Deep shale gas coiled tubing drilling and grinding fluid and preparation method thereof

Abstract

The invention provides a deep shale gas coiled tubing drilling and grinding fluid and a preparation method thereof, and the preparation method of the deep shale gas coiled tubing drilling and grinding fluid comprises the following steps: in a stirring state, adding an iron ion shielding agent into liquid preparation water; and adding a salt-resistant resistance-reducing agent to prepare the drilling and grinding fluid for the deep shale gas coiled tubing. The deep shale gas coiled tubing drilling and grinding fluid can be prepared through the preparation method of the deep shale gas coiled tubing drilling and grinding fluid, the liquid resistance reduction rate of the deep shale gas coiled tubing drilling and grinding fluid is larger than 70%, and the viscosity retention rate is larger than 45% after continuous shearing is conducted for 5 h at the temperature of 90 DEG C and the speed of 100 s <-1 >. The method has the beneficial effects that research is carried out aiming at the problems that the water for preparing the deep shale gas drilling and grinding fluid is complex in water quality and composition, high in reservoir temperature and the like, and the production problem that the deep shale gas drilling and grinding fluid is easy to lose efficacy is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coiled tubing drilling and grinding fluid in oil and gas field development stimulation, in particular, relates to a deep shale gas coiled tubing drilling and grinding fluid and a preparation method thereof. BACKGROUND

[0002] Bridge plug staged fracturing process is often used in oil and gas well stimulation, and when the fracturing operation is completed, coiled tubing drilling is used to remove the bridge plug to quickly restore the production channel of the wellbore. The coiled tubing drilling and grinding fluid at home and abroad mainly uses slickwater system, which has certain viscosity, good drag reduction rate and other properties, and meets the requirements of reducing pump pressure and carrying drill cuttings. Restricted by production cost, the drilling and grinding fluid for Sichuan and Chongqing shale gas usually uses fracturing flowback fluid, which is prepared under the condition of long time and high temperature, and is repeatedly used in circulation. The performance of the drilling and grinding fluid is unstable, which greatly increases the operation risk. Especially in deep shale gas operation, the performance of the drilling and grinding fluid fails frequently, and the most direct performance is that the viscosity of the liquid is greatly reduced or even lost, and even if the drag reduction agent is added, the effect is not satisfactory, which affects the drilling and grinding operation efficiency.

[0003] In view of the problem of failure of deep shale gas drilling and grinding fluid, the project team carried out water sample detection on 18 water samples of 5 well times of failure, and the results showed that the mineralization of 70% of the water samples was more than 20 g / L, and the total iron content of 60% of the water samples was more than 10 mg / L (characteristics of failed drilling and grinding fluid). The reasons for the failure of the working fluid are as follows: the water quality of the drilling and grinding fluid preparation liquid is complex (mineralization > 20 g / L, total iron content > 10 mg / L), the drilling and grinding continuous operation time is long, the working fluid is repeatedly used in circulation, and is affected by the steel corrosion products of surface equipment, drilling tools and pipe column and reservoir minerals, which significantly increases the total mineralization, calcium and magnesium ion content and iron ion content of the working fluid; the temperature of deep shale gas operation is high (the reservoir temperature is as high as 150℃, and the continuous oil pipe drilling and grinding operation temperature is > 70℃), which accelerates the failure of the working fluid. After multiple cycles, the water quality of the drilling and grinding fluid may be worse than that of the fracturing flowback fluid. Therefore, it is of great significance to provide a deep shale gas coiled tubing drilling and grinding fluid and a preparation method thereof.

[0004] A drilling and grinding fluid tackifier and a preparation method thereof are disclosed in a Chinese patent with the application number "CN202111266996.7" and the title "Drilling and grinding fluid tackifier and preparation method thereof". The raw materials of the drilling and grinding fluid tackifier include alkenyl sulfonic acid, alkenyl alkyl ketone and alkenyl quaternary ammonium salt, which are obtained by the following method: stirring the required amount of alkenyl sulfonic acid, alkenyl alkyl ketone, alkenyl quaternary ammonium salt and solvent uniformly to obtain a mixture, adjusting the pH of the mixture, passing nitrogen gas to make the mixture in a nitrogen atmosphere, then adding an initiator to the mixture for polymerization reaction, removing the solvent, drying and crushing to obtain the product. The drilling and grinding fluid tackifier can be applied in a drilling and grinding fluid system without bentonite or with low bentonite, and has good compatibility with various treatment agents; it can significantly improve the temperature resistance and rock carrying performance of the drilling and grinding fluid system without bentonite or with low bentonite, and reduce the complex accident rate in drilling and grinding operations.

[0005] A drilling and grinding fluid for long horizontal section wells and its preparation and use method are disclosed in a Chinese patent with the application number "CN202111241700.6" and the title "Drilling and grinding fluid for long horizontal section wells and its preparation and use method". The drilling and grinding fluid for long horizontal section wells is prepared by mixing the following substances in percentage by weight: 50-60% base oil, 15-18% anionic surfactant, 15-20% non-ionic surfactant, 0.01-0.05% thickening agent, 3-5% corrosion inhibitor, 1-3% pH regulator and the balance water. The drilling and grinding fluid can significantly reduce the frictional resistance between the drilling and grinding string and the wellbore, and between the drill bit and the drilling and grinding object, and improve the running efficiency of the string in the horizontal section and the drilling and grinding success rate. During the construction process, the drilling and grinding fluid is diluted into a water solution with a mass concentration of 1-2% for use, the diluted liquid is pumped into the drilling and grinding string by a ground pump set, flows out through the drill bit water eye, carries the cuttings back from the annulus between the wellbore and the drill pipe after drilling and grinding, and is recycled after simple settling and filtration. The drilling and grinding fluid has low cost, wide application range, low corrosion and is convenient to prepare and use on site.

[0006] However, the above existing technologies do not address the complex water quality composition and high reservoir temperature problems of deep shale gas drilling and grinding fluid preparation, to solve the production problem of deep shale gas drilling and grinding fluid failure. SUMMARY

[0007] The present application aims to solve at least one of the above deficiencies in the prior art. For example, one of the objectives of the present application is to provide a deep shale gas coiled tubing drilling and grinding fluid with good salt resistance, which can be used for a long time under high temperature conditions without losing liquid performance, and has stable performance. For another example, another objective of the present application is to provide a preparation method of deep shale gas coiled tubing drilling and grinding fluid, which can be prepared using fracturing flowback fluid and reduces production cost.

[0008] To achieve the above objectives, the present invention provides a method for preparing a deep shale gas coiled tubing drilling fluid. The method may include: adding an iron ion shielding agent to water for fluid preparation under stirring; and then adding an anti-salt drag reducing agent to prepare the deep shale gas coiled tubing drilling fluid.

[0009] According to one or more exemplary embodiments of one aspect of the present invention, in the method, the amount of each raw material used may be: 0.1-0.3% salt-resistant drag-reducing agent, 1-5% iron ion shielding agent and the balance being water for solution preparation, by mass percentage.

[0010] According to one or more exemplary embodiments of one aspect of the present invention, the formulation of the iron ion shielding agent may include: 5-20% tetrasodium glutamate diacetate, 3%-8% polyaspartic acid, 2-5% butane tricarboxylic acid phosphonate, 2-20% ammonium citrate, and the balance being water, by mass percentage.

[0011] According to one or more exemplary embodiments of one aspect of the present invention, the preparation method of the iron ion shielding agent may include: heating water to 30-50°C; adding tetrasodium glutamate diacetate, polyaspartic acid and phosphonate butane tricarboxylic acid sequentially to the water while stirring, stirring for 30-60 min; then adding ammonium citrate, stirring for 15-30 min; and cooling to room temperature to obtain the iron ion shielding agent.

[0012] According to one or more exemplary embodiments of one aspect of the present invention, the water used for preparing the solution may include fracturing flowback fluid.

[0013] According to one or more exemplary embodiments of one aspect of the present invention, the water used for preparing the solution may include brine having a mineralization degree of more than 20 g / L and an iron content of more than 10 mg / L; the method for preparing the water used for preparing the solution may include: adding NaCl and FeCl3 to clean water and stirring until completely dissolved.

[0014] According to one or more exemplary embodiments of one aspect of the present invention, the salt resistance drag reducing agent may include a polyacrylamide drag reducing agent, and the salt resistance of the salt resistance drag reducing agent may be greater than 30,000 mineralization.

[0015] According to one or more exemplary embodiments of one aspect of the present invention, adding an iron ion shielding agent to the water for preparing the solution may include: stirring for 15 to 30 minutes; adding an anti-salt drag reducing agent may include: adding the anti-salt drag reducing agent by suction and stirring for 20 to 40 minutes to prepare a deep shale gas coiled tubing drilling fluid.

[0016] According to one or more exemplary embodiments of one aspect of the present invention, the iron ion shielding agent may be a colorless to pale yellow transparent liquid; the salt resistance reducing agent may be an emulsion or a suspension emulsion; and the deep shale gas coiled tubing drilling fluid may be a colorless or milky white viscous liquid.

[0017] Another aspect of the present invention provides a deep shale gas coiled tubing drilling fluid, which may be prepared by the above-described method for preparing deep shale gas coiled tubing drilling fluid; the fluid drag reduction rate of the deep shale gas coiled tubing drilling fluid may be greater than 70%.

[0018] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0019] (1) The method for preparing drilling fluid for deep shale gas coiled tubing proposed in this invention solves the problem that the drilling fluid for deep shale gas coiled tubing is prepared by using flowback fluid and that the fluid performance fails due to high temperature and long-term circulation.

[0020] (2) The deep shale gas coiled tubing drilling fluid proposed in this invention has good salt resistance and can be prepared by fracturing flowback fluid. At the same time, the drilling fluid has relatively stable performance under high temperature (≥90℃, for example 90~120℃) and long time (≥5h, for example 5~10h) cyclic use, and can meet the requirements of deep shale gas coiled tubing drilling operations.

[0021] (3) The method for preparing drilling fluid for deep shale gas coiled tubing proposed in this invention can directly use high-mineralization flowback fluid to prepare drilling fluid, which addresses the water quality issues of high mineralization and high iron content, while also reducing production costs.

[0022] (4) The iron ion shielding agent used in this invention can effectively chelate the free iron ions in the solution water into the macromolecule, thereby achieving the shielding effect of iron ions, reducing the impact of iron ions on the performance of drilling fluid, and thus effectively ensuring the efficiency of deep shale gas drilling operations. Attached Figure Description

[0023] The above and other objects and features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1 A schematic flow chart of a method for preparing drilling fluid for deep shale gas coiled tubing, according to an exemplary embodiment of the present invention, is shown.

[0025] Figure 2 Examples 1 and 4 of the present invention illustrate the drilling fluid at 90°C for 100 seconds. -1 The results of the temperature and shear resistance test under continuous shearing conditions for 5 hours;

[0026] Figure 3 The drag reduction performance test results of the drilling fluids of Examples 1 to 4 of the present invention are shown;

[0027] Figure 4 The drilling fluid of Example 1 of the present invention is shown at 120°C for 100 seconds. -1 The results of the temperature and shear resistance test under continuous shearing conditions for 5 hours;

[0028] Figure 5 Example 4 of the present invention shows the drilling fluid at 90°C for 100 seconds. -1 The results of the temperature and shear resistance test under continuous shearing conditions for 10 hours. Detailed Implementation

[0029] In the following, a deep shale gas coiled tubing drilling fluid and its preparation method according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0030] In the description of this application, it should be understood that the terms "first" and the like are used merely for convenience of description and distinction, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0031] Exemplary Example 1

[0032] This exemplary embodiment provides a method for preparing drilling fluid for deep shale gas coiled tubing.

[0033] Figure 1 A schematic flow chart illustrating a method for preparing drilling fluid for deep shale gas coiled tubing, according to an exemplary embodiment of the present invention, is shown below. Figure 1 This describes a method for preparing drilling fluid for deep shale gas coiled tubing, as illustrated in this exemplary embodiment.

[0034] like Figure 1 As shown, the preparation method of deep shale gas coiled tubing drilling fluid may include: adding an iron ion shielding agent to the solution preparation water to obtain a first solution; adding an anti-salt drag reducing agent to the first solution to obtain deep shale gas coiled tubing drilling fluid.

[0035] Specifically, the method for preparing the drilling fluid for deep shale gas coiled tubing in this exemplary embodiment may include:

[0036] S1. Add water for solution preparation to the solution preparation tank, turn on the stirrer, and add iron ion shielding agent to the water for solution preparation while stirring. Stir for 15-30 minutes.

[0037] S2. Add an anti-salt drag-reducing agent to the solution obtained in step S1 and stir for 20-40 minutes to prepare a deep shale gas coiled tubing drilling fluid.

[0038] In this exemplary embodiment, the adverse effects of iron ions on the performance of the drilling fluid include: the main drag-reducing agent used in the drilling fluid is a polymer, and the presence of iron ions, especially Fe, in the liquid... 3+It will enhance the intermolecular condensation and dehydration of polymer molecules, and trace amounts of Fe 3+ This can cause polymer molecules to flocculate, significantly reducing the viscosity of the drilling fluid, thereby decreasing its drag-reducing properties and its ability to carry drill cuttings. This invention first adds an iron ion shielding agent, allowing the shielding agent to undergo a complexation reaction with iron ions, encapsulating the iron ions within the shielding agent and transforming them into compounds with larger molecular weights. This prevents the iron ions from flocculating the drag-reducing agent added later. In other words, the iron ion shielding agent can chelate free iron ions in the solution-mixing water within the large molecules (shielding agent), achieving a shielding effect against iron ions and reducing their impact on the drilling fluid's performance.

[0039] In this exemplary embodiment, in step S1, the stirrer is turned on, and the rotation speed can be set to 1000-1500 r / min.

[0040] In this exemplary embodiment, in step S2, the anti-salt drag-reducing agent may be added by suction.

[0041] In this exemplary embodiment, the amount of each raw material used in the preparation method of the deep shale gas coiled tubing drilling fluid can be as follows: by mass percentage, 0.1-0.3% salt resistance agent, 1-5% iron ion shielding agent, and the balance being water for fluid preparation.

[0042] In this exemplary embodiment, in step S1, the formulation of the iron ion shielding agent may include, by mass percentage, 5-20% tetrasodium glutamate diacetate, 3-8% polyaspartic acid, 2-5% butane tricarboxylic acid phosphonate, 2-20% ammonium citrate, and the balance being water.

[0043] Furthermore, the preparation method of the iron ion shielding agent may include: adding water to a reaction vessel, heating to 30-50°C, turning on the stirrer, and while stirring, sequentially adding tetrasodium glutamate diacetate, polyaspartic acid, and phosphonate butane tricarboxylic acid to the water, stirring for 30-60 minutes; then adding ammonium citrate, stirring for 15-30 minutes; and cooling to room temperature to obtain the iron ion shielding agent. Here, the iron ion shielding agent can be a colorless to pale yellow transparent liquid. Changing the order of addition does not alter the structure or effect of the final product. Because ammonium citrate has good solubility in water, adding it last facilitates uniform mixing during the preparation of the iron ion shielding agent, and makes it easier for the various substances to complex with iron ions, achieving synergistic effects and reaching the best results.

[0044] In this exemplary embodiment, in step S1, the water used for preparing the solution may include fracturing flowback fluid (high-mineralization flowback fluid).

[0045] In this exemplary embodiment, in step S1, the water used for preparing the solution may include brine with a mineralization degree > 20 g / L and a total iron content > 10 mg / L. For example, a brine with a mineralization degree of 30,000 ppm and a ferric ion content of 50 ppm. That is, a brine with a mineralization degree of 30 g / L and an iron content of 50 mg / L is used as the water for preparing the solution.

[0046] Furthermore, by adding only NaCl and FeCl3 to clean water, the mineralization and iron ion content of the water used for preparing drilling fluids can be simulated, or even higher, than those in the field. Specifically, the preparation method for the water used for preparing the fluid may include: adding NaCl and FeCl3 to clean water and stirring until completely dissolved. The water quality of this water used for preparing the fluid can be worse than that of the water used for preparing the fluid in the field. Here, there are no special instructions regarding the stirring conditions; stirring until uniform is sufficient. Most of the "water used for preparing the fluid in the field" is initially fracturing flowback fluid, but after repeated drilling operations, the water quality may be worse than that of fracturing flowback fluid; a small portion of the water used for preparing the fluid in the field is not simply fracturing flowback fluid, but may be a mixture of fracturing flowback fluid and drilling waste fluid.

[0047] In this exemplary embodiment, in step S2, the salt-resistant drag-reducing agent may include a polyacrylamide compound, and a polyacrylamide drag-reducing agent with excellent salt resistance may be used. The salt resistance of the salt-resistant drag-reducing agent may be greater than 30,000 salinity. That is, the salt-resistant drag-reducing agent may be a polyacrylamide drag-reducing agent with a salt resistance greater than 30 g / L salinity. Here, the salt-resistant drag-reducing agent may be an emulsion or a suspension emulsion. The salt-resistant drag-reducing agent may be, but is not limited to, purchased from Sichuan Chuanqing Well Technology Co., Ltd.

[0048] Exemplary Example 2

[0049] This exemplary embodiment provides a drilling fluid for deep shale gas coiled tubing.

[0050] Figure 2 Examples 1 and 4 of the present invention illustrate the drilling fluid at 90°C for 100 seconds. -1 The results of the temperature and shear resistance test under continuous shearing conditions for 5 hours; Figure 3 The drag reduction performance test results of the drilling fluids of Examples 1 to 4 of the present invention are shown; Figure 4 The drilling fluid of Example 1 of the present invention is shown at 120°C for 100 seconds. -1 The results of the temperature and shear resistance test under continuous shearing conditions for 5 hours; Figure 5 Example 4 of the present invention shows the drilling fluid at 90°C for 100 seconds. -1 The results of the temperature and shear resistance test after continuous shearing for 10 hours under the specified conditions are as follows. Figures 2 to 5 The drilling fluid for deep shale gas coiled tubing described in this exemplary embodiment.

[0051] The deep shale gas coiled tubing drilling fluid of this exemplary embodiment may include the product prepared by the method for preparing deep shale gas coiled tubing drilling fluid as described in Exemplary Embodiment 1 above.

[0052] The fluid drag reduction rate of the deep shale gas coiled tubing drilling fluid in this exemplary embodiment can be greater than 70%. (At 90°C for 100 seconds...) -1 Under continuous shearing for 5 hours, the viscosity retention rate can be greater than 45%.

[0053] To better understand the exemplary embodiments of the present invention described above, further explanation is provided below with reference to specific examples.

[0054] Example 1

[0055] (1) Preparation of iron ion shielding agent: Weigh 62g water, 5g tetrasodium glutamate diacetate, 8g polyaspartic acid, 5g phosphonate butane tricarboxylic acid, and 20g ammonium citrate for later use.

[0056] Preparation: Add water to a beaker, heat to 35°C, turn on the stirrer, add tetrasodium glutamate diacetate, polyaspartic acid, and phosphonate butane tricarboxylic acid in sequence, stir for 30 minutes, add ammonium citrate, continue stirring for 15 minutes, and cool to room temperature to obtain a colorless and transparent liquid (iron ion shielding agent).

[0057] (2) The salt resistance and drag reduction agent used is SD2-12 produced by Sichuan Chuanqing Well Technology Co., Ltd., which has a salt resistance performance of more than 30,000 mineralization degree.

[0058] (3) Preparation of drilling fluid:

[0059] Preparation of brine (water for solution preparation): Add 485g of water to a beaker, turn on the stirrer, and add 15g of NaCl and 0.025g of FeCl3 at a time. Stir for 15 minutes until the salt is completely dissolved. The salinity of this water for solution preparation is 30g / L, and the iron ion content is 50mg / L. Its water quality performance, particularly its salinity and iron content, is higher than that of the water used for preparing drilling fluid on-site, indicating a worse water quality. The brine samples in Examples 1-5 all meet the following requirements: salinity of 30g / L and iron ion content of 50mg / L.

[0060] Preparation of drilling fluid: Pour 474g of salt water into a beaker, turn on the stirrer, add 25g of the prepared iron ion shielding agent, stir for 15min, and after it is fully dispersed, add 1.5g of salt resistance and drag reduction agent, stir for 20min, and a milky white viscous liquid (drilling fluid) is prepared.

[0061] Example 2

[0062] (1) Preparation of iron ion shielding agent: Weigh 62g water, 15g tetrasodium glutamate diacetate, 5g polyaspartic acid, 3g phosphonate butane tricarboxylic acid, and 15g ammonium citrate for later use.

[0063] Preparation: Add water to a beaker, heat to 40°C, turn on the stirrer, add tetrasodium glutamate diacetate, polyaspartic acid, and phosphonate butane tricarboxylic acid in sequence, stir for 40 minutes, add ammonium citrate, continue stirring for 20 minutes, and cool to room temperature to obtain a colorless and transparent liquid.

[0064] (2) The salt resistance and drag reduction agent used is SD2-12 produced by Sichuan Chuanqing Well Technology Co., Ltd., which has a salt resistance performance of more than 30,000 mineralization degree.

[0065] (3) Preparation of drilling fluid:

[0066] To prepare the salt solution: Add 485g of water to a beaker, turn on the stirrer, add 15g of NaCl and 0.025g of FeCl3 at a time, stir for 15 minutes, and set aside after the salt has completely dissolved.

[0067] Preparation of drilling fluid: Pour 484g of salt water into a beaker, turn on the stirrer, add 15g of the prepared iron ion shielding agent, stir for 15min, and after it is fully dispersed, add 1g of salt resistance reducing agent, stir for 30min, and a milky white viscous liquid is prepared.

[0068] Example 3

[0069] (1) Preparation of iron ion shielding agent: Weigh 47g water, 20g tetrasodium glutamate diacetate, 8g polyaspartic acid, 5g phosphonate butane tricarboxylic acid, and 20g ammonium citrate for later use.

[0070] Preparation: Add water to a beaker, heat to 30°C, turn on the stirrer, add tetrasodium glutamate diacetate, polyaspartic acid, and phosphonate butane tricarboxylic acid in sequence, stir for 30 minutes, add ammonium citrate, continue stirring for 30 minutes, and cool to room temperature to obtain a colorless and transparent liquid.

[0071] (2) The salt resistance and drag reduction agent used is SD2-12 produced by Sichuan Chuanqing Well Technology Co., Ltd., which has a salt resistance performance of more than 30,000 mineralization degree.

[0072] (3) Preparation of drilling fluid:

[0073] To prepare the salt solution: Add 485g of water to a beaker, turn on the stirrer, add 15g of NaCl and 0.025g of FeCl3 at a time, stir for 15 minutes, and set aside after the salt has completely dissolved.

[0074] Preparation of drilling fluid: Pour 495g of salt water into a beaker, turn on the stirrer, add 5g of the prepared iron ion shielding agent, stir for 15min, and after it is fully dispersed, add 0.5g of salt resistance and drag reduction agent, stir for 40min, and a milky white viscous liquid is prepared.

[0075] Example 4

[0076] (1) Preparation of iron ion shielding agent: Weigh 60g water, 20g tetrasodium glutamate diacetate, 8g polyaspartic acid, 2g phosphonate butane tricarboxylic acid, and 10g ammonium citrate for later use.

[0077] Preparation: Add water to a beaker, heat to 50°C, turn on the stirrer, add tetrasodium glutamate diacetate, polyaspartic acid, and phosphonate butane tricarboxylic acid in sequence, stir for 60 minutes, add ammonium citrate, continue stirring for 30 minutes, and cool to room temperature to obtain a colorless and transparent liquid.

[0078] (2) The salt resistance and drag reduction agent used is SD2-12 produced by Sichuan Chuanqing Well Technology Co., Ltd., which has a salt resistance performance of more than 30,000 mineralization degree.

[0079] (3) Preparation of drilling fluid:

[0080] To prepare the salt solution: Add 485g of water to a beaker, turn on the stirrer, add 15g of NaCl and 0.025g of FeCl3 at a time, stir for 15 minutes, and set aside after the salt has completely dissolved.

[0081] Preparation of drilling fluid: Pour 484g of salt water into a beaker, turn on the stirrer, add 10g of the prepared iron ion shielding agent, stir for 15min, and after it is fully dispersed, add 1g of salt resistance reducing agent, stir for 40min, and a milky white viscous liquid is prepared.

[0082] If the amounts of the formulation substances included in Examples 1 to 4 of this invention are expressed as mass percentages, then:

[0083] Example 1:

[0084] Iron ion shielding agent formula: 5% tetrasodium glutamate diacetate + 8% polyaspartic acid + 5% butane phosphonate tricarboxylic acid + 20% ammonium citrate + water.

[0085] Drilling fluid formulation: 5% iron ion shielding agent + 0.3% salt resistance reducing agent.

[0086] Example 2:

[0087] Iron ion shielding agent formula: 15% tetrasodium glutamate diacetate + 5% polyaspartic acid + 3% butane phosphonate tricarboxylic acid + 15% ammonium citrate + water.

[0088] Drilling fluid formulation: 3% iron ion shielding agent + 0.2% salt resistance reducing agent.

[0089] Example 3:

[0090] Iron ion shielding agent formula: 20% tetrasodium glutamate diacetate + 8% polyaspartic acid + 5% butane phosphonate tricarboxylic acid + 20% ammonium citrate + water.

[0091] Drilling fluid formulation: 1% iron ion shielding agent + 0.1% salt resistance reducing agent.

[0092] Example 4:

[0093] Iron ion shielding agent formula: 20% tetrasodium glutamate diacetate + 8% polyaspartic acid + 2% butane phosphonate tricarboxylic acid + 10% ammonium citrate + water.

[0094] Drilling fluid formulation: 2% iron ion shielding agent + 0.2% salt resistance reducing agent.

[0095] The performance of the drilling fluids prepared in Examples 1 to 4 of this invention was evaluated, including temperature and shear resistance, and drag reduction performance.

[0096] Temperature and shear resistance tests: Rheometer tests were conducted at 90℃ for 100 seconds. -1 Under these conditions, continuous shearing was performed for 5 hours. Figure 2 It can be seen that the viscosity retention rate of the drilling fluid in Example 1 is 49.05%, and the viscosity retention rate of the drilling fluid in Example 4 is 51.59%. The temperature resistance and shear resistance of the drilling fluid in Example 1 were tested by changing the temperature conditions at 120℃ for 100 seconds. -1 Under these conditions, continuous shearing for 5 hours, from Figure 4 It can be seen that the viscosity retention rate of the drilling fluid in Example 1 is 43.5%. The temperature and shear resistance of the drilling fluid in Example 4 were tested by changing the time conditions at 90℃ for 100 seconds. -1 Under these conditions, continuous shearing for 10 hours, from Figure 5 It can be seen that the viscosity retention rate of the drilling fluid in Example 4 is about 48.9%.

[0097] Drag reduction performance test method: According to NB / T 14003.1—2015 "Shale Gas Fracturing Fluids Part 1: Slickwater Performance Indicators and Evaluation Methods". Figure 3 It can be seen that the drag reduction rate of the drilling fluid in Example 1 is 74.36%, the drag reduction rate of the drilling fluid in Example 2 is 70.21%, the drag reduction rate of the drilling fluid in Example 3 is 71.36%, and the drag reduction rate of the drilling fluid in Example 4 is 73.04%.

[0098] The performance of drilling fluids from five wells that failed in deep shale gas drilling was evaluated. A six-speed rotational viscometer was used to test the apparent viscosity of the fluids at room temperature, and the results are shown in Table 1. Table 1 shows that the apparent viscosity of the drilling fluids from these five wells decreased significantly, becoming comparable to that of water. Since the drag-reducing effect of drilling fluids is directly related to viscosity, a viscosity comparable to that of water indicates that the fluid has failed. Even after adding 0.2% drag-reducing agent to the drilling fluid, the viscosity remained low, indicating that the current drilling fluid is unsuitable for the needs of deep shale gas drilling.

[0099] Table 1 Apparent viscosity of drilling fluid in the field and apparent viscosity after replenishment

[0100]

[0101] The drilling fluids of Examples 1-4 were compared with existing drilling fluids. The results of the fluid performance evaluation (based on the above-mentioned temperature resistance and shear resistance test and drag reduction test methods) are shown in Table 2 below. Existing drilling fluid formulations can be water + drag reducer. The drag reducer has poor salt resistance, and its main component is polyacrylamide with a salt resistance of less than 10,000 salinity.

[0102] The water used for preparing conventional drilling fluid has the same properties as the water used for preparing fluid in Examples 1-4, and can be salt water: add 485g of water to a beaker, turn on the stirrer, add 15g of NaCl and 0.025g of FeCl3 at a time, stir for 15 minutes, and use it after the salt is completely dissolved.

[0103] Table 2 Evaluation results of drilling fluid liquid properties

[0104]

[0105] Note: Viscosity retention is not discussed when the apparent viscosity is less than 10 mPa·s.

[0106] In summary, the beneficial effects include:

[0107] This invention provides a deep shale gas coiled tubing drilling fluid and its preparation method, mainly applied in the field of coiled tubing drilling fluids for oil and gas field development and production enhancement operations. The preparation method of the deep shale gas coiled tubing drilling fluid solves the problem of fluid performance failure caused by the use of flowback fluid in deep shale gas coiled tubing drilling fluid preparation under high temperature and long-term circulation. It allows direct use of high-salinity flowback fluid for drilling fluid preparation, reducing production costs. The iron ion shielding agent used effectively shields iron ions, reducing their impact on drilling fluid performance and ensuring the efficiency of deep shale gas drilling operations. The resulting deep shale gas coiled tubing drilling fluid exhibits good salt resistance and stable performance under high temperature and long-term circulation conditions, meeting the requirements of deep shale gas coiled tubing drilling operations.

[0108] Although a deep shale gas coiled tubing drilling fluid and its preparation method have been described above in conjunction with exemplary embodiments, those skilled in the art should understand that various modifications and changes can be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. A method of preparing a coiled tubing drill-in fluid for deep shale gas, characterized in that, The method comprises: adding an iron ion shielding agent into the water for solution preparation under stirring; adding a salt-resistant friction reducer to prepare the deep shale gas coiled tubing drilling and grinding fluid.

2. The method of claim 1, wherein the CTDF is prepared by the steps of: In the method, the dosages of the raw materials are as follows: 0.1-0.3% of the salt-resistant friction reducer, 1-5% of the iron ion shielding agent and the rest of the water for solution preparation.

3. The method of claim 1, wherein the CT drilling fluid is prepared by the steps of: The formula of the iron ion shielding agent comprises: 5-20% of tetrasodium glutamate diacetate, 3-8% of polyaspartic acid, 2-5% of phosphonobutane tricarboxylic acid, 2-20% of ammonium citrate and the rest of water.

4. The method of claim 1 or 3, wherein the CTDF is prepared by the steps of: The preparation method of the iron ion shielding agent comprises: heating water to 30-50℃; adding tetrasodium glutamate diacetate, polyaspartic acid and phosphonobutane tricarboxylic acid into the water under stirring in sequence, stirring for 30-60 min; adding ammonium citrate, stirring for 15-30 min; and cooling to room temperature to obtain the iron ion shielding agent.

5. The method of claim 1, wherein the CT drilling fluid is prepared by the steps of: The water for solution preparation comprises fracturing flowback fluid.

6. The method of claim 1, wherein the CTDF fluid is prepared by the steps of: The water for solution preparation comprises brine with a salinity of more than 20 g / L and an iron content of more than 10 mg / L; and the preparation method of the water for solution preparation comprises: adding NaCl and FeCl3 into clean water and stirring until completely dissolved.

7. The method of claim 1, wherein the CTDF fluid is prepared by the steps of: The salt-resistant friction reducer comprises a polyacrylamide-based friction reducer, and the salt-resistant performance of the salt-resistant friction reducer is greater than 30,000 salinity.

8. The method of claim 1, wherein the CTDF is prepared by the steps of: The adding of the iron ion shielding agent into the water for solution preparation comprises: stirring for 15-30 min; and the adding of the salt-resistant friction reducer comprises: adding the salt-resistant friction reducer by pumping, stirring for 20-40 min to prepare the deep shale gas coiled tubing drilling and grinding fluid.

9. The method of claim 1, wherein the CT drilling fluid is prepared by the steps of: The iron ion shielding agent is a colorless to light yellow transparent liquid; the salt-resistant friction reducer is a milky liquid or a suspended emulsion; and the deep shale gas coiled tubing drilling and grinding fluid is a colorless or milky white viscous liquid.

10. A coiled tubing drill-in fluid for deep shale gas, characterized in that, The deep shale gas coiled tubing drilling and grinding fluid is prepared by the preparation method of the deep shale gas coiled tubing drilling and grinding fluid according to any one of claims 1-9; and the liquid friction reduction rate of the deep shale gas coiled tubing drilling and grinding fluid is greater than 70%.

Images