Ultra-low oil-water ratio oil-based drilling fluid without soil phase, preparation and application thereof

Abstract

This invention discloses an ultra-low oil-water ratio, soil-free oil-based drilling fluid with a density of 1.5 g / cm³. 3 ~1.8g / cm 3 The emulsion formed by the oil and water phases under the action of an emulsifier contains polymer filtration loss reducers, wetting agents, flow pattern modifiers, lignite filtration loss reducers, and quicklime; wherein the volume ratio of the oil phase to the water phase is (40:60) to (70:30). This invention also provides a method for preparing ultra-low oil-water ratio, soil-free oil-based drilling fluid. The ultra-low oil-water ratio, soil-free oil-based drilling fluid provided by this invention has a low oil-water ratio, low colloidal content, good rheological properties, and good reservoir protection capability; the demulsification voltage reaches over 600V, the high-temperature and high-pressure filtration loss is below 3mL, and the system has good sealing and lubrication properties. The ultra-low oil-water ratio, soil-free oil-based drilling fluid provided by this invention does not lose fluidity at -25℃, meeting the requirements for winter construction, has relatively low economic cost, is more competitive in the market, and has good reservoir protection effect, making it applicable to a wider range of situations.

Description

Technical Field

[0001] This invention relates to an ultra-low oil-water ratio, soil-free oil-based drilling fluid, its preparation, and its application. Background Technology

[0002] Drilling is the only engineering technology that connects underground oil and gas to the surface, and drilling fluid is the engineering fluid technology that ensures the safe, efficient and smooth implementation of drilling projects, also known as the "blood" of drilling projects.

[0003] Unconventional oil and gas reservoirs are typically more challenging to develop, often involving deep wells, ultra-deep wells, complex structure wells, and shale gas wells. Drilling operations face complex environments characterized by high temperatures, high pressures, and wellbore instability. This places higher technical demands on drilling engineering and drilling fluids. From a drilling fluid perspective, high-temperature, high-pressure formations impose higher requirements on the temperature resistance of drilling fluids; wellbore instability issues necessitate higher requirements for the fluid's filtration, inhibition, and plugging properties; and complex structure wells such as horizontal wells and multi-branch wells demand higher requirements for the fluid's rock-carrying capacity and lubrication performance. Water-based drilling fluids are commonly used for easily drillable formations, but they can lead to numerous accidents during drilling in challenging formations. Oil-based drilling fluids, on the other hand, are often the preferred choice for high-difficulty wells due to their superior wellbore stability, inhibition, high-temperature resistance, strong resistance to calcium contamination, good lubrication, good corrosion resistance, minimal susceptibility to external factors, and high reusability.

[0004] Oil-based drilling fluids are drilling fluids that use base oil as the continuous phase and exhibit certain properties of oil under specific conditions. They are primarily composed of oil, water, solids, and oil-soluble chemical treatment agents, with various additives used to meet the performance requirements of the drilling fluid.

[0005] As oil-based drilling fluid technology matures and is applied on a large scale, market competition is intensifying. Fluctuations in oil prices have led to a significant decrease in client investment, resulting in lower revenue from oil-based drilling fluid services. Therefore, the development of low-cost oil-based drilling fluids is urgently needed. Conventional oil-based drilling fluids typically have an oil-to-water ratio of 70:30 or higher, resulting in high costs and significant environmental treatment expenses. If the oil phase ratio can be reduced from 80% to 40%, the cost of oil-based drilling fluids could decrease by approximately 20%. Simultaneously, the increased water phase, such as using high-density brine, can further increase the liquid phase density, reduce barite usage, and decrease the solid content in the drilling fluid, which is beneficial for improving the rate of penetration (ROP) and thus further expanding the application range of oil-based drilling fluids. The establishment of soil-free oil-based drilling fluid systems can overcome the shortcomings of organic soils, such as easy failure at high temperatures and poor rheological properties at high densities. Especially when drilling into oil and gas reservoirs, by effectively controlling filtration loss and minimizing the use of strong oleophilic treatment agents, the drilling fluid maintains good rheological properties, suspension stability, and filtration loss, reducing circulating pressure loss. It can not only effectively improve the rate of penetration but also reduce reservoir damage. Therefore, ultra-low oil-water ratio soil-free oil-based drilling fluid technology has low cost, good reservoir protection effect, and can shorten drilling cycles, showing promising application prospects.

[0006] CN103788934B, "An Oil-Based Drilling Fluid Without Soil Phase," discloses an oil-based drilling fluid system without soil phase, with an oil-water ratio of 70:30 to 90:10 and a temperature resistance of 150℃. CN105062438B, "An Oil-Based Emulsified Drilling Fluid with an Ultra-Low Oil-Water Ratio of 40:60," discloses an oil-based drilling fluid with an ultra-low oil-water ratio of 40:60, but only specifies the case of an oil-water ratio of 40:60, and the temperature resistance is only 120℃. From the given examples, its stability is poor, the viscosity and shear of the drilling fluid are difficult to control, implementation is difficult, and the demulsification voltage does not meet industry standards.

[0007] CN107325797B, "A Low Oil-Water Ratio Oil-Based Drilling Fluid and Its Preparation Method," discloses a low oil-water ratio drilling fluid system with an oil-water ratio of 60:40 and an organic clay content of 3%. CN108034413B, "A Low Oil-Water Ratio Oil-Based Drilling Fluid," discloses a low oil-water ratio drilling fluid system with an oil-water ratio as low as 41:59, but still requires organic clay as a basic structural agent. CN114085551B, "Wellbore Strengthening Dual-Resistant, Clay-Free Oil-Based Drilling Fluid Containing Silica Combined Treatment Agent," discloses a clay-free oil-based drilling fluid system with an oil-water ratio as low as 70:30.

[0008] The existing oil-based drilling fluid technologies described above mainly address two aspects: low oil-to-water ratio drilling fluid systems and soil-free oil-based drilling fluid systems. While low oil-to-water ratio oil-based drilling fluid systems offer better cost-effectiveness, they rely heavily on organic clay as the primary flow modifier and use oxidized bitumen or organic lignite as filtration reducers. The high colloidal content negatively impacts drilling rates, while excessively low colloidal content hinders wellbore cleaning capabilities. While research reports exist on low oil-to-water ratio drilling fluid systems, these systems involve higher levels of emulsifiers and organic clay, which can alter the hydrophilicity and oleophilicity of rock surfaces and pores, causing some damage to the reservoir. Soil-free oil-based drilling fluid systems offer superior rheological properties and a unique gel structure; higher mechanical drilling rates; and better reservoir protection capabilities. However, the current minimum oil-to-water ratio is 70:30. Under high oil-to-water ratio conditions, the resulting drill cuttings have a high oil content, making environmental treatment difficult and resulting in poor low-temperature performance. Summary of the Invention

[0009] Existing low oil-water ratio and soil-free oil-based drilling fluid systems each have their own shortcomings. To address these deficiencies, this invention provides an ultra-low oil-water ratio, soil-free oil-based drilling fluid. While maintaining the basic properties of oil-based drilling fluids, it reduces oil content and colloidal content, eliminates organic clay, and replaces asphalt filtration reducers with polymer filtration reducers. This improves the rheological properties of oil-based drilling fluids, enhances reservoir protection capabilities, and reduces unit formulation costs. It is also suitable for conditions down to -25°C, offering better competitive prospects for widespread adoption. The oil-based drilling fluid provided by this invention uses diesel oil as the base oil, with low-volume emulsifiers, polymer filtration reducers, and flow modifiers as the main components, formulated into a water-in-oil, soil-free oil-based drilling fluid with an oil-water ratio of (40:60) to (60:40). The oil-based drilling fluid provided by this invention has the characteristics of low oil-water ratio, zero organic soil addition, moderate viscosity and shearing, strong resistance to salt and calcium pollution, strong resistance to low temperature, good anti-collapse inhibition, low cost, and strong reservoir protection.

[0010] As one aspect of the present invention, a low oil-water ratio, soil-free oil-based drilling fluid with a density of 1.5 g / cm³ is disclosed. 3 ~1.8g / cm 3The ultra-low oil-water ratio soil-free oil-based drilling fluid is an emulsion formed by the oil and water phases under the action of an emulsifier, containing a polymer filtration loss reducer, a wetting agent, a flow pattern modifier, a lignite filtration loss reducer, and quicklime. The volume ratio of the oil phase to the water phase is (40:60) to (70:30). Based on the total volume of the oil and water phases, the weight-volume ratio of the emulsifier is 2wt%-4wt%, the weight-volume ratio of the quicklime is 2wt%-3wt%, the weight-volume ratio of the flow pattern modifier is 0.5wt%-1.0wt%, the weight-volume ratio of the polymer filtration loss reducer is 0.5wt%-1wt%, the weight-volume ratio of the lignite filtration loss reducer is 2wt%-3wt%, and the weight-volume ratio of the wetting agent is 0.5wt%-1wt%.

[0011] In a specific implementation, the volume ratio of the oil phase to the water phase in the ultra-low oil-water ratio soil-free oil-based drilling fluid is (50:50) to (70:30).

[0012] In a specific implementation, the volume ratio of the oil phase to the water phase in the ultra-low oil-water ratio soil-free oil-based drilling fluid is (60:40) to (70:30).

[0013] In a specific implementation, the oil phase is #0 diesel oil; the aqueous phase is an aqueous solution of calcium chloride.

[0014] As another aspect of the present invention, a method for preparing ultra-low oil-water ratio, soil-free oil-based drilling fluid is provided, comprising:

[0015] (1) Mix 95-100 parts of octadecenoic acid, 95-100 parts of stearic acid and 95-100 parts of rosin acid, add 60-70 parts of ethylenediamine at 95-100℃, and heat to 180-190℃.

[0016] (2) Cool down to 120-130℃ and add 100-110 parts of chlorosulfonic acid;

[0017] (3) Add 130-140 parts of dispersant, stir, and obtain emulsifier;

[0018] (4) Based on the total volume of the oil phase and the water phase being 100v%, add 2wt%-4wt% of the emulsifier obtained in step (3) to the oil phase and water phase with a volume ratio of (40:60) to (70:30), stir, and obtain an emulsion;

[0019] (5) Add 2wt%-3wt% quicklime to the emulsion and stir; add 0.5wt%-1wt% polymer filtration loss reducer and stir; add 2wt%-3wt% lignite filtration loss reducer and stir; add 0.5wt%-1.0wt% flow pattern modifier and stir; add 0.5wt%-1wt% wetting agent and stir; add weighting agent to adjust the density to 1.5 g / cm³. 3 ~1.8g / cm 3 .

[0020] In a specific implementation, the volume ratio of the oil phase to the water phase in step (4) of the above method is preferably (50:50) to (70:30).

[0021] In a specific implementation, the volume ratio of the oil phase to the water phase in step (4) is further preferably (60:40) to (70:30).

[0022] In a specific implementation, the dispersant in the above preparation method is diethylene glycol butyl ether.

[0023] In a specific implementation, in the above preparation method, the oil phase is 0# diesel oil; the aqueous phase is calcium chloride aqueous solution; and the weighting agent is barite.

[0024] As another aspect of the present invention, it relates to the application of the above-mentioned ultra-low oil-water ratio soil-free oil-based drilling fluid in oil and gas development.

[0025] The ultra-low oil-water ratio, soil-free oil-based drilling fluid provided by this invention has at least the following advantages:

[0026] (1) The ultra-low oil-water ratio soil-free oil-based drilling fluid provided by the present invention has a low oil-water ratio, low colloidal content, good rheological properties, and good reservoir protection ability.

[0027] (2) The demulsification voltage of the ultra-low oil-water ratio soil-free oil-based drilling fluid provided by the present invention reaches more than 600V, which is higher than the requirement of SY / T 6615-2005 for demulsification voltage of water-in-oil drilling fluid emulsifier (≥400V). The high temperature and high pressure filtration loss is less than 3mL, and the system has good sealing and lubrication properties.

[0028] (3) The ultra-low oil-water ratio soil-free oil-based drilling fluid provided by the present invention has zero organic soil addition, relatively low structural strength, and easier performance adjustment. At the same time, a high proportion of plugging agent can be added, resulting in better anti-collapse performance.

[0029] (4) The ultra-low oil-water ratio, soil-free oil-based drilling fluid system of this invention can withstand temperatures up to 150℃ and has a maximum density of 1.5 g / cm³. 3It does not lose its fluidity at -25℃, which can meet the requirements of winter construction. It has a relatively low economic cost, is more competitive in the market, and has a good reservoir protection effect, making it more widely applicable.

[0030] (5) The ultra-low oil-water ratio soil-free oil-based drilling fluid provided by the present invention is applicable to high-angle directional wells, unconventional oil and gas horizontal wells, complex formation drilling and special process wells. Detailed Implementation

[0031] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0032] Unless otherwise specified, the parts referred to in this application are parts by weight.

[0033] In this application:

[0034] The “v%” refers to volume percentage.

[0035] The “wt%” refers to the weight-to-volume ratio, which is expressed in g / 100mL in this application.

[0036] The polymer filtration loss reducer is GW-HTV, a multi-olefin copolymer produced and sold by Great Wall Drilling Engineering Co., Ltd.

[0037] The flow pattern regulator is GW-OIS, a cutting agent produced and sold by Great Wall Drilling Engineering Co., Ltd.

[0038] The lignite filtration loss reducer mentioned above is an organic lignite filtration loss reducer produced and sold by Jiyuan Tiancheng Company.

[0039] The wetting agent is GW-WET, which is produced and sold by Great Wall Drilling Engineering Co., Ltd.

[0040] Unless otherwise specified, the raw materials used in the preparation of the ultra-low oil-water ratio soil-free oil-based drilling fluid used in this invention can all be commercially available.

[0041] The performance evaluation test method in this embodiment of the invention is as follows:

[0042] (1) The density of the drilling fluid was determined using the methods and instruments specified in GB / T 16783.2-2012 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids";

[0043] (2) The plastic viscosity, dynamic shear force, 6-repeat reading (Φ6) and 3-repeat reading (Φ3) of the drilling fluid were determined using the methods and instruments specified in GB / T 16783.2-2012 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids".

[0044] (3) The demulsification voltage of the drilling fluid was determined using the methods and instruments specified in GB / T 16783.2-2012 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids";

[0045] (4) The API filtration loss and high-temperature and high-pressure filtration loss of drilling fluid were determined using the methods and instruments specified in GB / T 16783.2-2012 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids"; the test conditions for high-temperature and high-pressure filtration loss were 150℃ and 3.5MPa.

[0046] Example 1

[0047] The formulation of an ultra-low oil-water ratio (40:60) soil-free oil-based drilling fluid is as follows: Based on the total volume of the oil and water phases, the composition is as follows: 0# diesel oil: 40 wt%; 30% CaCl2 aqueous solution: 60 wt%; emulsifier: 4 wt%; quicklime: 3.0 wt%; flow pattern modifier: 1 wt%; polymer filtration reducer: 0.75 wt%; lignite filtration reducer: 3.0 wt%; wetting agent: 1.0 wt%; barite weighted to 1.5 g / cm³. 3 The density.

[0048] Preparation of emulsifiers:

[0049] Add 95 parts of octadecenoic acid, 95 parts of stearic acid, and 100 parts of rosin acid to a reaction vessel, heat to 100°C, add 60 parts of ethylenediamine, heat to 180°C and maintain for 8 hours; cool to 120°C, add 100 parts of chlorosulfonic acid, and maintain at 120°C for 4 hours; add 130 parts of diethylene glycol butyl ether (dispersant), stir and mix to obtain an emulsifier.

[0050] Preparation method of ultra-low oil-water ratio, soil-free oil-based drilling fluid: According to the above component ratio, add 16g of emulsifier to 160mL of diesel (0# diesel) and stir at 11000r / min for 20min; add 240mL of 30% CaCl2 aqueous solution and stir at 11000r / min for 30min; add 12g of quicklime and stir at 11000r / min for 30min; while stirring, add 3.0g of polymer filtration loss reducer and stir at 11000r / min for 30min; while stirring, add 12g of lignite filtration loss reducer and stir at 11000r / min for 20min; while stirring, add 4g of flow pattern modifier and stir at 11000r / min for 20min; while stirring, add 4g of wetting agent and stir at 11000r / min for 20min; add barite until the density is 1.5g / cm³. 3 .

[0051] The quicklime is calcium oxide.

[0052] Performance evaluation:

[0053] The performance of the ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was tested at 50℃. The results are shown in Table 1.

[0054] The ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment was placed in a high-temperature aging tank and aged at 150°C for 16 hours. After cooling to 50°C, the performance of the ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment after aging was tested, and the results are shown in Table 1.

[0055] The ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was aged and allowed to stand at -25℃ for 24 hours to evaluate its performance. The results are shown in Table 2.

[0056] Example 2

[0057] Formula for an ultra-low oil-water ratio (50:50) soil-free oil-based drilling fluid: Based on the total volume of the oil and water phases, the formulation is as follows: 0# diesel oil: 50 wt%; 30% CaCl2 aqueous solution: 50 wt%; emulsifier: 3.5 wt%; quicklime: 3.0 wt%; flow pattern modifier: 1 wt%; polymer filtration reducer: 1.0 wt%; lignite filtration reducer: 3.0 wt%; wetting agent: 0.75 wt%; barite weighted to 1.5 g / cm³. 3 The density.

[0058] Preparation of emulsifiers:

[0059] Add 100 parts of octadecenoic acid, 100 parts of stearic acid and 95 parts of rosin acid to a reaction vessel, heat to 100°C, add 70 parts of ethylenediamine, heat to 190°C and maintain for 8 hours; cool to 130°C, add 110 parts of chlorosulfonic acid, maintain at 130°C for 4 hours; add 140 parts of diethylene glycol butyl ether (dispersant), stir and mix to obtain an emulsifier.

[0060] Preparation method of ultra-low oil-water ratio, soil-free oil-based drilling fluid: The above-mentioned components are proportioned as follows: 14g emulsifier is added to 200mL of diesel (0# diesel), and the mixture is stirred at 11000r / min for 20min; 200mL of 30% CaCl2 aqueous solution is added; the mixture is stirred at 11000r / min for 30min; 12g quicklime is added; the mixture is stirred at 11000r / min for 30min; 4.0g polymer filtration loss reducer is added while stirring; the mixture is stirred at 11000r / min for 30min; 12g lignite filtration loss reducer is added while stirring; the mixture is stirred at 11000r / min for 20min; 4g flow pattern modifier is added while stirring; the mixture is stirred at 11000r / min for 20min; 3g wetting agent is added while stirring; the mixture is stirred at 11000r / min for 20min; finally, barite is added until the density reaches 1.5g / cm³. 3 .

[0061] The quicklime is calcium oxide.

[0062] Performance evaluation:

[0063] The performance of the ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was tested at 50℃. The results are shown in Table 1.

[0064] The ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment was placed in a high-temperature aging tank and aged at 150°C for 16 hours. After cooling to 50°C, the performance of the ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment after aging was tested, and the results are shown in Table 1.

[0065] The ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was aged and allowed to stand at -25℃ for 24 hours to evaluate its performance. The results are shown in Table 2.

[0066] Example 3

[0067] Formula for an ultra-low oil-water ratio (60:40) soil-free oil-based drilling fluid: Based on the total volume of the oil and water phases, the formulation is as follows: 0# diesel oil: 60 wt%; 30% CaCl2 aqueous solution: 40 wt%; emulsifier: 3 wt%; quicklime: 2.0 wt%; flow pattern modifier: 1 wt%; polymer filtration reducer: 0.5 wt%; lignite filtration reducer: 3.0 wt%; wetting agent: 0.5 wt%; barite weighted to 1.5 g / cm³. 3 The density.

[0068] Preparation of emulsifiers:

[0069] 100 parts of octadecenoic acid, 96 parts of stearic acid and 96 parts of rosin acid were added to a reaction vessel, heated to 100°C, 65 parts of ethylenediamine were added, the temperature was raised to 190°C and maintained for 8 hours; the temperature was lowered to 120°C, 110 parts of chlorosulfonic acid were added, and the temperature was maintained at 120°C for 4 hours; 140 parts of diethylene glycol butyl ether (dispersant) were added, and the mixture was stirred to obtain an emulsifier.

[0070] Preparation method of ultra-low oil-water ratio, soil-free oil-based drilling fluid: The above-mentioned components are proportioned as follows: 12g emulsifier is added to 240mL of diesel (0# diesel), and the mixture is stirred at 11000r / min for 20min; 160mL of 30% CaCl2 aqueous solution is added; the mixture is stirred at 11000r / min for 30min; 8g quicklime is added; the mixture is stirred at 11000r / min for 30min; 2.0g polymer filtration loss reducer is added while stirring; the mixture is stirred at 11000r / min for 30min; 12g lignite filtration loss reducer is added while stirring; the mixture is stirred at 11000r / min for 20min; 4g flow pattern modifier is added while stirring; the mixture is stirred at 11000r / min for 20min; 2.0g wetting agent is added while stirring; the mixture is stirred at 11000r / min for 20min; finally, barite is added until the density reaches 1.5g / cm³. 3 .

[0071] Performance evaluation:

[0072] The performance of the ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was tested at 50℃. The results are shown in Table 1.

[0073] The ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment was placed in a high-temperature aging tank and aged at 150°C for 16 hours. After cooling to 50°C, the performance of the ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment after aging was tested, and the results are shown in Table 1.

[0074] The ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was aged and allowed to stand at -25℃ for 24 hours to evaluate its performance. The results are shown in Table 2.

[0075] Example 4

[0076] Formula for an ultra-low oil-water ratio (70:30) soil-free oil-based drilling fluid: Based on the total volume of the oil and water phases, the formulation is as follows: 0# diesel oil: 70 wt%; 30% CaCl2 aqueous solution: 30 wt%; emulsifier: 2 wt%; quicklime: 2.0 wt%; flow pattern modifier: 0.5 wt%; polymer filtration reducer: 0.5 wt%; lignite filtration reducer: 2.0 wt%; wetting agent: 0.5 wt%; barite weighted to 1.5 g / cm³. 3The density.

[0077] Preparation of emulsifiers:

[0078] Add 100 parts of octadecenoic acid, 100 parts of stearic acid and 100 parts of rosin acid to a reaction vessel, heat to 95°C, add 60 parts of ethylenediamine, heat to 190°C and maintain for 8 hours; cool to 130°C, add 110 parts of chlorosulfonic acid, maintain at 130°C for 4 hours; add 130 parts of diethylene glycol butyl ether (dispersant), stir and mix to obtain an emulsifier.

[0079] Preparation method of ultra-low oil-water ratio, soil-free oil-based drilling fluid: The above-mentioned components are proportioned as follows: 8g emulsifier is added to 280mL of diesel (0# diesel), and the mixture is stirred at 11000r / min for 20min; 120mL of 30% CaCl2 aqueous solution is added; the mixture is stirred at 11000r / min for 30min; 8g quicklime is added; the mixture is stirred at 11000r / min for 30min; 2.0g polymer filtration loss reducer is added while stirring; the mixture is stirred at 11000r / min for 30min; 8g lignite filtration loss reducer is added while stirring; the mixture is stirred at 11000r / min for 20min; 2g flow pattern modifier is added while stirring; the mixture is stirred at 11000r / min for 20min; 2.0g wetting agent is added while stirring; the mixture is stirred at 11000r / min for 20min; finally, barite is added until the density reaches 1.5g / cm³. 3 of.

[0080] The quicklime is calcium oxide.

[0081] Performance evaluation:

[0082] The performance of the ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was tested at 50℃. The results are shown in Table 1.

[0083] The ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment was placed in a high-temperature aging tank and aged at 150°C for 16 hours. After cooling to 50°C, the performance of the ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment after aging was tested, and the results are shown in Table 1.

[0084] The ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was aged and allowed to stand at -25℃ for 24 hours to evaluate its performance. The results are shown in Table 2.

[0085] Example 5

[0086] The formulation of an ultra-low oil-water ratio (40:60) soil-free oil-based drilling fluid is as follows: Based on the total volume of the oil and water phases, the composition is as follows: 0# diesel oil: 40 wt%; 30% CaCl2 aqueous solution: 60 wt%; emulsifier: 4 wt%; quicklime: 3.0 wt%; flow pattern modifier: 1 wt%; polymer filtration reducer: 0.75 wt%; lignite filtration reducer: 3.0 wt%; wetting agent: 1.0 wt%; barite weighted to 1.8 g / cm³. 3 The density.

[0087] Preparation of emulsifiers:

[0088] Add 95 parts of octadecenoic acid, 95 parts of stearic acid, and 100 parts of rosin acid to a reaction vessel, heat to 100°C, add 60 parts of ethylenediamine, heat to 180°C and maintain for 8 hours; cool to 120°C, add 100 parts of chlorosulfonic acid, and maintain at 120°C for 4 hours; add 130 parts of diethylene glycol butyl ether (dispersant), stir and mix to obtain an emulsifier.

[0089] Preparation method of ultra-low oil-water ratio, soil-free oil-based drilling fluid: According to the above component ratio, add 16g of emulsifier to 160mL of diesel (0# diesel) and stir at 11000r / min for 20min; add 240mL of 30% CaCl2 aqueous solution and stir at 11000r / min for 30min; add 12g of quicklime and stir at 11000r / min for 30min; while stirring, add 3.0g of polymer filtration loss reducer and stir at 11000r / min for 30min; while stirring, add 12g of lignite filtration loss reducer and stir at 11000r / min for 20min; while stirring, add 4g of flow pattern modifier and stir at 11000r / min for 20min; while stirring, add 4g of wetting agent and stir at 11000r / min for 20min; add barite until the density is 1.8g / cm³. 3 .

[0090] The quicklime is calcium oxide.

[0091] Performance evaluation:

[0092] The performance of the ultra-low oil-water ratio soil-free oil-based drilling fluid prepared in this embodiment was tested at 50℃. The results are shown in Table 1.

[0093] The ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment was placed in a high-temperature aging tank and aged at 150°C for 16 hours. After cooling to 50°C, the performance of the ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in this embodiment after aging was tested, and the results are shown in Table 1.

[0094] Example 6

[0095] The ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in Example 1 was placed in a high-temperature aging tank and aged at 180°C for 16 hours. After cooling to 50°C, the performance of the ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared in Example 1 after aging was tested, and the results are shown in Table 1.

[0096] Table 1

[0097]

[0098] Table 2

[0099]

[0100] As can be seen from the data in Examples 1-4 of Table 1, with the increase of the oil-water ratio, the plastic viscosity of the ultra-low oil-water ratio soil-free oil-based drilling fluid decreases, the demulsification voltage increases, and its rheological properties are relatively good due to the absence of soil phase. For the ultra-low oil-water ratio soil-free oil-based drilling fluid of the present invention, even under conditions where the oil-water ratio is as low as 40:60, it exhibits good electrical stability and sedimentation stability, indicating that the drilling fluid system has excellent performance. At the same time, the reduction in the oil-water ratio significantly saves on the cost of drilling fluid base oil, and the better rheological properties also increase the amount of plugging material that can be added, thereby improving reservoir protection capabilities.

[0101] As can be seen from the data in Examples 1-4 in Table 2, even with an oil-water ratio as low as 40:60, the material still has good fluidity and stability after freezing at -25℃, which can meet the needs of on-site construction at -25℃ in winter.

[0102] As can be seen from the data of Examples 1 and 6 in Table 1, under the conditions of oil-water ratio 40:60 and soil-free oil-based drilling fluid, the demulsification voltage decreased slightly with the increase of aging temperature; the plastic viscosity and dynamic shear force of the drilling fluid decreased slightly, indicating that the stability of the system was weakened at 180℃, but the impact was not significant within the adjustable range; the high-temperature and high-pressure filtration loss was still no more than 3mL, indicating that the filtration loss reducer had good temperature resistance. The ultra-low oil-water ratio soil-free oil-based drilling fluid of the present invention can withstand 180℃.

[0103] As can be seen from the data in Examples 1 and 5 of Table 1, under the conditions of an oil-water ratio of 40:60 and soil-free oil-based drilling fluid, the density increased to 1.8 g / cm³. 3 The plastic viscosity and shear strength of the oil-based drilling fluid are improved, but its rheological properties are better and there is no sedimentation compared to the soil-containing system at the same density. This indicates that the density range of the ultra-low oil-water ratio soil-free oil-based drilling fluid of this invention is 1.5-1.8 g / cm³. 3 Adjustable within the range.

[0104] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described by way of typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not restrictive terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An ultra-low oil-water ratio, soil-free oil-based drilling fluid, characterized in that, Density is 1.5 g / cm³ 3 ~1.8g / cm 3 The ultra-low oil-water ratio soil-free oil-based drilling fluid is an emulsion formed by the oil and water phases under the action of an emulsifier, containing a polymer filtration loss reducer, a wetting agent, a flow pattern modifier, a lignite filtration loss reducer, and quicklime. The volume ratio of the oil phase to the water phase is (40:60) to (70:30). Based on the total volume of the oil and water phases, the weight-volume ratio of the emulsifier is 2wt%-4wt%, the weight-volume ratio of the quicklime is 2wt%-3wt%, the weight-volume ratio of the flow pattern modifier is 0.5wt%-1.0wt%, the weight-volume ratio of the polymer filtration loss reducer is 0.5wt%-1wt%, the weight-volume ratio of the lignite filtration loss reducer is 2wt%-3wt%, and the weight-volume ratio of the wetting agent is 0.5wt%-1wt%.

2. The ultra-low oil-water ratio, soil-free oil-based drilling fluid according to claim 1, characterized in that, The volume ratio of the oil phase to the water phase is (50:50) to (70:30).

3. The ultra-low oil-water ratio, soil-free oil-based drilling fluid according to claim 1, characterized in that, The volume ratio of the oil phase to the water phase is (60:40) to (70:30).

4. The ultra-low oil-water ratio, soil-free oil-based drilling fluid according to any one of claims 1-3, characterized in that, The oil phase is 0# diesel oil; the aqueous phase is calcium chloride aqueous solution.

5. A method for preparing ultra-low oil-water ratio, soil-free oil-based drilling fluid, characterized in that, include: (1) Mix 95-100 parts of octadecenoic acid, 95-100 parts of stearic acid and 95-100 parts of rosin acid, add 60-70 parts of ethylenediamine at 95-100℃, and heat to 180-190℃. (2) Cool down to 120-130℃ and add 100-110 parts of chlorosulfonic acid; (3) Add 130-140 parts of dispersant, stir, and obtain emulsifier; (4) Based on the total volume of the oil phase and the water phase, add 2wt%-4wt% of the emulsifier obtained in step (3) to the oil phase and water phase with a volume ratio of (40:60) to (70:30), stir, and obtain an emulsion; (5) Add 2wt%-3wt% quicklime to the emulsion and stir; add 0.5wt%-1wt% polymer filtration loss reducer and stir; add 2wt%-3wt% lignite filtration loss reducer and stir; add 0.5wt%-1.0wt% flow pattern modifier and stir; add 0.5wt%-1wt% wetting agent and stir; add weighting agent to adjust the density to 1.5 g / cm³. 3 ~1.8g / cm 3 .

6. The method according to claim 5, characterized in that, The volume ratio of the oil phase and the water phase in step (4) is (50:50) to (70:30).

7. The method according to claim 5, characterized in that, The volume ratio of the oil phase and the water phase in step (4) is (60:40) to (70:30).

8. The method according to claim 5, characterized in that, The dispersant is diethylene glycol butyl ether.

9. The method according to claim 5, characterized in that, The oil phase is 0# diesel oil; the aqueous phase is calcium chloride aqueous solution; and the weighting agent is barite.

10. Application of ultra-low oil-water ratio, soil-free oil-based drilling fluid in oil and gas development, characterized in that... The ultra-low oil-water ratio, soil-free oil-based drilling fluid is the ultra-low oil-water ratio, soil-free oil-based drilling fluid according to any one of claims 1-5 or the ultra-low oil-water ratio, soil-free oil-based drilling fluid prepared by any one of claims 5-9.

Images