A kind of release liquid and its preparation method and application

Abstract

The present invention belongs to the technical field of oil development drilling and completion fluids and relates to a release fluid, its preparation method, and its application. The release fluid of the present invention comprises a slow-release acid, a brine stabilizer, a surfactant, and water. The release fluid of the present invention reacts only after a period of contact with the mud cake, providing the advantage of effective reservoir protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of drilling and completion fluids for petroleum development, and relates to a release fluid, a preparation method and an application thereof, and in particular to a release fluid with the function of delaying the dissolution of non-aqueous drilling fluid mud cake, a preparation method and an application thereof. Background Art

[0002] Currently, acid-soluble solid particles are widely used in non-aqueous drilling fluids as effective weighting agents and temporary plugging fluid loss additives. However, these acid-soluble solid particles inevitably damage the reservoir near the wellbore. Therefore, it is necessary to efficiently and evenly remove these particles from the drilling fluid mudcake to quickly restore the formation's conductivity and maximize the development of oil and gas resources.

[0003] In the past, strong acid dissolution was often used on oilfield sites. However, strong acid mudcake removers react quickly, reacting immediately upon contact with the mudcake. This often creates wormholes on the mudcake surface, causing the remover to flow into the formation prematurely and resulting in incomplete mudcake dissolution. Furthermore, conventional strong acid mudcake removers also carry significant HSE risks, incurring additional costs and, if not handled properly, posing a corrosion risk to downhole completion equipment. Summary of the Invention

[0004] In order to solve the technical problem of reservoir damage in the near-wellbore area caused by acid-soluble solid particles in non-aqueous drilling fluid, the present invention provides a release fluid and a preparation method and application thereof.

[0005] Specifically, the present invention is achieved through the following technical solutions:

[0006] A release liquid comprises: slow-release acid, a saline stabilizer, a surfactant and water.

[0007] The above-mentioned release liquid comprises, by weight, 5 to 20 parts of slow-release acid, 1 to 3 parts of saline stabilizer, 0.02 to 0.47 parts of surfactant and 100 parts of water.

[0008] The above-mentioned release solution comprises, by weight, 10 to 20 parts of slow-release acid, 1 to 2 parts of saline stabilizer, 0.02 to 0.1 parts of surfactant and 100 parts of water.

[0009] The above-mentioned release solution further comprises, by weight, 0.3 to 3.5 parts of a sustained-release acid inhibitor.

[0010] The above-mentioned release solution further comprises, by weight, 1.3 to 3.5 parts of a sustained-release acid inhibitor.

[0011] The above-mentioned release liquid further comprises: one or more of a defoaming agent and a weighting salt.

[0012] In the above-mentioned release solution, the slow-release acid comprises 50 parts of water, 1 to 6 parts of acid compounds, 1 to 5 parts of ester compounds and 10 to 40 parts of ammonium compounds.

[0013] In the above-mentioned desolvent, the acid compound includes one or more of hydrochloric acid, chloric acid, oxalic acid, lactic acid, acetic acid, oxalic acid, malonic acid, sulfamic acid, and chloroacetic acid; the ester compound includes one or more of gluconolactone, monoaminopolycarboxylic acid ester, triethyl orthoformate, polyaminocarboxylic acid ester, and triethyl orthoacetate; and the ammonium compound includes one or more of ammonium formate, ammonium acetate, ammonium bicarbonate, ammonium fluoride, and ammonium chloride.

[0014] In the above-mentioned release liquid, the sustained-release acid inhibitor includes, by weight, organic salts and inorganic salts.

[0015] In the above-mentioned decontamination liquid, the organic salt includes one or more of sodium formate, sodium acetate, and potassium formate; and the inorganic salt is selected from one or more of sodium chloride, sodium hypochlorite, hydrogen phosphate, and dihydrogen phosphate.

[0016] In the above-mentioned release liquid, the brine stabilizer includes one or more of sodium tripolyphosphate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate.

[0017] In the above-mentioned debonding liquid, the surfactant includes one or more of sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and hexadecyltrimethylammonium bromide.

[0018] In the above-mentioned release liquid, the weighting salt includes one or more of sodium chloride, sodium bromide, potassium chloride, calcium chloride, calcium bromide, sodium formate, and potassium formate.

[0019] The water in the above-mentioned release liquid is one of seawater, filtered seawater and fresh water.

[0020] On the other hand, the present invention also provides a method for preparing the above-mentioned release solution, comprising: adding a slow-release acid, a salt water stabilizer, and a surfactant to water in order according to a ratio under stirring.

[0021] The preparation method of the above-mentioned release solution comprises adding a slow-release acid, a slow-release acid inhibitor, a salt water stabilizer and a surfactant into water in order according to a ratio under stirring.

[0022] In another aspect, the present invention further provides the use of the above-mentioned release fluid in delaying the dissolution of a non-aqueous-based drilling fluid mud cake in a reservoir.

[0023] The above application is characterized in that the reservoir temperature does not exceed 100°C and the density of the used / workover fluid is not higher than 1.3g / cm 3 reservoir.

[0024] The technical solution of the present invention has the following beneficial effects:

[0025] (1) The release liquid provided by the present invention reacts with the mud cake after a period of contact, and has the characteristics of good reservoir protection effect;

[0026] (2) The release fluid provided by the present invention can not only match different on-site construction processes and improve operation efficiency, but also can efficiently and safely restore the production capacity of the near-wellbore area after the non-water-based drilling fluid operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Various other advantages and benefits will become apparent to those skilled in the art by reading the following detailed description of the preferred embodiment.The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention.

[0028] Figure 1 This is a curve of the time it takes for the solution prepared in Example 1 to delay dissolving the mud cake;

[0029] Figure 2 This is a curve diagram of the time it takes for the solution prepared in Example 2 to delay the dissolution of the mud cake;

[0030] Figure 3 This is a curve diagram of the time it takes for the solution prepared in Example 3 to delay the dissolution of the mud cake;

[0031] Figure 4 The pH value of the solution prepared in Example 5 changes;

[0032] Figure 5 This is a curve of the time it takes for the solution prepared in Comparative Example 1 to delay the dissolution of the mud cake. DETAILED DESCRIPTION

[0033] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0034] In the present application, the terms "removal liquid", "delayed mud cake removing liquid" and "delayed mud cake removing liquid system" all have the same meaning and can be used interchangeably.

[0035] Specifically, the release solution provided by the present invention includes: slow-release acid, a saline stabilizer, a surfactant and water.

[0036] The slow-release acid used in the present invention has the characteristic that the concentration of released acid is affected by temperature, which makes the release liquid system only weakly acidic at room temperature, but will produce free acid when it is at a higher downhole temperature. By using slow-release acid, the effect of slow acid generation is achieved. The surfactant used in the present invention can change the wettability of the surface of the acid-soluble solid phase in the mud cake from oil-wet to water-wet, thereby improving the mud cake dissolution efficiency. The present invention can effectively improve the stability of each component of the system in high-density brine by adding a brine stabilizer, increase the density application range of the system, and effectively prevent the formation of secondary precipitation, protecting the reservoir seepage channel. Finally, by adding weighted salt, the overall density of the mud cake release liquid is adjusted to match the actual development and operation needs of different strata. The release liquid of the present invention cooperates with each other through various functional treatment agents, thereby realizing a mud cake release technology that controls the mud cake dissolution rate and does not cause filtration loss within a specific time.

[0037] Preferably, the release solution provided by the present invention further comprises a slow-release acid inhibitor. The slow-release acid inhibitor can inhibit the acid release rate of the slow-release acid, and the slow-release acid inhibitor will gradually lose its inhibitory effect as the temperature rises, causing the H + The concentration increases significantly over time.

[0038] The components of the release solution of the present invention are introduced in detail below.

[0039] Slow-release acid

[0040] The slow-release acid used in the present invention is used to release acidic substances into the mud cake.

[0041] In some preferred embodiments, the slow-release acid used in the present invention includes water, acid compounds, ester compounds and ammonium compounds.

[0042] Among them, acid compounds can directly release acidic substances, ester compounds can be decomposed into corresponding carboxylic acids through hydrolysis, and ammonium compounds undergo proton transfer reactions in water, making the solution acidic. The slow-release acid of the present invention achieves a slow-release effect of acid by using acid compounds, ester compounds, and ammonium compounds.

[0043] Further preferably, in the sustained-release acid, the ratio of the water, the acid compound, the ester compound and the ammonium compound is 50 parts, 1 to 6 parts, 1 to 5 parts, or 10 to 40 parts by weight.

[0044] In some preferred embodiments, the acid compound includes one or more of hydrochloric acid, chloric acid, oxalic acid, lactic acid, acetic acid, oxalic acid, malonic acid, sulfamic acid, and chloroacetic acid.

[0045] Wherein, the hydrochloric acid is dilute hydrochloric acid, and its concentration is 0.005-0.015 mol / L.

[0046] In some preferred embodiments, the ester compound includes one or more of gluconolactone, monoaminopolycarboxylic acid ester, triethyl orthoformate, polyaminocarboxylic acid ester, and triethyl orthoacetate.

[0047] Optionally, the polyaminocarboxylate is a mixture of one or more of n-butylaminoethyl methacrylate, aminoethyl methacrylate, and N-ethylurethane.

[0048] In some preferred embodiments, the ammonium compound includes one or more of ammonium formate, ammonium acetate, ammonium bicarbonate, ammonium fluoride, and ammonium chloride.

[0049] Optionally, the slow-release acid further includes a trace amount of alkali, such as sodium hydroxide, potassium hydroxide, etc.

[0050] Wherein, the ratio of the alkali solution in the sustained-release acid is 0.5 to 1 parts by weight, and the concentration of the alkali solution is 0.005 to 0.015 mol / L.

[0051] In the release liquid of the present invention, the proportion of the slow-release acid is 5 to 20 parts based on 100 parts by weight of water.

[0052] The ratio of slow-release acid affects the time it takes to delay the dissolution of the mud cake. As the ratio of slow-release acid in the solution increases, the mud cake dissolution rate accelerates.

[0053] More preferably, the ratio of the slow-release acid is 10 to 20 parts per 100 parts by weight of water.

[0054] Brine stabilizer

[0055] In the present invention, the brine stabilizer is used to improve the stability of the components of the release liquid system in high-density brine, increase the density application range of the release liquid system, and effectively prevent the formation of secondary precipitation.

[0056] In some preferred embodiments, the brine stabilizer used in the present invention includes one or more of sodium tripolyphosphate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate.

[0057] In the desolventizing liquid of the present invention, the proportion of the salt water stabilizer is 1 to 3 parts based on 100 parts by weight of water.

[0058] The concentration of brine stabilizer should be proportional to the concentration of slow-release acid. The higher the slow-release acid concentration, the higher the brine stabilizer ratio should be. If the brine stabilizer ratio is too low, it may cause secondary precipitation after the mud cake is released, which may accumulate in the near-wellbore area and cause reservoir damage.

[0059] More preferably, the ratio of the brine stabilizer is 1 to 2 parts based on 100 parts by weight of water.

[0060] surfactants

[0061] The surfactant used in the present invention can change the wettability of the surface of the acid-soluble solid phase in the mud cake from oil-wet to water-wet, thereby improving the mud cake dissolution efficiency.

[0062] In some preferred embodiments, the surfactant includes one or more of sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and hexadecyltrimethylammonium bromide.

[0063] In the decontamination liquid of the present invention, the proportion of the surfactant is 0.02 to 0.47 parts based on 100 parts by weight of water.

[0064] The ratio of surfactants will affect the time it takes to delay dissolving the mud cake in the system. When a high concentration is selected, the mud cake dissolution rate will be relatively increased.

[0065] More preferably, the surfactant is present in an amount of 0.02 to 0.1 parts per 100 parts by weight of water.

[0066] sustained-release acid inhibitors

[0067] In the present invention, the sustained-release acid inhibitor is used to control the rate at which the sustained-release acid releases the acidic substance.

[0068] In some preferred embodiments, the sustained-release acid inhibitor used in the present invention is an aqueous solution of an organic salt and / or an inorganic salt.

[0069] When organic and / or inorganic salts act as slow-release acid inhibitors, the hydroxide ions generated by their hydrolysis reaction neutralize with the hydrogen ions in the slow-release acid, thereby slowing or inhibiting the release of the acidic properties of the slow-release acid. Organic or inorganic salts can also affect the solubility and release rate of the slow-release acid by altering the pH and ionic strength of the solution. For example, high ion concentrations can reduce the solubility of the slow-release acid, thereby slowing its release rate.

[0070] Further preferably, the sustained-release acid inhibitor comprises, by weight, an organic salt and an inorganic salt.

[0071] In some preferred embodiments, the organic salt includes one or more of sodium formate, sodium acetate, and potassium formate.

[0072] In some preferred embodiments, the inorganic salt is selected from one or more of sodium chloride, sodium hypochlorite, hydrogen phosphate, and dihydrogen phosphate.

[0073] In the release solution of the present invention, the proportion of the sustained-release acid inhibitor is 0.3 to 3.5 parts based on 100 parts by weight of water.

[0074] The ratio of slow-acting acid inhibitors will affect the time of delaying the dissolution of the mud cake. When a high organic salt concentration is selected, the mud cake dissolution rate will be reduced accordingly.

[0075] More preferably, the ratio of the sustained-release acid inhibitor is 1.3 to 3.5 parts based on 100 parts by weight of water.

[0076] Other additives

[0077] In some preferred embodiments, weighting salt may be optionally added according to the density requirement of the release liquid.

[0078] Preferably, the weighted salt is an inorganic weighted salt or an organic weighted salt.

[0079] More preferably, the inorganic weighting salt may be one or a mixture of sodium chloride, sodium bromide, potassium chloride, calcium chloride, calcium bromide, etc.

[0080] More preferably, the organic weighting salt may be one or a mixture of sodium formate, potassium formate, etc.

[0081] In some preferred embodiments, a defoaming agent may be added to the release liquid according to actual conditions.

[0082] Preferably, the defoaming agent is selected from tributyl phosphate.

[0083] water

[0084] The removal liquid of the present invention has low requirements on water, and it can be seawater, filtered seawater or fresh water.

[0085] On the other hand, the present invention also provides a method for preparing the above-mentioned release solution, comprising: adding a slow-release acid, a slow-release acid inhibitor, a saline stabilizer, and a surfactant to water in order according to a ratio under stirring.

[0086] Preferably, when preparing the dissolving solution, the system temperature should be ≥5°C and the stirring time should be ≥30 minutes.

[0087] In another aspect, the present invention further provides the use of the above-mentioned release fluid in delaying the dissolution of a non-aqueous-based drilling fluid mud cake in a reservoir.

[0088] The reservoir temperature is no more than 100°C, and the density of the used / workover fluid is no more than 1.3g / cm 3 reservoir.

[0089] Through practice, the release fluid of the present invention has the following advantages: first, the delayed release time of the mud cake can be precisely controlled by the content of each component of the release fluid, accurately matching the needs of the on-site construction process; second, the reaction with the mud cake is "on-off type", and the acidic substance can be released in large quantities in a short time, avoiding incomplete mud cake release caused by uneven dissolution of the mud cake and premature leakage of acid into the formation under downhole pressure conditions; third, it has a high mud cake dissolution efficiency, can almost completely dissolve the mud cake, open up the fluid flow channel in the near-well area downhole, and maximize the oil well production capacity; fourth, compared with traditional strong acid release fluids, it has good safety. After the release fluid system is prepared, it is only weakly acidic. After entering the well, the pH gradually decreases as the temperature rises, which is more convenient for on-site application and construction safety.

[0090] Example

[0091] The present invention is further illustrated by way of examples below, but the invention is not limited to the scope of the examples. The experimental methods in the following examples where specific conditions are not specified were based on conventional methods and conditions. The raw materials used in the following examples were all commercially available.

[0092] Example 1

[0093] Preparation of slow-release acid: Measure 50 parts of fresh water, add 1 part of 0.01 mol / L dilute hydrochloric acid, 2 parts of sulfamic acid, 1.5 parts of triethyl orthoacetate, 0.5 parts of aminoethyl methacrylate, 4 parts of ammonium formate, and 16 parts of ammonium acetate. After stirring thoroughly to dissolve, add 1 part of 0.01 mol / L sodium hydroxide solution dropwise to the solution to obtain a slow-release acid solution.

[0094] Preparation of sustained-release acid inhibitor solution: Measure 100 parts of fresh water, add 20 parts of sodium formate and 10 parts of potassium dihydrogen phosphate, stir thoroughly and dissolve to obtain a sustained-release acid inhibitor solution.

[0095] Prepare a surfactant solution: add 20 parts of sodium dodecylbenzenesulfonate and 10 parts of cetyltrimethylammonium bromide to 100 parts of fresh water, and stir at 100 rpm / min for 15 minutes to obtain a surfactant solution.

[0096] Preparation of delayed mud cake removing liquid: 100 parts of fresh water, 20 parts of the slow-release acid in Example 1, 10 parts of the slow-release acid inhibitor solution in Example 1 (equivalent to 2.3 parts of the slow-release acid inhibitor), 2 parts of the brine stabilizer disodium ethylenediaminetetraacetic acid, and 0.2 parts of the surfactant solution in Example 1 (equivalent to 0.046 parts of the surfactant) were measured and added to a beaker in sequence, and stirred at a high speed of 800 r / min for 30 minutes using a magnetic stirrer to obtain a delayed mud cake removing liquid.

[0097] After using non-aqueous drilling fluid to press the drilling fluid mud cake on a ceramic sand disc with a permeability of 750mD at 60℃ and 500psi, the non-aqueous drilling fluid in the pressure vessel is replaced with a delayed mud cake release fluid, and the experimental conditions of 60℃ and 500psi are maintained. The mud cake loss is recorded. The time from the start of pressurization to the complete loss of the release fluid is recorded as the system delayed mud cake release time. The experimental results are as follows: Figure 1 shown.

[0098] pass Figure 1 It can be seen that the delayed mudcake removal fluid is completely filtered out after 460 minutes of contact with the non-aqueous drilling fluid mudcake, indicating that the system has the function of delaying the dissolution of the non-aqueous drilling fluid mudcake.

[0099] Example 2

[0100] The slow-release acid, slow-release acid inhibitor solution and surfactant solution were prepared in the same manner as in Example 1.

[0101] Preparation of delayed mud cake removing liquid: 100 parts of fresh water, 20 parts of the slow-release acid in Example 1, 15 parts of the slow-release acid inhibitor solution in Example 1 (equivalent to 3.46 parts of the slow-release acid inhibitor), 2 parts of the brine stabilizer disodium ethylenediaminetetraacetic acid, and 0.2 parts of the surfactant solution in Example 1 (equivalent to 0.046 parts of the surfactant) were measured and added to a beaker in sequence, and stirred at a high speed of 800 r / min for 30 minutes using a magnetic stirrer to obtain a delayed mud cake removing liquid.

[0102] After using non-aqueous drilling fluid to press the drilling fluid mud cake on a ceramic sand disc with a permeability of 750mD at 60℃ and 500psi, the non-aqueous drilling fluid in the pressure vessel is replaced with a delayed mud cake release fluid. The experimental conditions of 60℃ and 500psi are maintained, and the mud cake loss is recorded. The time from the start of pressurization to the complete loss of the release fluid is recorded as the system delayed mud cake release time. The experimental results are shown in Figure 2. Figure 2 shown.

[0103] pass Figure 2 It can be seen that the delayed mudcake removal fluid was completely filtered out after 590 minutes of contact with the non-aqueous drilling fluid mudcake, indicating that the time for delaying the dissolution of the non-aqueous drilling fluid mudcake in this system will be further increased after increasing the concentration of the slow-release acid inhibitor.

[0104] Example 3

[0105] The slow-release acid and surfactant solutions were prepared in the same manner as in Example 1.

[0106] Preparation of delayed mud cake removing liquid: 100 parts of fresh water, 20 parts of the slow-release acid in Example 1, 2 parts of the brine stabilizer disodium ethylenediaminetetraacetic acid, and 0.2 parts of the surfactant solution in Example 1 (equivalent to 0.046 parts of the surfactant) were measured and added to a beaker in sequence, and stirred at a high speed of 800 rpm for 30 minutes using a magnetic stirrer to obtain a delayed mud cake removing liquid.

[0107] After using non-aqueous drilling fluid to press the drilling fluid mud cake on a ceramic sand disc with a permeability of 750mD at 60℃ and 500psi, the non-aqueous drilling fluid in the pressure vessel is replaced with a delayed mud cake release fluid. The experimental conditions of 60℃ and 500psi are maintained, and the mud cake loss is recorded. The time from the start of pressurization to the complete loss of the release fluid is recorded as the system delayed mud cake release time. The experimental results are shown in Figure 2. Figure 3 shown.

[0108] pass Figure 3 It can be seen that the delayed mudcake removal fluid was completely lost only after 180 minutes of contact with the non-aqueous drilling fluid mudcake, indicating that when no slow-release acid inhibitor was added, the system still had the function of delaying the dissolution of the non-aqueous drilling fluid mudcake.

[0109] Example 4

[0110] Preparation of sustained-release acid: Measure 50 parts of fresh water, add 1 part of 0.01 mol / L dilute hydrochloric acid, 5 parts of sulfamic acid, 4.5 parts of triethyl orthoacetate, 0.5 part of aminoethyl methacrylate, 10 parts of ammonium formate, and 30 parts of ammonium chloride. After stirring thoroughly to dissolve, add 1 part of 0.01 mol / L sodium hydroxide solution dropwise to the solution to obtain a sustained-release acid solution.

[0111] Preparation of sustained-release acid inhibitor solution: Measure 100 parts of fresh water, add 10 parts of sodium formate and 5 parts of potassium dihydrogen phosphate, stir thoroughly and dissolve to obtain a sustained-release acid inhibitor solution.

[0112] Prepare a surfactant solution: add 20 parts of sodium dodecylbenzenesulfonate and 10 parts of cetyltrimethylammonium bromide to 100 parts of fresh water, and stir at a speed of 100 rpm / min for 15 minutes to obtain a surfactant.

[0113] A delayed mud cake removing liquid was prepared by measuring 100 parts of fresh water, 15 parts of the slow-release acid in Example 4, 10 parts of the slow-release acid inhibitor solution in Example 4 (equivalent to 1.3 parts of the slow-release acid inhibitor), 2 parts of the brine stabilizer disodium ethylenediaminetetraacetic acid, and 0.2 parts of the surfactant solution in Example 4 (equivalent to 0.046 parts of the surfactant), and adding them to a beaker in sequence. The mixture was stirred at a high speed of 800 rpm for 30 minutes using a magnetic stirrer to obtain a delayed mud cake removing liquid.

[0114] When 5 parts of calcium carbonate were mixed with 100 parts of the delayed cake removal solution from Example 4, no bubbles were observed. When the mixed solution was heated to 60°C, trace bubbles were observed. After about 2 hours, the amount of bubbles in the solution increased significantly.

[0115] This indicates that calcium carbonate and delayed mud cake release liquid hardly react at room temperature. Only after heating for a period of time will the reaction occur significantly, accompanied by the generation of carbon dioxide gas.

[0116] Example 5

[0117] The slow-release acid, slow-release acid inhibitor solution and surfactant solution were prepared in the same manner as in Example 4.

[0118] A delayed mud cake removing liquid was prepared by measuring 100 parts of fresh water, 15 parts of the slow-release acid in Example 4, 10 parts of the slow-release acid inhibitor solution in Example 4 (equivalent to 1.3 parts of the slow-release acid inhibitor), 2 parts of the brine stabilizer disodium ethylenediaminetetraacetic acid, and 0.2 parts of the surfactant solution in Example 4 (equivalent to 0.046 parts of the surfactant), and adding them to a beaker in sequence. The mixture was stirred at a high speed of 800 rpm for 30 minutes using a magnetic stirrer to obtain a delayed mud cake removing liquid.

[0119] Place it in a 60℃ water bath and test the pH value of the solution every 60 minutes. The test results are as follows: Figure 4 shown.

[0120] pass Figure 4 The delayed mudcake removal liquid system is weakly acidic at room temperature, with a pH of 5.77. After heating to 60°C, the pH of the solution begins to decrease. After approximately three hours, the pH reaches a minimum of around 3.5 and remains stable thereafter. This further demonstrates the delayed mudcake removal liquid system's ability to release acidity after heating.

[0121] Comparative Example 1

[0122] Prepare 1 part of strong acid mud cake remover: measure 100 parts of fresh water, add 20 parts of dilute hydrochloric acid with a concentration of 0.01 mol / L, and 1 part of the surfactant solution in Example 1 (equivalent to 0.23 parts of surfactant), add them into a beaker in sequence, and stir at a high speed of 800 r / min for 30 minutes using a magnetic stirrer to obtain a strong acid mud cake remover.

[0123] The mud cake release time was tested in the same manner as in Example 1. The experimental results are as follows: Figure 5 shown.

[0124] pass Figure 5It can be seen that after the strong acid comes into contact with the non-aqueous drilling fluid mud cake, it quickly dissolves the acid-soluble solid particles in the mud cake and quickly forms liquid seepage channels. The filtration loss occurs almost instantly at the time of contact.

[0125] The results of Examples 1-3 and Comparative Example 1 verified the effectiveness of the descaling liquid system of the present invention in descaling mud cakes and the controllability of the descaling time of the system.

[0126] Comparative Example 2

[0127] Prepare 1 part of strong acid mud cake remover: measure 100 parts of fresh water, add 20 parts of dilute hydrochloric acid with a concentration of 0.01 mol / L, and after fully dissolving, obtain strong acid mud cake remover.

[0128] When 5 parts of calcium carbonate were mixed with 100 parts of the strong acid mud cake remover solution in Comparative Example 2, an immediate reaction was observed with the appearance of continuous bubbles.

[0129] This indicates that calcium carbonate reacts rapidly with the strong acid mud cake remover and is accompanied by the generation of carbon dioxide gas.

[0130] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art will appreciate that these embodiments are intended only to illustrate the present invention and are not to be construed as limiting the scope of the present invention. It should be noted that any equivalent variations and substitutions to these embodiments are to be considered encompassed within the scope of the claims of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A release liquid, characterized in that: include: Slow-release acid, brine stabilizer, surfactant and water; The sustained-release acid comprises 50 parts of water, 1 to 6 parts of an acid compound, 1 to 5 parts of an ester compound, and 10 to 40 parts of an ammonium compound; the acid compound comprises one or more of hydrochloric acid, oxalic acid, lactic acid, acetic acid, oxalic acid, malonic acid, sulfamic acid, and chloroacetic acid; the ester compound comprises one or more of gluconolactone, monoaminopolycarboxylic acid ester, triethyl orthoformate, polyaminocarboxylic acid ester, and triethyl orthoacetate; the ammonium compound comprises one or more of ammonium formate, ammonium acetate, ammonium bicarbonate, ammonium fluoride, and ammonium chloride; The brine stabilizer includes one or more of sodium tripolyphosphate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate; The surfactant includes one or more of sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and hexadecyltrimethylammonium bromide.

2. The release liquid according to claim 1, characterized in that The composition comprises, by weight, 5 to 20 parts of a slow-release acid, 1 to 3 parts of a saline stabilizer, 0.02 to 0.47 parts of a surfactant, and 100 parts of water.

3. The release liquid according to claim 1, characterized in that The composition comprises, by weight, 10-20 parts of slow-release acid, 1-2 parts of saline stabilizer, 0.02-0.1 parts of surfactant and 100 parts of water.

4. The release liquid according to claim 1, characterized in that Calculated by weight, it also includes 0.3 to 3.5 parts of a sustained-release acid inhibitor.

5. The release liquid according to claim 1, characterized in that Calculated by weight, it also includes 1.3 to 3.5 parts of a sustained-release acid inhibitor.

6. The release liquid according to claim 1, characterized in that Also includes: One or more of defoaming agents and weighting salts.

7. The release liquid according to claim 4 or 5, characterized in that The sustained-release acid inhibitor includes, by weight, organic salts and inorganic salts.

8. The release liquid according to claim 7, characterized in that The organic salt includes one or more of sodium formate, sodium acetate, and potassium formate; the inorganic salt is selected from one or more of sodium chloride, sodium hypochlorite, hydrogen phosphate, and dihydrogen phosphate.

9. The release liquid according to claim 6, characterized in that The weighting salt includes one or more of sodium chloride, sodium bromide, potassium chloride, calcium chloride, calcium bromide, sodium formate, and potassium formate.

10. The release liquid according to claim 1, characterized in that The water is one of seawater, filtered seawater and fresh water.

11. The method for preparing the release solution according to any one of claims 1 to 10, characterized in that: include: Under stirring, add the slow-release acid, brine stabilizer and surfactant into the water in sequence according to the ratio.

12. The method for preparing a release liquid according to claim 11, characterized in that: include: Under stirring, add the slow-release acid, slow-release acid inhibitor, brine stabilizer and surfactant into water in sequence according to the proportion.

13. Use of the release fluid according to any one of claims 1 to 10 in delayed dissolution of non-aqueous drilling fluid mud cake in a reservoir.

14. The use according to claim 13, characterized in that The reservoir has an operating temperature not exceeding 100°C and a density of used / workover fluid not exceeding 1.3 g / cm 3 reservoir.

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