Oil and gas reservoir protective agent for drilling fluid

Abstract

The invention relates to the technical field of reservoir protection in oil and gas exploitation, and particularly discloses a hydrocarbon reservoir protective agent for drilling fluid. The hydrocarbon reservoir protective agent for the drilling fluid is prepared from the following raw materials in parts by mass: 15 to 20 parts of boron-zinc composite oxide modified carbon microspheres, 8 to 12 parts of a magnesium oxide-vermiculite compound, 6 to 8 parts of a gelatinized starch-cyclodextrin compound, 0.8 to 1.2 parts of short-chain fluorosiloxane, 10 to 12 parts of phenolic epoxy vinyl ester resin and 12 to 15 parts of poly (ethylene 2, 5-furandicarboxylate). According to the oil and gas reservoir protective agent for the drilling fluid, through the synergistic effect of multiple components, effective plugging of multi-scale pores is achieved, and the oil and gas reservoir protection effect is remarkably improved.

Description

Technical Field

[0001] The present application relates to the technical field of reservoir protection in oil and natural gas exploitation, and more specifically, to an oil and gas layer protective agent for drilling fluid. Background Art

[0002] Reservoir protectants are core functional materials used to prevent reservoir damage during oil and gas field exploration and development. They maintain the reservoir's original permeability and productivity by inhibiting foreign fluid intrusion, stabilizing formation minerals, and reducing pore blockage. However, existing technologies still have significant limitations in complex formation conditions. Traditional temporary blocking technologies (such as calcium carbonate and oil-soluble resins) rely on a strict match between particle size and formation pore throats. However, actual oil and gas reservoirs are often highly heterogeneous, with a wide distribution of pore throat diameters (0.1 to 500 μm). Temporary blocking particles of a single or limited size struggle to cover the entire range of pore throats, resulting in incomplete blocking and a high risk of drilling fluid intrusion and contamination. On the other hand, although the broad-spectrum "oil film" temporary plugging technology reduces the dependence on pore size matching through particle deformation and electrostatic adsorption, and can adapt to a wider range of pore throat plugging, its core defects are highlighted in the high temperature and high pressure environment often faced by deep oil and gas reservoirs: the temporary plugging agent particles are easily over-softened or even melted due to high temperature, losing their deformation and plugging ability; at the same time, high temperature causes the surface charge density of the particles to decay, weakening the electrostatic adsorption effect with the formation rock, causing the "oil film" barrier to decrease in toughness and increase in permeability, ultimately causing the plugging ring to rupture and lose its protective effectiveness.

[0003] The patent application document with publication number CN118460191A discloses an oil and gas layer protective agent for drilling fluid, which includes the following raw materials, in parts by weight: calcium carbonate, 40-50 parts; silane coupling agent, 0.1-0.5 parts; oil-soluble resin, 15-20 parts; cross-linking accelerator, 0.01-0.03 parts; oil-absorbing swelling resin, 5-8 parts; water-absorbing swelling resin, 1-1.5 parts; antioxidant, 0.1-1 parts; dispersant, 0 .5~1.5 parts; wherein, calcium carbonate accounting for 10~20wt% of the total weight of calcium carbonate is first mixed with a silane coupling agent, an antioxidant and a dispersant, and then kneaded and dispersed with an oil-soluble resin and a cross-linking accelerator at 135~145°C for 1~5h, crushed to a D90 particle size of less than 1mm after natural cooling, and finally cross-linked by electron irradiation; the irradiation time is 5~30min, the irradiation dose is 5~20kGy, and the irradiation time is inversely proportional to the irradiation dose.

[0004] This solution uses calcium carbonate (40-50 parts) as the core temporary plugging particle. After crushing, the D90 particle size of the calcium carbonate is only controlled to 1mm, which is far from adapting to the widely distributed pore throats in the reservoir, especially the microcracks and submicron pores, resulting in the formation of microchannels inside the plugging layer. In addition, only 10-20wt% of the calcium carbonate is modified with a silane coupling agent. The interfacial bonding force between the unmodified particles and the oil-soluble resin is weak, and the unmodified particles are easily detached from the system, causing microcracks to form inside the plugging layer and accelerating the overall instability of the plugging layer. Summary of the Invention

[0005] In order to improve the sealing ability of the protective agent on multi-scale pores, the present application provides an oil and gas layer protective agent for drilling fluid.

[0006] The oil and gas layer protective agent for drilling fluid of the present application adopts the following technical solution: An oil and gas layer protective agent for drilling fluid is prepared by including the following raw materials in parts by weight: 15-20 parts of boron zinc composite oxide modified carbon microspheres, 8-12 parts of magnesium oxide-vermiculite composite, 6-8 parts of gelatinized starch-cyclodextrin composite, 0.8-1.2 parts of short-chain fluorosilicone, 10-12 parts of phenolic epoxy vinyl ester resin and 12-15 parts of polyethylene 2,5-furandicarboxylate.

[0007] In this technical solution, a boron-zinc composite oxide layer is constructed on the surface and pores of carbon microspheres. The boron-zinc composite oxide forms a local positive charge area due to charge imbalance, and produces electrostatic adsorption with clay minerals with permanent negative charge, thereby achieving effective blocking of micropores. The magnesium oxide-vermiculite composite is based on the filling of magnesium oxide, which neutralizes the acidic fluid in the short term and reduces the initial acid etching rate. The magnesium oxide between the vermiculite layers can also delay the diffusion of hydrogen ions and extend the life of the blocking layer. At the same time, based on the bridging effect of the vermiculite layer structure, it forms a blockage for larger cracks. The gelatinized starch-cyclodextrin composite fills the tiny pores with the colloidal properties of pre-gelatinized starch, and combines the inclusion effect of cyclodextrin to enhance the adhesion of the blocking layer. Short-chain fluorosilicone forms a bond anchor with the silanol group on the rock surface. The fluoroalkyl chain imparts superhydrophobicity, increases capillary resistance, blocks water intrusion, and thus improves the permeability recovery rate.

[0008] Under high temperature conditions (>160°C), the mobility of the flexible vinyl ester segments in the molecular chain of phenolic epoxy vinyl ester resin is significantly enhanced, and it transforms from a glassy state to a highly elastic state. At this time, its rigidity decreases but the cross-linked network remains intact. It can compensate for the expansion of microcracks caused by temperature stress through the elastic deformation of the segments, dynamically fill pore defects, and effectively prevent the sealing layer from being brittle due to excessive rigidity. Due to the rigid structure of the furan ring, polyethylene 2,5-furandicarboxylate forms a rigid skeleton in the form of solid particles, providing temperature structural support for the sealing layer, resisting the erosion and pressure shock of high-temperature fluids, and ensuring continuous sealing of cracks. The two work together to achieve a rigid-flexible balance in the sealing layer under high temperature.

[0009] Preferably, the method for preparing the boron-zinc composite oxide modified carbon microspheres comprises the following steps: S11: After mixing sugarcane bagasse and kelp bagasse evenly, add water, ultrasonicate for 30-50 minutes, heat to 200-220°C, hydrothermally react for 3-5 hours, cool, separate solid and liquid, wash, and dry to obtain a carbon microsphere precursor; S12: Immerse the carbon microsphere precursor in a zinc nitrate solution containing boric acid and tartaric acid, ultrasonicate for 30-50 minutes, mix for 2-4 hours, separate the solid and liquid, wash, dry, and then in an inert atmosphere at 380-420°C for 120-150 minutes, cool, and crush to obtain boron-zinc composite oxide modified carbon microspheres.

[0010] In this technical solution, the preparation of carbon microspheres modified with boron-zinc composite oxides uses bagasse and kelp residue as composite carbon sources, and generates a porous carbon microsphere precursor through a hydrothermal reaction. The carbon microsphere precursor is impregnated with a zinc nitrate solution containing boric acid and tartaric acid. During the zinc salt pretreatment and impregnation process, boric acid and zinc nitrate form a complex under the control of tartaric acid, which is evenly anchored on the surface and pores of the carbon microspheres. After thermal conversion, a boron-zinc composite oxide layer is formed. Under the high-temperature drilling environment, this boron-zinc composite structure makes the surface of the carbon microspheres locally positively charged, thereby generating a strong electrostatic attraction with the naturally negatively charged clay minerals in the oil and gas reservoirs, prompting the carbon microspheres to aggregate in a directional manner and block the microporous channels around the clay minerals, thereby improving the targeting and efficiency of the blockage.

[0011] Preferably, the mass ratio of the bagasse to kelp bagasse is (5.5-6.5): (3.5-4.5).

[0012] Preferably, the mass concentration of zinc nitrate in the zinc nitrate solution is 8% to 12%.

[0013] Preferably, the mass concentration of boric acid in the zinc nitrate solution is 2.5% to 3.5%.

[0014] Preferably, the mass concentration of tartaric acid in the zinc nitrate solution is 7% to 9%.

[0015] Preferably, the particle size distribution of the boron-zinc composite oxide modified carbon microspheres is 0.1-5 μm.

[0016] Preferably, the preparation method of the magnesium oxide-vermiculite composite comprises the following steps: The vermiculite was added to a hexadecyltrimethylammonium bromide solution, heated to 70-90°C, ultrasonically treated for 2-3 hours, solid-liquid separated, washed, immersed in a magnesium nitrate solution, mixed for 2-4 hours, solid-liquid separated, washed, dried, and then transferred to a sintering furnace, first heated to 240-260°C, kept warm for 60-80 minutes, continued to heat to 380-420°C, kept warm for 60-80 minutes, and cooled to obtain a magnesium oxide-vermiculite composite.

[0017] In this scheme, hexadecyltrimethylammonium bromide is inserted into the interlayer of vermiculite through the hydrophobic chain. Its cationic head group combines with the negative charge on the surface of vermiculite, improving the hydrophilicity and hydrophobicity of the vermiculite surface and enhancing the adsorption capacity of vermiculite for magnesium nitrate. Ultrasonic treatment further promotes the uniform dispersion of surfactant molecules and expands the distance between vermiculite layers, providing space for subsequent magnesium oxide loading. When vacuum impregnating magnesium nitrate solution, Mg 2+ It enters the interlayers and surface of vermiculite through ion exchange; during the sintering process, magnesium nitrate is first dehydrated at 240-260°C to form basic salt, and then heated to 380-420°C to decompose into magnesium oxide, which evenly fills the pores between the vermiculite layers and on the surface. It not only uses the bridging effect of the vermiculite layer structure to seal larger cracks, but also uses the chemical inertness of magnesium oxide to delay the erosion of the sealing layer by the formation acidic fluid, thereby extending the sealing life.

[0018] Preferably, the vermiculite has a particle size distribution of 1 to 50 μm.

[0019] Preferably, the mass concentration of the magnesium nitrate solution is 10% to 15%.

[0020] Preferably, the mass concentration of the hexadecyltrimethylammonium bromide solution is 2% to 5%.

[0021] Preferably, the preparation method of the gelatinized starch-cyclodextrin complex comprises the following steps: Add 5-7 parts by mass of hydroxypropyl-β-cyclodextrin to water, heat it to 65-75°C, mix it evenly, add 10-15 parts by mass of pregelatinized starch, mix it evenly, cool it to 40-50°C, add 0.5-1 parts by mass of citric acid, mix it evenly, and spray dry it to obtain a gelatinized starch-cyclodextrin complex.

[0022] Preferably, in the preparation method of the gelatinized starch-cyclodextrin complex, 5-7 parts by mass of hydroxypropyl-β-cyclodextrin is added to water, heated to 65-75° C., and mixed uniformly, and further comprises the step of adding 1-2 parts by mass of quaternary ammonium salt.

[0023] Preferably, the quaternary ammonium salt is selected from any one of hexadecyltrimethylammonium chloride and didodecyldimethylammonium chloride.

[0024] In this scheme, the annular cavity of hydroxypropyl-β-cyclodextrin can form an inclusion complex with the quaternary ammonium salt, and citric acid serves as a pH-responsive trigger: when the formation fluid is weakly acidic, the hydrogen ions ionized by citric acid destroy the inclusion bond between cyclodextrin and the quaternary ammonium salt, prompting the targeted release of the quaternary ammonium salt to the clay-rich area, neutralizing the negative charge of the clay through cation exchange, and inhibiting its hydration expansion; at the same time, the pregelatinized starch forms a viscoelastic gel to fill the pores and provide adhesion; the cyclodextrin inclusion complex with the quaternary ammonium salt realizes the sustained release of the anti-swelling agent.

[0025] Preferably, the short-chain fluorosilicone is selected from any one of perfluorobutyltriethoxysilane and perfluorooctyltriethoxysilane.

[0026] Preferably, the oil and gas layer protective agent for drilling fluid further includes 1 to 2 parts by mass of chopped carbon fibers.

[0027] In this solution, the chopped fibers can construct a three-dimensional mesh support structure in the plugging layer, synergistically improving the impact strength and crack resistance of the plugging layer and avoiding damage to the plugging layer caused by fluctuations in the drilling fluid circulation pressure.

[0028] Preferably, the carbon fiber has a length of 0.5-2 mm and a diameter of 5-10 μm.

[0029] Preferably, the oil and gas layer protective agent for drilling fluid further includes 2 to 4 parts by mass of fluororubber micropowder.

[0030] In this technical solution, fluororubber micropowders fill cracks through elastic deformation, effectively alleviating the brittleness of polyethylene 2,5-furandicarboxylate and synergizing with the resin matrix to achieve a balance of rigidity and toughness. Furthermore, the strong electronegativity of fluorine atoms imparts excellent permeability and swelling resistance to acidic fluids, significantly enhancing the corrosion resistance of the sealing layer and extending its service life in acidic formations.

[0031] Preferably, the method for preparing the oil and gas layer protective agent for drilling fluid comprises the following steps: S1: dissolving polyethylene 2,5-furandicarboxylate in a cyclohexanone-acetone mixed solvent at 70-80° C. to obtain a polyethylene 2,5-furandicarboxylate solution; In an inert atmosphere, a phenolic epoxy vinyl ester resin is added to a mixer, the temperature is raised to 145-155° C., a polyethylene 2,5-furandicarboxylate solution is added, the mixture is distilled, cooled, and crushed to obtain a composite resin; S2: mixing the boron zinc composite oxide modified carbon microspheres, the magnesium oxide-vermiculite composite, the short-chain fluorosilicone and the gelatinized starch-cyclodextrin composite uniformly, and drying to obtain granules; S3: Under an inert atmosphere, melt the composite resin into atomized form and spray it onto the surface of the particles. Then, keep the temperature at 165-170°C for 60-70 minutes, cool it, and crush it to obtain an oil and gas layer protective agent for drilling fluid.

[0032] Preferably, in step S2, after adding the gelatinized starch-cyclodextrin complex, the step of adding chopped fibers is further included.

[0033] Preferably, in step S1, when adding the phenolic epoxy vinyl ester resin, the step of adding fluororubber powder is also included.

[0034] In summary, this application has the following beneficial effects: This application uses boron zinc composite oxide modified carbon microspheres to target and plug clay mineral micropores, and magnesium oxide-vermiculite composites to bridge and plug slightly larger cracks, and the two work together to form a gradient plug. And with the help of the gel effect of gelatinized starch-cyclodextrin composites, tiny pores are filled and the bonding strength of each component is strengthened. Short-chain fluorosilicone and the hydroxyl groups on the rock surface are partially bonded and anchored to form a hydrophobic barrier-hydrophilic filling interface strengthening mechanism. Afterwards, a composite resin is used for coating treatment. The chain segment mobility of phenolic epoxy vinyl ester resin is enhanced at high temperature, and it exhibits moderate elasticity to dynamically fill microcracks. Polyethylene 2,5-furandicarboxylate maintains a stable morphology by virtue of its molecular chain structure containing furan rings, and forms good compatibility with phenolic epoxy vinyl ester resin. The two work together to effectively alleviate the high-temperature brittle fracture of the plugging layer and significantly improve the impact strength. DETAILED DESCRIPTION

[0035] The present application is further described in detail below with reference to the embodiments.

[0036] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0037] The oil and gas layer protective agent for drilling fluid prepared in the embodiment of the present application is suitable for high-temperature deep well oil and gas layer protection scenarios above 160°C, especially for complex formations rich in clay minerals and developed fractures.

[0038] The weight average molecular weight of polyethylene 2,5-furandicarboxylate is 80,000 to 150,000; The phenolic epoxy vinyl ester resin adopts phenolic epoxy vinyl ester resin 907; The model of fluororubber micropowder is FKM-26; Before use, crush the sugarcane bagasse and kelp residue, first pass through a 20-mesh standard sieve, take the material under the sieve, then pass through a 40-mesh standard sieve, take the material on the sieve, dry at 60℃ for 2h, and set aside.

[0039] Before use, the vermiculite was crushed and passed through a 300-mesh standard sieve. The sieve was taken and sieved by air flow. The particles with a particle size distribution of about 1 to 50 μm were collected and dried at 100 ° C for 2 h for later use.

[0040] Preparation Examples 1-3 Boron-zinc composite oxide modified carbon microspheres Preparation Example 1 The preparation method of the boron-zinc composite oxide modified carbon microspheres of this preparation example comprises the following steps: S11: 1.65 kg of sugarcane bagasse and 1.35 kg of kelp bagasse were added to the reactor, stirred and mixed, and water was added to a solid-liquid ratio of 1:5. The mixture was transferred to an ultrasonic device and ultrasonically treated at a power of 500 W and a frequency of 40 Hz for 30 min. The mixture was heated to 200 ° C and reacted for 5 h. The mixture was cooled to room temperature and centrifuged. The mixture was washed twice with deionized water, dried at 105 ° C to constant weight, and pulverized by air flow (0.6 MPa). The mixture was passed through a 100-mesh standard sieve to obtain a carbon microsphere precursor. S12: The carbon microsphere precursor was immersed in a zinc nitrate solution containing boric acid and tartaric acid, transferred to an ultrasonic device, and ultrasonically treated for 30 minutes at a power of 500 W and a frequency of 40 Hz. The mixture was stirred and immersed for 2 hours, centrifuged, rinsed twice with deionized water, dried at 105°C to constant weight, and heated to 380°C at a rate of 3°C / min under a nitrogen atmosphere. The mixture was kept warm for 150 minutes, cooled, air flow crushed (0.75 MPa), and air flow sieved to obtain boron zinc composite oxide modified carbon microspheres with a particle size distribution of 0.1~5 μm.

[0041] The amount of zinc nitrate solution used is based on the ability to completely immerse the carbon microsphere precursor; in the zinc nitrate solution, the mass concentration of zinc nitrate is 8%, the mass concentration of boric acid is 2.5%, and the mass concentration of tartaric acid is 7%.

[0042] After testing, the surface Zeta potential of the carbon microspheres modified with boron zinc composite oxide was 16.2mV.

[0043] Preparation Example 2 The preparation method of the boron-zinc composite oxide modified carbon microspheres of this preparation example comprises the following steps: S11: 1.95 kg of sugarcane bagasse and 1.05 kg of kelp bagasse were added to the reactor, stirred and mixed, and water was added to a solid-liquid ratio of 1:10. The mixture was transferred to an ultrasonic device and ultrasonicated at a power of 500 W and a frequency of 40 Hz for 50 min. The mixture was heated to 220 ° C and reacted for 3 h. The mixture was cooled to room temperature and centrifuged. The mixture was washed twice with deionized water, dried at 105 ° C to constant weight, and pulverized by air flow (0.6 MPa). The mixture was passed through a 100-mesh standard sieve to obtain a carbon microsphere precursor. S12: The carbon microsphere precursor was immersed in a zinc nitrate solution containing boric acid and tartaric acid, transferred to an ultrasonic device, ultrasonically treated at a power of 500 W and a frequency of 40 Hz for 50 min, stirred and immersed for 4 h, centrifuged, rinsed twice with deionized water, dried at 105 ° C to constant weight, heated to 420 ° C at 5 ° C / min under a nitrogen atmosphere, kept warm for 120 min, cooled, air flow crushed (0.75 MPa), and air flow sieved to obtain boron zinc composite oxide modified carbon microspheres with a particle size distribution of 0.1~5 μm.

[0044] The amount of zinc nitrate solution used is based on the ability to completely immerse the carbon microsphere precursor; in the zinc nitrate solution, the mass concentration of zinc nitrate is 12%, the mass concentration of boric acid is 3.5%, and the mass concentration of tartaric acid is 9%.

[0045] After testing, the surface Zeta potential of the carbon microspheres modified with boron-zinc composite oxide was 21.8 mV.

[0046] Preparation Example 3 The preparation method of the boron-zinc composite oxide modified carbon microspheres of this preparation example comprises the following steps: S11: 1.8 kg of sugarcane bagasse and 1.2 kg of kelp bagasse were added to the reactor, stirred and mixed, and water was added to a solid-liquid ratio of 1:8. The mixture was transferred to an ultrasonic device and ultrasonically treated at a power of 500 W and a frequency of 40 Hz for 40 min. The mixture was heated to 210 ° C and reacted for 4 h. The mixture was cooled to room temperature and centrifuged. The mixture was washed twice with deionized water, dried at 105 ° C to constant weight, and pulverized by air flow (0.6 MPa). The mixture was passed through a 100-mesh standard sieve to obtain a carbon microsphere precursor. S12: The carbon microsphere precursor was immersed in a zinc nitrate solution containing boric acid and tartaric acid, transferred to an ultrasonic device, and ultrasonically treated for 40 minutes at a power of 500 W and a frequency of 40 Hz. The mixture was stirred and immersed for 3 hours, centrifuged, rinsed twice with deionized water, dried at 105°C to constant weight, heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere, kept warm for 130 minutes, cooled, air flow crushed (0.75 MPa), and air flow sieved to obtain boron zinc composite oxide modified carbon microspheres with a particle size distribution of 0.1~5 μm.

[0047] The amount of zinc nitrate solution used is based on the ability to completely immerse the carbon microsphere precursor; in the zinc nitrate solution, the mass concentration of zinc nitrate is 10%, the mass concentration of boric acid is 3%, and the mass concentration of tartaric acid is 8%.

[0048] After testing, the surface Zeta potential of the carbon microspheres modified with boron zinc composite oxide was 19.5mV.

[0049] Preparation Examples 4-6 Magnesium Oxide-Vermiculite Composites Preparation Example 4 The preparation method of the magnesium oxide-vermiculite composite of this preparation example comprises the following steps: 300 g of vermiculite was added to a 2% mass concentration of hexadecyltrimethylammonium bromide solution, transferred to an ultrasonic device, and synchronously heated to 70°C at a power of 300 W and a frequency of 40 Hz. The mixture was ultrasonically treated for 2 h, centrifuged, washed three times with 85°C hot water, immersed in a magnesium nitrate solution, stirred at 25°C for 2 h under a vacuum degree of -0.09 MPa, centrifuged, rinsed twice with deionized water, dried at 60°C to constant weight, transferred to a sintering furnace, heated to 240°C at a rate of 5°C / min, kept warm for 80 min, then heated to 380°C at a rate of 3°C / min, kept warm for 80 min, and cooled to room temperature with the furnace to obtain a magnesium oxide-vermiculite composite.

[0050] Preparation Example 5 The preparation method of the magnesium oxide-vermiculite composite of this preparation example comprises the following steps: 300 g of vermiculite was added to a 5% mass concentration of hexadecyltrimethylammonium bromide solution, transferred to an ultrasonic device, and synchronously heated to 70°C at a power of 300 W and a frequency of 40 Hz. The mixture was ultrasonically treated for 3 hours, centrifuged, washed three times with 85°C hot water, immersed in a magnesium nitrate solution, stirred at 20°C for 4 hours under a vacuum degree of -0.09 MPa, centrifuged, rinsed twice with deionized water, dried at 60°C to constant weight, transferred to a sintering furnace, heated to 260°C at a rate of 5°C / min, kept warm for 60 minutes, then heated to 420°C at a rate of 3°C / min, kept warm for 60 minutes, and cooled to room temperature with the furnace to obtain a magnesium oxide-vermiculite composite.

[0051] Preparation Example 6 The preparation method of the magnesium oxide-vermiculite composite of this preparation example comprises the following steps: 300 g of vermiculite was added to a 4% mass concentration of hexadecyltrimethylammonium bromide solution, transferred to an ultrasonic device, and synchronously heated to 70°C at a power of 300 W and a frequency of 40 Hz. The mixture was ultrasonically treated for 2.5 h, centrifuged, washed three times with 85°C hot water, immersed in a magnesium nitrate solution, stirred at 25°C for 3 h under a vacuum degree of -0.09 MPa, centrifuged, rinsed twice with deionized water, dried at 60°C to constant weight, transferred to a sintering furnace, heated to 250°C at a rate of 5°C / min, kept warm for 70 min, then heated to 400°C at a rate of 3°C / min, kept warm for 70 min, and cooled to room temperature with the furnace to obtain a magnesium oxide-vermiculite composite.

[0052] Preparation Examples 7-10 Gelatinized Starch-Cyclodextrin Complex Preparation Example 7 The preparation method of the gelatinized starch-cyclodextrin complex of this preparation example comprises the following steps: 150 g of hydroxypropyl-β-cyclodextrin was added to 350 g of water, the temperature was raised to 65° C., and the mixture was stirred and mixed for 30 minutes. 300 g of pregelatinized starch was added, and the mixture was stirred and mixed for 30 minutes. The temperature was lowered to 40° C., 15 g of citric acid was added, and the mixture was stirred and mixed for 5 minutes. The inlet temperature was set to 170° C. and the outlet temperature was set to 80° C. The mixture was spray-dried and the powder was collected to obtain a gelatinized starch-cyclodextrin complex.

[0053] Preparation Example 8 The preparation method of the gelatinized starch-cyclodextrin complex of this preparation example comprises the following steps: 150 g of hydroxypropyl-β-cyclodextrin was added to 350 g of water, the temperature was raised to 65° C., and the mixture was stirred and mixed for 30 minutes. A cetyltrimethylammonium chloride solution was added, and the mixture was stirred and mixed for 30 minutes. 300 g of pregelatinized starch was added, and the mixture was stirred and mixed for 30 minutes. The temperature was lowered to 40° C., 15 g of citric acid was added, and the mixture was stirred and mixed for 30 minutes. The inlet temperature was set to 170° C., and the outlet temperature was set to 80° C. The mixture was spray dried, and the powder was collected to obtain a gelatinized starch-cyclodextrin complex.

[0054] The cetyltrimethylammonium chloride solution includes 30 g of cetyltrimethylammonium chloride and 100 mL of an ethanol aqueous solution, and the ethanol aqueous solution is prepared by mixing ethanol and deionized water in a volume ratio of 2:8.

[0055] Preparation Example 9 The preparation method of the gelatinized starch-cyclodextrin complex of this preparation example comprises the following steps: 210 g of hydroxypropyl-β-cyclodextrin was added to 500 g of water, the temperature was raised to 75° C., and the mixture was stirred and mixed for 50 minutes. A didodecyldimethylammonium chloride solution was added, and the mixture was stirred and mixed for 50 minutes. 450 g of pregelatinized starch was added, and the mixture was stirred and mixed for 50 minutes. The temperature was lowered to 50° C., 30 g of citric acid was added, and the mixture was stirred and mixed for 50 minutes. The inlet temperature was set to 170° C., and the outlet temperature was set to 80° C. The mixture was spray dried, and the powder was collected to obtain a gelatinized starch-cyclodextrin complex.

[0056] The didodecyl dimethyl ammonium chloride solution includes 60 g didodecyl dimethyl ammonium chloride and 200 mL of an ethanol aqueous solution, and the ethanol aqueous solution is prepared by mixing ethanol and deionized water in a volume ratio of 2:8.

[0057] Preparation Example 10 The preparation method of the gelatinized starch-cyclodextrin complex of this preparation example comprises the following steps: 180 g of hydroxypropyl-β-cyclodextrin was added to 400 g of water, the temperature was raised to 70° C., and the mixture was stirred and mixed for 40 minutes. 45 g of didodecyldimethylammonium chloride was added, and the mixture was stirred and mixed for 40 minutes. 400 g of pregelatinized starch was added, and the mixture was stirred and mixed for 40 minutes. The temperature was lowered to 45° C., 25 g of citric acid was added, and the mixture was stirred and mixed for 40 minutes. The inlet temperature was set to 170° C. and the outlet temperature was set to 80° C. The mixture was spray dried, and the powder was collected to obtain a gelatinized starch-cyclodextrin complex.

[0058] The didodecyl dimethyl ammonium chloride solution includes 45 g didodecyl dimethyl ammonium chloride and 150 mL of an ethanol aqueous solution, and the ethanol aqueous solution is prepared by mixing ethanol and deionized water in a volume ratio of 2:8.

[0059] Example 1 The oil and gas layer protective agent for drilling fluid of this embodiment is prepared by including the following raw materials in parts by weight: 150g of boron zinc composite oxide modified carbon microspheres, 80g of magnesium oxide-vermiculite composite, 60g of gelatinized starch-cyclodextrin mixture, 8g of short-chain fluorosilicone, 100g of phenolic epoxy vinyl ester resin and 120g of polyethylene 2,5-furandicarboxylate.

[0060] Among them, the boron zinc composite oxide modified carbon microspheres are from Preparation Example 1; the magnesium oxide-vermiculite composite is from Preparation Example 4; and the gelatinized starch-cyclodextrin mixture is from Preparation Example 7.

[0061] The preparation method of the oil and gas layer protective agent for drilling fluid of this embodiment comprises the following steps: S1: Poly (ethylene 2,5-furandicarboxylate) and a cyclohexanone-acetone mixed solvent (cyclohexanone:acetone volume ratio of 1:1, solid-liquid ratio of 1:5) were mixed evenly, the mixture was heated to 70°C, and stirred for 50 minutes to obtain a polyethylene 2,5-furandicarboxylate solution; Under a nitrogen atmosphere, a phenolic epoxy vinyl ester resin was added to a mixer, heated to 145°C, stirred at this temperature until softened, and a polyethylene 2,5-furandicarboxylate solution was slowly added. The mixture was evacuated to -0.08 MPa and stirred until no solvent evaporated. The mixture was cooled to 130°C and crushed into 80-100 mesh powder to obtain a composite resin. S2: Add boron zinc composite oxide modified carbon microspheres and magnesium oxide-vermiculite composite into a mixer and mix for 10 minutes. Then, spray short-chain fluorosilicone and continue mixing for 5 minutes after spraying. Then, add gelatinized starch-cyclodextrin mixture and mix for 15 minutes. Dry at 40°C until the moisture content is ≤3.0% to obtain granules. S3: Under a nitrogen atmosphere, add the composite resin into a melting tank, raise the temperature to 200°C, adjust the nitrogen pressure to 1.0 MPa, spray the molten composite resin onto the surface of the particles, and then keep the temperature at 165°C for 70 minutes. During this period, nitrogen is continuously introduced at a nitrogen flow rate of 8 L / min. Cool to room temperature, and air flow pulverize to D90 ≤ 50 μm. Pass through a 325-mesh standard sieve to obtain an oil and gas layer protective agent for drilling fluid.

[0062] Example 2 The oil and gas layer protective agent for drilling fluid of this embodiment is prepared by including the following raw materials in parts by weight: 200g of boron zinc composite oxide modified carbon microspheres, 120g of magnesium oxide-vermiculite composite, 80g of gelatinized starch-cyclodextrin mixture, 12g of short-chain fluorosilicone, 120g of phenolic epoxy vinyl ester resin and 150g of polyethylene 2,5-furandicarboxylate.

[0063] Among them, the boron zinc composite oxide modified carbon microspheres are from Preparation Example 2; the magnesium oxide-vermiculite composite is from Preparation Example 5; and the gelatinized starch-cyclodextrin mixture is from Preparation Example 8.

[0064] The preparation method of the oil and gas layer protective agent for drilling fluid of this embodiment comprises the following steps: S1: Poly (ethylene 2,5-furandicarboxylate) and a cyclohexanone-acetone mixed solvent (cyclohexanone:acetone volume ratio of 1:1, solid-liquid ratio of 1:5) were mixed evenly, the mixture was heated to 80°C, and stirred for 40 minutes to obtain a polyethylene 2,5-furandicarboxylate solution; Under a nitrogen atmosphere, a phenolic epoxy vinyl ester resin was added to a mixer, heated to 155°C, stirred at this temperature until softened, and a polyethylene 2,5-furandicarboxylate solution was slowly added. The mixture was vacuumed to -0.08 MPa, stirred and mixed until no solvent evaporated, cooled to 140°C, and crushed into 80-100 mesh powder to obtain a composite resin. S2: Add boron zinc composite oxide modified carbon microspheres and magnesium oxide-vermiculite composite into a mixer and mix for 15 minutes. Then, spray short-chain fluorosilicone and continue mixing for 7 minutes after spraying. Then, add gelatinized starch-cyclodextrin mixture and mix for 20 minutes. Dry at 40°C until the moisture content is ≤3.0% to obtain granules. S3: Under nitrogen atmosphere, add the composite resin into the melting tank, raise the temperature to 205°C, adjust the nitrogen pressure to 1.2 MPa, spray the molten composite resin onto the surface of the particles, and then keep it at 165°C for 65 minutes. During this period, nitrogen is continuously introduced at a nitrogen flow rate of 10 L / min. Cool to room temperature, and air flow pulverize to D90 ≤ 50 μm. Pass through a 325-mesh standard sieve to obtain an oil and gas layer protective agent for drilling fluid.

[0065] Example 3 The oil and gas layer protective agent for drilling fluid of this embodiment is prepared by including the following raw materials in parts by weight: 180g of boron zinc composite oxide modified carbon microspheres, 100g of magnesium oxide-vermiculite composite, 70g of gelatinized starch-cyclodextrin mixture, 10g of short-chain fluorosilicone, 110g of phenolic epoxy vinyl ester resin and 135g of polyethylene 2,5-furandicarboxylate.

[0066] Among them, the boron zinc composite oxide modified carbon microspheres are from Preparation Example 3; the magnesium oxide-vermiculite composite is from Preparation Example 6; and the gelatinized starch-cyclodextrin mixture is from Preparation Example 9.

[0067] The preparation method of the oil and gas layer protective agent for drilling fluid of this embodiment comprises the following steps: S1: Poly (ethylene 2,5-furandicarboxylate) and a cyclohexanone-acetone mixed solvent (cyclohexanone:acetone volume ratio of 1:1, solid-liquid ratio of 1:5) were mixed evenly, the mixture was heated to 75°C, and stirred for 40 minutes to obtain a polyethylene 2,5-furandicarboxylate solution; Under nitrogen atmosphere, add phenolic epoxy vinyl ester resin into a mixer, heat to 150°C, keep stirring until softened, slowly add polyethylene 2,5-furandicarboxylate solution, evacuate to -0.08MPa, stir and mix until no solvent evaporates, cool to 135°C, and grind into 80-100 mesh powder to obtain a composite resin; S2: Add boron zinc composite oxide modified carbon microspheres and magnesium oxide-vermiculite composite into a mixer and mix for 12 minutes. Then, spray short-chain fluorosilicone and continue mixing for 6 minutes after spraying. Then, add gelatinized starch-cyclodextrin mixture and mix for 18 minutes. Dry at 40°C until the moisture content is ≤3.0% to obtain granules. S3: Under nitrogen atmosphere, add the composite resin into the melting tank, raise the temperature to 205°C, adjust the nitrogen pressure to 1.2MPa, spray the molten composite resin onto the surface of the particles, and then keep the temperature at 170°C for 60 minutes. During this period, nitrogen is continuously introduced at a nitrogen flow rate of 8L / min. Cool to room temperature, and air flow pulverize to D90≤50μm. Pass through a 325-mesh standard sieve to obtain an oil and gas layer protective agent for drilling fluid.

[0068] Example 4 The difference between this embodiment and embodiment 3 is that: The oil and gas layer protective agent for drilling fluid in this embodiment also includes 10g of chopped carbon fiber; The length distribution of carbon fibers is 0.5~2mm, and the diameter distribution is 5~10μm.

[0069] The gelatinized starch-cyclodextrin mixture comes from Preparation Example 10.

[0070] In step S2, the boron zinc composite oxide modified carbon microspheres and the magnesium oxide-vermiculite composite are added to a mixer and mixed for 12 minutes. Short-chain fluorosilicone is sprayed and mixed for 6 minutes after the spraying is completed. The gelatinized starch-cyclodextrin mixture is then added and mixed for 18 minutes. The chopped carbon fibers are then added and mixed at a speed of 200 rpm for 15 minutes. The mixture is dried at 40° C. until the moisture content is ≤3.0% to obtain a granular material. Other details are the same as in Example 3.

[0071] Example 5 The difference between this embodiment and embodiment 4 is that: The amount of chopped carbon fiber used was 20 g.

[0072] In step S2, the boron zinc composite oxide modified carbon microspheres and the magnesium oxide-vermiculite composite are added to a mixer and mixed for 12 minutes. Short-chain fluorosilicone is sprayed and mixed for 6 minutes after the spraying is completed. The gelatinized starch-cyclodextrin mixture is then added and mixed for 18 minutes. The chopped carbon fibers are then added and mixed at a speed of 200 rpm for 20 minutes. The mixture is dried at 40° C. until the moisture content is ≤3.0% to obtain a granular material. Other details are the same as in Example 4.

[0073] Example 6 The difference between this embodiment and embodiment 5 is that: The oil and gas layer protective agent for drilling fluid in this embodiment also includes 20g of fluororubber powder; In step S1, polyethylene 2,5-furandicarboxylate and a cyclohexanone-acetone mixed solvent (the volume ratio of cyclohexanone to acetone is 1:1, and the solid-liquid ratio is 1:5) are mixed uniformly, the temperature is raised to 75° C., and the mixture is stirred for 40 minutes to obtain a polyethylene 2,5-furandicarboxylate solution; Under a nitrogen atmosphere, phenolic epoxy vinyl ester resin and fluororubber micropowder were added to a mixer, heated to 150°C, stirred at this temperature until softened, and polyethylene 2,5-furandicarboxylate solution was slowly added. The mixture was vacuumed to -0.08 MPa and stirred until no solvent evaporated. The mixture was cooled to 135°C and crushed into 80-100 mesh powder to obtain a composite resin. Other details are the same as in Example 5.

[0074] Example 7 The difference between this embodiment and embodiment 6 is that: The amount of fluororubber micropowder used is 40g.

[0075] Other details are the same as in Example 6.

[0076] Comparative Example 1 The difference between this comparative example and Example 1 is: Carbon microspheres of equal mass are used to replace the boron-zinc composite oxide modified carbon microspheres.

[0077] The preparation method of the carbon microspheres of this comparative example comprises the following steps: 1.65 kg of sugarcane bagasse and 1.35 kg of kelp bagasse were added to the reactor, stirred and mixed evenly, and water was added to a solid-liquid ratio of 1:5. The mixture was transferred to an ultrasonic device and ultrasonically treated for 30 minutes at a power of 500 W and a frequency of 40 Hz. The mixture was heated to 200 ° C and reacted for 5 hours. The mixture was cooled to room temperature and centrifuged. The mixture was washed twice with deionized water and dried at 105 ° C to constant weight. After air flow crushing (0.6 MPa), the mixture was passed through a 100-mesh standard sieve, air flow crushed (0.75 MPa) for the second time, and air flow screening was performed to obtain carbon microspheres with a particle size distribution of 0.1~5 μm.

[0078] Other details are the same as in Example 1.

[0079] Comparative Example 2 The difference between this comparative example and Example 1 is: An equal mass of vermiculite was used to replace the magnesium oxide-vermiculite composite.

[0080] Before use, the vermiculite was crushed and passed through a 300-mesh standard sieve. The sieve was taken and sieved by air flow to collect particles with a particle size distribution of about 1 to 50 μm. The particles were dried at 100°C to constant weight.

[0081] Other details are the same as in Example 1.

[0082] Comparative Example 3 The difference between this comparative example and Example 1 is: The gelatinized starch-cyclodextrin mixture was replaced with an equal mass portion of gelatinized starch.

[0083] Other details are the same as in Example 1.

[0084] Performance testing Base slurry: Mix 4% sodium bentonite, 3% sodium chloride and 93% clean water, stir at 3000r / min for 20min, let it stand for hydration for 24h, hot roll aging at 180℃ for 16h, and then set aside. The density is about 1.05g / cm 3 .

[0085] Test 1: Effect of the amount of the oil and gas layer protective agent for drilling fluid prepared in Example 1 on the permeability barrier performance Test conditions: Instrument: FA type non-permeation filter loss meter; Quartz sand bed: 20~50 mesh, 80~100 mesh, 200~300 mesh, 400~600 mesh and 800~1000 mesh; Protective agent dosage: 0%, 1.5%, 2.5%, 4% of the total drilling fluid mass; Test time: 60 min, pressure difference 3.5 MPa, record the penetration depth (cm) of drilling fluid in different sand beds, see Table 1.

[0086] Table 1 Effect of the amount of oil and gas layer protective agent for drilling fluid prepared in Example 1 on the permeability barrier performance

[0087] Test 2: Effect of the same amount of protective agent in different examples and comparative examples on the barrier performance Test conditions: Protective agent dosage: 2.5% of the total mass of drilling fluid; other test conditions are the same as those in Test 1, see Table 2.

[0088] Table 2 Effect of the oil and gas layer protective agents for drilling fluids prepared in Examples 2 to 7 and Comparative Examples 1 to 3 on the permeability barrier properties

[0089] Test 3: Comparison of comprehensive performance of protective agents in different embodiments and comparative examples Test conditions: (1) Protective agent dosage: 2.5% of the total mass of drilling fluid, see Table 3; (2) AV, PV, YP: measured at 50°C using a six-speed rotary viscometer, see Table 3; (3) Permeability recovery rate: artificial Bere core was used, see Table 3; (4) HTHP filtration loss: A high temperature and high pressure filtration tester was used, with the test conditions being 180°C, 3.5 MPa (simulating the typical operating conditions of a 160-210°C system), and the test time being 30 min, as shown in Table 3; (5) Sealing layer bearing pressure (MPa): Using an artificial Bailey core, pressurize at a rate of 0.5 MPa / min at 180°C and a base pressure difference of 3.5 MPa until the sealing layer ruptures, and record the peak pressure (see Table 3).

[0090] Table 3 Comprehensive properties of the oil and gas layer protective agents for drilling fluids prepared in Examples 1 to 7 and Comparative Examples 1 to 3

[0091] Analysis of the performance test data in Tables 1 to 3 shows that: From the perspective of permeability resistance, the amount of oil and gas layer protective agent added to the drilling fluid in Example 1 has a significant effect on the plugging effect. As the amount is increased from 0% to 4%, the penetration depth of the drilling fluid in the sand bed of each mesh size continues to decrease. Among them, the permeability optimization of the fine-grained sand bed is more obvious, indicating that the synergistic effect of the modified components can enhance the gradient plugging effect. Specifically, the boron-zinc composite oxide modified carbon microspheres target the plugging of clay micropores, the magnesium oxide-vermiculite composite bridges the cracks, and the filling effect of the gel synergistically covers the full-scale pores. At a dosage of 2.5%, the permeability resistance of Examples 2 to 7 is better than that of Comparative Examples 1 to 3, indicating that the modified components achieve precise plugging of the formation pores through the synergistic effect of surface bonding, bridging stability and gel filling.

[0092] In terms of comprehensive performance, all indicators of Examples 1 to 7 are better than those of the comparative example, and gradually improve with the optimization of components, indicating that the synergistic effect of components such as boron zinc composite oxide modified carbon microspheres and magnesium oxide-vermiculite composites not only enhances the permeation barrier performance, but also significantly improves the high-temperature stability and mechanical strength of the protective agent.

[0093] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An oil and gas layer protective agent for drilling fluid, characterized in that: The invention is prepared by comprising the following raw materials in parts by weight: 15-20 parts of boron zinc composite oxide modified carbon microspheres, 8-12 parts of magnesium oxide-vermiculite composite, 6-8 parts of gelatinized starch-cyclodextrin composite, 0.8-1.2 parts of short-chain fluorosilicone, 10-12 parts of phenolic epoxy vinyl ester resin and 12-15 parts of polyethylene 2,5-furandicarboxylate.

2. The oil and gas layer protective agent for drilling fluid according to claim 1, characterized in that: The preparation method of the boron-zinc composite oxide modified carbon microspheres comprises the following steps: S11: After mixing sugarcane bagasse and kelp bagasse evenly, add water, ultrasonicate for 30-50 minutes, heat to 200-220°C, hydrothermally react for 3-5 hours, cool, separate solid and liquid, wash, and dry to obtain a carbon microsphere precursor; S12: Immerse the carbon microsphere precursor in a zinc nitrate solution containing boric acid and tartaric acid, ultrasonicate for 30-50 minutes, mix for 2-4 hours, separate the solid and liquid, wash, dry, and then in an inert atmosphere at 380-420°C for 120-150 minutes, cool, and crush to obtain boron-zinc composite oxide modified carbon microspheres.

3. The oil and gas layer protective agent for drilling fluid according to claim 2, characterized in that: The mass ratio of the bagasse to the kelp bagasse is (5.5-6.5): (3.5-4.5).

4. The oil and gas layer protective agent for drilling fluid according to claim 1, characterized in that: The preparation method of the magnesium oxide-vermiculite composite comprises the following steps: The vermiculite was added to a hexadecyltrimethylammonium bromide solution, heated to 70-90°C, ultrasonically treated for 2-3 hours, solid-liquid separated, washed, immersed in a magnesium nitrate solution, mixed for 2-4 hours, solid-liquid separated, washed, dried, and then transferred to a sintering furnace, first heated to 240-260°C, kept warm for 60-80 minutes, continued to heat to 380-420°C, kept warm for 60-80 minutes, and cooled to obtain a magnesium oxide-vermiculite composite.

5. The oil and gas layer protective agent for drilling fluid according to claim 1, characterized in that: The preparation method of the gelatinized starch-cyclodextrin complex comprises the following steps: Add 5-7 parts by mass of hydroxypropyl-β-cyclodextrin to water, heat it to 65-75°C, mix it evenly, add 10-15 parts by mass of pregelatinized starch, mix it evenly, cool it to 40-50°C, add 0.5-1 parts by mass of citric acid, mix it evenly, and spray dry it to obtain a gelatinized starch-cyclodextrin complex.

6. The oil and gas layer protective agent for drilling fluid according to claim 5, characterized in that: In the preparation method of the gelatinized starch-cyclodextrin complex, 5 to 7 parts by mass of hydroxypropyl-β-cyclodextrin are added to water, heated to 65 to 75° C., and mixed uniformly, and the step of adding 1 to 2 parts by mass of quaternary ammonium salt is further included.

7. The oil and gas layer protective agent for drilling fluid according to claim 1, characterized in that: The short-chain fluorosilicone is selected from any one of perfluorobutyltriethoxysilane and perfluorooctyltriethoxysilane.

8. The oil and gas layer protective agent for drilling fluid according to claim 1, characterized in that: The oil and gas layer protective agent for drilling fluid further comprises 1 to 2 parts by mass of chopped carbon fibers.

9. The oil and gas layer protective agent for drilling fluid according to any one of claims 1 to 7, characterized in that The preparation method of the oil and gas layer protective agent for drilling fluid comprises the following steps: S1: dissolving polyethylene 2,5-furandicarboxylate in a cyclohexanone-acetone mixed solvent at 70-80° C. to obtain a polyethylene 2,5-furandicarboxylate solution; In an inert atmosphere, a phenolic epoxy vinyl ester resin is added to a mixer, the temperature is raised to 145-155° C., a polyethylene 2,5-furandicarboxylate solution is added, the mixture is distilled, cooled, and crushed to obtain a composite resin; S2: mixing the boron zinc composite oxide modified carbon microspheres, the magnesium oxide-vermiculite composite, the short-chain fluorosilicone and the gelatinized starch-cyclodextrin composite uniformly, and drying to obtain granules; S3: Under an inert atmosphere, melt the composite resin into atomized form and spray it onto the surface of the particles. Then, keep the temperature at 165-170°C for 60-70 minutes, cool it, and crush it to obtain an oil and gas layer protective agent for drilling fluid.

10. The oil and gas layer protective agent for drilling fluid according to claim 9, characterized in that: In step S2, after adding the gelatinized starch-cyclodextrin complex, the step of adding chopped fibers is also included.

Images