Removal liquid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of drilling and completion fluids for oil development, and relates to a relieving fluid as well as a preparation method and application thereof. The removing liquid comprises slow-release acid, a salt water stabilizer, a surfactant and water. The release liquid provided by the invention reacts after being in contact with a mud cake for a period of time, and has the advantage of good reservoir protection effect.

Description

Technical Field

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

[0002] At present, acid-soluble solid particles have been widely used in non-aqueous drilling fluids as good weighting agents and temporary plugging fluid loss reducers. These acid-soluble solid particles will inevitably cause damage to the reservoir near the wellbore area. Therefore, it is necessary to efficiently and evenly remove such materials contained in the drilling fluid mud cake, quickly restore the formation's conductivity, and maximize the development effect of oil and gas resources.

[0003] In the past, strong acid dissolution was mostly used at oilfield sites. However, strong acid mud cake remover reacts quickly and reacts immediately when it comes into contact with mud cake, which often forms wormholes on the surface of the mud cake, causing the remover to flow into the formation prematurely, resulting in incomplete dissolution of the mud cake. In addition, conventional strong acid mud cake remover also has significant HSE risks, which not only generates additional costs, but also poses a corrosion risk to downhole completion equipment if not handled properly. 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 phase 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: a slow-release acid, a salt water stabilizer, a surfactant and water.

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

[0008] The above-mentioned release liquid 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.

[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 also includes: 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 release liquid, the acid compound includes one or more of hydrochloric acid, chloric acid, oxalic acid, lactic acid, acetic acid, oxalic acid, malonic acid, aminosulfonic acid, and chloroacetic acid; the ester compound includes one or more of gluconolactone, monoaminopolycarboxylic acid ester, triethyl orthoformate, polyaminocarboxylic acid ester, and triethyl orthoacetate; the ammonium compound includes one or more of ammonium formate, ammonium acetate, ammonium bicarbonate, ammonium fluoride, and ammonium chloride.

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

[0015] In the above-mentioned release liquid, 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.

[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 release liquid, the surfactant includes one or more of sodium dodecylbenzene sulfonate, 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 into water in order according to a ratio under stirring.

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

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

[0023] The above application is characterized in that the reservoir has an operating temperature not exceeding 100°C and a density of the used / repairing fluid not exceeding 1.3 g / cm 3 of the 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 construction processes on site and improve operation efficiency, but also 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 of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0028] Figure 1 This is a time curve of delayed dissolution of mud cake by the release liquid prepared in Example 1;

[0029] Figure 2 This is a time curve of delayed dissolution of mud cake by the release liquid prepared in Example 2;

[0030] Figure 3 This is a time curve of delayed dissolution of mud cake by the release liquid prepared in Example 3;

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

[0032] Figure 5 This is a time curve of the delayed dissolution of the mud cake by the release liquid prepared in Comparative Example 1. 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 method 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 "release liquid", "delayed mud cake release liquid" and "delayed mud cake release liquid system" all represent the same meaning and can be used interchangeably.

[0035] Specifically, the release liquid provided by the present invention includes: a slow-release acid, a salt water 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 when it is at a higher downhole temperature, free acid will be generated. By using the slow-release acid, the effect of slow acid generation can be 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 salt water stabilizer, improve 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 formations. 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 also includes 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 in the system to + The concentration increases significantly over time.

[0038] The various components of the release solution of the present invention are described 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 sustained-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 by hydrolysis, and ammonium compounds undergo proton transfer reaction in water to make the solution acidic. The slow-release acid of the present invention achieves the 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, aminosulfonic 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-ethyl ethyl carbamate.

[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 also includes a trace amount of alkali, such as sodium hydroxide, potassium hydroxide, etc.

[0050] Wherein, the proportion of the alkali solution in the sustained-release acid is 0.5 to 1 part 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 of delayed dissolution of mud cake in the system. As the ratio of slow-release acid in the solution increases, the mud cake dissolution rate increases.

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

[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 release 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 concentration of slow-release acid, the higher the proportion of brine stabilizer should be. If the proportion of brine stabilizer is too low, it may cause the formation of secondary precipitation after the mud cake is released, which will be deposited in the near-well 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 dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and hexadecyltrimethylammonium bromide.

[0063] In the remover of the present invention, the surfactant is contained in an amount of 0.02 to 0.47 parts based on 100 parts by weight of water.

[0064] The ratio of surfactants will affect the delayed dissolution time of the mud cake in the system. When a high concentration is selected, the mud cake dissolution rate is relatively increased.

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

[0066] Slow-release acid inhibitors

[0067] In the present invention, the sustained-release acid inhibitor is used to control the speed 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 salts and / or inorganic salts are used as slow-release acid inhibitors, the hydroxide ions generated by their hydrolysis reaction will react with the hydrogen ions in the slow-release acid to neutralize, thereby slowing down or inhibiting the acid release of the slow-release acid. Organic salts or inorganic salts can also affect the solubility and release rate of the slow-release acid by changing the pH value and ionic strength of the solution. For example, a high concentration of ions can reduce the solubility of the slow-release acid, thereby slowing down 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 acid inhibitor will affect the time of delaying the dissolution of mud cake. When high organic salt concentration is used, the dissolution rate of mud cake will be reduced accordingly.

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

[0076] Other additives

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

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

[0079] Further 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 release liquid of the present invention has low requirements on water, and it can be sea water, filtered sea water 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 salt water stabilizer and a surfactant into water in order according to a ratio under stirring.

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

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

[0088] The reservoir has an operating temperature not exceeding 100°C and a density of the used / workover fluid not exceeding 1.3 g / cm 3 of the 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 accurately controlled by the content of each component of the release fluid, and accurately matches the needs of the on-site construction process; second, the reaction with the mud cake is "switch-type", and the acidic substance can be released in large quantities in a short time, avoiding incomplete release of the mud cake due to uneven dissolution of the mud cake and premature leakage of the 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 downhole near-well area, and maximize the production capacity of the oil well; fourth, compared with the traditional strong acid release fluid, it has good safety. After the release fluid system is prepared, it is only weakly acidic. After entering the well, as the temperature rises, the pH gradually decreases, which is more convenient for on-site application and construction safety.

[0090] Example

[0091] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions. The raw materials used in the following examples are all conventionally purchased.

[0092] Example 1

[0093] Preparation of sustained-release acid: measure 50 parts of fresh water, add 1 part of 0.01mol / L dilute hydrochloric acid, 2 parts of aminosulfonic acid, 1.5 parts of triethyl orthoacetate, 0.5 parts of aminoethyl methacrylate, 4 parts of ammonium formate, and 16 parts of ammonium acetate, stir thoroughly to dissolve, and then drop 1 part of 0.01mol / L sodium hydroxide solution into the solution to obtain a sustained-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 and dissolve thoroughly to obtain a sustained-release acid inhibitor solution.

[0095] Prepare surfactant solution: measure 100 parts of fresh water, add 20 parts of sodium dodecylbenzene sulfonate, add 10 parts of hexadecyltrimethylammonium bromide, stir at a speed of 100 rpm / min for 15 minutes to obtain a surfactant solution.

[0096] Preparation of delayed mud cake releasing 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 ethylenediaminetetraacetate, and 0.2 parts of the surfactant solution in Example 1 (equivalent to 0.046 parts of the surfactant) are measured and added into 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 releasing 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℃&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℃&500psi are maintained, and the mud cake filtration loss is recorded. The time from the start of pressurization to the complete loss of the release fluid is recorded as the system delayed release mud cake time. The experimental results are shown in Figure 1 shown.

[0098] pass Figure 1 It can be seen that the delayed mud cake release fluid was completely filtered out after being in contact with the non-aqueous drilling fluid mud cake for 460 minutes, indicating that the system has the function of delaying the dissolution of the non-aqueous drilling fluid mud cake.

[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 releasing 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 ethylenediaminetetraacetate, and 0.2 parts of the surfactant solution in Example 1 (equivalent to 0.046 parts of the surfactant) are measured and added into 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 releasing 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℃&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℃&500psi are maintained. The mud cake filtration loss is recorded, and 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 shown.

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

[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 releasing liquid: 100 parts of fresh water, 20 parts of the slow-release acid in Example 1, 2 parts of the brine stabilizer disodium ethylenediaminetetraacetate, and 0.2 parts of the surfactant solution in Example 1 (equivalent to 0.046 parts of the surfactant) are measured and added into 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 releasing 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℃&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℃&500psi are maintained. The mud cake filtration loss is recorded, and 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 3 shown.

[0108] pass Figure 3 It can be seen that the delayed mud cake release fluid was completely filtered out after being in contact with the non-aqueous drilling fluid mud cake for 180 minutes, indicating that when the slow-release acid inhibitor is not added, the system still has the function of delaying the dissolution of the non-aqueous drilling fluid mud cake.

[0109] Example 4

[0110] Preparation of sustained-release acid: measure 50 parts of fresh water, add 1 part of 0.01mol / L dilute hydrochloric acid, 5 parts of aminosulfonic acid, 4.5 parts of triethyl orthoacetate, 0.5 parts of aminoethyl methacrylate, 10 parts of ammonium formate, and 30 parts of ammonium chloride, stir thoroughly to dissolve, and then drop 1 part of 0.01mol / L sodium hydroxide solution into 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 to dissolve, and then obtain a sustained-release acid inhibitor solution.

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

[0113] Preparation of delayed mud cake releasing liquid: 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 ethylenediaminetetraacetate, and 0.2 parts of the surfactant solution in Example 4 (equivalent to 0.046 parts of the surfactant) are measured and added into 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 releasing liquid.

[0114] When 5 parts of calcium carbonate were mixed with 100 parts of the delayed mud cake release liquid in Example 4, no bubbles were observed. When the mixed liquid 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 hardly reacts with the delayed mud cake release liquid at room temperature. After being heated for a period of time, the reaction will 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] Preparation of delayed mud cake releasing liquid: 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 ethylenediaminetetraacetate, and 0.2 parts of the surfactant solution in Example 4 (equivalent to 0.046 parts of the surfactant) are measured and added into 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 releasing 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 It can be seen that the delayed mud cake release liquid system has weak acidity at room temperature, with a pH value of 5.77 at room temperature; after heating at 60°C, the pH of the solution began to decrease; after about 3 hours, the pH reached a minimum value of about 3.5, and has remained in a stable range since then. This further illustrates that the delayed mud cake release liquid system has the ability to delay the release of acidity after heating.

[0121] Comparative Example 1

[0122] Prepare 1 part of strong acid mud cake removing liquid: 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 removing liquid.

[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 a liquid seepage channel, and the filtration loss occurs almost instantly at the time of contact.

[0125] The results of Examples 1-3 and Comparative Example 1 verify the effectiveness of the release liquid system of the present invention in releasing mud cake and the controllability of the time for releasing mud cake of the system.

[0126] Comparative Example 2

[0127] Prepare 1 part of strong acid mud cake removing liquid: 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 the strong acid mud cake removing liquid.

[0128] When 5 parts of calcium carbonate were mixed with 100 parts of the strong acid mud cake remover in Comparative Example 2, it was observed that the reaction occurred immediately and continuous bubbles appeared.

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

[0130] The present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that these embodiments are only used to describe the present invention and should not be understood as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to these embodiments should be deemed to be included in the scope of the claims of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined in the claims.

Claims

1. A release liquid, characterized in that: include: Slow-release acid, brine stabilizer, surfactant and water.

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

3. The release liquid according to claim 1, characterized in that: Calculated by weight, it includes: 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 sustained-release acid inhibitor.

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

7. The release liquid according to claim 1, characterized in that: 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.

8. The release liquid according to claim 7, characterized in that: The acid compound includes one or more of hydrochloric acid, chloric acid, oxalic acid, lactic acid, acetic acid, oxalic acid, malonic acid, aminosulfonic acid, and chloroacetic acid; the ester compound includes one or more of gluconolactone, monoaminopolycarboxylic acid ester, triethyl orthoformate, polyaminocarboxylic acid ester, and triethyl orthoacetate; the ammonium compound includes one or more of ammonium formate, ammonium acetate, ammonium bicarbonate, ammonium fluoride, and ammonium chloride.

9. 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.

10. The release liquid according to claim 9, 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.

11. The release liquid according to claim 1, characterized in that: The brine stabilizer includes one or more of sodium tripolyphosphate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate.

12. The release liquid according to claim 1, characterized in that The surfactant includes one or more of sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether, alkyl glycoside, and hexadecyltrimethylammonium bromide.

13. 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.

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

15. The method for preparing a release solution according to any one of claims 1 to 14, characterized in that: include: Under stirring, add the slow-release acid, brine stabilizer and surfactant into the water in sequence according to the proportion.

16. The method for preparing a release liquid according to claim 15, 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.

17. Use of the release fluid according to any one of claims 1 to 14 in delaying the dissolution of non-aqueous-based drilling fluid mud cake in a reservoir.

18. The use according to claim 17, characterized in that The reservoir has an operating temperature not exceeding 100°C and a density of the used / workover fluid not exceeding 1.3 g / cm 3 of the reservoir.

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