Low-activity desulfonated complex salt weak gel drilling fluid and preparation method thereof

Abstract

The application relates to the technical field of drilling fluids, and discloses a low-activity desulfonated composite salt weak gel drilling fluid and a preparation method thereof. The low-activity desulfonated composite salt weak gel drilling fluid is prepared from the following raw materials in parts by mass: 80-120 parts of water, 2-4 parts of sodium-based bentonite, 0.5-1 part of a gel protector, 0.5-1 part of an inhibitor, 1-2 parts of a high-temperature-resistant desulfonated fluid loss reducer, 2-3 parts of a resin plugging agent, 2-3 parts of an asphalt plugging agent, 0.5-1 part of a wall stabilizer, 2-4 parts of a lubricant, 10-20 parts of an organic salt, 15-27 parts of an inorganic salt, 0.3-0.8 parts of a pH regulator, 0.5-1 part of a weak gel yield point enhancer and 1-2 parts of superfine calcium carbonate. The low-activity desulfonated composite salt weak gel drilling fluid has good inhibition, plugging and cuttings carrying properties, is beneficial to wellbore stability and wellbore cleaning, and the heavy metal content of the cuttings meets the environmental protection requirements.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, specifically to a low-activity desulfonated composite salt weak gel drilling fluid and its preparation method. Background Technology

[0002] As oil exploration and development progresses towards deeper and more complex formations, the number of deep and complex wells is increasing. The formations encountered are becoming increasingly complex, and problems such as lost circulation, well collapse, borehole narrowing, and severe mud-making are prone to occur during drilling, leading to increased downhole complexity. Data shows that 70% to 90% of wellbore problems are related to the instability of shale and mudstone. Shale and mudstone are highly susceptible to hydration, expansion, and dispersion upon contact with water, causing wellbore collapse. Therefore, it is crucial to minimize the intrusion of drilling fluid filtrate into the formation to ensure wellbore stability.

[0003] Currently, for drilling deep wells, deep horizontal wells, and complex blocks, oil-based drilling fluids are the preferred system for achieving wellbore stability. This is primarily because research shows that the use of inorganic salts such as calcium chloride in oil-based drilling fluids reduces the activity of the drilling fluid filtrate. While the activity of shale is generally above 0.7, oil-based drilling fluid activity can be reduced to below 0.4. This low-activity oil-based filtrate effectively inhibits the hydration, dispersion, and swelling of shale. Studies indicate that shale subjected to strong compaction or with low porosity can act as a semi-permeable membrane. Reducing the water activity in the drilling fluid can decrease the tendency for water to diffuse, infiltrate, and react physicochemically with formation minerals near the wellbore in shale formations, thus contributing to wellbore stability. However, oil-based drilling fluids suffer from high formulation costs and poor environmental performance. In fractured formations, leakage of oil-based drilling fluids often causes significant economic losses and is difficult to manage.

[0004] With the increasingly severe environmental protection situation and higher requirements for environmental protection, the environmental impact of drilling fluids and drill cuttings has become a key focus for researchers, and the discharge of drilling waste fluids and solids is strictly limited. Currently, although many water-based drilling fluids aim to stabilize the wellbore of shale by reducing drilling fluid activity, the drilling fluid treatment agents used contain a considerable proportion of sulfonated materials, or the activity regulators are singular and have limited activity adjustment capabilities.

[0005] Furthermore, deep, long-section horizontal well drilling has gradually become an important technical means for developing deep oil and gas reservoirs. If the drilling fluid has poor cuttings carrying capacity, cuttings cannot be carried away from the wellbore in time, and cuttings accumulate in the horizontal section, which will seriously affect the drilling speed and threaten the safety of drilling operations. Therefore, it is necessary to develop desulfonated water-based drilling fluids with strong low-activity anti-collapse capabilities, good cuttings carrying capacity, good high-temperature stability, and the ability to replace oil-based drilling fluids. Summary of the Invention

[0006] This invention provides a low-activity desulfonated composite salt weak gel drilling fluid, which overcomes the shortcomings of the prior art. It can effectively solve the problems of existing water-based drilling fluids using only sulfonating agents and activity regulators, resulting in poor rock-carrying effect and difficulty in meeting the safe drilling requirements of deep wells and deep horizontal wells.

[0007] One of the technical solutions of this invention is achieved through the following measures: a low-activity desulfonated composite salt weak gel drilling fluid, the raw materials comprising, by mass parts: 80 to 120 parts water, 2 to 4 parts sodium bentonite, 0.5 to 1 part protective agent, 0.5 to 1 part inhibitor, 1 to 2 parts anti-high temperature desulfonation filtration loss reducer, 2 to 3 parts resin plugging agent, 2 to 3 parts asphalt plugging agent, 0.5 to 1 part wall-stabilizing agent, 2 to 4 parts lubricant, 10 to 20 parts organic salt, 15 to 27 parts inorganic salt, 0.3 to 0.8 parts pH adjuster, 0.5 to 1 part weak gel shearing agent, and 1 to 2 parts ultrafine calcium carbonate.

[0008] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0009] The sodium-based bentonite mentioned above is bentonite powder for drilling fluids.

[0010] The aforementioned protective agent is low-viscosity sodium carboxymethyl cellulose (LV-CMC) or low-viscosity polyanionic cellulose (PAC-LV).

[0011] The aforementioned inhibitor is ZNP-1, a polyacrylamide derivative used as an inhibitor of collapse in drilling fluids.

[0012] The aforementioned high-temperature desulfonation filtration reducer is either the propylene-based polymer DRGJ-1 for drilling fluids or the potassium acrylate filtration reducer SP-9 for drilling fluids.

[0013] The aforementioned resin plugging agent is DRGF-1, a propylene-based resin plugging agent for drilling fluids.

[0014] The aforementioned asphalt plugging agent is either cationic emulsified asphalt powder DF-LSF for drilling fluid or liquid emulsified asphalt ZK-A01 for drilling fluid.

[0015] The aforementioned wall-stabilizing agent is a drilling fluid plugging and anti-collapse agent, methacrylate copolymer XZ-GBJ.

[0016] The above-mentioned lubricant is WR-1, a modified cottonseed oil for drilling fluids.

[0017] The aforementioned organic salt is industrial sodium formate.

[0018] The above inorganic salt is a mixture of sodium chloride (NaCl) and potassium chloride (KCl) in a mass ratio of 10 to 20:5 to 7.

[0019] The pH adjusters mentioned above are industrial-grade sodium hydroxide (NaOH) and sodium carbonate (Na2CO3).

[0020] The aforementioned weak gel shearing agent is TCLT-1, a multi-component copolymer of AMPS / NVP used as a flow pattern modifier for drilling fluids.

[0021] The aforementioned ultrafine calcium carbonate is 800 to 2000 mesh ultrafine calcium carbonate.

[0022] The density of the aforementioned low-activity desulfonated composite salt weak gel drilling fluid is 1.2 g / cm³. 3 Up to 1.85 g / cm 3 .

[0023] The above-mentioned low-activity desulfonated composite salt weak gel drilling fluid is prepared according to the following steps: First, the required amounts of bentonite, sodium hydroxide, sodium carbonate and water are mixed and stirred at low speed for 4 to 8 hours, and cured at room temperature for 24 to 48 hours to obtain bentonite-based slurry; Second, the required amounts of protective agent, inhibitor, inorganic salt, organic salt, high-temperature desulfonation filtration loss reducer, weak gel shearing agent, resin plugging agent, asphalt plugging agent, wall-stabilizing agent, ultrafine calcium carbonate and lubricant are added to the cured bentonite-based slurry in sequence. Each time a raw material is added, it is stirred thoroughly for 0.5 to 1 hour before adding the next raw material. Then, the density is adjusted with drilling fluid barite powder to obtain the low-activity desulfonated composite salt weak gel drilling fluid.

[0024] The second technical solution of the present invention is achieved through the following measures: A method for preparing a low-activity desulfonated composite salt weak gel drilling fluid is carried out according to the following steps: First, the required amount of bentonite, sodium hydroxide, sodium carbonate and water are mixed and stirred at low speed for 4 to 8 hours, and cured at room temperature for 24 to 48 hours to obtain bentonite-based slurry; Second, the required amount of protective agent, inhibitor, inorganic salt, organic salt, anti-high temperature desulfonation filtration loss reducer, weak gel cutting agent, resin plugging agent, asphalt plugging agent, wall solidifying agent, ultrafine calcium carbonate and lubricant are added to the cured bentonite-based slurry in sequence. Each time a raw material is added, it is stirred thoroughly for 0.5 to 1 hour before adding the next raw material. Then, the density is adjusted with drilling fluid barite powder to obtain the low-activity desulfonated composite salt weak gel drilling fluid.

[0025] The present invention provides a low-activity desulfonated composite salt weak gel drilling fluid and its preparation method. The low-activity desulfonated composite salt weak gel drilling fluid has good inhibition, plugging and rock-carrying properties, which is beneficial to wellbore stability and wellbore purification, and the heavy metal content of rock cuttings meets environmental protection requirements. Attached Figure Description

[0026] Appendix Figure 1 The graph shows the linear expansion rate of the low-activity desulfonated composite salt weak gel drilling fluid prepared in Example 19 over 16 hours.

[0027] Appendix Figure 2 The graph shows the results of the shale rolling recovery rate of the low-activity desulfonated composite salt weak gel drilling fluid prepared in Example 19. Detailed Implementation

[0028] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0029] The present invention will be further described below with reference to embodiments:

[0030] Example 1: This low-activity desulfonated composite salt weak gel drilling fluid comprises the following raw materials by weight: 80 to 120 parts water, 2 to 4 parts sodium bentonite, 0.5 to 1 part protective agent, 0.5 to 1 part inhibitor, 1 to 2 parts high-temperature desulfonation filtration reduction agent, 2 to 3 parts resin plugging agent, 2 to 3 parts bitumen plugging agent, 0.5 to 1 part wall-stabilizing agent, 2 to 4 parts lubricant, 10 to 20 parts organic salt, 15 to 27 parts inorganic salt, 0.3 to 0.8 parts pH adjuster, 0.5 to 1 part weak gel shearing agent, and 1 to 2 parts ultrafine calcium carbonate. In addition, a weighting agent, namely barite powder for drilling fluid, is added according to the final drilling fluid density requirements, meeting the Class I requirements of Q / SY 17008-2019 standard.

[0031] Example 2: This low-activity desulfonated composite salt weak gel drilling fluid comprises the following raw materials by weight: 100 parts water, 2 to 4 parts sodium bentonite, 0.5 to 1 part protective agent, 0.5 to 1 part inhibitor, 1 to 2 parts high-temperature desulfonation filtration reduction agent, 2 to 3 parts resin plugging agent, 2 to 3 parts bitumen plugging agent, 0.5 to 1 part wall-stabilizing agent, 2 to 4 parts lubricant, 10 to 20 parts organic salt, 15 to 27 parts inorganic salt, 0.3 to 0.8 parts pH adjuster, 0.5 to 1 part weak gel shearing agent, and 1 to 2 parts ultrafine calcium carbonate. In addition, a weighting agent, namely barite powder for drilling fluid, is added according to the final drilling fluid density requirements, meeting the Class I requirements of Q / SY 17008-2019 standard.

[0032] This invention provides a low-activity desulfonated composite salt weak gel drilling fluid. This drilling fluid, while meeting environmental protection requirements by desulfonating the treatment agent, can also meet the safe drilling needs of deep wells and deep horizontal wells.

[0033] Example 3: As an optimization of the above examples, sodium-based bentonite is bentonite powder for drilling fluid. In this invention, the bentonite powder for drilling fluid meets the Class I requirements of Q / SY17009-2019 standard.

[0034] Example 4: As an optimization of the above examples, the protective agent is low-viscosity sodium carboxymethyl cellulose (LV-CMC) or low-viscosity polyanionic cellulose (PAC-LV). In this invention, the protective agent functions by adsorbing onto the clay surface to form an adsorption layer, preventing clay particles from flocculating and increasing in size, thus promoting the formation of a dense mud cake. LV-CMC can be the low-viscosity sodium carboxymethyl cellulose product for drilling fluid filtration reduction from Ningjin County Chengyuan Chemical Technology Co., Ltd.; PAC-LV can be the low-viscosity polyanionic cellulose product for drilling fluid filtration reduction from Jingzhou Xuecheng Industrial Co., Ltd.

[0035] Example 5: As an optimization of the above examples, the inhibitor is ZNP-1, a polyacrylamide derivative for drilling fluids used as an inhibitor of collapse. In this invention, the inhibitor inhibits the hydration, dispersion, and swelling of clay minerals, thereby improving the drilling fluid's ability to inhibit collapse. ZNP-1 can be a polyacrylamide derivative product for drilling fluids from Xinxiang Zhenhua Drilling Fluid Materials Co., Ltd.

[0036] Example 6: As an optimization of the above examples, the high-temperature desulfonation filtration loss reducer is either the drilling fluid anti-temperature filtration loss reducer DRGJ-1 (propylene-based polymer) or the drilling fluid filtration loss reducer potassium acrylate SP-9. In this invention, the function of the high-temperature desulfonation filtration loss reducer is to increase viscosity, reduce drilling fluid filtration loss, and improve the high-temperature stability of the drilling fluid. It replaces traditional sulfonated materials such as sulfonated phenolic resin, sulfonated lignite, and sulfonated phenolic humic acid. Traditional synthetic sulfonated materials have toxic monomers, high heavy metal ion content, and poor biodegradability, failing to meet current environmental protection requirements. Replacing sulfonation treatment agents with desulfonation treatment agents is more environmentally friendly. DRGJ-1 can be the drilling fluid anti-temperature filtration loss reducer product of Tianjin Kangbuer Petroleum Technology Development Co., Ltd.; SP-9 is the drilling fluid filtration loss reducer potassium acrylate product of Karamay Aoze Industry and Trade Co., Ltd.

[0037] Example 7: As an optimization of the above examples, the resin plugging agent is DRGF-1, a propylene-based resin plugging agent for drilling fluid. In this invention, the role of the resin plugging agent is to improve the particle size distribution of the drilling fluid and obtain a good plugging and filtration loss reduction effect. DRGF-1 can be a micron-sized plugging agent resin product for drilling fluid from Xi'an Kangbuer Petroleum Technology Development Co., Ltd.

[0038] Example 8: As an optimization of the above examples, the asphalt plugging agent is either DF-LSF cationic emulsified asphalt powder for drilling fluid anti-collapse or ZK-A01 liquid emulsified asphalt for drilling fluid anti-collapse. The asphalt plugging agent has the functions of plugging and reducing water loss, improving mud cake quality, and achieving good plugging and filtration loss reduction effects. DF-LSF can be a cationic emulsified asphalt product for drilling fluid anti-collapse from Bazhou Zhongke Petroleum Technology Service Co., Ltd.; ZK-A01 is a cationic emulsified asphalt colloidal product from Bazhou Zhongke Petroleum Technology Service Co., Ltd.

[0039] Example 9: As an optimization of the above examples, the wall-stabilizing agent is XZ-GBJ, a drilling fluid plugging and anti-collapse copolymer of methacrylate. In this invention, the wall-stabilizing agent functions to form a cemented layer with strong adhesion and cohesion between rock particles within the formation. Its main function is to maintain wellbore stability through a synergistic coupling of reinforcement, inhibition, and plugging via a "mechanical-chemical" approach, thereby achieving shale strengthening. XZ-GBJ can be a methacrylate copolymer product of drilling fluid anti-collapse agent from Zhangjiakou Chongli Zhongrui Drilling and Production Technology Co., Ltd.

[0040] Example 10: As an optimization of the above examples, the lubricant is WR-1, a modified cottonseed oil for drilling fluids. Its function is to enhance the lubrication capacity of the system in high-solids drilling fluids, prevent sticking, and has low fluorescence so as not to affect logging. WR-1 can be a modified cottonseed oil product for drilling fluids from the Tuha Oilfield Engineering Technology Research Institute.

[0041] Example 11: As an optimization of the above examples, the organic salt is industrial-grade sodium formate. Its function is to enhance the chemical inhibition and anti-collapse effect of the drilling fluid, form a thin film on the wellbore, and reduce the activity of the drilling fluid.

[0042] Example 12: As an optimization of the above example, the inorganic salt is a mixture of sodium chloride (NaCl) and potassium chloride (KCl) in a mass ratio of 10 to 20:5 to 7. The role of the inorganic salt is to improve the chemical inhibition and anti-collapse ability of the drilling fluid and reduce the activity of the drilling fluid.

[0043] Example 13: As an optimization of the above example, the pH adjuster is industrial-grade sodium hydroxide (NaOH) and sodium carbonate (Na2CO3). After adding the pH adjuster, the pH value of the drilling fluid system is 9 to 10.

[0044] Example 14: As an optimization of the above examples, the weak gel shearing agent is TCLT-1, a flow pattern modifier for drilling fluids and an AMPS / NVP multi-component copolymer. The weak gel shearing agent selected in this invention is a novel weak gelling agent prepared by adding natural biopolymers as the main raw material to an aqueous surfactant solution for activation, and then grafting it with macromolecular modifiers and high-temperature oxidizing agents. It possesses unique rheological properties and can improve the dynamic sand-carrying and static sand-suspending capacity of drilling fluids. TCLT-1 can be the AMPS / NVP multi-component copolymer product for drilling fluids from Tianjin Tiancheng Tuoyuan Technology Development Co., Ltd.

[0045] Example 15: As an optimization of the above examples, the ultrafine calcium carbonate is 800 to 2000 mesh. Its function is to promote the formation of a dense mud cake and seal microcracks.

[0046] Example 16: As an optimization of the above example, the density of this low-activity desulfonated composite salt weak gel drilling fluid is 1.2 g / cm³. 3 Up to 1.85 g / cm 3 .

[0047] Example 17: The preparation method of this low-activity desulfonated composite salt weak gel drilling fluid is carried out according to the following steps:

[0048] The first step is to mix the required amount of bentonite, sodium hydroxide, sodium carbonate and water and stir at low speed for 4 to 8 hours, and then cure at room temperature for 24 to 48 hours to obtain bentonite-based slurry.

[0049] The second step involves sequentially adding the required amounts of protective agent, inhibitor, inorganic salt, organic salt, high-temperature desulfonation filtration loss reducer, weak gel cutting agent, resin plugging agent, asphalt plugging agent, wall-stabilizing agent, ultrafine calcium carbonate, and lubricant to the cured bentonite-based slurry. Each new material is thoroughly stirred for 0.5 to 1 hour before adding the next. The density is then adjusted using drilling fluid barite powder to obtain a low-activity desulfonation composite salt weak gel drilling fluid.

[0050] The low-activity desulfonated composite salt weak gel drilling fluid of the present invention has the following advantages:

[0051] (1) The system has low activity (less than 0.65), which can improve the compactness and membrane efficiency of shale, reduce the positive migration of drilling fluid to the formation, reduce the intrusion of filtrate and pressure transmission, and has excellent shale wellbore stability performance, which is sufficient to meet the needs of suppressing shale collapse.

[0052] (2) The system utilizes weak gel to increase the dynamic-plastic ratio of the system (above 0.40), and the drilling fluid has a better suspension and cuttings carrying capacity, reducing the accumulation of cuttings in the directional and horizontal sections, preventing the cuttings bed from being too thick, which would lead to increased friction and torque, as well as stuck pipe, and can ensure the safe extension of deep, long horizontal wells.

[0053] (3) The system uses desulfonation treatment agents, which have excellent high temperature stability and lubricity. The performance is stable at 180℃, taking into account both safe and fast drilling and environmental protection requirements.

[0054] (4) The system uses resin plugging agent, asphalt plugging agent and wall solidifying agent in combination to effectively improve the particle size distribution of drilling fluid, strengthen the plugging and wall building, reduce the water phase intrusion into mudstone and shale, and further improve the stability of mudstone well walls.

[0055] Example 18: This example provides a density of 1.35 g / cm³. 3 This is a low-activity desulfonated composite salt weak gel drilling fluid with a high temperature resistance of 180℃. The raw materials, by weight, include: 100 parts water, 3.5 parts sodium bentonite, 1 part gel protectant, 0.5 parts inhibitor, 1.2 parts high-temperature resistant desulfonated filtration loss reducer, 2.1 parts resin plugging agent, 2.3 parts asphalt plugging agent, 0.5 parts wall-stabilizing agent, 2 parts lubricant, 15 parts sodium formate, 15 parts sodium chloride, 5 parts potassium chloride, 0.3 parts sodium hydroxide, 0.5 parts sodium carbonate, 0.5 parts weak gel shearing agent, and 1 part ultrafine calcium carbonate. The fluid is weighted to a density of 1.35 g / cm³ using drilling fluid barite powder. 3 .

[0056] According to the above formula, the first step is to mix sodium-based bentonite, sodium hydroxide, sodium carbonate, and water at low speed for 6 hours, and then cure at room temperature under sealed conditions for 24 hours to obtain bentonite-based slurry. The second step involves adding the following ingredients sequentially to the cured bentonite-based slurry according to the designed dosage: a protective agent, an inhibitor, sodium chloride, potassium chloride, sodium formate, a high-temperature desulfonation filtration reducer, a weak gel lifting agent, a resin plugging agent, an asphalt plugging agent, a wall-stabilizing agent, ultrafine calcium carbonate, and a lubricant. Each new ingredient is thoroughly stirred for 1 hour before adding the next. Finally, the slurry is weighted to a density of 1.35 g / cm³ using drilling fluid barite powder. 3 spare.

[0057] Example 19: This example provides a density of 1.60 g / cm³. 3This is a low-activity desulfonated composite salt weak gel drilling fluid with a high temperature resistance of 180℃. The raw materials, by weight, include: 100 parts water, 2.5 parts sodium bentonite, 0.8 parts gel protectant, 0.8 parts inhibitor, 1.5 parts high-temperature resistant desulfonated filtration loss reducer, 2.5 parts resin plugging agent, 2 parts asphalt plugging agent, 0.7 parts wall-stabilizing agent, 2.2 parts lubricant, 10 parts sodium formate, 20 parts sodium chloride, 7 parts potassium chloride, 0.2 parts sodium hydroxide, 0.4 parts sodium carbonate, 0.6 parts weak gel shearing agent, and 1 part ultrafine calcium carbonate. The fluid is weighted to a density of 1.60 g / cm³ using drilling fluid barite powder. 3 .

[0058] According to the above formula, the first step is to mix sodium-based bentonite, sodium hydroxide, sodium carbonate, and water at low speed for 6 hours, and then cure at room temperature under sealed conditions for 24 hours to obtain bentonite-based slurry. The second step involves adding the following ingredients sequentially to the cured bentonite-based slurry according to the designed dosage: a protective agent, inhibitor, sodium chloride, potassium chloride, sodium formate, high-temperature desulfonation filtration reducer, weak gel lifting agent, resin plugging agent, asphalt plugging agent, wall-stabilizing agent, ultrafine calcium carbonate, and lubricant. Each new ingredient is thoroughly stirred for 1 hour before adding the next. Finally, the slurry is weighted to a density of 1.60 g / cm³ using drilling fluid barite powder. 3 spare.

[0059] Example 20: This example provides a density of 1.80 g / cm³. 3 A low-activity desulfonated composite salt weak gel drilling fluid resistant to high temperatures up to 180℃, comprising the following raw materials by mass parts:

[0060] The mixture consists of 100 parts water, 2 parts sodium bentonite, 0.6 parts protective agent, 1 part inhibitor, 1.8 parts high-temperature desulfonation filtration loss reducer, 3 parts resin plugging agent, 0.6 parts wall-stabilizing agent, 3 parts lubricant, 20 parts sodium formate, 15 parts sodium chloride, 5 parts potassium chloride, 0.2 parts sodium hydroxide, 0.2 parts sodium carbonate, 0.8 parts weak gelling agent, and 1.5 parts ultrafine calcium carbonate, weighted to a density of 1.80 g / cm³ using drilling fluid barite powder. 3 .

[0061] According to the above formula, the first step is to mix sodium-based bentonite, sodium hydroxide, sodium carbonate, and water at low speed for 6 hours, and then cure at room temperature under sealed conditions for 24 hours to obtain bentonite-based slurry. The second step involves adding the following ingredients sequentially to the cured bentonite-based slurry according to the designed dosage: a protective agent, inhibitor, sodium chloride, potassium chloride, sodium formate, high-temperature desulfonation filtration reducer, weak gel lifting agent, resin plugging agent, asphalt plugging agent, wall-stabilizing agent, ultrafine calcium carbonate, and lubricant. Each new ingredient is thoroughly stirred for 1 hour before adding the next. Finally, the slurry is weighted to a density of 1.80 g / cm³ using drilling fluid barite powder. 3 spare.

[0062] Comparative Example 1: The difference between its drilling fluid formulation and that of Example 18 is that it does not contain a weak gelling agent, the purpose of which is to verify the compatibility of the weak gelling agent with other treatment agents in the formulation.

[0063] Comparative Example 2: Its drilling fluid formulation differs from that of Example 19 in that it does not contain a weak gelling agent, the purpose of which is to verify the compatibility of the weak gelling agent with other treatment agents in the formulation.

[0064] Comparative Example 3: The difference between its drilling fluid formulation and that of Example 19 is that no resin plugging agent is added. The purpose is to verify that the resin plugging agent can be used in combination with wall-stabilizing agents and asphalt plugging agents to further improve the sealing performance of the drilling fluid.

[0065] Comparative Example 4: The difference between its drilling fluid formulation and that of Example 18 is that no wall-stabilizing agent is added. The purpose is to verify that the wall-stabilizing agent can be used in combination with resin plugging agent and asphalt plugging agent to further improve the sealing performance of the drilling fluid.

[0066] Comparative Example 5: The difference between its drilling fluid formulation and that of Example 19 is that no asphalt plugging agent is added. The purpose is to verify that the asphalt plugging agent can be used in combination with wall-stabilizing agents and resin plugging agents to further improve the sealing performance of the drilling fluid.

[0067] The performance of the low-activity desulfonated composite salt weak gel drilling fluids prepared in Examples 17 to 19 and the drilling fluid systems in Comparative Examples 1 to 5 were tested:

[0068] (1) Rheological filtration performance and activity value test

[0069] Referring to GB / T 16783.1-2014 Oil and Gas Working Drilling Fluid Field Testing Part 1: Water-based Drilling Fluids, the experimental slurry was placed in a high-temperature aging tank and hot-rolled at 180℃ for 24 hours. The rheological and filtration properties of the low-activity desulfonated composite salt weak gel drilling fluids obtained in Examples 18 to 20 before and after hot rolling at 180℃ / 24h were investigated. The results are shown in Table 1 (in Table 1, AV is the apparent viscosity of the drilling fluid; PV is the plastic viscosity of the drilling fluid; YP is the dynamic shear force of the drilling fluid; G...). 10s / G 10minFor initial / final cut of drilling fluid; FLAPI is the medium-pressure fluid loss of drilling fluid; FLHTHP is the high-temperature, high-pressure fluid loss of drilling fluid. As shown in Table 1, the low-activity desulfonated composite salt weak gel drilling fluid of the present invention has a dynamic-to-plastic ratio of over 0.40 after hot rolling, suitable initial / final shear ratio, low thixotropy, and is suitable for long horizontal dynamic sand carrying and static suspended sand; API filtration loss is less than 4.0 mL, high-temperature and high-pressure filtration loss is less than 10 mL, mud cake thickness is less than 0.3 mm, thin and dense, with 10% of particles smaller than 2.05 μm, 50% smaller than 17.79 μm, and 90% smaller than 68.24 μm. The drilling fluid has a wide particle size distribution, high packing efficiency, and is conducive to maximum density packing, effectively sealing pore throats and microfractures in shale and mudstone, and has excellent sealing and anti-collapse performance; low activity (less than 0.65) can reduce the forward migration of drilling fluid to the formation; good high-temperature stability at 180℃, which can meet the technical requirements of deep well and deep horizontal well drilling.

[0070] A comparison of the rheological and filtration loss properties of Example 18 and Comparative Example 1, and Example 19 and Comparative Example 2 before and after hot rolling at 180℃ / 24h (see Table 2) shows that adding a weak gel shearing agent to the drilling fluid increases the dynamic and static shear forces and significantly improves the dynamic-to-plastic ratio, which is beneficial for improving the dynamic sand-carrying capacity and static sand-suspending capacity of the drilling fluid. The weak gel shearing agent has good compatibility with other treatment agents, reduces filtration loss under medium pressure and high temperature and high pressure, and also has a filtration loss reduction effect.

[0071] The performance of Example 19 was compared with that of Comparative Examples 3, 4, and 5. The experimental results are shown in Table 3. As can be seen from Table 3, the resin plugging agent, the wall-stabilizing agent, and the asphalt plugging agent all have the ability to reduce drilling fluid filtration loss. They have low rheological properties to the drilling fluid and good compatibility with other treatment agents. Moreover, the combination of the three has the best effect on reducing filtration loss. This is mainly because the combination of the resin plugging agent, the wall-stabilizing agent, and the asphalt plugging agent improves the particle size distribution of the drilling fluid, thereby strengthening the plugging and wall-building, reducing the intrusion of water phase into shale, and further improving the stability of the shale wellbore.

[0072] (2) Evaluation of suppression performance

[0073] The Wutonggou and Jiucaiyuan formations in the Satan 1 block of the Turpan-Hami Oilfield have high clay mineral content (40%-50%), and mixed montmorillonite content (up to 60%), with mixed montmorillonite content reaching 40%-50%. Microfractures are well-developed, and the mudstone is prone to hydration, dispersion, and spalling, resulting in poor wellbore stability. Mudstone samples from Wutonggou and Jiucaiyuan were selected, and a rolling dispersion experiment was used to evaluate the hydration-inhibiting performance of the low-activity desulfonated composite salt weak gel drilling fluid prepared in Example 19. A shale linear dilatometer was used to evaluate its hydration-inhibiting swelling performance. The 16-hour linear swelling rate and shale rolling recovery rate are shown below. Figure 1 , Figure 2As shown in the figure. The experimental results show that the low-activity desulfonated composite salt weak gel drilling fluid of the present invention has excellent ability to inhibit mudstone hydration dispersion and expansion. The expansion rate of mudstone and shale cores after 16 hours is <5%, and the rolling recovery rate of mudstone and shale is >92%. Moreover, in field applications, the rock cuttings are in granular form, which has good ability to inhibit collapse.

[0074] (3) Evaluation of pollution resistance

[0075] To test the anti-fouling ability of the low-activity desulfonated composite salt weak gel drilling fluid provided by this invention, 10% rock cuttings, 20% rock cuttings, 3% CaSO4, and 5% CaSO4 by mass percentage were added to the low-activity desulfonated composite salt weak gel drilling fluid prepared in Example 19, respectively. After hot rolling at 180℃ for 24 hours, performance tests were conducted, and the experimental results are shown in Table 4. As can be seen from the experimental data in Table 4, the low-activity desulfonated composite salt weak gel drilling fluid of this invention exhibits strong resistance to both rock cuttings and gypsum contamination. Even after 20% rock cuttings contamination, the system still maintains good rheological properties after high-temperature aging. When the gypsum content reaches 5%, the high-temperature and high-pressure filtration loss remains below 10 mL, indicating that the system has strong stability and strong resistance to both rock cuttings and gypsum contamination, meeting the drilling requirements of salt-gypsum layers and gypsum-rich mudstone.

[0076] (4) Detection of heavy metal content in rock fragments

[0077] To verify the environmental performance of the low-activity desulfonated composite salt weak gel drilling fluid provided by this invention, the heavy metal content of the drilling fluid soaking rock cuttings was tested. The test results are shown in Table 5 (the standard values ​​in Table 5 are based on the implementation standard DB65 / T3997-2017 "Pollution Control Requirements for Comprehensive Utilization of Solid Waste from Oil and Gas Field Drilling"). As can be seen from Table 5, since this system does not use a sulfonation treatment agent, the tested heavy metal content is far lower than the standard values.

[0078] In summary, the low-activity desulfonated composite salt weak gel drilling fluid of the present invention has good inhibition, plugging and rock-carrying properties, which is beneficial to wellbore stability and wellbore purification. Moreover, the heavy metal content of rock cuttings meets environmental protection requirements, and it has achieved good results in field applications, meeting the drilling needs of deep wells and deep horizontal wells.

[0079] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0080]

[0081]

Claims

1. A low-activity desulfonated complex salt weak-gel drilling fluid, characterized in that The raw materials include, by mass fraction: water 80 to 120 parts, sodium bentonite 2 to 4 parts, gum protector 0.5 to 1 part, inhibitor 0.5 to 1 part, high-temperature resistant desulfonation filtrate reducer 1 to 2 parts, resin plugging agent 2 to 3 parts, asphalt plugging agent 2 to 3 parts, wall stabilizer 0.5 to 1 part, lubricant 2 to 4 parts, organic salt 10 to 20 parts, inorganic salt 15 to 27 parts, pH regulator 0.3 to 0.8 parts, weak gel thickening agent 0.5 to 1 part, and ultra-fine calcium carbonate 1 to 2 parts; The inhibitor is a drilling fluid inhibitor anti-sloughing agent polyacrylamide derivative ZNP-1; The high-temperature resistant desulfonation filtrate reducer is a drilling fluid temperature-resistant filtrate reducer propylene-based polymer DRGJ-1 or a drilling fluid filtrate reducer potassium acrylate SP-9; The resin plugging agent is a drilling fluid propylene-based resin plugging agent DRGF-1; The asphalt plugging agent is a drilling fluid anti-sloughing agent cationic emulsified asphalt powder DF-LSF or a drilling fluid anti-sloughing agent liquid emulsified asphalt ZK-A01; The wall stabilizer is a drilling fluid plugging anti-sloughing agent methacrylate copolymer XZ-GBJ; The weak gel thickening agent is a drilling fluid flow pattern regulator AMPS / NVP multi-component copolymer TCLT-1.

2. The low activity desulfonated complex salt weak gel drilling fluid of claim 1, wherein The sodium bentonite is a drilling fluid bentonite powder; or / and the gum protector is low-viscosity carboxymethyl cellulose sodium LV-CMC or low-viscosity polyanionic cellulose PAC-LV.

3. The low activity desulfonated complex salt weak gel drilling fluid of claim 1 or 2, wherein The lubricant is a drilling fluid liquid lubricant modified cottonseed oil WR-1.

4. The low activity desulfonated complex salt weak gel drilling fluid of claim 1 or 2, wherein The organic salt is an industrial sodium formate; or / and the inorganic salt is a mixture of sodium chloride NaCl and potassium chloride KCl, with a mass ratio of 10 to 20:5 to 7.

5. The low activity desulfonated complex salt weak gel drilling fluid of claim 1 or 2, wherein The pH regulator is an industrial sodium hydroxide NaOH and sodium carbonate Na2CO3.

6. The low activity desulfonated complex salt weak gel drilling fluid of claim 1, wherein Ultrafine calcium carbonate is an ultrafine calcium carbonate having a mesh size of 800 to 2,000; or / and, the density of the low-activity desulfonated composite salt weak gel drilling fluid is 1.2 g / cm 3 to 1.85 g / cm 3 .

7. The low activity desulfonated complex salt weak gel drilling fluid of claim 5, wherein The following steps are used: first, the required amount of bentonite, sodium hydroxide, sodium carbonate, and water are mixed and stirred at low speed for 4 to 8 hours, and then cured at room temperature for 24 to 48 hours to obtain a bentonite-based slurry; second, the required amount of gum protector, inhibitor, inorganic salt, organic salt, high-temperature resistant desulfonation filtrate reducer, weak gel thickening agent, resin plugging agent, asphalt plugging agent, wall stabilizer, ultra-fine calcium carbonate, and lubricant are sequentially added to the cured bentonite-based slurry, and each is stirred for 0.5 to 1 hour before adding the next one; and then drilling fluid barite powder is used to adjust the density, thereby obtaining the low-activity desulfonation composite salt weak gel drilling fluid.

8. A method of preparing a low-activity desulfonated complex salt weak gel drilling fluid according to claim 5, characterized in that The following steps are used: first, the required amount of bentonite, sodium hydroxide, sodium carbonate, and water are mixed and stirred at low speed for 4 to 8 hours, and then cured at room temperature for 24 to 48 hours to obtain a bentonite-based slurry; second, the required amount of gum protector, inhibitor, inorganic salt, organic salt, high-temperature resistant desulfonation filtrate reducer, weak gel thickening agent, resin plugging agent, asphalt plugging agent, wall stabilizer, ultra-fine calcium carbonate, and lubricant are sequentially added to the cured bentonite-based slurry, and each is stirred for 0.5 to 1 hour before adding the next one; and then drilling fluid barite powder is used to adjust the density, thereby obtaining the low-activity desulfonation composite salt weak gel drilling fluid.

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