Anti-collapse oil-based drilling fluid composition, anti-collapse oil-based drilling fluid and their applications

Abstract

The present invention relates to the technical field of drilling engineering, and specifically relates to an anti-collapse oil-based drilling fluid composition, an anti-collapse oil-based drilling fluid and their applications. Calculated by weight parts, the composition includes: 25-30 parts of base oil, 1-2 parts of main emulsifier, 1-2 parts of auxiliary emulsifier, 1-2 parts of wetting agent, 1-2 parts of calcium chloride aqueous solution, 1-3 parts of quicklime, 3-4 parts of viscosifier, 2-4 parts of filtrate reducer, 1-2 parts of oil-based anti-collapse agent, 1-2 parts of plugging agent; the plugging agent is selected from nano oil-based carbon black and / or calcium carbonate with an oleophilic surface. The drilling fluid of the present invention can reduce the high-temperature and high-pressure filtrate loss, improve the plugging and anti-collapse ability of the drilling fluid, solve the problem of well collapse during the drilling of fractured and broken formations, and has a stable emulsion state and strong anti-fracturing fluid pollution ability.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling engineering, and particularly relates to an anti-collapse oil-based drilling fluid composition, an anti-collapse oil-based drilling fluid and their applications. Background Art

[0002] Shale gas is a clean energy currently being key developed in China. The use of horizontal well development and large-scale hydraulic fracturing is the basis for shale gas to have industrial production capacity. However, large-scale hydraulic fracturing causes fragmentation of shale formations, development of fractures, and invasion of fracturing fluid, which brings huge challenges to the drilling work of adjacent wells, especially parallel horizontal wells with relatively short spacing. At present, conventional diesel-based drilling fluid systems are used in shale gas formation drilling in China. When drilling through the continuously fractured formation caused by horizontal section fracturing, the invasion of fracturing fluid will cause the performance of oil-based drilling fluid to deteriorate, accompanied by severe well collapse, pump jamming, frequent sticking of the drill string, long time for dealing with well collapse, and extremely high risk of drill string burial by well collapse when downhole tools such as rotary steerable systems are drilling in this well section. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems of wellbore instability during drilling in fractured formations of shale gas horizontal sections and contamination of oil-based drilling fluid by fracturing fluid existing in the prior art, and to provide an anti-collapse oil-based drilling fluid composition, an anti-collapse oil-based drilling fluid and their applications. The drilling fluid has a high demulsification voltage and strong resistance to fracturing fluid contamination.

[0004] To achieve the above purpose, in the first aspect of the present invention, an anti-collapse oil-based drilling fluid composition is provided. Calculated by volume parts, the composition includes:

[0005] 25 - 30 parts of base oil, 1 - 2 parts of main emulsifier, 1 - 2 parts of auxiliary emulsifier, 1 - 2 parts of wetting agent, 1 - 2 parts of calcium chloride aqueous solution, 1 - 3 parts of quicklime, 3 - 4 parts of viscosifier, 2 - 4 parts of filtrate reducer, 1 - 2 parts of oil-based anti-collapse agent, 1 - 2 parts of plugging agent;

[0006] The plugging agent is selected from nano oil-based carbon black and / or calcium carbonate with an oleophilic surface.

[0007] In the second aspect of the present invention, an anti-collapse oil-based drilling fluid is provided. The anti-collapse oil-based drilling fluid is prepared by mixing raw materials including the anti-collapse oil-based drilling fluid composition of the present invention.

[0008] In the third aspect of the present invention, an application of the anti-collapse oil-based drilling fluid of the present invention in preventing well collapse during drilling in fractured formations of shale gas is provided.

[0009] Through the above technical solution, the anti-collapse oil-based drilling fluid provided by the present invention uses oily carbon black and / or calcium carbonate with a lipophilic surface as a plugging agent in combination with other components of the present invention to reduce the filtration loss at high temperature and high pressure, improve the plugging and anti-collapse ability of the drilling fluid, and solve the problem of well collapse during the drilling process in a fractured formation. The viscosity of the drilling fluid of the present invention is controlled at 80-100S, and the dynamic shear force is greater than 15 Pa, which can carry out large fallen blocks in time and reduce the scouring and disturbance of the fractured formation, ensuring the smoothness of the wellbore and downhole safety. The flow state of the drilling fluid is laminar flow, reducing the disturbance to the fractured formation. The demulsification voltage of the drilling fluid of the present invention is high, and the emulsion state is stable; the formed oil-based drilling fluid can resist 10% of the fracturing fluid pollution. This drilling fluid can meet the requirements of safe drilling in large sections of fractured shale gas formations. Detailed implementation mode

[0010] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0011] The first aspect of the present invention provides an anti-collapse oil-based drilling fluid composition, which, in terms of volume parts, comprises:

[0012] 25-30 parts of base oil, 1-2 parts of main emulsifier, 1-2 parts of auxiliary emulsifier, 1-2 parts of wetting agent, 1-2 parts of calcium chloride aqueous solution, 1-3 parts of quicklime, 3-4 parts of thickening agent, 2-4 parts of filtration reducer, 1-2 parts of oil-based anti-collapse agent, 1-2 parts of plugging agent;

[0013] The plugging agent is selected from nano-oily carbon black and / or calcium carbonate with a lipophilic surface.

[0014] In the present invention, the nano-oily carbon black can achieve the purpose of the present invention. According to a preferred embodiment of the present invention, the average particle size of the nano-oily carbon black is 10-100 nm, preferably 10-40 nm. It is beneficial to improve the comprehensive performance of the anti-collapse oil-based drilling fluid.

[0015] The present invention does not particularly limit the preparation method of the oily carbon black. For example, the oily carbon black is made by the furnace black method. At 1200-1650 °C, oil is sprayed into the reaction furnace and a type of carbon black is generated through incomplete combustion and cracking.

[0016] In the present invention, calcium carbonate with a lipophilic surface can achieve the object of the present invention. According to a preferred embodiment of the present invention, the average particle size of the calcium carbonate with a lipophilic surface is 0.5 - 5 μm, preferably 0.5 - 2 μm, which is beneficial to improving the comprehensive performance of the anti-collapse oil-based drilling fluid.

[0017] According to a preferred embodiment of the present invention, the plugging agent is a mixture of oil-based carbon black and calcium carbonate with a lipophilic surface. Preferably, the mass ratio of oil-based carbon black to calcium carbonate with a lipophilic surface is 1:1 - 3:1, which is beneficial to improving the comprehensive performance of the anti-collapse oil-based drilling fluid.

[0018] In the present invention, there is no special requirement for the preparation method of the calcium carbonate with a lipophilic surface. As long as the surface of the calcium carbonate is a lipophilic group, the object of the present invention can be achieved. According to a preferred embodiment of the present invention, the present invention provides a preparation method of calcium carbonate with a lipophilic surface, which includes: mixing calcium carbonate with a substance containing hydrophilic and lipophilic groups and grinding to obtain the calcium carbonate with a lipophilic surface; during the mixing and grinding process, the substance with hydrophilic and lipophilic properties is adsorbed on the hydrophilic surface of the calcium carbonate, thereby obtaining calcium carbonate with a lipophilic surface; preferably, the substance containing hydrophilic and lipophilic groups accounts for 2% - 10% of the mass of calcium carbonate, preferably 3% - 5%.

[0019] According to a preferred embodiment of the present invention, the substance containing hydrophilic and lipophilic groups is selected from at least one of lecithin, octylphenol polyoxyethylene ether, and sorbitan monolaurate.

[0020] In the present invention, there is no special requirement for the type of the base oil, and conventional base oils in the art can be used in the present invention. Preferably, the base oil is selected from at least one of No. 0 diesel oil, white oil, and gas-made oil.

[0021] In the present invention, there is no special requirement for the type of the main emulsifier, and conventional main emulsifiers in the art can be used in the present invention. Preferably, the main emulsifier is selected from at least one of polyamide carboxylic acid, calcium naphthenate, and polyamide.

[0022] In the present invention, there is no special requirement for the type of the auxiliary emulsifier, and conventional auxiliary emulsifiers in the art can be used in the present invention. Preferably, the auxiliary emulsifier is selected from sodium dodecylbenzenesulfonate and / or sorbitan monooleate.

[0023] In the present invention, there is no special requirement for the type of the wetting agent, and conventional wetting agents in the art can be used in the present invention. Preferably, the wetting agent is selected from at least one of octylphenol polyoxyethylene ether, sorbitan monolaurate, and lecithin; and / or

[0024] In the present invention, the concentration range of the calcium chloride aqueous solution is relatively wide. Preferably, the concentration of the calcium chloride aqueous solution is 25 wt% to 30 wt%; and / or

[0025] In the present invention, there is no particular requirement for the type of the organic bentonite, and conventional organic bentonites in the art can be used in the present invention. Preferably, the thickener is an organic bentonite; and / or

[0026] In the present invention, there is no particular requirement for the type of the filtrate reducer, and conventional filtrate reducers in the art can be used in the present invention. Preferably, the filtrate reducer is selected from at least one of humic acid amide filtrate reducer, organosilicon humic acid amide filtrate reducer, and sulfonated α-olefin-styrene polymer; and / or

[0027] In the present invention, there is no particular requirement for the type of the oil-based hole stabilizer, and conventional oil-based hole stabilizers in the art can be used in the present invention. Preferably, the oil-based hole stabilizer is selected from at least one of oxidized asphalt, natural asphalt, and cationic emulsified asphalt.

[0028] According to a preferred embodiment of the present invention, the composition further includes a density regulator. Preferably, the density regulator is selected from at least one of barite, iron ore powder, and calcium carbonate.

[0029] The addition amount of the density regulator is determined according to the requirement of the working fluid density.

[0030] The second aspect of the present invention provides an anti-collapse oil-based drilling fluid, which is prepared by mixing raw materials including the anti-collapse oil-based drilling fluid composition of the present invention. The drilling fluid emulsion of the present invention has a stable state, strong ability to resist the pollution of fracturing fluid, and a laminar flow state, can solve the problem of well collapse during the drilling process of fractured formations, can carry out large fallen blocks in time, and reduce the erosion and disturbance of the fractured formations, ensuring wellbore smoothness and downhole safety.

[0031] According to a preferred embodiment of the present invention, the mixing steps of the anti-collapse oil-based drilling fluid include:

[0032] (1) Input base oil, main emulsifier, auxiliary emulsifier, and wetting agent in proportion, and carry out high-speed stirring and mixing evenly;

[0033] (2) Then add the calcium chloride aqueous solution, and carry out high-speed stirring and mixing evenly;

[0034] (3) Then add quicklime, and carry out high-speed stirring and mixing evenly;

[0035] (4) Then add the thickener, and carry out high-speed stirring and mixing evenly;

[0036] (5) Add filtration reducer, oil-based anti-collapse agent and plugging agent, and stir at high speed to mix evenly.

[0037] According to a preferred embodiment of the present invention, the high-speed stirring conditions include: a rotation speed of 10000-12000 r / min; preferably, the stirring time is reasonably adjusted according to the stirring speed, as long as the mixture is mixed evenly, preferably, the stirring time is 10-30 min.

[0038] According to a preferred embodiment of the present invention, a density regulator can be added at last according to the density requirement of the working fluid, and high-speed stirring and mixing are performed to obtain the anti-collapse oil-based drilling fluid.

[0039] A third aspect of the present invention provides an application of the anti-collapse oil-based drilling fluid of the present invention in preventing collapse during drilling in shale gas fracturing fractured formations.

[0040] The present invention will be described in detail below through examples.

[0041] In the following examples, the drilling fluid properties are measured according to GB / T 16783.2-2012 Field Test of Drilling Fluids in Petroleum and Natural Gas Industry Part 2: Test Methods for Oil-Based Drilling Fluids, and the wellbore flow test is calculated according to API RP 13D Rheology and Hydraulics of Oil-well Drilling Fluids.

[0042] In the following examples, the No. 0 diesel used is a commercial product; the gas-to-liquids are commercial products from Total of France;

[0043] The main emulsifier is polyamide carboxylic acid, which comes from Sinopec Petroleum Engineering Technology Research Institute;

[0044] The auxiliary emulsifier is sorbitan monooleate (i.e. SPAN80), which comes from Sinopec Petroleum Engineering Technology Research Institute;

[0045] The wetting agent was sorbitan monolaurate, which was obtained from the Petroleum Engineering Technology Research Institute of Sinopec;

[0046] The mass concentration of calcium chloride brine is 28%;

[0047] Quicklime comes from a conventional commercial product;

[0048] The organobentonite is a cationic organobentonite from Sinopec Nanjing Research Institute of Chemical Industry;

[0049] The fluid loss reducer is oxidized asphalt, which comes from Sinopec Petroleum Engineering Technology Research Institute;

[0050] The particle size of oily carbon black is 10-100nm, the particle size D90 is 40nm, and it comes from Shandong Kekai Petroleum Technology Company;

[0051] The calcium carbonate has a particle size of 0.5 - 5 μm, a D90 particle size of 2 μm, and is from Shandong Kekai Petroleum Technology Company; the lecithin is from Sinopec Research Institute of Petroleum Engineering Technology.

[0052] In the following examples, the drilling fluid properties of the anti-collapse oil-based drilling fluid, such as density, viscosity (FS), emulsion-breaking voltage (ES), high-temperature and high-pressure filtration loss (FLHTHP), etc., are tested according to GB / T 16783.2 - 2012 Petroleum and natural gas industries - Field testing of drilling fluids - Part 2: Testing of oil-based drilling fluids, and the wellbore flow regime is calculated according to the API RP 13D Rheology and Hydraulics of Oil-well Drilling Fluids method.

[0053] In the following examples, the preparation method of the anti-collapse oil-based drilling fluid includes the following steps:

[0054] (1) Place the gas-to-liquid oil in a high-speed mixer cup, add the main emulsifier, auxiliary emulsifier, and wetting agent, and stir at a high speed for 10 min at a rotation speed of 12000 r / min;

[0055] (2) Add calcium chloride brine and stir at a high speed for 10 min at a rotation speed of 12000 r / min;

[0056] (3) Add calcium oxide powder and stir at a high speed for 10 min at a rotation speed of 12000 r / min;

[0057] (4) Add organophilic bentonite and stir at a high speed for 20 min at a rotation speed of 12000 r / min;

[0058] (5) Add a filtration loss reducer, an oil-based anti-collapse agent, and a micro-nano plugging agent, and stir at a high speed for 10 min at a rotation speed of 12000 r / min.

[0059] (6) Finally, add a density regulator and stir at a high speed for 30 min at a rotation speed of 12000 r / min. After mixing evenly, the anti-collapse oil-based drilling fluid is prepared.

[0060] Preparation Example 1

[0061] Mix and grind calcium carbonate (with a particle size of 0.5 - 5 μm and a D90 particle size of 2 μm) with 5% of the mass of calcium carbonate of lecithin to prepare the calcium carbonate with a lipophilic surface.

[0062] Preparation Example 2

[0063] Mix and grind calcium carbonate (with a particle size of 0.5 - 5 μm and a D90 particle size of 2 μm) with 10% of the mass of calcium carbonate of lecithin to prepare the calcium carbonate with a lipophilic surface.

[0064] Example 1

[0065] The anti-collapse oil-based drilling fluid composition comprises, by volume parts:

[0066] Diesel No. 0: main emulsifier: auxiliary emulsifier: wetting agent: calcium chloride brine: quicklime: organic bentonite: filtration reducer: oil-based anti-collapse agent: plugging agent: conventional barite powder = 30:2:2:2:1:2:4:3:2:2:13;

[0067] Among them, the plugging agent is a mixture of oil-based carbon black and calcium carbonate with an oleophilic surface prepared in Preparation Example 1, and the weight ratio is 1:1. The drilling fluid test results are shown in Table 1.

[0068] Example 2

[0069] The difference from Example 1 is that the nano plugging agent is nano oil-based carbon black and calcium carbonate with an oleophilic surface prepared in Preparation Example 1, and the mass ratio of oil-based carbon black to calcium carbonate with an oleophilic surface is 2:1. The drilling fluid test results are shown in Table 1.

[0070] Example 3

[0071] The difference from Example 1 is that the nano plugging agent is nano oil-based carbon black and calcium carbonate with an oleophilic surface prepared in Preparation Example 1, and the mass ratio of oil-based carbon black to calcium carbonate with an oleophilic surface is 3:1. The drilling fluid test results are shown in Table 1.

[0072] Example 4

[0073] The difference from Example 1 is that the base oil uses natural gas-to-liquid oil, trade name EDC95-11, from Total Company of France. The drilling fluid test results are shown in Table 1.

[0074] Example 5

[0075] The difference from Example 1 is that the plugging agent is calcium carbonate with an oleophilic surface prepared in Preparation Example 1. The drilling fluid test results are shown in Table 1.

[0076] Example 6

[0077] The difference from Example 1 is that the volume ratio of Diesel No. 0 to calcium chloride brine is 30:2. The drilling fluid test results are shown in Table 1.

[0078] Example 7

[0079] The difference from Example 1 is that the plugging agent is oil-based carbon black. The drilling fluid test results are shown in Table 1.

[0080] Example 8

[0081] The difference from Example 5 is that the plugging agent is calcium carbonate with a lipophilic surface prepared in Preparation Example 2. The test results of the drilling fluid are shown in Table 1.

[0082] Comparative Example 1

[0083] In parts by volume, the conventional oil-based drilling fluid composition comprises:

[0084] Diesel No. 0: main emulsifier: auxiliary emulsifier: wetting agent: calcium chloride brine: quicklime: organophilic bentonite: oil-based filtrate reducer: conventional barite = 30:1:1:1:4:1:2:2:12.

[0085] The results are shown in Table 1.

[0086] Comparative Example 2

[0087] Compared with Example 5, the difference is that the plugging agent uses unmodified calcium carbonate with a particle size of 0.5 - 5 μm and a particle size D90 of 2 μm. The results are shown in Table 1.

[0088] Comparative Example 3

[0089] Compared with Example 7, the difference is that the plugging agent uses conventional graphite powder with a particle size of 10 - 500 μm and a particle size D90 of 300 μm, from Shandong Kekai Petroleum Technology Company. The results are shown in Table 1.

[0090] Table 1

[0091]

[0092] Table 2 Evaluation experiment on the ability of oil-based drilling fluid to resist fracturing fluid pollution

[0093]

[0094] The fracturing fluid formula is 0.50% thickening agent + 0.10% crosslinking agent + 1% clay stabilizer + 0.10% drainage aid + 0.05% breaker.

[0095] Field application

[0096] The Nanchuan shale gas oilfield is located in Nanchuan, Chongqing, with a vertical depth of 3300 m and a horizontal section length of 1500 - 2000 m. The main purpose is to develop shale gas in the Longmaxi Formation. During the development of this oilfield, newly drilled wells are greatly affected by large-scale fracturing in the horizontal section of adjacent wells. Compared with before fracturing, the formation of new wells near the fractured wells is broken, microfractures are developed, the fracturing fluid seriously pollutes the drilling fluid during the horizontal section drilling process, and at the same time, serious well collapses, pump jams and top drive jams occur frequently, and the time for dealing with complexities is long.

[0097] Using the drilling fluid prepared in Comparative Example 1

[0098] The horizontal distance difference between Well Shengye 14-2 and the fractured well is 350 m. When the fractured fracture zone was encountered during drilling, the drilling fluid was contaminated by 15 m 3 of fracturing fluid. The demulsification voltage of the drilling fluid dropped to 200 V, and the viscosity of the drilling fluid increased to 86 s. At the same time, the well collapse was severe. The density of the drilling fluid was increased to 1.86 g / cm 3 to balance the formation collapse pressure, but the downhole collapse was still severe. The top drive was frequently stuck and the pump was blocked, and the drill pipe was stuck many times. At the same time, there was leakage of oil-based drilling fluid. The time for dealing with the well collapse of this well was as long as 30 d. Due to continuous collapse, it was difficult to ream the well, and the well had to be filled. During the period of dealing with the complexity, a total of 123 m 3 of oil-based drilling fluid was lost.

[0099] The drilling fluid prepared in Example 1 was used.

[0100] Well Shengye 14-3 is a well on the same platform as Well Shengye 14-2. The horizontal distance difference from the fractured well is 280 m. When the fractured fracture zone was encountered during drilling, the drilling fluid was contaminated by 15 m 3 of fracturing fluid. The demulsification voltage of the drilling fluid dropped from 1200 V to 850 V and quickly returned to normal after adjustment. The amount of cuttings returned at the wellhead increased by 10% - 15% compared with normal drilling. There was no phenomenon of pump blocking and top drive sticking during the drilling process. The density of the drilling fluid remained at 1.6 g / cm 3 , the funnel viscosity remained at about 100 s, and the demulsification voltage remained at 1200 V. The drilling fluid had good plugging and anti-collapse capabilities, and there was no phenomenon of drilling fluid leakage.

[0101] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An anti-collapse oil-based drilling fluid composition, characterized in that, In parts by volume, the composition comprises: 25 - 30 parts of base oil, 1 - 2 parts of main emulsifier, 1 - 2 parts of auxiliary emulsifier, 1 - 2 parts of wetting agent, 1 - 2 parts of calcium chloride aqueous solution, 1 - 3 parts of quicklime, 3 - 4 parts of viscosifier, 2 - 4 parts of filtrate reducer, 1 - 2 parts of oil - based anti - sloughing agent, 1 - 2 parts of plugging agent; The plugging agent is a mixture of nano - oil - based carbon black and calcium carbonate with a lipophilic surface, and the mass ratio of nano - oil - based carbon black to calcium carbonate with a lipophilic surface is 1 - 3:1; The average particle size of the nano - oil - based carbon black is 10 - 100 nm; The preparation method of the calcium carbonate with a lipophilic surface comprises: Mixing calcium carbonate with a substance containing hydrophilic - lipophilic groups and grinding to obtain the calcium carbonate with a lipophilic surface, and the substance containing hydrophilic - lipophilic groups accounts for 2% - 10% of the mass of calcium carbonate; the particle size of calcium carbonate is 0.5 - 5 μm.

2. The composition according to claim 1, wherein, The average particle size of the nano - oil - based carbon black is 10 - 40 nm.

3. The composition according to claim 1 or 2, wherein, The substance containing hydrophilic - lipophilic groups is selected from at least one of lecithin, octylphenol polyoxyethylene ether and sorbitan monolaurate.

4. The composition according to claim 1 or 2, wherein, The base oil is selected from at least one of No. 0 diesel oil, white oil and gas - made oil; and / or The main emulsifier is selected from at least one of polyamide carboxylic acid, calcium naphthenate and polyamide; and / or The auxiliary emulsifier is selected from sodium dodecylbenzenesulfonate and / or sorbitan monooleate.

5. The composition according to claim 1 or 2, wherein, The wetting agent is selected from at least one of octylphenol polyoxyethylene ether, sorbitan monolaurate and lecithin; and / or The concentration of the calcium chloride aqueous solution is 25 wt% - 30 wt%; and / or The viscosifier is organobentonite; and / or The filtrate reducer is selected from at least one of humic acid amide filtrate reducer, organosilicon humic acid amide filtrate reducer and sulfonated α - olefin - styrene polymer; and / or The oil - based anti - sloughing agent is selected from at least one of oxidized asphalt, natural asphalt and cationic emulsified asphalt.

6. The composition according to claim 1 or 2, wherein The composition further comprises a density regulator.

7. The composition according to claim 6, wherein, The density regulator is selected from at least one of barite, iron ore powder and calcium carbonate.

8. An anti-collapse oil-based drilling fluid, characterized in that, This anti - sloughing oil - based drilling fluid is prepared by mixing the raw materials comprising the anti - sloughing oil - based drilling fluid composition according to any one of claims 1 - 7.

9. Application of the anti - sloughing oil - based drilling fluid according to claim 8 in preventing sloughing during drilling in shale gas fracturing and crushing formations.

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