Cleanable rinsing fluid suitable for pressure water testing, its preparation method and application

Abstract

This invention discloses a removable flushing fluid suitable for water pressure testing, its preparation method, and its application, belonging to the field of drilling flushing fluid technology. To resolve the contradiction between drilling safety and downhole testing, this invention provides a removable flushing fluid suitable for water pressure testing, comprising: 3-5% calcium carbonate powder, 0.2-0.4% sodium carbonate, 0.15-0.21% xanthan gum, 0.15-0.21% konjac gum, 0.5-1.6% potassium humate, 0.70-1.25% low-viscosity hydroxyethyl cellulose, and 100% water. The flushing fluid of this invention features excellent performance of the compounded viscosity improver, reducing dosage and cost; it also exhibits excellent and stable rheological properties, effectively decomposing the mud cake formed on the wellbore under acidic cleaning agents, enabling accurate formation parameters to be measured in water pressure testing. Furthermore, the fluid effectively breaks down the mud cake under the action of acidic cleaning agents, reducing viscosity and facilitating drainage and subsequent treatment.

Description

Technical Field

[0001] This invention relates to the field of drilling flushing fluid technology, and in particular to a removable flushing fluid suitable for water pressure testing, its preparation method, and its application. Background Technology

[0002] In recent years, the demand for geological exploration in water conservancy and hydropower projects has been increasing. In these explorations, conducting necessary well-drilling tests is a crucial method for obtaining the engineering characteristics of the surrounding rock. Well pressure testing is one of the common well-drilling tests in water conservancy and hydropower project exploration. However, due to frequent tripping of drilling tools, short pure drilling time, and long auxiliary time, there is a practical problem that testing efficiency decreases with deeper drilling. In the complex environment of deep well drilling, conventional flushing fluids (such as ordinary bentonite mud, water, or low-solids polymer mud) exhibit significant performance defects, such as high-temperature failure, insufficient lubrication, difficulty in solid phase control, and poor wall protection. Mud-based flushing fluids can physically block the wellbore, severely interfering with well-drilling tests. Flushing fluids prepared with bentonite can form a mud cake of considerable strength on the borehole wall, sealing fractures and affecting the formation permeability measured by the pressure test. This necessitates numerous and cumbersome well-washing procedures, severely impacting project progress. Therefore, how to enhance the performance of the flushing fluid while making it easy to remove from the well, and create a clean and accurate well environment for the water pressure test, is one of the important issues of concern in the field of water conservancy and hydropower engineering survey.

[0003] Currently, many biodegradable flushing fluid systems focus on the fluid's biodegradability, highlighting its excellent biodegradability and resolving the conflict between drilling safety and downhole testing. These systems also utilize a large amount of biodegradable materials, making them environmentally friendly. However, in the water conservancy and hydropower industry, particularly in downhole testing, how to utilize biodegradable flushing fluid materials to ensure both drilling safety and good cleanability remains an engineering challenge.

[0004] CN109796947A discloses a drilling flushing fluid with excellent anti-collapse performance, comprising the following raw materials in parts by weight: per cubic meter of water: 12.5-50 kg of matrix, 0.8-1.2 kg of alkali, 1.8-2.2 kg of thickener, 0.4-0.6 kg of inhibitor, 5-15 kg of water loss reducing agent, and 1.2-1.8 kg of liquid lubricant, wherein the matrix is ​​selected from bentonite and / or calcium carbonate, the alkali is sodium hydroxide, the thickener is carboxymethyl cellulose, the inhibitor is potassium polyacrylate, and the water loss reducing agent is selected from one or more of sulfonated lignite resin, sulfonated asphalt powder, and potassium humate. This method, through the rational selection of basic materials and the optimized design of the proportions, achieves flushing fluid parameters that meet ideal standards, such as density, viscosity, water loss, mud cake thickness, and colloid content. Optimization effectively reduces the continuous infiltration of free water into the borehole wall and ensures that the fluid column pressure within the borehole consistently exceeds the formation collapse pressure, resulting in excellent anti-collapse performance. It is particularly suitable for application in borehole wall collapse formations in the Muli coalfield of Qinghai Province, effectively preventing borehole wall instability and reducing the incidence of drilling accidents in the Muli coalfield. Of course, it can also be applied to other situations where existing anti-collapse drilling flushing fluids are ineffective in preventing collapse.

[0005] CN110343513B discloses a flushing fluid comprising: a diluent and a cleaning agent in a mass ratio of 75–95:18–24; the diluent comprising: water, sulfonated tannin, sodium hexametaphosphate, and hydroxyethyl cellulose in a mass ratio of 75–85:8–12:6–10:1–4; the cleaning agent comprising: ethylene glycol, fatty alcohol polyoxyethylene ether, and octylphenol polyoxyethylene ether in a mass ratio of 65–75:15–25:5–15. This method uses sulfonated tannin, sodium hexametaphosphate, and hydroxyethyl cellulose to prepare the diluent. The diluent and cleaning agent work synergistically to dilute the flushing fluid in its mixture with drilling fluid and / or cement slurry, effectively preventing the mixing of cement slurry and drilling fluid, avoiding cement slurry flocculation, shortening thickening time, and ensuring good rheological properties in the mixed section. The cleaning agent is prepared by compounding ethylene glycol, fatty alcohol polyoxyethylene ether, and octylphenol polyoxyethylene ether. The cleaning agent and diluent work synergistically to effectively flush the drilling fluid, casing, and annulus of the well wall, thus ensuring the quality of deepwater cementing.

[0006] CN101935519B discloses a drilling fluid with the following composition: N ml of water, where N is a positive number; 0.002N to 0.005N g of anhydrous sodium carbonate; 0.04N g of drilling fluid bentonite; 0.003N to 0.006N g of coating agent; 0.015N to 0.02N g of viscosifier; 0.01N to 0.02N g of filtration reducer; 0.015N to 0.03N g of anti-collapse agent; 0.02N to 0.03N g of lubricant; 0.01N to 0.015N g of dispersant; 0.05N to 0.08N g of rigid crosslinker; and 0.08N to 0.15N g of rigid filler; wherein the coating agent... The coating agents are natural polymer coating agent IND30, high-viscosity polyanionic cellulose PAC-HV, acrylic multi-component copolymer HXB, potassium polyacrylate K-PAM, and acrylamide multi-component copolymer Coater-10; the thickeners are high-viscosity carboxymethyl cellulose CMC-HV, biopolymer XC, biopolymer graft modified GEL30, hydroxyethyl cellulose HEC, and biopolymer copolymer HF-1; the filtration loss reducers are medium-viscosity carboxymethyl cellulose CMC-MV, low-viscosity carboxymethyl cellulose CMC-LV, carboxymethyl starch CMS, sulfomethylphenolic resin SMP, potassium humate OSAM-K, and acrylonitrile copolymer JHG-1. This drilling fluid is suitable for complex formations and also has anti-collapse and anti-leakage functions, and it has an anti-collapse effect on easily dispersed and easily collapsed formations.

[0007] However, the above methods are difficult to resolve the contradiction between drilling safety and downhole testing in the water conservancy and hydropower industry, especially in the downhole testing industry. Therefore, it is necessary to develop a new type of flushing fluid that can balance the performance requirements of water pressure testing and the biodegradability of geological testing. Summary of the Invention

[0008] In view of the deficiencies of the prior art, the present invention provides a removable rinsing fluid suitable for pressure water testing, which can effectively solve the problems existing in the prior art.

[0009] To achieve the above-mentioned objectives, in a first aspect, the present invention provides a removable rinsing solution suitable for pressure water testing, comprising the following raw materials in the indicated mass percentages: 3-5% calcium carbonate powder, 0.2-0.4% sodium carbonate, 0.15-0.21% xanthan gum, 0.15-0.21% konjac gum, 0.5-1.6% potassium humate, 0.70-1.25% low-viscosity hydroxyethyl cellulose, and 100% water.

[0010] In the above-mentioned removable rinsing solution, the mass ratio of xanthan gum to konjac gum is 1±0.1:1±0.1.

[0011] The aforementioned removable rinsing solution contains 4% calcium carbonate powder.

[0012] The aforementioned removable rinsing solution contains 0.3% sodium carbonate.

[0013] The aforementioned removable rinsing solution contains 0.2% xanthan gum.

[0014] In the above-mentioned removable rinsing solution, 0.2% konjac gum is contained.

[0015] The aforementioned removable rinsing solution contains 1.5% potassium humate.

[0016] The aforementioned removable rinsing solution contains 0.75% low-viscosity hydroxyethyl cellulose.

[0017] In the above-mentioned removable rinsing solution, the particle size of calcium carbonate powder is 200~800 mesh.

[0018] In the above-mentioned removable rinsing solution, the viscosity of low-viscosity hydroxyethyl cellulose is 16~20 mPa·s (apparent viscosity measured at 1% dosage).

[0019] Secondly, the present invention also provides a method for preparing the above-mentioned removable rinsing solution suitable for pressure water testing, which includes the following steps: according to the formula, xanthan gum, konjac gum, calcium carbonate powder, sodium carbonate, potassium humate, and low-viscosity hydroxyethyl cellulose are added to water sequentially while stirring, and stirring is continued until the mixture is uniform to obtain the rinsing solution. A more preferred preparation method is: strictly following the order of xanthan gum, konjac gum, calcium carbonate powder, sodium carbonate, potassium humate, and low-viscosity hydroxyethyl cellulose, water is added slowly in sequence, and after each material is added to the water, it is thoroughly circulated, stirred, and dissolved before adding the next material.

[0020] In the above preparation method, the stirring speed is 800~1200 r / min.

[0021] In the above preparation method, the stirring time is 0.5~2h.

[0022] Thirdly, the present invention also provides the application of the above-mentioned removable flushing fluid suitable for pressure water testing in the construction of pressure water test holes in the water conservancy industry.

[0023] Fourthly, the present invention also provides a cleaning method for the above-mentioned removable flushing fluid suitable for water pressure testing, which includes the following steps: pumping the above-mentioned flushing fluid into the well to complete the drilling process, then pumping the acidic cleaning agent into the formation in a positive circulation manner to shut off the well and wait for the reaction, after the reaction is completed, using water to push out the residual liquid, and then flushing with water until the return water after well washing is clean, colorless and transparent, and free of visible mud, rock powder and other construction residues.

[0024] In the above cleaning method, the acidic cleaning agent is a conventional acidic cleaning agent in the art, and its formulation can be a mixed aqueous solution of 1~10wt% hydrochloric acid and 0.3~1.5wt% water-soluble imidazoline, or an aqueous solution of 1~15wt% hydrochloric acid.

[0025] In the above cleaning method, the reaction time is 12-24 hours.

[0026] The beneficial effects of this invention are: The raw materials for the flushing fluid of this invention are readily available, and the preparation process is simple and quick. The formulation materials have low environmental pollution and are environmentally friendly. The compounded thickener has excellent performance, which can reduce the amount used and reduce costs. The flushing fluid has excellent and stable performance and a wide range of applications. The mud cake formed by the flushing fluid on the well wall can be effectively decomposed under the cleaning of acidic cleaning agents, so that the water pressure test can measure the true formation parameters, which solves the contradiction between drilling safety and downhole testing. At the same time, the viscosity of the flushing fluid can be effectively reduced under the action of acidic cleaning agents, which is conducive to discharge and subsequent treatment. Attached Figure Description

[0027] Figure 1 This is a graph showing the effect of the viscosity-enhancing agent compounding ratio on the viscosity of the rinsing fluid in Example 2 of the present invention.

[0028] Figure 2 This is a graph showing the effect of different pH values ​​on the viscosity of the rinsing solution in Example 2 of the present invention.

[0029] Figure 3 This is a comparison chart of the stability of rinsing solutions with different thickeners in Example 2 of the present invention.

[0030] Figure 4 This is a graph showing the decomposition effect of rinsing solution on mud skin under different concentrations of hydrochloric acid aqueous solution in Example 5 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the following embodiments are provided to further illustrate this invention in detail.

[0032] Example

[0033] To screen for easily cleanable matrices for rinsing solutions, the experiment included the following materials: calcite powder (200-800 mesh), iron ore powder (200-800 mesh), walnut shell powder (200-800 mesh), modified lignin fiber, calcium carbonate powder (200-800 mesh), and a 15% hydrochloric acid aqueous solution.

[0034] Weigh each dried solid sample m0 and place it in a beaker. Add 50 mL of 15% hydrochloric acid aqueous solution, cover, and place in an 80℃ constant temperature water bath for 2 hours to dissolve. Then transfer to a Buchner funnel to filter the acid residue. Weigh the filter paper m2, dry it, cool it, and weigh it m1. The acid solubility calculation results are shown in Table 1.

[0035] Table 1 shows that calcite powder, iron ore powder, and calcium carbonate powder have excellent acid solubility, with an acid solubility rate of over 90%. Walnut shell powder and modified lignocellulose, however, have poor solubility, only around 40%. To improve the cleaning effect of mud on acidic cleaning agents such as hydrochloric acid, calcium carbonate powder was selected as the matrix for the rinsing solution based on a comparison of decomposition rates.

[0036] For water pressure test wells, the use of wall-protecting materials such as mud that may form a mud film on the well wall or block rock fissures should be strictly prohibited. This is because if fissures are blocked, the water pressure test results will not accurately reflect the formation's permeability. Using bentonite to prepare flushing fluid will form a mud cake of a certain strength on the well wall, blocking fissures and affecting the formation permeability measured by the water pressure test. This mud cake cannot be effectively removed by acidic cleaning agents. However, the "mud cake" formed by flushing fluid prepared with calcium carbonate can be effectively removed by acidic cleaning agents, reducing the error in the water pressure test results caused by mud cake blocking formation fissures.

[0037] Table 1. Decomposition rate of the rinsing fluid matrix

[0038] Example 2 The thickener was modified by compounding. The experiment included the following materials: water, xanthan gum (XC), konjac gum (KGM), sodium carboxymethyl cellulose (CMC), and calcium carbonate powder (200~800 mesh).

[0039] Xanthan gum (XC) + konjac gum (KGM): The dosage was 0.6% of the water weight. This study investigated the effects of different proportions of xanthan gum and konjac gum at a 0.6% dosage. Konjac gum and xanthan gum were added sequentially to 1000g of tap water according to the experimental design. The mixture was then stirred at 1000.0 r / min for 1h to obtain a rinsing solution sample (without calcium carbonate powder). Simultaneously, xanthan gum and konjac gum solutions (without calcium carbonate powder) were prepared separately according to the compounding ratio. The sum of their apparent viscosity and plastic viscosity was calculated and compared with the corresponding compounded solution. The superimposed viscosity was the sum of the viscosities of the solutions prepared individually at that ratio, and the compounded viscosity was the viscosity of the compounded solution at that ratio. This study investigated the thickening effect of the compounding of xanthan gum and konjac gum. The results are as follows: Figure 1 As shown.

[0040] Depend on Figure 1It can be seen that the viscosity of the compounded solutions with different proportions increased compared to the original solutions, indicating that xanthan gum and konjac gum have a good synergistic thickening effect. The thickening effect was most significant when the compounding ratio of xanthan gum and konjac gum was 3:3, or 1:1. The apparent viscosity of the compounded solution increased by 671% compared to the sum of the apparent viscosity before compounding, and the plastic viscosity of the compounded solution increased by 475% compared to the sum of the plastic viscosity before compounding. This compounding ratio was subsequently selected as the thickening agent compounding ratio for the subsequent rinsing solution.

[0041] A rinsing solution sample (without calcium carbonate powder) was prepared by adding xanthan gum (XC) and konjac gum (KGM) at a ratio of 0.4% of water weight in a 1:1 ratio. The pH value was approximately 8 at this stage. The pH was adjusted by adding hydrochloric acid or sodium carbonate solution dropwise using a dropper, and the pH value was measured using pH paper. The experiment showed that this rinsing solution system exhibited excellent acid-induced gum-breaking properties and excellent system stability. The results are as follows: Figure 2 As shown. By Figure 2 It is known that the viscosity of the flushing fluid reaches its maximum at a pH of 6. As the pH decreases, the viscosity drops rapidly. When the pH is around 3, the flushing fluid has completely broken down, and the viscosity no longer decreases. The flushing fluid after breaking down has better flow properties, which can significantly reduce the pressure and energy consumption of well washing, facilitate efficient well washing in one go, facilitate the discharge of flushing fluid, and simplify the well washing process.

[0042] Unlike bentonite, the calcium carbonate matrix selected in Example 1 cannot form a stable colloid in water. Calcium carbonate precipitates rapidly in the rinsing solution and is completely precipitated after standing for 24 hours. To visually evaluate the stability of the rinsing solution, rinsing solution samples prepared with different concentrations of carboxymethyl cellulose and compound thickener were left to stand for 24 hours, and their colloid content, precipitation, and supernatant were analyzed. The results are as follows: Figure 3 As shown. By Figure 3 It can be seen that the rinsing solutions of different concentrations of compound thickeners all have excellent system stability. There is no obvious precipitation at the bottom of the sample and no obvious clear liquid at the top. The colloidal rate is above 95%. However, the rinsing solutions of different concentrations of carboxymethyl cellulose (CMC) all have obvious precipitation at the bottom and obvious clear liquid at the top. This will seriously damage the rinsing solution system, leading to a decrease in the performance of the rinsing solution or even the complete failure of the rinsing solution.

[0043] Figure 3In the experiment, the formulations of samples 1-3 (from left to right) were: water + 4% calcium carbonate powder (200-800 mesh) + 0.2-0.4% carboxymethyl cellulose (CMC); the formulation of sample 4 was: water + 4% calcium carbonate powder (200-800 mesh); and the formulations of samples 5-7 (from left to right) were: water + 4% calcium carbonate powder (200-800 mesh) + 0.2-0.4% compound thickener (xanthan gum: konjac gum = 1:1). The preparation method was to add carboxymethyl cellulose (CMC) or compound thickener and 4% calcium carbonate powder (200-800 mesh) to 1000g of tap water according to the experimental design, and then stir the mixed solution at 1000.0 r / min for 1h to obtain the rinsing solution sample.

[0044] To investigate the optimal dosage range of the thickener in the rinsing solution, 0.1-0.6% of the compound thickener (xanthan gum: konjac gum = 1:1) was added to 1000g of tap water according to the experimental design. The mixture was then stirred at 1000.0 r / min for 1h to obtain rinsing solution samples. The viscosity and filtration loss of each sample were then measured. The experimental results are shown in Table 2.

[0045] Table 2. Effect of compound thickeners on the performance of flushing fluids

[0046] The experimental results show that the viscosity and dynamic shear force of the flushing fluid at a dosage of 0.1% dosing dosing dosing do not meet the performance requirements. At dosages of 0.5% and 0.6%, the viscosity and dynamic shear force of the flushing fluid are too high, increasing flow resistance and pump pressure, severely affecting drilling speed. The optimal dosage range for the compounded viscosity modifier is 0.2% to 0.4% of the water dosage, within which suitable viscosity, dynamic shear force, and dynamic plasticity ratio are achieved.

[0047] The xanthan gum-konjac gum compound modified rinsing solution has a higher viscosity than traditional rinsing solutions. It can achieve the required rinsing solution viscosity with a lower dosage, saving a lot of costs. At the same time, the modified rinsing solution has excellent acid-induced gum breaking performance and system stability, which are not found in traditional rinsing solutions, and can meet the requirements for easy cleaning performance of rinsing solutions.

[0048] Example 3

[0049] The following materials were used to screen filtrate loss reducers for the rinsing solution: water, xanthan gum (XC), konjac gum (KGM), calcium carbonate powder (200-800 mesh), sodium carboxymethyl cellulose (CMC), low-viscosity hydroxyethyl cellulose (HEC), potassium humate (KHM), sulfonated asphalt, sodium carboxymethyl starch (CMS-Na), and low-viscosity polyanionic cellulose (PAC-LV). The viscosity of low-viscosity hydroxyethyl cellulose (HEC) was 16-20 mPa·s (apparent viscosity measured at 1% dosage), and the viscosity of low-viscosity polyanionic cellulose (PAC-LV) was 12-15 mPa·s (apparent viscosity measured at 1% dosage).

[0050] Xanthan gum (XC): 0.15% of water weight; Konjac gum (KGM): 0.15% of water weight; Calcium carbonate powder (200-800 mesh): 4% of water weight; Filtration loss reducers: Sodium carboxymethyl cellulose (CMC), low-viscosity hydroxyethyl cellulose (HEC), potassium humate (KHM), sulfonated asphalt, sodium carboxymethyl starch (CMS-Na), and low-viscosity polyanionic cellulose (PAC-LV): 1% of water weight. To investigate the filtration loss reduction effect of various filtration loss reducers at a 1% dosage, xanthan gum, konjac gum, calcium carbonate powder, and filtration loss reducers were added sequentially to 1000g of tap water according to the experimental design. The mixture was then stirred at 1000.0 r / min for 1h to obtain rinsing solution samples. The viscosity, dynamic plasticity ratio, and filtration loss of each sample were measured. The experimental results are shown in Table 3.

[0051] Table 3 shows that among the non-viscosity-enhancing filtration loss reducers, potassium humate exhibits the best filtration loss reduction effect and excellent dynamic-to-plasticity ratio. Among the viscosity-enhancing filtration loss reducers, low-viscosity hydroxyethyl cellulose (HHFC) shows the best filtration loss reduction effect, significantly reducing filtration loss while also possessing good dynamic shear strength. Compared to low-viscosity polyanionic fibers, HHFC offers superior filtration loss reduction without significantly increasing viscosity, as excessive viscosity can degrade the performance of the rinsing fluid. Therefore, potassium humate and low-viscosity hydroxyethyl cellulose (HHFC) were selected as the filtration loss reduction materials for subsequent formulation optimization.

[0052] Table 3 Performance of different types of filtration loss reducers

[0053] To investigate the specific dosage range of potassium humate and low-viscosity hydroxyethyl cellulose, rinsing solution samples were prepared under different dosage conditions, and the performance of each sample was measured. The results are shown in Tables 4 and 5.

[0054] Table 4. Effects of different amounts of low-viscosity hydroxyethyl cellulose on the performance of the rinsing solution.

[0055] As shown in Table 4, with the increase of low-viscosity hydroxyethyl cellulose, the viscosity, dynamic plasticity ratio and dynamic shear force of the rinsing solution all increase to varying degrees, while the filtration loss decreases; however, excessive addition will cause a significant increase in viscosity and dynamic shear force, exceeding the suitable range; the optimal addition range of low-viscosity hydroxyethyl cellulose is 0.55~1.25%.

[0056] Table 5. Effects of different amounts of potassium humate on the performance of the rinsing solution.

[0057] As shown in Table 5, the optimal dosage range of potassium humate is 0.5-1.5%. Within this range, potassium humate has a good effect on reducing filtration loss and has an excellent dynamic-to-plastic ratio. When the dosage range exceeds 1.5%, its effect on reducing filtration loss reaches the boundary value. With the increase of dosage, the filtration loss increases instead of decreasing.

[0058] Example 4

[0059] The optimization of the rinsing solution formulation involved the following materials: water, xanthan gum (XC), konjac gum (KGM), calcium carbonate powder (200-800 mesh), anhydrous sodium carbonate (Na2CO3), potassium humate (KHM), and low-viscosity hydroxyethyl cellulose (HEC).

[0060] Xanthan gum (XC): 0.1-0.2% of water by weight; Konjac gum (KGM): 0.1-0.2% of water by weight; Calcium carbonate powder (200-800 mesh): 4% of water by weight; Anhydrous sodium carbonate (Na2CO3): 0.3% of water by weight; Potassium humate (KHM): 0.5-1.5% of water by weight; Low-viscosity carboxyhydroxyethyl cellulose (HEC): 0.5-1.5% of water by weight.

[0061] The preferred materials in Examples 1, 2, and 3, as well as the dosage range of the thickener and filtration loss reducer, were subjected to a three-factor, three-level orthogonal experiment, as shown in Table 6.

[0062] Xanthan gum, konjac gum, calcium carbonate powder and other reagents were added to 1000g of tap water in sequence according to the experimental design. The mixture was then stirred at 1000.0 r / min for 1h to obtain the rinsing solution sample. The viscosity, dynamic plasticity ratio and filtration loss of each sample were measured.

[0063] Table 6 Orthogonal Experimental Formulation

[0064] The performance of each formulation of the rinsing solution sample is shown in Table 7.

[0065] Table 7 Performance of each formulation in the orthogonal experiment

[0066] By analyzing the results of the orthogonal experiment, and using appropriate apparent viscosity, dynamic plasticity ratio, dynamic shear force, and maximum API filtration loss as evaluation indicators, a range analysis was conducted on the experimental results to obtain the optimal flushing solution formula: water + 0.2% xanthan gum + 0.2% konjac gum + 4% calcium carbonate + 0.3% anhydrous sodium carbonate + 1.5% potassium humate + 0.75% low-viscosity hydroxyethyl cellulose.

[0067] Water pressure testing is primarily applicable to rock formations. Generally, to stabilize the wellbore, API filtration loss must be controlled below 15 ml. The flushing fluid must possess excellent rheological properties to ensure good rock-carrying capacity and shear dilution performance, with dynamic shear stress controlled within the range of 10-15 Pa. It should also have a high dynamic-to-plastic ratio, and its plastic viscosity should be controlled within the range of 10-20 mPa·s. Formulas 1 and 2 have lower viscosity and higher filtration loss, indicating that 0.2% of the compound viscosifier cannot meet the viscosity requirements of the flushing fluid. Formulas 3, 5, and 7 have higher dynamic shear stress, which will lead to abnormal increases in pump pressure and decreases in drilling speed. This indicates that the addition of 1.5% low-viscosity hydroxyethyl cellulose is too high. Controlling the addition of hydroxyethyl cellulose within the range of 0.75-1.25% will meet the performance requirements.

[0068] The performance of the above-mentioned optimal flushing solution formulation is shown in Table 8.

[0069] Table 8 Performance of the Optimal Formulation

[0070] Example 5 To analyze the decomposition effect of the rinsing solution on mud skin, the experiment included the following materials: water, xanthan gum (XC), konjac gum (KGM), calcium carbonate powder (200~800 mesh), anhydrous sodium carbonate (Na2CO3), potassium humate (KHM), low-viscosity hydroxyethyl cellulose (HEC), and hydrochloric acid aqueous solutions of different concentrations.

[0071] Xanthan gum (XC): 0.2% by weight of water; Konjac gum (KGM): 0.2% by weight of water; Calcium carbonate powder (200~800 mesh): 4% by weight of water; Anhydrous sodium carbonate (Na2CO3): 0.3% by weight of water; Potassium humate (KHM): 1.5% by weight of water; Low-viscosity hydroxyethyl cellulose (HEC): 0.75% by weight of water; Hydrochloric acid aqueous solution: hydrochloric acid mass concentration of 1%, 5%, 10%; Distilled water.

[0072] First, the solution was stirred at 1000.0 r / min for 1 hour according to the above formula to obtain a rinsing fluid sample. This sample was then filtered for 7.5 minutes using a medium-pressure filter under standard atmospheric pressure (0.69 MPa), and a mud cake was obtained from the rinsing fluid sample on slow-speed filter paper. The obtained mud cake and filter paper were placed in a constant-temperature drying oven and dried at 75℃ for 4 hours. The dried mud cake and filter paper were then weighed to obtain their dry mass m1. Next, the dried mud cake and filter paper were placed in an acid solution of a specific concentration for degradation. After a specific reaction time, they were placed back in the drying oven and dried under the same conditions to obtain their dry mass m2. Because the filter paper hardly decomposes under acidic conditions, its dry mass m0 also needs to be measured. The decomposition rate η of the mud cake at this concentration and time can then be obtained using the formula. By adjusting the concentration of the cleaning agent and the reaction time, the decomposition rate under different conditions can be obtained.

[0073] The following experiment investigated the effect of different concentrations of hydrochloric acid aqueous solutions on mud skin decomposition. The results are as follows: Figure 4 As shown.

[0074] analyze Figure 4 The following conclusions can be drawn: (1) The decomposition of mud skin in 1% hydrochloric acid was measured from 1 to 24 hours. It can be seen that the decomposition degree of mud skin was about 40% in the first 4 hours, 80% after 8 hours, and 90% after 24 hours; (2) Under higher concentrations of hydrochloric acid, the decomposition rate of mud skin is faster. The decomposition rate is faster at the beginning, but the decomposition rate gradually slows down after 8 hours. The final decomposition degree is not much different. The decomposition degree is basically the same after 24 hours. In practical applications, the concentration of cleaning agents such as hydrochloric acid can be adjusted according to actual needs to control the decomposition rate of mud skin; (3) Mud skin also has a certain degree of decomposition in clean water. The reason is that long-term soaking causes the mud skin to lose some strength, resulting in the shedding of some solid substances in the mud skin.

[0075] As can be seen from the five embodiments, the various properties of the flushing fluid system of the present invention and the influence of different materials on the flushing fluid performance can be adjusted by selecting appropriate dosages for different application environments and usage requirements to meet the needs of actual engineering.

Claims

1. A removable rinsing solution suitable for pressure water testing, characterized in that: The raw materials include the following components by weight: 3-5% calcium carbonate powder, 0.2-0.4% sodium carbonate, 0.15-0.21% xanthan gum, 0.15-0.21% konjac gum, 0.5-1.6% potassium humate, 0.70-1.25% low-viscosity hydroxyethyl cellulose, and 100% water.

2. The washable rinsing solution suitable for pressure water testing according to claim 1, characterized in that: The mass ratio of xanthan gum to konjac gum was 1±0.1:1±0.

1.

3. The removable rinsing solution suitable for pressure water testing according to claim 1, characterized in that: At least one of the following must be met: Calcium carbonate powder 4%; Sodium carbonate 0.3%; Xanthan gum 0.2%; Konjac gum 0.2%; Potassium humate 1.5%; Low-viscosity hydroxyethyl cellulose 0.75%.

4. The removable rinsing solution suitable for pressure water testing according to claim 1, characterized in that: The particle size of calcium carbonate powder is 200~800 mesh.

5. The removable rinsing solution suitable for pressure water testing according to claim 1, characterized in that: The viscosity of low-viscosity hydroxyethyl cellulose is 16~20 mPa·s.

6. The method for preparing the washable rinsing solution suitable for pressure water testing according to any one of claims 1 to 5, characterized in that: The process includes the following steps: According to the specified ratio, xanthan gum, konjac gum, calcium carbonate powder, sodium carbonate, potassium humate, and low-viscosity hydroxyethyl cellulose are added to water in sequence while stirring, and stirring is continued until the mixture is uniform to obtain the rinsing solution.

7. The preparation method according to claim 6, characterized in that: At least one of the following must be met: The stirring speed is 800~1200 r / min; Continue stirring for 0.5 to 2 hours.

8. The application of the washable flushing fluid for pressure testing as described in any one of claims 1 to 5 in the construction of pressure test holes in the water conservancy industry.

9. The cleaning method of the washable rinsing solution suitable for pressure water testing according to any one of claims 1 to 5, characterized in that: Includes the following steps: The flushing fluid described in any one of claims 1 to 5 is pumped into the well to complete the drilling process. Then, the acidic cleaning agent is pumped to the formation in a positive circulation manner, the well is shut off, and the well is sealed to wait for the reaction. After the reaction is completed, the residual liquid is pushed out with water, and then flushed with water until the return water after well washing is clean, colorless and transparent, and free of visible mud, rock powder and other construction residues.

10. The cleaning method according to claim 9, characterized in that: At least one of the following must be met: The acidic cleaning agent is formulated as a mixed aqueous solution of 1-10 wt% hydrochloric acid and 0.3-1.5 wt% water-soluble imidazoline, or an aqueous solution of 1-15 wt% hydrochloric acid. The reaction time is 12-24 hours.

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