However, in actual applications, due to the complex and changeable application environment of oil and water wells in oil fields, various formation conditions and working conditions vary greatly, and not all unblocking methods can be applied to different actual scenarios. The existing technology lacks adaptive adjustment solutions for different application environments, resulting in certain limitations in actual use.

[0004] In addition, when the existing technology is used to carry out unblocking construction for oil and water wells in oil fields, the evaluation system for the unblocking effect is still imperfect, and there is a lack of systematic evaluation procedures and data analysis methods. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a deep-penetrating clean slow acid acidizing and plugging removal method, which dynamically adjusts the composition ratio of the pre-acid, main acid and displacement fluid by real-time monitoring of formation porosity, permeability, temperature, pressure and other data, and combines initial evaluation and comprehensive evaluation to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: a deep penetrating clean slow acid acidification plugging removal method, comprising an acid solution preparation step, wherein the acid solution preparation step comprises pre-acid preparation, main acid preparation, and displacement fluid preparation;

[0007] In the preparation of the preacid, the components of the preacid include hydrochloric acid and additives, and the components of the additives include acetic acid, an iron ion stabilizer, a mutual solvent, a clay stabilizer, and clean water;

[0008] In the preparation of the main acid, the main acid components include hydrochloric acid, acetic acid, ammonium fluoride, retarder, iron ion stabilizer, scale inhibitor, activator, and clean water;

[0009] In the preparation of the displacement fluid, the components of the displacement fluid include hydrochloric acid and a surfactant; the concentration of hydrochloric acid in the displacement fluid is lower than the concentration of hydrochloric acid in the preacid or the main acid;

[0010] Before configuring the acid solution, the application environment is initially evaluated. The initial evaluation includes formation characteristics and environmental parameters. Formation characteristics include the porosity and permeability of the well. Environmental parameters include the temperature and pressure of the well. Conditions 1 and 2 are established based on the initial evaluation. If condition 1 or condition 2 is judged to be abnormal, the comprehensive evaluation step is entered.

[0011] In the comprehensive evaluation step of the application environment, a comprehensive evaluation model is established, and the concentration of hydrochloric acid in the pre-acid, the concentration of ammonium fluoride in the main acid, and the concentration of hydrochloric acid in the displacement fluid are dynamically adjusted according to the comprehensive evaluation model; the comprehensive evaluation model includes the evaluation of formation characteristics, environmental parameters, fluid characteristics, and blockage types;

[0012] Then, pre-acid injection, main acid injection and displacement fluid injection are carried out in stages.

[0013] In a preferred embodiment, condition 1 is: if the porosity is less than a preset porosity threshold, and the permeability is less than a preset permeability threshold, it is determined to be abnormal;

[0014] Condition 2 is: if the temperature is greater than a preset temperature threshold, and the pressure is greater than a preset pressure threshold, it is determined to be abnormal.

[0015] In a preferred embodiment, when the pre-acid, main acid and displacement fluid are injected, the formation data in the acidizing process is monitored in real time. The formation data includes three aspects:

[0016] The first aspect is the changes in acid injection pressure and flow rate;

[0017] The second aspect is the changes in bottom hole pressure and temperature;

[0018] The third aspect is the dissolution curve and formation response data after acidification reaction;

[0019] Finally, after the construction is completed, the acidification effect is evaluated.

[0020] In a preferred embodiment, the porosity of the downhole formation is , Permeability ,temperature and pressure Perform calculations to provide basic data for initial assessment;

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] in is the pore volume; is the total formation volume; is the fluid flow rate; is the fluid viscosity; is the formation thickness; is the pressure difference; Flow cross-sectional area; is the surface temperature; is the geothermal gradient; for the depth of the well; is the formation fluid density; is the acceleration due to gravity.

[0026] In a preferred embodiment, a comprehensive evaluation model is established. ;

[0027] ;

[0028] in , , , is the weight coefficient, which indicates the influence weight of different factors on the ratio;

[0029] scoring formation properties, which takes into account porosity and permeability;

[0030] ;

[0031] Score environmental parameters, which take into account temperature and pressure;

[0032] ;

[0033] Score the fluid properties, which take into account the fluid's viscosity, density, and surface tension;

[0034] ;

[0035] Score the type of plugging, which takes into account the particle size, thickness and hardness of the plug;

[0036] ;

[0037] in is the porosity; is the permeability; is the peak value of porosity; is the peak value of permeability;

[0038] in is temperature; For pressure; is the reference temperature; is the reference pressure;

[0039] in is the fluid viscosity; is the fluid density; is the surface tension; , , They are the reference value of fluid viscosity, fluid density and surface tension respectively;

[0040] in is the clogging particle size; is the plugging thickness; For the plugging hardness.

[0041] In a preferred embodiment, the preacid ratio adjustment formula is:

[0042] ;

[0043] in is the concentration of hydrochloric acid in the preacid; is the initial hydrochloric acid concentration in the preacid; is the current formation porosity; is the peak porosity; is the current formation pressure; is the peak pressure; is the influence function of additives in preacid; scoring the comprehensive assessment model;

[0044] ;

[0045] in is the actual concentration of the additive in the preacid; is the peak concentration of the additive in the preacid; is the peak value of the assessment score;

[0046] The main acid ratio adjustment formula is:

[0047] ;

[0048] in is the concentration of ammonium fluoride; is the initial ammonium fluoride concentration; scoring formation assessments; is the peak value of the assessment score; is the formation temperature; is the peak temperature; is the formation permeability; is the peak permeability;

[0049] The displacement fluid ratio adjustment formula is:

[0050] ;

[0051] in is the concentration of hydrochloric acid in the displacement fluid; is the concentration of surfactant; is the peak concentration of the surfactant.

[0052] In a preferred embodiment, a dynamic model of acid injection pressure and a flow rate variation model are established based on the first aspect of the formation data;

[0053] ;

[0054] ;

[0055] ;

[0056] ;

[0057] ;

[0058] in injecting pressure into the acid; is the formation back pressure; is the pipeline friction factor; is the density of acid solution; is the acid flow rate; Real-time flow rate of acid; is the cross-sectional area of ​​the pipe; is the length of the pipeline; is the inner diameter of the pipe; is the acid viscosity; is the permeability; is the formation flow cross-sectional area; is the real-time pressure difference; is the path length of the acid fluid flowing through the formation.

[0059] In a preferred embodiment, a bottom hole pressure model and a bottom hole temperature change model are established based on the second aspect of the formation data;

[0060] ;

[0061] ;

[0062] in is the bottom hole pressure; injecting pressure into the acid; is the density of acid solution; is the acceleration due to gravity; for the depth of the well; is the bottom hole temperature; is the surface temperature; The geothermal gradient.

[0063] In a preferred embodiment, a dissolution curve model and a formation response model after acidification reaction are established based on the third aspect of the formation data;

[0064] ;

[0065] ;

[0066] in is the mass of dissolved matter; is the mass of initial soluble matter; is the chemical reaction rate constant; is the reaction time; is the porosity change; , is the porosity after and before acidification; is a constant; is the dissolved mass; is the rock density.

[0067] Technical effects and advantages of the present invention:

[0068] By real-time monitoring of formation porosity, permeability, temperature, pressure and other data, the composition ratio of pre-acid, main acid and displacement fluid is dynamically adjusted to meet the needs of different formation conditions; this method can increase the probability that the acid can effectively penetrate into the deep blockage area, while avoiding overreaction and waste of resources, thereby improving the efficiency of unblocking and construction adaptability;

[0069] The comprehensive evaluation model integrates multiple factors such as formation characteristics, environmental parameters, fluid characteristics and blockage types, and optimizes the acid-liquid ratio by calculating the weight coefficient. It can not only formulate targeted blockage removal plans according to specific formation conditions, but also dynamically adjust them during implementation to adapt to formation changes.

[0070] During acid injection, the distribution and reaction of the acid in the well can be dynamically analyzed by monitoring the injection pressure, flow rate changes, bottom hole pressure and temperature data to ensure a uniform and efficient acidizing process. The acquisition and analysis of real-time data can increase the probability of discovering anomalies, and facilitate timely adjustment of construction parameters, reduce construction risks, and improve the reliability of acidizing effects.

[0071] By analyzing the pressure, temperature changes and dissolution curves during the acidizing process and combining them with the formation response data, a quantitative evaluation system is formed; this helps to more intuitively evaluate the differences in formation conditions before and after acidizing, and provides a basis for further optimizing the construction plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0073] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] Refer to the instruction manual Figure 1 The deep-penetrating cleaning slow-rate acid acidification plugging removal method of one embodiment of the present invention comprises an acid solution preparation step, wherein the acid solution preparation step comprises a pre-acid preparation, a main acid preparation, and a displacement fluid preparation; the pre-acid can clean the surface layer, the main acid can remove the plugging in the deep layer, and the displacement fluid can push the acid solution, thereby achieving the plugging removal target;

[0075] In the preparation of pre-acid, the pre-acid composition includes hydrochloric acid and additives, which dissolve carbonate components in the formation and isolate formation water. The additive composition includes acetic acid, iron ion stabilizer, mutual solvent, clay stabilizer, and clean water. In the composition of the additive, the sum of the mass percentages of the components is 100%, which is used to dissolve carbonate components in the formation and isolate formation water.

[0076] In the preparation of the main acid, the main acid includes hydrochloric acid, acetic acid, ammonium fluoride, retarder, iron ion stabilizer, scale inhibitor HEDP, OP-10 active agent, and clean water; the sum of the mass percentages of the above components is 100%; HEDP is the abbreviation of 1-hydroxyethylidene-1,1-diphosphonic acid, which is a commonly used organic phosphonic acid chelating agent. HEDP is often used as a scale inhibitor or metal ion stabilizer in acid solution to avoid the formation of secondary blockages during the acidification reaction, thereby improving the acidification and plugging removal effect; OP-10 is a non-ionic surfactant, the full name of which is alkylphenol polyoxyethylene ether. In the acidification and plugging removal system, OP-10 is usually added as a surfactant, which is particularly suitable for acidification and plugging removal of low permeability reservoirs, complex multi-mineral formations or oil-bearing and water-bearing wells, and improves the penetration depth and efficiency of the acid solution; the main acid is used for deep plugging removal, dissolving carbonate and silicate minerals, and preventing secondary precipitation;

[0077] In the preparation of displacement fluid, the components of displacement fluid include low-concentration hydrochloric acid and surfactant; displacement fluid is used to push the main acid solution to the deep formation to ensure uniform distribution and reduce the corrosion of acid solution to the pipe column; the concentration of hydrochloric acid in displacement fluid is lower than that in pre-acid or main acid; the reasons include three aspects, namely: reduce pipe column corrosion and avoid corrosion of wellbore equipment by excessively high concentration of hydrochloric acid; maintain displacement efficiency and optimize acid utilization without affecting the advancement of main acid to the deep formation; reduce the risk of side reactions and reduce the ineffective consumption of excessive acid solution and the generation of by-products in shallow areas;

[0078] In the configuration scheme of the acid solution of this scheme, the acid solution with low viscosity and easy to pump at room temperature absorbs heat and heats up, and then rapidly increases viscosity to reduce filtration and slow down the speed, thereby ensuring the stable unblocking effect of the acid solution during the unblocking process, and realizing uniform acid distribution during the acidizing of heterogeneous oil reservoirs; in addition, the main agent of the acid solution is a linear polymer, and its main chain is linear with branches; the acid solution has low viscosity at room temperature and is easy to pump; the acid solution absorbs heat during injection, and the temperature rises. Under the action of temperature and activator, chain growth or chain connection occurs, and the viscosity of the acid solution increases rapidly; the organic acid treats the gray and iron components of the formation, ionizes them step by step, and effectively controls the reaction rate;

[0079] Before the acid solution preparation step, the oil and water wells in the application environment oil field are initially evaluated. The initial evaluation includes formation characteristics and environmental parameters. Formation characteristics include the porosity and permeability of the well. Environmental parameters include the temperature and pressure of the well. Conditions 1 and 2 are established based on the initial evaluation. If condition 1 or condition 2 is determined to be abnormal, the comprehensive evaluation step is entered.

[0080] In the comprehensive evaluation step of the application environment, a comprehensive evaluation model is established, and the concentration of hydrochloric acid in the pre-acid, the concentration of ammonium fluoride in the main acid, and the concentration of hydrochloric acid in the displacement fluid are dynamically adjusted according to the comprehensive evaluation model to configure concentrations suitable for different formation conditions; the comprehensive evaluation model includes evaluation of formation characteristics, environmental parameters, fluid characteristics, and blockage types;

[0081] Then, pre-acid injection, main acid injection and displacement fluid injection are carried out in stages.

[0082] Condition 1: If the porosity is less than the preset porosity threshold, and the permeability is less than the preset permeability threshold, it is judged as abnormal; the reason is that lower porosity will limit the acid distribution space, increase the difficulty of plugging removal, and lower permeability may cause uneven acid penetration, affecting the deep plugging removal effect;

[0083] Condition 2 is: if the temperature is greater than the preset temperature threshold, and the pressure is greater than the preset pressure threshold, it is judged as abnormal; the reason is that high temperature may accelerate the reaction rate of the acid and reduce the action time of the slow acid, and high pressure may increase the flow resistance of the acid, and put forward higher requirements for injection pressure and displacement control; the above conditions are applicable to the evaluation of acidizing processes under high temperature and high pressure environments, such as deep wells or ultra-deep wells.

[0084] When pre-acid, main acid and displacement fluid are injected, the formation data in the acidizing process is monitored in real time. The formation data includes three aspects:

[0085] The first aspect is the changes in acid injection pressure and flow rate;

[0086] The second aspect is the changes in bottom hole pressure and temperature;

[0087] The third aspect is the dissolution curve and formation response data after acidification reaction;

[0088] Finally, after the construction is completed, the acidification effect is evaluated;

[0089] It should be noted that after the construction is completed, the specific methods for evaluating the acidizing effect include the following points: first, compare the changes in formation porosity and permeability before and after acidizing through rock sample analysis or downhole measurement technology to determine the improvement of formation structure; second, measure the increase in water absorption capacity of water injection wells or the change in oil production of oil production wells to evaluate the degree of improvement in injection and production capacity; at the same time, record the injection pressure and flow data during and after the acidizing process, analyze the magnitude of pressure drop and flow increase, and determine the effectiveness of acidizing; further, analyze whether the change in dissolution volume meets expectations through dissolution curves to ensure that the acid has acted thoroughly and there is no residual blockage; finally, combine the formation response data and acid distribution monitoring results to determine the effect of the acidizing construction.

[0090] The porosity of the underground formation , Permeability ,temperature and pressure Perform calculations to provide basic data for initial assessment;

[0091] ;

[0092] ;

[0093] ;

[0094] ;

[0095] in is the porosity, which indicates the proportion of pore volume in the formation to the total volume; is the pore volume, which represents the total volume of all pores in the formation; is the total formation volume; is the permeability, which indicates the formation's ability to allow fluid flow; is the fluid flow rate, which indicates the volume of fluid passing through the formation per unit time; is the fluid viscosity, which represents the internal friction of the fluid; is the formation thickness, indicating the path length of the fluid; is the pressure difference, which indicates the pressure change of the fluid at both ends of the formation; Flow cross-sectional area, which represents the effective cross-sectional area through which the fluid passes; is the surface temperature; is the geothermal gradient, in units of , which represents the rate at which temperature changes with depth; for the depth of the well; is the formation fluid density; is the acceleration due to gravity.

[0096] Establishing a comprehensive assessment model ;

[0097] ;

[0098] in , , , is the weight coefficient, which indicates the influence weight of different factors on the ratio;

[0099] scoring formation properties, which takes into account porosity and permeability;

[0100] ;

[0101] Score environmental parameters, which take into account temperature and pressure;

[0102] ;

[0103] Score the fluid properties, which take into account the fluid's viscosity, density, and surface tension;

[0104] ;

[0105] Score the type of plugging, which takes into account the particle size, thickness and hardness of the plug;

[0106] ;

[0107] in is the porosity; is the permeability; is the peak value of porosity, that is, the maximum value of porosity, usually derived from geological survey data; The peak value of permeability, that is, the maximum value of permeability, usually comes from formation research data; the formation property score is calculated by normalizing the porosity and permeability to calculate the permeability score of the formation. Higher porosity and permeability usually mean that the acid can penetrate and react more easily;

[0108] in is temperature; For pressure; is the reference temperature, usually the surface temperature or a set standard temperature; is the reference pressure, usually the standard pressure; the natural logarithm term in the environmental parameter score It is used to express the effect of temperature change on the acid reaction rate; increasing temperature will accelerate the acidification reaction, while the pressure term The effect of downhole pressure changes on fluid mobility and acid ratio is simulated; excessively high or low pressure may affect the penetration capacity of the acid;

[0109] in is the fluid viscosity; is the fluid density; is the surface tension, which represents the attraction between fluid molecules; , , They are fluid viscosity reference value, fluid density reference value, and surface tension reference value. The reference values ​​are set based on common fluid properties. The viscosity and density of the fluid directly affect the fluidity and permeability of the acid in the formation. High-viscosity fluids are difficult to penetrate the formation, which may lead to uneven distribution of the acid and increase friction losses during the acidizing process. The surface tension of the fluid determines the interaction between the fluid and the rock surface, affecting the contact and reaction rate of the acid.

[0110] in is the clogging particle size, which indicates the average particle size of the clogging material; is the blockage thickness, indicating the thickness of the blockage layer; The plugging hardness indicates the compressive strength of the plugging material. The plugging type score is calculated by the ratio of the plugging particle size and thickness. To indicate the severity of the blockage; blockages with smaller particle size and greater thickness have a greater impact on the permeability of the acid; while using Simulates the effect of blockage hardness on acid intrusion and dissolution; harder blockages are more difficult to dissolve and therefore require stronger acid mixes.

[0111] The main function of pre-acid is to perform preliminary cleaning, remove mild blockages and soluble substances in the formation; hydrochloric acid is the most common pre-acid, which is used to dissolve minerals and blockages. In order to enhance the stability of the pre-acid and adapt to different formation environments, additives such as acetic acid and iron ion stabilizer are also required; the formula for adjusting the pre-acid ratio is:

[0112] ;

[0113] in is the concentration of hydrochloric acid in the preacid; is the initial hydrochloric acid concentration in the preacid; is the current formation porosity; is the porosity peak value, that is, the maximum porosity, which is used to reflect the adaptability of acid under different porosity conditions; is the current formation pressure; It is the peak pressure, that is, the maximum pressure, which is used to reflect the adaptability of the acid ratio under high pressure environment; The influence function of the additives in the preacid is used to dynamically adjust the proportion of the additives based on the score of the comprehensive evaluation model; It is a comprehensive evaluation model score that reflects the demand for additives from formation and environmental conditions. It determines the optimal ratio of additives based on a comprehensive analysis of formation characteristics, temperature, pressure and other factors. This score ensures that the ratio of additives in the acid can be dynamically adjusted according to actual needs under different operating environments, thereby optimizing the performance and effect of the acid.

[0114] ;

[0115] in is the actual concentration of the additive in the preacid; is the peak concentration of the additive in the preacid, representing the upper limit concentration of the additive; It is the peak value of the evaluation score, that is, the maximum value; for the pre-acid ratio, it should be noted that: and The effects of porosity and pressure on the pre-acid ratio are respectively: porosity and pressure determine the penetration rate and reaction depth of the acid in the formation; Dynamically adjust the impact of additives to ensure that additives, such as acetic acid, iron ion stabilizer, etc., are optimized based on comprehensive evaluation to enhance the stability and solubility of the acid solution;

[0116] The purpose of the main acid preparation is to effectively remove deeper blockages, such as silicates, iron compounds, clay, etc., and provide the required acidification depth; the main acid ratio adjustment formula is:

[0117] ;

[0118] in is the concentration of ammonium fluoride; is the initial ammonium fluoride concentration; Provide formation assessment scores to reflect specific formation conditions, such as porosity, permeability, etc. is the peak value of the evaluation score, that is, the maximum value; is the formation temperature, which is used to affect the reaction rate and stability of the acid; is the peak temperature, used to adjust the impact of temperature changes; is the formation permeability, which affects the penetration and reaction efficiency of the acid; is the peak permeability, that is, the maximum permeability, which optimizes the reaction effect of the acid in formations with different permeabilities; for the main acid, it should be noted that, Used to dynamically adjust the concentration of ammonium fluoride, based on and The ratio of reflects the influence of formation complexity on the concentration of ammonium fluoride; among them, Higher scores indicate more complex formation plugging, requiring higher concentrations of ammonium fluoride to ensure adequate reactivity; When the temperature increases, the concentration adjustment ratio of ammonium fluoride also increases to ensure that it generates enough hydrogen fluoride with hydrochloric acid to effectively dissolve silicate minerals;

[0119] In the formula This part is passed and The ratio of , dynamically adjusts the concentration of ammonium fluoride to adapt to the effect of temperature on the reaction rate of the acid solution; The higher the reaction rate of ammonium fluoride and hydrochloric acid, the faster the concentration of hydrogen fluoride generated; Increase, the reaction rate of the acid solution increases. In order to avoid excessive reaction of the acid solution leading to waste or generation of by-products, it is necessary to control the reaction rate by reducing the concentration of ammonium fluoride to ensure the stability of the reaction and the utilization efficiency of the acid solution.

[0120] In the formula It reflects the influence of formation permeability on the concentration of ammonium fluoride. and The ratio of dynamically adjusts the concentration; The higher the value, the easier it is for the acid to diffuse and lose, and the reaction efficiency will decrease. If the acid flows too fast in the high permeability formation, it may cause inadequate reaction. Therefore, it is necessary to increase the concentration of ammonium fluoride to increase the content of hydrogen fluoride generated, enhance the reaction depth of the acid and the dissolution effect of the blockage, and ensure the success rate of the acidizing operation;

[0121] The purpose of preparing displacement fluid is to maintain the stability of acid, prevent acid from reacting or losing too quickly, and increase the fluidity of acid in the formation. Displacement fluid is usually composed of hydrochloric acid and surfactant, and the concentration of hydrochloric acid is low; the displacement fluid ratio adjustment formula is:

[0122] ;

[0123] in is the concentration of hydrochloric acid in the displacement fluid; The concentration of surfactant enhances the fluidity and stability of the acid solution; is the peak concentration of the surfactant, which is used to control the fluidity of the acid solution; it should be noted that Adjust the concentration of hydrochloric acid in the displacement fluid. When the formation porosity is high, the concentration of hydrochloric acid needs to be reduced to ensure that the acid does not penetrate too quickly; Adjust the influence of temperature. At higher temperature, the acid needs stabilizer to maintain the uniformity of the acid reaction and prevent too fast reaction; Adjust the surfactant concentration to increase the fluidity of the acid and ensure better penetration of the acid in complex formations;

[0124] The ratio of hydrochloric acid and additives is considered in the pre-acid, which is mainly used to remove mild blockages and soluble substances in the formation; hydrochloric acid and surfactants are considered in the displacement fluid, with the purpose of maintaining the stability of the acid and enhancing the fluidity of the acid in the formation to avoid too rapid penetration of the acid; the main acid has ammonium fluoride as the core component, and ammonium fluoride can react with hydrochloric acid to generate hydrogen fluoride. Hydrogen fluoride has a strong dissolving effect and is particularly suitable for treating insoluble blockages such as silicates, clays, and iron compounds. Ammonium fluoride reacts with silicon, aluminum, and iron in minerals through the generated hydrogen fluoride to form soluble compounds, thereby more effectively removing deep and complex blockages and ensuring the depth and effect of the acidizing operation; with ammonium fluoride as the core component of the main acid, its reaction rate can be adjusted relatively accurately to avoid too rapid reaction of the acid or dissolution of irrelevant minerals, thereby improving the pertinence and efficiency of the acid.

[0125] Based on the first aspect of formation data, a dynamic model of acid injection pressure and a flow rate variation model are established;

[0126] ;

[0127] ;

[0128] ;

[0129] ;

[0130] ;

[0131] in The acid injection pressure indicates the real-time pressure of the acid at the injection point; is the formation back pressure, which is used to indicate the resistance of the formation to the acid solution; is the pipeline friction factor, Related to pipe roughness and flow regime, including laminar or turbulent flow; is the density of acid solution; is the acid flow rate, real-time flow rate; is the real-time flow rate of acid, which indicates the volume of acid flowing into the formation per unit time; is the cross-sectional area of ​​the pipe; is the pipeline length, the total distance the acid flows in the pipeline; is the inner diameter of the pipe; is the acid viscosity; is the permeability; is the formation flow cross-sectional area; is the real-time pressure difference; is the path length of the acid fluid flowing through the formation; it should be noted that It represents the friction pressure drop term, which is used to describe the pressure loss of the acid in the pipeline due to friction; It represents the formation permeability loss term, which is used to describe the pressure drop caused by viscous resistance when the acid passes through the formation. The above formula combines Darcy's law in fluid mechanics and the pipeline friction loss model to calculate the injection pressure change in real time. The larger it is, the higher the flow rate; It indicates the formation permeability parameter. The larger the permeability and cross-sectional area, the easier it is for the acid to flow. Indicates flow resistance. The higher the viscosity and path length, the more difficult the flow. Based on Darcy's law, combined with the physical properties of the acid and the formation characteristics, the flow rate change over time is calculated.

[0132] The bottom hole pressure model and bottom hole temperature change model are established based on the second aspect of formation data;

[0133] ;

[0134] ;

[0135] in is the bottom hole pressure, indicating the pressure of the acid at the bottom of the well; injecting pressure into the acid; is the density of acid solution; is the acceleration due to gravity; is the well depth; it should be noted that the components of the above formula are: It represents the gravity head loss of acid fluid. As the well depth increases, the pressure loss increases. The above formula is based on the static pressure calculation model, combining gravity and injection pressure to calculate the bottom hole pressure. is the bottom hole temperature; is the surface temperature; is the geothermal gradient; Indicates the initial temperature of the acid fluid entering the wellbore; It represents the effect of depth on temperature. The formation temperature increases linearly with depth. The temperature model combines the formation depth and temperature gradient to calculate the bottom hole temperature.

[0136] The third aspect based on the formation data is to establish the dissolution curve model and formation response model after the acidification reaction;

[0137] ;

[0138] ;

[0139] in is the mass of dissolved matter; is the mass of initial soluble matter; is the chemical reaction rate constant; is the reaction time; for the components in the above formula It indicates the time dependence of the dissolution process, and the reaction rate gradually decreases. The above formula describes the dissolution process by using a first-order kinetic model, reflecting the nonlinear characteristics of the dissolution of substances over time. is the porosity change; , is the porosity after and before acidification; is a constant, which indicates the sensitivity of pore change to the amount of dissolution; is the dissolved mass; is the rock density; it should be noted that, It represents the effect of dissolved substances on porosity and reflects the nonlinear growth relationship. It describes the formation response characteristics through the relationship between material mass and porosity changes.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A deep penetrating cleaning slow acid acidification plugging removal method, including an acid solution preparation step, wherein the acid solution preparation step includes pre-acid preparation, main acid preparation, and displacement fluid preparation; In the preparation of the preacid, the components of the preacid include hydrochloric acid and additives, and the components of the additives include acetic acid, an iron ion stabilizer, a mutual solvent, a clay stabilizer, and clean water; In the preparation of the main acid, the main acid components include hydrochloric acid, acetic acid, ammonium fluoride, retarder, iron ion stabilizer, scale inhibitor, activator, and clean water; In the preparation of the displacement fluid, the components of the displacement fluid include hydrochloric acid and a surfactant; the concentration of hydrochloric acid in the displacement fluid is lower than the concentration of hydrochloric acid in the preacid or the main acid; Features: Before configuring the acid solution, the application environment is initially evaluated. The initial evaluation includes formation characteristics and environmental parameters. Formation characteristics include the porosity and permeability of the well. Environmental parameters include the temperature and pressure of the well. Conditions 1 and 2 are established based on the initial evaluation. If condition 1 or condition 2 is judged to be abnormal, the comprehensive evaluation step is entered. In the comprehensive evaluation step of the application environment, a comprehensive evaluation model is established, and the concentration of hydrochloric acid in the pre-acid, the concentration of ammonium fluoride in the main acid, and the concentration of hydrochloric acid in the displacement fluid are dynamically adjusted according to the comprehensive evaluation model; the comprehensive evaluation model includes the evaluation of formation characteristics, environmental parameters, fluid characteristics, and blockage types; Then, pre-acid injection, main acid injection, and displacement fluid injection are carried out in stages; Condition 1 is: if the porosity is less than a preset porosity threshold, and the permeability is less than a preset permeability threshold, it is determined to be abnormal; Condition 2 is: if the temperature is greater than a preset temperature threshold, and the pressure is greater than a preset pressure threshold, it is determined to be abnormal; Establishing a comprehensive assessment model ; ； in , , , is the weight coefficient, which indicates the influence weight of different factors on the ratio; scoring formation properties, which takes into account porosity and permeability; ； Score environmental parameters, which take into account temperature and pressure; ； Score the fluid properties, which take into account the fluid's viscosity, density, and surface tension; ； Score the type of plugging, which takes into account the particle size, thickness and hardness of the plug; ； in is the porosity; is the permeability; is the peak value of porosity; is the peak value of permeability; in is temperature; For pressure; is the reference temperature; is the reference pressure; in is the fluid viscosity; is the fluid density; is the surface tension; , , They are the reference value of fluid viscosity, fluid density and surface tension respectively; in is the clogging particle size; is the plugging thickness; For the plugging hardness.

2. The deep penetration cleaning slow acid acidification plugging removal method according to claim 1 is characterized by: When pre-acid, main acid and displacement fluid are injected, the formation data in the acidizing process is monitored in real time. The formation data includes three aspects: The first aspect is the changes in acid injection pressure and flow rate; The second aspect is the bottom hole pressure and temperature changes; The third aspect is the dissolution curve and formation response data after acidification reaction; Finally, after the construction is completed, the acidification effect is evaluated.

3. The deep penetration cleaning slow acid acidification plugging removal method according to claim 2 is characterized by: The porosity of the underground formation , Permeability ,temperature and pressure Perform calculations to provide basic data for initial assessment; ； ； ； ； in is the pore volume; is the total formation volume; is the fluid flow rate; is the fluid viscosity; is the formation thickness; is the pressure difference; Flow cross-sectional area; is the surface temperature; is the geothermal gradient; for the depth of the well; is the formation fluid density; is the acceleration due to gravity.

4. The deep penetrating cleaning slow acid acidification plugging removal method according to claim 3 is characterized by: The formula for adjusting the preacid ratio is: ； in is the concentration of hydrochloric acid in the preacid; is the initial hydrochloric acid concentration in the preacid; is the current formation porosity; is the peak porosity; is the current formation pressure; is the peak pressure; is the influence function of additives in preacid; scoring the comprehensive assessment model; ； in is the actual concentration of the additive in the preacid; is the peak concentration of the additive in the preacid; is the peak value of the assessment score; The main acid ratio adjustment formula is: ； in is the concentration of ammonium fluoride; is the initial ammonium fluoride concentration; scoring formation assessments; is the peak value of the assessment score; is the formation temperature; is the peak temperature; is the formation permeability; is the peak permeability; The displacement fluid ratio adjustment formula is: ； in is the concentration of hydrochloric acid in the displacement fluid; is the concentration of surfactant; is the peak concentration of the surfactant.

5. The deep penetration cleaning slow acid acidification plugging removal method according to claim 4 is characterized by: Based on the first aspect of formation data, a dynamic model of acid injection pressure and a flow rate variation model are established; ； ； ； ； ； in injecting pressure into the acid; is the formation back pressure; is the pipeline friction factor; is the density of acid solution; is the acid flow rate; Real-time flow rate of acid; is the cross-sectional area of ​​the pipe; is the length of the pipeline; is the inner diameter of the pipe; is the acid viscosity; is the permeability; is the formation flow cross-sectional area; is the real-time pressure difference; is the path length of the acid fluid flowing through the formation.

6. The deep penetration cleaning slow acid acidification plugging removal method according to claim 5 is characterized by: The bottom hole pressure model and bottom hole temperature change model are established based on the second aspect of formation data; ； ； in is the bottom hole pressure; Injecting pressure into the acid; is the density of acid solution; is the acceleration due to gravity; for the depth of the well; is the bottom hole temperature; is the surface temperature; The geothermal gradient.

7. The deep penetrating cleaning slow acid acidification plugging removal method according to claim 6 is characterized by: The third aspect based on the formation data is to establish the dissolution curve model and formation response model after the acidification reaction; ； ； in is the mass of dissolved matter; is the mass of initial soluble matter; is the chemical reaction rate constant; is the reaction time; is the porosity change; , is the porosity after and before acidification; is a constant; is the dissolved mass; is the rock density.

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