Pickering emulsion type drilling fluid with stable cellulose nanomaterial and preparation method of Pickering emulsion type drilling fluid

Abstract

The invention provides a Pickering emulsion type drilling fluid with a stable cellulose nanomaterial and a preparation method of the Pickering emulsion type drilling fluid. The Pickering emulsion type drilling fluid is prepared from the following components: a modified cellulose nanomaterial aqueous dispersion, a water-soluble cellulose derivative, biodiesel and bentonite, the modified cellulose nanomaterial is a cellulose nanomaterial modified by a silane coupling agent, and the ratio of the silane coupling agent to the cellulose nanomaterial is 0.05-0.3 mmol / g; the concentration of the modified cellulose nanomaterial aqueous dispersion is 0.1-2.0 wt%; the addition amount of the water-soluble cellulose derivative is 1-10% of the mass of the modified cellulose nanomaterial. The Pickering emulsion type drilling fluid provided by the invention is an oil-in-water Pickering emulsion type drilling fluid which is high in stability, low in filter loss and low in permeability.

Description

Technical Field

[0001] The invention relates to a Pickering emulsion drilling fluid stabilized by cellulose nanomaterials and a preparation method thereof, belonging to the technical field of drilling fluids. Background Art

[0002] Drilling operations establish a channel between the surface and the reservoir, and drilling fluid is key to ensuring rapid, safe, and efficient drilling operations. Drilling fluid is a mixture of chemical reagents used to transport fracturing debris from the drill bit to the surface. It also stabilizes the wellbore by maintaining hydrostatic pressure, sealing the wellbore, and reducing fluid loss to the formation. Emulsion drilling fluid is a multifunctional fluid composed of oil, water, and surfactants. It has great application potential due to its high stability, good fluidity, good inhibition, and good lubricity. However, the large amount of surfactants used in surfactant emulsions is not conducive to sustainable development, and the problems of removal and recovery have limited its application space.

[0003] Pickering emulsions are a new type of emulsion that uses solid particles as stabilizers, replacing traditional surfactants. Compared to traditional emulsions, these new emulsions offer advantages such as lower stabilizer requirements, improved emulsion stability, reduced toxicity, increased resistance to environmental changes, and greater adjustability. They are gaining widespread attention and are expected to address the poor stability of surfactant-based emulsion drilling fluids in harsh environments, while also improving their biodegradability and sustainability.

[0004] Stabilizers for Pickering emulsions include a variety of organic or inorganic solid particles, such as montmorillonite, titanium dioxide, carbon nanotubes (CNTs), graphene oxide (GO), magnetic particles, and polymer particles. Pickering emulsions have begun to be used in drilling fluids and have great development potential. Among them, Pickering emulsions stabilized by nano-solid particles not only have the function of adjusting rheological properties and reducing filtration loss, but also maintain higher stability of the emulsion due to the strong adsorption effect brought about by the larger specific surface area. However, due to the fact that solid particles flow into the formation during the mining process, non-degradable solid particles will cause certain damage to the oil and gas reservoirs as they accumulate in large quantities and exist for a long time, which to a certain extent limits the application of Pickering emulsions in the field of drilling fluids.

[0005] Therefore, it is very necessary to develop high-performance, biodegradable and stable Pickering emulsion drilling fluid, which meets the development needs of green ecological oil fields.

[0006] Cellulose is a renewable, biodegradable natural polymer widely found in nature. Cellulose nanomaterials (CNMs) extracted from cellulose possess hydrophobic chain structures, hydrophilic hydroxyl groups, and nanoscale dimensions, as well as inherent non-toxicity and biocompatibility, making them ideal stabilizers for Pickering emulsions. However, due to the inherent hydrophilicity of CNMs, the long-term stability of Pickering emulsions stabilized by them is poor. Therefore, by modifying CNMs to a certain degree of hydrophobicity and compounding them with water-soluble, inexpensive cellulose derivatives, the stabilization effect of cellulose nanomaterials on Pickering emulsions can be enhanced while also helping to reduce costs, facilitating their further application in Pickering emulsion drilling fluids.

[0007] CN113980660A discloses a Pickering emulsion drilling fluid prepared by mixing and emulsifying a nanocellulose aqueous dispersion (cellulose nanofibrils (CNF), cellulose nanocrystals (CNC)), bentonite, and biodiesel. CNF and CNC are prepared from eucalyptus wood powder using TEMPO oxidation and acid hydrolysis, and then mixed and emulsified with biodiesel and bentonite to obtain a Pickering emulsion drilling fluid.

[0008] CN105994697A discloses a technical solution for preparing a Pickering emulsion using a suspension of a composite of nanocellulose and a water-soluble cellulose derivative and edible oil, thereby forming an edible oil gel.

[0009] The drilling fluid disclosed in the above-mentioned prior art still has certain deficiencies in terms of stability and fluid loss reduction. There is still a need in the art to develop a Pickering emulsion drilling fluid with both good stability and fluid loss reduction. Summary of the Invention

[0010] In order to solve the above technical problems, the object of the present invention is to provide a Pickering emulsion drilling fluid, which has good stability and fluid loss reduction properties.

[0011] To achieve the above object, the present invention provides a Pickering emulsion drilling fluid stabilized by cellulose nanomaterials, wherein the components of the Pickering emulsion drilling fluid include: a modified cellulose nanomaterial aqueous dispersion, a water-soluble cellulose derivative, biodiesel and bentonite;

[0012] The modified cellulose nanomaterial is a cellulose nanomaterial modified by a silane coupling agent, and the ratio of the silane coupling agent to the cellulose nanomaterial is 0.05-0.3 mmol / g;

[0013] The concentration of the modified cellulose nanomaterial aqueous dispersion is 0.1-2.0 wt %;

[0014] The amount of the water-soluble cellulose derivative added is 1-10% of the mass of the modified cellulose nanomaterial;

[0015] The volume ratio of the modified cellulose nanomaterial aqueous dispersion to the biodiesel is 1:1-4:1;

[0016] The mass ratio of the modified cellulose nanomaterial aqueous dispersion to the bentonite is 0-3:1.

[0017] This invention modifies the hydrophobicity of cellulose nanomaterials to a certain degree using a silane coupling agent, then compounding them with a water-soluble, inexpensive cellulose derivative. The synergistic effect of the modified cellulose nanomaterial and the water-soluble cellulose derivative significantly improves the stability of the cellulose nanomaterial in Pickering emulsions. The invention provides a high-performance, biodegradable, cellulose nanomaterial-stabilized Pickering emulsion drilling fluid.

[0018] According to a specific embodiment of the present invention, preferably, the concentration of the modified cellulose nanomaterial aqueous dispersion is 0.1-1.5 wt %.

[0019] According to a specific embodiment of the present invention, preferably, the ratio of the silane coupling agent to the cellulose nanomaterial is 0.15-0.3 mmol / g.

[0020] According to a specific embodiment of the present invention, preferably, the added amount of the water-soluble cellulose derivative is 1-8% of the mass of the modified cellulose nanomaterial.

[0021] According to a specific embodiment of the present invention, preferably, the mass ratio of the modified cellulose nanomaterial aqueous dispersion to the bentonite is 1-3:1.

[0022] According to a specific embodiment of the present invention, cellulose nanomaterials are a green and environmentally friendly biomass material that is safe, non-toxic, biodegradable, and can reduce the use of surfactants, which is conducive to promoting the development and construction of green oil fields; preferably, the cellulose nanomaterials are selected from one or a combination of cellulose nanocrystals (CNC) and cellulose nanofibers (CNF).

[0023] According to a specific embodiment of the present invention, preferably, the diameter of the cellulose nanocrystals is 1-200 nm, and the length is less than or equal to 1 μm; the diameter of the cellulose nanofibers is 1-50 nm, and the length is greater than or equal to 1 μm.

[0024] According to a specific embodiment of the present invention, preferably, the silane coupling agent is selected from one or a combination of two of phenyltrimethoxysilane (PTS), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), vinyltrimethoxysilane (A171), γ-glycidyloxypropyltrimethoxysilane (KH560), γ-aminopropyltriethoxysilane (KH550), etc.

[0025] According to a specific embodiment of the present invention, preferably, the water-soluble cellulose derivative is selected from one or a combination of two of methyl cellulose (MC), carboxymethyl cellulose (CMC), polyanionic cellulose (PAC), hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), hydroxyethyl carboxymethyl cellulose (HECMC), etc.

[0026] According to a specific embodiment of the present invention, preferably, the bentonite is sodium bentonite.

[0027] According to a specific embodiment of the present invention, preferably, the cellulose nanomaterial is a combination of cellulose nanocrystals and cellulose nanofibers;

[0028] The modified cellulose nanomaterial aqueous dispersion comprises a modified cellulose nanocrystal dispersion and a modified cellulose nanofiber dispersion, wherein the concentration of the modified cellulose nanocrystal dispersion is 0.3-0.4 wt %, and the concentration of the modified cellulose nanofiber dispersion is 0.2-0.4 wt %;

[0029] The silane coupling agent is modified into γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane; the ratio of the silane coupling agent to the cellulose nanomaterial is 0.15-0.3 mmol / g;

[0030] The water-soluble cellulose derivative is carboxymethyl cellulose and / or hydroxypropyl methyl cellulose; the amount of the water-soluble cellulose derivative added is 5-6% of the mass of the modified cellulose nanomaterial;

[0031] The volume ratio of the modified cellulose nanomaterial aqueous dispersion to the biodiesel is 1:1-3:1;

[0032] The mass ratio of the modified cellulose nanomaterial aqueous dispersion to the bentonite is 1-2:1.

[0033] The present invention also provides a method for preparing the Pickering emulsion drilling fluid stabilized by the cellulose nanomaterial, which comprises the following steps:

[0034] reacting the cellulose nanomaterial aqueous dispersion with the hydrolyzed silane coupling agent at 10-25° C. to obtain a modified cellulose nanomaterial aqueous dispersion;

[0035] mixing a modified cellulose nanomaterial dispersion with a water-soluble cellulose derivative to obtain a first mixed solution;

[0036] adding biodiesel and bentonite to the first mixed liquid to obtain a second mixed liquid;

[0037] The second mixed liquid is emulsified to obtain a homogeneous emulsion, that is, the Pickering emulsion drilling fluid stabilized by the cellulose nanomaterial.

[0038] According to a specific embodiment of the present invention, preferably, the above preparation method includes the following specific steps:

[0039] Fully dissolving the water-soluble cellulose derivative and then uniformly mixing it with the modified cellulose nanomaterial aqueous dispersion to prepare a first mixed solution;

[0040] Mixing the first mixed liquid, biodiesel and bentonite to prepare a second mixed liquid;

[0041] The second mixed liquid is ultrasonically emulsified until a homogeneous emulsion is obtained, that is, a Pickering emulsion drilling fluid synergistically stabilized by the modified cellulose nanomaterial and the water-soluble cellulose derivative is obtained.

[0042] According to a specific embodiment of the present invention, the hydrolysis of the silane coupling agent can be carried out in a conventional manner, for example, water, methanol and the silane coupling agent are mixed in a mass ratio of 20:72:8 and then hydrolyzed at 25° C. for 1 hour.

[0043] According to a specific embodiment of the present invention, preferably, the modified cellulose nanomaterial aqueous dispersion is obtained by reacting a cellulose nanomaterial aqueous dispersion having a solid content of 1-2 wt% and a hydrolyzed silane coupling agent at 20° C. and stirring at a speed of 1000-2000 r / min for 1-3 hours.

[0044] The cellulose nanomaterial-stabilized Pickering emulsion drilling fluid provided by the present invention utilizes a cellulose nanomaterial modified with a silane coupling agent as the aqueous phase and diesel as the oil phase. The cellulose nanomaterial is hydrophobically modified as the aqueous phase, a water-soluble, inexpensive and readily available cellulose derivative is added for synergistic stabilization, and bentonite is then added. The resulting Pickering emulsion drilling fluid is highly stable, has low fluid loss, and has low permeability.

[0045] The preparation process of the Pickering emulsion drilling fluid of the present invention is simple and easy to control, and has great application potential and application space. DETAILED DESCRIPTION

[0046] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0047] In the present invention, “including” and “comprising” should be understood as meaning “including, but not limited to”. The specific details disclosed are intended to make the present invention easier to understand. Technicians in the relevant fields who adopt one or more technical details to implement this solution also belong to the technical solution of the present invention.

[0048] Unless otherwise specified, all reagents used in the examples can be purchased from the market.

[0049] The silane coupling agent used in the examples and comparative examples is a hydrolyzed silane coupling agent, and the specific process is as follows:

[0050] Water, methanol, and silane coupling agent were mixed in a mass ratio of 20:72:8 and hydrolyzed at 25° C. for 1 h.

[0051] Example 1

[0052] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, and its formulation is as follows: the concentration of the modified CNF aqueous dispersion is 0.1wt%, the amount of MC added is 5% of the mass of the modified CNF, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 2:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 1:1.

[0053] The modified CNF aqueous dispersion was prepared by mixing KH550 as the silane coupling agent in this example with CNF at a ratio of 0.15 mmol / g. The mixture was then added dropwise to a 1 wt% CNF aqueous dispersion at 20°C and 1000 rpm with stirring for 1 hour. The mixture was then vacuum filtered through a 0.45 μm aqueous filter membrane and washed twice with methanol and once with water to obtain the KH550-modified CNF aqueous dispersion. This dispersion can be diluted or concentrated to the desired concentration for use.

[0054] The MC and modified CNF aqueous dispersions were mixed and stirred until uniformly mixed, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion, thereby obtaining a Pickering emulsion drilling fluid synergistically stabilized by modified CNF and MC.

[0055] Example 2

[0056] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, the formulation of which is as follows: the concentration of the modified CNF aqueous dispersion is 0.1wt%, the amount of HPMC added is 2% of the mass of the modified CNF, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 2:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 1:1.

[0057] Among them, the preparation method of the modified CNF aqueous dispersion is: KH550 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH550 and CNF are mixed at a ratio of KH550:CNF = 0.15 mmol / g, and are added dropwise to a 1 wt% CNF aqueous dispersion under stirring at 20 ° C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH550-modified CNF aqueous dispersion.

[0058] HPMC and modified CNF aqueous dispersion were mixed and stirred evenly, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid synergistically stabilized by modified CNF and HPMC.

[0059] Example 3

[0060] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, the formulation of which is as follows: the concentration of the modified CNF aqueous dispersion is 0.1wt%, the amount of HPMC added is 5% of the mass of the modified CNF, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 2:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 1:1.

[0061] Among them, the preparation method of the modified CNF aqueous dispersion is as follows: KH550 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH550 and CNF are mixed at a ratio of KH550:CNF = 0.15 mmol / g, and the mixture is added dropwise to a 1 wt% CNF aqueous dispersion under stirring at 20 ° C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH550-modified CNF aqueous dispersion.

[0062] HPMC and modified CNF aqueous dispersion were mixed and stirred evenly, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid synergistically stabilized by modified CNF and HPMC.

[0063] Example 4

[0064] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, the formulation of which is as follows: the concentration of the modified CNF aqueous dispersion is 0.5wt%, the amount of CMC added is 5% of the mass of the modified CNF, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 2:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 1:1.

[0065] Among them, the preparation method of the modified CNF aqueous dispersion is as follows: KH560 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH560 and CNF are mixed at a ratio of KH560:CNF = 0.15 mmol / g, and the mixture is added dropwise to a 1 wt% CNF aqueous dispersion under stirring at 20 ° C and a speed of 1000 r / min for 2 hours, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH560-modified CNF aqueous dispersion.

[0066] The CMC and modified CNF aqueous dispersions were mixed and stirred until uniformly mixed, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion, thereby obtaining a Pickering emulsion drilling fluid synergistically stabilized by the modified CNF and CMC.

[0067] Example 5

[0068] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, the formulation of which is as follows: the concentration of the modified CNF aqueous dispersion is 0.5wt%, the amount of PAC added is 2% of the mass of the modified CNF, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 3:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 2:1.

[0069] Among them, the preparation method of the modified CNF aqueous dispersion is: A171 is selected as the silane coupling agent of this embodiment, and the hydrolyzed A171 and CNF are mixed at a ratio of A171:CNF = 0.05mmol / g, and the mixture is added dropwise to a 1wt% CNF aqueous dispersion under stirring at 20°C and a speed of 1000r / min for 2h, and then vacuum filtered with a 0.45μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain an A171-modified CNF aqueous dispersion.

[0070] The PAC and modified CNF aqueous dispersions were mixed and stirred until uniformly mixed, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion, thereby obtaining a Pickering emulsion drilling fluid synergistically stabilized by modified CNF and PAC.

[0071] Example 6

[0072] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives. The formulation is as follows: the concentration of the modified CNF aqueous dispersion is 1.0 wt%, the amount of HEC added is 8% of the mass of the modified CNF, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 1:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 2:1.

[0073] Among them, the preparation method of the modified CNF aqueous dispersion is as follows: KH792 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH792 and CNF are mixed at a ratio of KH792: CNF = 0.20 mmol / g, and the mixture is added dropwise to a 1.5 wt% CNF aqueous dispersion under stirring at 20 ° C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH792-modified CNF aqueous dispersion.

[0074] The HEC and modified CNF aqueous dispersions were mixed and stirred until uniformly mixed, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion, thereby obtaining a Pickering emulsion drilling fluid synergistically stabilized by modified CNF and HEC.

[0075] Example 7

[0076] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, the formulation of which is as follows: the concentration of the modified CNF aqueous dispersion is 0.2wt%, the amount of HECMC added is 1% of the mass of the modified CNF, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 4:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 3:1.

[0077] Among them, the preparation method of the modified CNF aqueous dispersion is: PTS is selected as the silane coupling agent of this embodiment, and the hydrolyzed PTS and CNF are mixed at a ratio of PTS:CNF = 0.25mmol / g, and the mixture is added dropwise to a 1.5wt% CNF aqueous dispersion under stirring at 20°C and a speed of 1000r / min for 3h, and then vacuum filtered with a 0.45μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a PTS-modified CNF aqueous dispersion.

[0078] The HECMC and modified CNF aqueous dispersions were mixed and stirred until uniformly mixed, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion, thereby obtaining a Pickering emulsion drilling fluid synergistically stabilized by the modified CNF and HECMC.

[0079] Example 8

[0080] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, the formulation of which is as follows: the concentration of the modified CNC aqueous dispersion is 0.5wt%, the amount of CMC added is 5% of the mass of the modified CNC, the volume ratio of the modified CNC aqueous dispersion to biodiesel is 2:1, and the mass ratio of the modified CNC aqueous dispersion to sodium bentonite is 1:1.

[0081] Among them, the preparation method of the modified CNC aqueous dispersion is as follows: KH560 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH560 and CNC are mixed at a ratio of KH560:CNC = 0.15 mmol / g, and the mixture is added dropwise to a 1 wt% CNC aqueous dispersion under stirring at 20°C and a speed of 1000 r / min for 2 hours, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH560-modified CNC aqueous dispersion.

[0082] The CMC and modified CNC aqueous dispersions are mixed and stirred to be uniform, and then biodiesel and sodium bentonite are added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid synergistically stabilized by the modified CNC and CMC.

[0083] Example 9

[0084] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives. The formulation is as follows: the concentration of the modified CNC aqueous dispersion is 0.5wt%, the amount of PAC added is 4% of the mass of the modified CNC, the volume ratio of the modified CNC aqueous dispersion to biodiesel is 3:1, and the mass ratio of the modified CNC aqueous dispersion to sodium bentonite is 2:1.

[0085] Among them, the preparation method of the modified CNC aqueous dispersion is as follows: KH560 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH560 and CNC are mixed at a ratio of KH560:CNC = 0.25 mmol / g, and the mixture is added dropwise to a 1 wt% CNC aqueous dispersion under stirring at 20°C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH560-modified CNC aqueous dispersion.

[0086] The PAC and modified CNC aqueous dispersions were mixed and stirred to be uniform, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid synergistically stabilized by the modified CNC and PAC.

[0087] Example 10

[0088] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives. The formulation is as follows: the concentration of the modified CNC aqueous dispersion is 1.5wt%, the amount of HPMC added is 6% of the mass of the modified CNC, the volume ratio of the modified CNC aqueous dispersion to biodiesel is 4:1, and the mass ratio of the modified CNC aqueous dispersion to sodium bentonite is 1:1.

[0089] Among them, the preparation method of the modified CNC aqueous dispersion is as follows: KH550 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH550 and CNC are mixed at a ratio of KH550:CNC = 0.30 mmol / g, and the mixture is added dropwise to a 1 wt% CNC aqueous dispersion under stirring at 20°C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH550-modified CNC aqueous dispersion.

[0090] HPMC and modified CNC aqueous dispersions are mixed and stirred to be uniform, and then biodiesel and sodium bentonite are added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid synergistically stabilized by modified CNC and HPMC.

[0091] Example 11

[0092] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by modified cellulose nanomaterials and water-soluble cellulose derivatives, and its formulation is as follows: the concentration of the modified CNC aqueous dispersion is 0.4wt%, the concentration of the modified CNF aqueous dispersion is 0.4wt%, the mass ratio of the two is CNC:CNF=2:3, the amount of CMC added is 5% of the mass of the modified cellulose nanomaterial, the volume ratio of the modified cellulose nanomaterial aqueous dispersion to biodiesel is 3:1, and the mass ratio of the modified cellulose nanomaterial aqueous dispersion to sodium bentonite is 1:1.

[0093] Among them, the preparation method of the modified cellulose nanomaterial aqueous dispersion is as follows: KH550 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH550 is mixed with CNC and CNF respectively at a ratio of KH550: cellulose nanomaterial = 0.15 mmol / g, and is added dropwise to a 1 wt% cellulose nanomaterial aqueous dispersion under stirring at 20°C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH550-modified cellulose nanomaterial aqueous dispersion, that is, a dispersion of modified CNC and a dispersion of modified CNF.

[0094] CMC and modified cellulose nanomaterial aqueous dispersion are mixed and stirred evenly, and then biodiesel and sodium bentonite are added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid synergistically stabilized by the modified cellulose nanomaterial aqueous dispersion and CMC.

[0095] Example 12

[0096] This embodiment provides a Pickering emulsion drilling fluid synergistically stabilized by a modified cellulose nanomaterial and a water-soluble cellulose derivative. The formulation is as follows: the concentration of the modified CNC aqueous dispersion is 0.4wt%, the concentration of the modified CNF aqueous dispersion is 0.4wt%, the mass ratio of the two is CNC:CNF = 1:1, the amount of HPMC added is 6% of the mass of the modified cellulose nanomaterial, the volume ratio of the modified cellulose nanomaterial aqueous dispersion to biodiesel is 3:1, and the mass ratio of the modified cellulose nanomaterial aqueous dispersion to sodium bentonite is 2:1.

[0097] Among them, the preparation method of the modified cellulose nanomaterial aqueous dispersion is as follows: KH560 is selected as the silane coupling agent of this embodiment, and the hydrolyzed KH560 is mixed with CNC and CNF respectively at a ratio of KH560: cellulose nanomaterial = 0.15 mmol / g, and is added dropwise to a 1 wt% cellulose nanomaterial aqueous dispersion under stirring at 20°C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH560-modified cellulose nanomaterial aqueous dispersion, that is, a dispersion of modified CNC and a dispersion of modified CNF.

[0098] HPMC and modified cellulose nanomaterial aqueous dispersion are mixed and stirred evenly, and then biodiesel and sodium bentonite are added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid synergistically stabilized by the modified cellulose nanomaterial aqueous dispersion and HPMC.

[0099] Comparative Example 1

[0100] This comparative example provides a Pickering emulsion drilling fluid stabilized by cellulose nanomaterials, the formulation of which is as follows: the concentration of CNF aqueous dispersion is 0.1wt%, the amount of MC added is 5% of the CNF mass, the volume ratio of CNF aqueous dispersion to biodiesel is 2:1, and the mass ratio of CNF to sodium bentonite is 1:1.

[0101] The MC and CNF aqueous dispersions were mixed and stirred until uniformly mixed, and then biodiesel and sodium bentonite were added and ultrasonically emulsified to a homogeneous emulsion, thereby obtaining a CNF-MC-stabilized Pickering emulsion drilling fluid.

[0102] Comparative Example 2

[0103] This comparative example provides a Pickering emulsion drilling fluid stabilized by modified cellulose nanomaterials, the formulation of which is as follows: the concentration of the modified CNF aqueous dispersion is 0.1wt%, the volume ratio of the modified CNF aqueous dispersion to biodiesel is 3:1, and the mass ratio of the modified CNF aqueous dispersion to sodium bentonite is 2:1. The mixed liquid is ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid stabilized by the modified CNF aqueous dispersion.

[0104] Among them, the preparation method of the modified CNF aqueous dispersion is: KH560 is selected as the silane coupling agent of this comparative example, and the hydrolyzed KH560 and CNF are mixed at a ratio of KH560:CNF = 0.15 mmol / g, and the mixture is added dropwise to a 1 wt% CNF aqueous dispersion under stirring at 20 ° C and a speed of 1000 r / min for 1 hour, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH560-modified CNF aqueous dispersion.

[0105] Comparative Example 3

[0106] This comparative example provides a Pickering emulsion drilling fluid stabilized by cellulose nanomaterials, the formulation of which is as follows: the concentration of the CNC aqueous dispersion is 0.5wt%, the addition amount of CMC is 5% of the mass of the CNC, the volume ratio of the CNC aqueous dispersion to biodiesel is 3:1, and the mass ratio of CNF to sodium bentonite is 1:1.

[0107] The CMC and CNC aqueous dispersions are mixed and stirred until uniformly mixed, and then biodiesel and sodium bentonite are added and ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid stabilized by CNC and CMC.

[0108] Comparative Example 4

[0109] This comparative example provides a Pickering emulsion drilling fluid stabilized by modified cellulose nanomaterials. The formulation is as follows: the volume ratio of the modified CNC aqueous dispersion to biodiesel is 2:1, the concentration of the modified CNC aqueous dispersion is 0.5wt%, and the mass ratio of the modified CNC aqueous dispersion to sodium bentonite is 1:1. The mixed liquid is ultrasonically emulsified to a homogeneous emulsion to obtain a Pickering emulsion drilling fluid stabilized by the modified CNC aqueous dispersion.

[0110] Among them, the preparation method of the modified CNC aqueous dispersion is as follows: KH550 is selected as the silane coupling agent of this comparative example, and the hydrolyzed KH550 and CNC are mixed at a ratio of KH550:CNC = 0.20 mmol / g, and are added dropwise to a 1 wt% CNC aqueous dispersion under stirring at 20 ° C and a speed of 1000 r / min for 1 h, and then vacuum filtered with a 0.45 μm aqueous filter membrane, washed twice with methanol, and washed once with water to obtain a KH550-modified CNC aqueous dispersion.

[0111] Performance Testing

[0112] The fluid loss reduction performance of the Pickering emulsion drilling fluids prepared in the examples and comparative examples was tested in the following manner:

[0113] Inject 100 mL of Pickering emulsion drilling fluid into the water loss meter, adjust the pressure to 100 Psi, open the pressure reducing valve and start timing. Record the filtrate volume in 30 minutes as FL. API Filtration loss.

[0114] The viscosity test of the Pickering emulsion drilling fluids prepared in the examples and comparative examples was performed to evaluate the rheological properties of the emulsions, specifically in the following manner:

[0115] The prepared Pickering emulsion drilling fluid was subjected to rheological tests (steady-state shear tests) using a rheometer (MCR 301, Anton Paar, Austria). The test conditions for all samples were as follows: constant temperature 25°C, shear rate range 0.1-1000s -1 .

[0116] Table 1

[0117]

[0118] According to the data in Table 1, we can see that:

[0119] Compared with Comparative Examples 1-4, the Pickering emulsion drilling fluids prepared in Examples 1-12 exhibited lower fluid loss, indicating superior fluid loss reduction performance. Specifically, Examples 11 and 12, utilizing a combination of CNF and CNC modified with a silane coupling agent, achieved fluid loss below 1.8 mL, significantly lower than that of Comparative Examples 1-4 and the other Examples, demonstrating excellent fluid loss reduction performance.

[0120] The data of the rheological properties of the emulsion show that the Pickering emulsion system exhibits shear thinning characteristics, which is consistent with the regular characteristics of cellulose nanomaterials used as Pickering emulsion stabilizers. Compared with comparative examples 1-4, examples 1-12 have a shear rate of 0.1s-1 It has a higher viscosity when the emulsion is thicker, indicating that the cellulose nanomaterials and water-soluble cellulose can work synergistically in the emulsion to form a more stable internal network structure, thereby improving the stability of the emulsion. At the same time, a more stable and stronger network structure also helps to reduce the filtration loss.

Claims

1. A Pickering emulsion drilling fluid stabilized by cellulose nanomaterials, wherein: The Pickering emulsion drilling fluid comprises: a modified cellulose nanomaterial aqueous dispersion, a water-soluble cellulose derivative, biodiesel and bentonite; The modified cellulose nanomaterial is a cellulose nanomaterial modified by a silane coupling agent, and the ratio of the silane coupling agent to the cellulose nanomaterial is 0.05-0.3 mmol / g; The concentration of the modified cellulose nanomaterial aqueous dispersion is 0.1-2.0 wt %; The amount of the water-soluble cellulose derivative added is 1-10% of the mass of the modified cellulose nanomaterial; The volume ratio of the modified cellulose nanomaterial aqueous dispersion to the biodiesel is 1:1-4:1; The mass ratio of the modified cellulose nanomaterial aqueous dispersion to the bentonite is 0-3:

1.

2. The Pickering emulsion drilling fluid according to claim 1, wherein The concentration of the modified cellulose nanomaterial aqueous dispersion is 0.1-1.5 wt %.

3. The Pickering emulsion drilling fluid according to claim 1, wherein The ratio of the silane coupling agent to the cellulose nanomaterial is 0.15-0.3 mmol / g.

4. The Pickering emulsion drilling fluid according to claim 1, wherein The added amount of the water-soluble cellulose derivative is 1-8% of the mass of the modified cellulose nanomaterial.

5. The Pickering emulsion drilling fluid according to claim 1, wherein The mass ratio of the modified cellulose nanomaterial aqueous dispersion to the bentonite is 1-3:

1.

6. The Pickering emulsion drilling fluid according to claim 1, wherein The cellulose nanomaterial is selected from one or a combination of cellulose nanocrystals and cellulose nanofibers.

7. The Pickering emulsion drilling fluid according to claim 6, wherein: The diameter of the cellulose nanocrystals is 1-200 nm, and the length is less than or equal to 1 μm; the diameter of the cellulose nanofibers is 1-50 nm, and the length is greater than or equal to 1 μm.

8. The Pickering emulsion drilling fluid according to claim 1, wherein: The silane coupling agent is selected from one or a combination of two of phenyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, vinyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane.

9. The Pickering emulsion drilling fluid according to claim 1, wherein: The water-soluble cellulose derivative is selected from one or a combination of two of methyl cellulose, carboxymethyl cellulose, polyanionic cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl carboxymethyl cellulose.

10. The Pickering emulsion drilling fluid according to claim 1, wherein: The cellulose nanomaterial is a combination of cellulose nanocrystals and cellulose nanofibers; The modified cellulose nanomaterial aqueous dispersion comprises a modified cellulose nanocrystal dispersion and a modified cellulose nanofiber dispersion, wherein the concentration of the modified cellulose nanocrystal dispersion is 0.3-0.4 wt %, and the concentration of the modified cellulose nanofiber dispersion is 0.2-0.4 wt %; The silane coupling agent is modified into γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane; the ratio of the silane coupling agent to the cellulose nanomaterial is 0.15-0.3 mmol / g; The water-soluble cellulose derivative is carboxymethyl cellulose and / or hydroxypropyl methyl cellulose; the amount of the water-soluble cellulose derivative added is 5-6% of the mass of the modified cellulose nanomaterial; The volume ratio of the modified cellulose nanomaterial aqueous dispersion to the biodiesel is 1:1-3:1; The mass ratio of the modified cellulose nanomaterial aqueous dispersion to the bentonite is 1-2:

1.

11. A method for preparing a Pickering emulsion drilling fluid stabilized by cellulose nanomaterials according to any one of claims 1 to 10, comprising the following steps: reacting the cellulose nanomaterial aqueous dispersion with the hydrolyzed silane coupling agent at 10-25° C. to obtain a modified cellulose nanomaterial aqueous dispersion; mixing a modified cellulose nanomaterial dispersion with a water-soluble cellulose derivative to obtain a first mixed solution; adding biodiesel and bentonite to the first mixed liquid to obtain a second mixed liquid; The second mixed liquid is emulsified to obtain a homogeneous emulsion, that is, the Pickering emulsion drilling fluid stabilized by the cellulose nanomaterial.

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