41results about How to "Good reservoir protection performance" patented technology

The invention relates to an oil-based drilling fluid for development drilling of a shale gas, and belongs to the technical field of drilling fluids for petroleum drilling engineering. The oil-based drilling fluid is characterized by being prepared from the following components by weight percent: 0.2% to 2% of main emulsifier, 0.1% to 1% of auxiliary emulsifier, 0% to 1.5% of wetting agent, 0.2% to 1.5% of alkalinity regulating agent, 0% to 1.5% of organic soil, 0% to 1.5% of tackifier, 0.2% to 2% of filtrate reducer, 0% to 80% of weighting agent, 0% to 20% of water phase and the balance of oil phase. The oil-based drilling fluid can be used for meeting a special requirement of the shale gas drilling to the drilling fluid, and is good in stability, inhibitory capability and lubricity even under low and high temperatures. The oil-based drilling fluid has the characteristics of high dynamic plastic ratio, low plastic viscosity, wide application range and good economic benefit.

The invention provides a self-plugging releasing temperature resistant temporary plugging agent used for water-based drilling fluid, the self-plugging releasing temperature resistant temporary plugging agent comprises nano calcium carbonate and a product which is obtained by reacting starch, alkali metal hydroxide, halogenated organic acid, carbonate, a hydrophobic modification agent and alcohol with water. The invention also provides a preparation method of the self-plugging releasing temperature resistant temporary plugging agent used for the water-based drilling fluid, and the self-plugging releasing temperature resistant temporary plugging agent used for the water-based drilling fluid can be obtained by proportionally adding components into a kneading machine for kneading. The self-plugging releasing temperature resistant temporary plugging agent has strong high temperature resistance, and can resist the temperature up to 140 DEG C; and the self-plugging releasing temperature resistant temporary plugging agent has good temporary plugging effect and significant reservoir protection effect, and the water-based drilling fluid added with the temporary plugging agent has high temporary plugging rate and oil phase permeability recovery rate; at the same time, the temporary plugging agent has self-plugging releasing ability. During the late flowback, the self-plugging releasing can be realized by formation of a hydrophobic channel without acid washing for mud cake removal and other processes, and secondary damage to a reservoir can be avoided.

The invention discloses a preparation method of a synthetic base drilling fluid. The preparation method comprises the steps of a. adding 2.0%-4.0% of organic soil, 3.0%-5.0% of main emulsifier, 2.0%-4.0% of auxiliary emulsifier, 0.1%-0.2% of wetting agent, 0.5%-2.0% of flow pattern conditioning agent and 2.0%-3.0% of CaO to 60-70% of synthetic base in percent by weight under a stirring condition, and stirring for 30min; b. preparing a CaCl2 solution with the mass concentration of 20%, and enabling CaCl2 to completely dissolve; c. slowly adding 10%-15% of CaCl2 aqueous solution in percent by weight to the synthetic base under a stirring condition; and d. adding 4.0%-6.0% of filtrate-loss reducer and 2.0%-3.0% of anti-sloughing blocking agent in percent by weight to the synthetic base under a stirring condition to form the synthetic base drilling fluid. The preparation method is simple in processing steps and easy in operation. The synthetic base drilling fluid prepared by the method has the characteristics of strong anti-sloughing inhibition capability, good salt and calcium erosion resistance performance and obvious lubrication performance.

The invention relates to a nanometer plugging agent for a water-based drilling fluid, a preparing method of the nanometer plugging agent and the drilling fluid. The nanometer plugging agent for the water-based drilling fluid is obtained in a manner that multi-walled carbon nanotubes are covalently coated with sodium polystyrenesulfonate, wherein the tube diameter of the multi-walled carbon nanotubes is 20 nm to 30 nm, and the tube length of the multi-walled carbon nanotubes is 10 microns to 30 microns; the number-average molecular weight of the grafted sodium polystyrenesulfonate is 75 kDa, and the degree of polymerization (DOP) is 900; the drilling fluid is prepared from 100 parts by weight of water, 1-8 parts by weight of bentonite, 4-10 parts by weight of a flow-pattern adjusting agent,0.2-1.2 parts by weight of a thickening agent, 4-10 parts by weight of a fluid loss agent, 30-60 parts by weight of a plugging agent, 10-50 parts by weight of a weighting agent, 0.1-4 parts by weightof a lubricating agent and 0.1-0.4 part by weight of a pH adjusting agent. According to the nanometer plugging agent for the water-based drilling fluid, the preparing method of the nanometer pluggingagent and the drilling fluid, the sodium-polystyrenesulfonate-modified multi-walled carbon nanotubes are used as the plugging agent, micron-and-nanometer-size pores of the mud shale well wall can beeffectively plugged, and the nanometer plugging agent is particularly suitable for drilling construction of stratums with low porosity, low permeability, micro-pore micro-crack development and a remarkable capillary effect.

The invention provides a drilling fluid. The drilling fluid is prepared from cationic alkyl glucoside, polyether amino alkyl glucoside, a treating agent and water, wherein the cationic alkyl glucosideis of a structure shown as formula I; the polyether amino alkyl glucoside is of a structure shown as formula II. Compared with the prior art, the drilling fluid adopts the cationic alkyl glucoside and the polyether amino alkyl glucoside with specific structures as main components, so that the obtained drilling fluid has better inhibition performance, lubricity, heat resistance and reservoir protectiveness under joint action of the cationic alkyl glucoside and the polyether amino alkyl glucoside, and the drilling fluid is not only applicable to horizontal drilling of sloughing formations suchas shale, mudstone and the like as well as shale gas, but also applicable to drilling of formations with higher requirements for reservoir protectiveness. The drilling fluid is a water-based drillingfluid, is lower in cost, safe and environmentally friendly and can be directly discharged and applied to formations with higher environmental requirements.

The invention relates to nanometer drilling fluid. The concentration of the nanometer drilling fluid comprises 900kg / m<3> of water, 40-50kg / m<3> of bentonite, 25-30kg / m<3> of nanometer emulsion JDL-3, 2-3kg / m<3> of cationic gel MMH, 3-5kg / m<3> of high molecular polymer PAM, 10-15kg / m<3> of sulfonated gilsonite FT-1, 15-20kg / m<3> of sulfonated phenolic resin SMP, 15-20kg / m<3> of salt and temperature resistant fluid loss agent LS-1, 10-15kg / m<3> of flow type regulating agent DS-2 and 8-10kg / m<3> of sodium hydroxide (NaOH). The nanometer drilling fluid has good colloid dispersivity and high heat stability, improves the rheology of the drilling fluid, increases the compactness of mud cakes, improves the thickness of the mud cakes, quickly forms a layer of nanometer film on a well wall, prevents the drilling fluid from invading stratums near the well wall and pressure from being transmitted and has good anti-caving performance and good storage layer protection performance.

The invention relates to the technical field of underbalanced well completion and oil production, in particular to a method for underbalanced tubing descending, non-well-killing gas lifting, rotary pumping, pump maintaining and tubing maintaining. The method includes the steps: firstly, fixedly mounting an in-tubing blowout preventer and a lifting basket at the bottom end of a tubing string in sequence from top to bottom, and mounting a float valve in the in-tubing blowout preventer. The in-tubing blowout preventer is fixedly mounted at the bottom of the tubing string, so that tubing descending operation can be completed smoothly in the well completion phase, a gas lift liquid discharge or production passage can be established during gas-lift oil production, tubing descending, gas-lift oil production, oil pumping, oil-well pump maintenance and tubing maintenance can be closely integrated, operation cycle is shortened, operation of putting into production is simplified, reservoir protection effect of underbalanced well drilling is enhanced, oil-gas wells can be put into production timely to keep an excellent productivity increase effect, further competitiveness of the underbalanced technique is improved, and oil production cost is lowered.

The invention relates to an environment-friendly nano water-based drilling fluid for low permeability reservoirs and a preparation method thereof. The drilling fluid is made from water, nano bentonite, anhydrous sodium carbonate, an environment-friendly nano tackifying stripping agent, an environment-friendly nano filtrate loss reducer, an environment-friendly inhibitive anti-collapse agent, an environment-friendly lubricant, an environment-friendly nano blocking agent, and an environment-friendly nano flow pattern regulator. The preparation method includes: adding nano bentonite into water, and mixing well; adding anhydrous sodium carbonate, mixing well, and hydrating for 24 h; adding an environment-friendly nano tackifying stripping agent, an environment-friendly nano filtrate loss reducer, an environment-friendly inhibitive anti-collapse agent, an environment-friendly lubricant, an environment-friendly nano blocking agent, and an environment-friendly nano flow pattern regulator in sequence, and mixing well to obtain the environment-friendly nano water-based drilling fluid. The environment-friendly nano water-based drilling fluid can well inhibit hydrating swelling of clay, and has good filtration and wall-building property, as well as good rock-carrying property, excellent environmental friendliness and zero environmental harm.

The invention provides a soilless polyether amine alkyl glucoside drilling fluid including 2 wt%-7 wt% of polyether amine alkyl glycoside, 0.4 wt%-1.2 wt% of a tackifier, 2.6 wt%-8 wt% of a filtrate loss reducer, 1 wt%-4 wt% of a plugging agent, 0.6 wt%-1 wt% of a pH regulator, 0.1 wt%-0.4 wt% of carbonate, 10 wt%-24 wt% of sodium chloride, 0.2 wt%-0.6 wt% of a sulfur-containing antioxidant, and the balance water. The polyether amine alkyl glucoside has good inhibition, lubricity, temperature resistance and reservoir protection, and through intercoordination of the polyether amine alkyl glycoside with other components, the drilling fluid has good inhibition, temperature resistance, lubricity, fouling resistance and reservoir protection. The invention also provides a preparation method of the soilless polyether amine alkyl glucoside drilling fluid.

The invention provides low-solid-content reservoir protection workover fluid and a preparation method thereof.The low-solid-content reservoir protection workover fluid comprises pre-gelatinized starch and salt-resistant and corrosion-resistant saturated sodium chloride water, wherein the ratio of the weight of the pre-gelatinized starch to the volume of the salt-resistant and corrosion-resistant saturated sodium chloride water is 80-100:300-350.The pre-gelatinized starch comprises, by weight, 10 parts of modified starch, 0.4-1.0 parts of sodium hydroxide and 100 parts of water.The salt-resistant and corrosion-resistant saturated sodium chloride water comprises, by weight, 100 parts of water, 32 parts of sodium chloride, 2-4 parts of acid-soluble shielding temporary plugging agent, 4 parts of sterilizing agent, 2 parts of corrosion inhibitor and 0.1-0.2 part of defoaming agent.The low-solid-content reservoir protection workover fluid has the advantages that the workover fluid is stable in performance, and mud cake can be acidized and degraded.

The invention relates to a hydrophobic starch-nanometer calcium carbonate compound and a preparation method thereof, and belongs to the technical filed of hydrophobization temporary plugging. The preparation method of the compound comprises the following steps: placing 1000-2000g of starch in a kneader, sequentially adding 100-200g of sodium carbonate, 100-200mL of water and 125-250mL of ethanol, and carrying out a closed kneading reaction at a preset temperature; sequentially adding 125-250mL of ethanol and 150-300Ml of benzoyl chloride, and carrying out a closed kneading reaction at 30-40DEG C; slowly adding 500-1500g of nanometer calcium carbonate, and carrying out a closed kneading reaction at 30-50DEG C; and stopping stirring, cooling to room temperature, allowing the obtained material to stand for 3-6h, discharging the material, washing, drying, and crushing to obtain a product. The product has a same substitution value with products obtained through an organic solvent method, can effectively reduce the oil phase starting pressure, increases the oil water passing ratio, maintains high permeability restoration ratio, and has a good reservoir protection effect.

The invention relates to the technical field of underbalance well-completion practice and oil production operation, in particular to an underbalance tubing, no-killing gas lifting, shaft pumping and pump detecting combined method. The underbalance tubing, no-killing gas lifting, shaft pumping and pump detecting combined method is carried out according to the following step: a first step of sequentially and fixedly arranging an oil tube inner blowout preventer and a lifting basket at the bottom end of a tubing string from top to bottom, fixedly arranging a valve fixing seat in the oil tube inner blowout preventer and arranging a valve in the valve fixing seat. According to the invention, by fixedly arranging the oil tube inner blowout preventer at the bottom of the tubing string, not only can the tubing operation be successfully completed in the well completion stage, but also in the gas-lifting oil production process, a gas lifting drainage or production passage can be established, the tubing operation, the gas-lifting oil production operation, the oil pumping operation and the oil-well pump overhauling operation are tightly combined, the operation period is shortened, the production operation is simplified, a reservoir protection effect of an underbalance drilled well is reinforced and an oil / gas well can be timely put into production and is kept having an excellent capacity promoting effect, so that competitiveness of the underbalance technology is improved.

The embodiments of the invention provide an intelligent prediction method and apparatus for reservoir sensitivity, belonging to the technical field of reservoir sensitivity prediction. The method includes: acquiring a reservoir sensitivity influence factor item related to a reservoir sensitivity result to be predicted and numerical values of corresponding reservoir sensitivity influence factors; determining a corresponding type of database according to the reservoir sensitivity influence factor item; determining whether numerical values of reservoir sensitivity influence factors corresponding to core parameters in the numerical values of the reservoir sensitivity influence factors include a first upper boundary value or a first lower boundary value; and using, according to whether the first upper boundary value or the first lower boundary value is included, different intelligent sensitivity prediction models to calculate the reservoir sensitivity result to be predicted.

The invention provides oil-in-water drilling fluid taking biodiesel as a dispersion phase as well as a preparation method and application thereof. The oil-in-water drilling fluid comprises 40-70 parts by volume of water and 30-60 parts by volume of biodiesel, wherein the total volume of water and biodiesel is 100%; the oil-in-water drilling fluid further comprises the following components: bentonite with the mass-to-volume ratio (g / mL) of 1%-6%, sodium carbonate with the mass-to-volume ratio of 0.05%-0.3%, sodium hydroxide with the mass-to-volume ratio of 0.02%-0.05%, a main emulsifier with the mass-to-volume ratio of 2%-5%, an auxiliary emulsifier with the mass-to-volume ratio of 0.2%-1%, a shale inhibitor with the mass-to-volume ratio of 0.5%-5% and a filtrate reducer with the mass-to-volume ratio of 0.5%-5%. The oil-in-water drilling fluid provided by the invention has the characteristics of being low in cost, non-toxic, non-fluorescent, low in density, adjustable, good in rheological property, low in filter loss, excellent in lubricating property and high in upper temperature resistance limit, and further has advantages of being excellent in antifouling property, shale inhibition property, reservoir protection property and environment acceptability.

The invention discloses an oil-based drilling fluid for protecting a shale gas reservoir, wherein the oil-based drilling fluid includes, in parts by volume, 70-90 parts of base oil and 10-30 parts of an aqueous phase; based on the total volume of the base oil and the aqueous phase, the oil-based drilling fluid further includes the components by the mass / volume ratio: 1-3% of a main emulsifier, 0.5-1.5% of an auxiliary emulsifier, 1-3% of lime, 1-3% of organic soil, 1-3% of a tackifier, 1-5% of a filtration loss reduction agent, 1-3% of a plugging agent, 3-8% of a reservoir protective agent, and 0-100% of a weighting agent, wherein the reservoir protective agent is a compound mixture of calcium carbonate, magnesium oxide and magnesium carbonate. The drilling fluid has relatively good inhibition and lubrication performance, and can protect the shale gas reservoir.

A super-amphiphobic composite material and use of the same as an inhibitor, lubricant, reservoir protectant, and accelerator in water-based drilling fluids. A method for preparing the amphiphobic composite material includes: performing a first mixing of nano-titanium dioxide and nano-silicon dioxide in an alcohol-water mixed solvent under an alkaline condition, to obtain a dispersion of nano-titanium dioxide and nano-silicon dioxide; then introducing a fluorosilicone-containing coupler into the dispersion of nano-titanium dioxide and nano-silicon dioxide and performing a second mixing. The amphiphobic composite material may be applied in water-based drilling fluids. It has an effect of strongly inhibiting hydrated swelling and disintegration, low toxicity and high compatibility; can solve problems such as well wall instability, blockage of drilling tools, and reservoir damage, etc.; and has long-term practical value in complicated wells such as extra-deep wells, horizontal wells and extended reach wells, and in mud-bearing shale formations.

The invention discloses an unconsolidated sandstone reservoir protection drilling fluid and a preparation method thereof. The unconsolidated sandstone reservoir protection drilling fluid comprises 1-3% of a starch filtrate reducer, 0.5-2% of xanthan gum, 0.5-3% of hydroxyethyl cellulose, 1-2% of sodium hydroxide, 0.1-0.5% of sodium sulfite, 1-2% of polyethylene wax, 5-15% of fine calcium and 1-2%of aminotrimethylenephosphonic acid potassium salt. The unconsolidated sandstone reservoir protection drilling fluid has the characteristics of strong inhibition capability, low solid-phase content and excellent reservoir protection effect and is suitable for unconsolidated sandstone reservoir drilling protection.

The invention relates to an oil-based drilling fluid for development drilling of a shale gas, and belongs to the technical field of drilling fluids for petroleum drilling engineering. The oil-based drilling fluid is characterized by being prepared from the following components by weight percent: 0.2% to 2% of main emulsifier, 0.1% to 1% of auxiliary emulsifier, 0% to 1.5% of wetting agent, 0.2% to 1.5% of alkalinity regulating agent, 0% to 1.5% of organic soil, 0% to 1.5% of tackifier, 0.2% to 2% of filtrate reducer, 0% to 80% of weighting agent, 0% to 20% of water phase and the balance of oil phase. The oil-based drilling fluid can be used for meeting a special requirement of the shale gas drilling to the drilling fluid, and is good in stability, inhibitory capability and lubricity even under low and high temperatures. The oil-based drilling fluid has the characteristics of high dynamic plastic ratio, low plastic viscosity, wide application range and good economic benefit.

The invention relates to the technical field of underbalance well-completion practice and oil production operation, in particular to an underbalance well-completion tubing and gas lifting production combined method. The underbalance well-completion tubing and gas lifting production combined method is carried out according to the following step: a first step of sequentially and fixedly arranging an oil tube inner blowout preventer and a lifting basket at the bottom end of a tubing string from top to bottom, fixedly arranging a valve fixing seat in the oil tube inner blowout preventer, arranging a valve in the valve fixing seat, fixedly arranging at least one reverse gas lifting valve at the middle part of the tubing string and fixing the upper end of a sleeve on a wellhead. According to the invention, by fixedly arranging the oil tube inner blowout preventer at the bottom of the tubing string, not only can the tubing operation be successfully completed in the well completion stage, but also in the gas-lifting oil production process, a gas lifting drainage or production passage can be established, the gas-lifting oil production operation is successfully carried out, the operation period is shortened, a reservoir protection effect of an underbalance drilled well is reinforced and an oil / gas well can be timely put into production and is kept having an excellent capacity promoting effect, so that competitiveness of the underbalance technology is improved.

The invention relates to the technical field of petroleum drilling, and discloses a reservoir protection agent intermediate product, a reservoir protection agent, preparation methods and applications thereof, as well as drilling fluid and an application thereof. The reservoir protection agent intermediate product is prepared by the following raw materials: acrylamide, a cationic monomer, a cross-linking agent, an initiator, a toughening material and water, based on 100 parts by weight of the raw materials, the raw materials comprise the following components in parts by weight: 8-30 parts of acrylamide, 1-10 parts of the cationic monomer, 0.01-0.5 parts of the cross-linking agent, 0.01-0.1 parts of the initiator, and 5-25 parts of the toughening material. The reservoir protection agent comprises the intermediate product, alkali, salt and water, based on 100 parts by weight of the reservoir protection agent, the reservoir protection agent comprises 5-40 parts by weight of the intermediate product, 1-10 parts of alkali, and 1-12 parts by weight of salt. The reservoir protection agent has good sealing effects, improves reservoir protection capability of drilling fluid, and enhances capability of drilling fluid for stabilization of borehole walls.

The invention relates to the technical field of petroleum drilling, and discloses a nanofilm structure reservoir protection agent and preparation method thereof and drilling fluid and application of the nanofilm structure reservoir protection agent or drilling fluid in low permeability reservoir drilling. The nanofilm structure reservoir protection agent comprises a montmorillonite lamella, a structure unit shown in formula (1) as shown in the description and a structure unit shown in formula (2) as shown in the description, wherein R1, R2, R3, R4 and R5 are respectively and independently hydrogen, CD-C4 alkyl or C1-C4 alkoxy, and R6 is C1-C6 alkylene. The invention further provides the drilling fluid containing the nanofilm structure reservoir protection agent disclosed by the invention. The drilling fluid containing the nanofilm structure reservoir protection agent shows good rheological property, anti-temperature property, anti-collapsing property and reservoir protection property when being applied for the low permeability reservoir drilling.

The invention relates to a preparation method of an inert dilution agent for an oil-based drilling fluid. According to the technical scheme, the preparation method comprises the following steps that 1, low-viscosity synthetic base oil is added in a beaker with a stirrer and a thermometer, and a reaction is carried out at the 50-90 DEG C for 3-6 hours, and then heating is stopped; 2, an emulsifyingagent is added into the reactor in the step 1, and stirring is conducted 3-6 hours; 3, a filtrate reducer, a wetting agent, an alkalinity regulating agent and a calcium chloride water solution are mixed in a ratio and then added into the reactor in the step 1, and stirring is conducted for 6-8 hours; 4, the mixture in the reactor is stirred at a high speed, a reaction is carried out at the temperature of 50-90 DEG C for 3-6 hours, cooling is conducted until to the room temperature, an emulsion is formed, and the emulsion is the inert dilution agent for the oil-based drilling fluid. The preparation method has the advantages that under the condition that the inhibitive ability and the shear thinning performance of the oil-based drilling fluid are not changed, the plastic viscosity can be reduced, and the drilling fluid obtained before and after addition of the inert dilution agent cannot affect construction safety even in the construction process.

The invention provides a self-plugging releasing temperature resistant temporary plugging agent used for water-based drilling fluid, the self-plugging releasing temperature resistant temporary plugging agent comprises nano calcium carbonate and a product which is obtained by reacting starch, alkali metal hydroxide, halogenated organic acid, carbonate, a hydrophobic modification agent and alcohol with water. The invention also provides a preparation method of the self-plugging releasing temperature resistant temporary plugging agent used for the water-based drilling fluid, and the self-plugging releasing temperature resistant temporary plugging agent used for the water-based drilling fluid can be obtained by proportionally adding components into a kneading machine for kneading. The self-plugging releasing temperature resistant temporary plugging agent has strong high temperature resistance, and can resist the temperature up to 140 DEG C; and the self-plugging releasing temperature resistant temporary plugging agent has good temporary plugging effect and significant reservoir protection effect, and the water-based drilling fluid added with the temporary plugging agent has high temporary plugging rate and oil phase permeability recovery rate; at the same time, the temporary plugging agent has self-plugging releasing ability. During the late flowback, the self-plugging releasing can be realized by formation of a hydrophobic channel without acid washing for mud cake removal and other processes, and secondary damage to a reservoir can be avoided.

The present invention relates to underbalanced Well Operations and Production Operations In the technical field, it is a method for joint operation of underbalanced well completion downhole tubing and gas lift production, which is carried out as follows: the first step is to fixedly install the blowout preventer in the tubing and the Basket, fixedly install the valve fixing seat in the blowout prevention device in the tubing, install the valve in the valve fixing seat, and install no less than one reverse gas lift valve in the middle of the tubing string, and fix the upper end of the casing on the wellhead . The invention fixedly installs the blowout preventer in the tubing at the bottom of the tubing string, not only can successfully complete the tubing operation in the well completion stage, but also can establish a gas-lift drainage or production channel during the gas-lift production process, so that the gas-lift production The operation is carried out smoothly, the operation cycle is shortened, and the underbalanced The reservoir protection effect of drilling, oil and gas wells can be put into production in time, and maintain a good productivity improvement effect, thereby improving the competitiveness of underbalanced technologies 。

A provided novel oil protection material comprises the following compositions: 30-60 parts of 600-mesh fine-mesh calcium carbonate, 30-60 parts of 300-mesh fine-mesh calcium carbonate and 20-50 parts of 100-mesh fine-mesh calcium carbonate. When for use, the above compositions are mixed, the mixture is added into a drilling fluid, and the oil protection material forms a plugging layer on the surface of a storage layer for preventing a harmful solid phase from entering the storage layer and influencing later-period output. During later-period exploitation, fine-mesh calcium carbonate is dissolved only by employing an acid for washing and a channel for storage is recovered. The beneficial effects comprise that the combination of fine-mesh calcium carbonate with different fineness helps to give play to relatively good storage layer protection effect, and the novel oil protection material is especially suitable for new areas with unascertained porosity.

The invention relates to a nano-sealing agent for water-based drilling fluid, a preparation method thereof and drilling fluid. The nano-sealing agent for water-based drilling fluid is polystyrene sulfonate sodium covalently coated multi-walled carbon nanotubes, wherein the multi-walled carbon nanotubes have a diameter of 20-30 nm and a tube length of 10-30 μm; The number-average molecular weight of the sodium polystyrene sulfonate of described grafting is 75kDa, and degree of polymerization (DOP) is 900; Described drilling fluid contains the water of 100 weight parts, and bentonite is 1-8 weight parts, and flow regulator is 4-10 parts by weight, 0.2-1.2 parts by weight of viscosifier, 4-10 parts by weight of fluid loss control agent, 30-60 parts by weight of plugging agent, 10-50 parts by weight of weighting agent, and 0.1 parts by weight of lubricant -4 parts by weight, the content of the pH regulator is 0.1-0.4 parts by weight. The present invention uses sodium polystyrene sulfonate modified multi-walled carbon nanotubes as the plugging agent, which can effectively plug micro- and nano-sized pores on the well wall of mud shale, and is especially suitable for low-space and low-permeability, development of micro-pores and micro-cracks, and capillary Drilling operations in formations with outstanding effects.

The invention relates to an anti-emulsification workover fluid for an offshore oilfield as well as a preparation method and a use method of the anti-emulsification workover fluid. The anti-emulsification workover fluid for the offshore oilfield comprises the following components in percentage by mass: 0.5-1.5% of a drainage-aiding cleaning agent, 0.1-0.5% of a demulsifying agent and the balance of water, the water is selected from production sewage and / or water source well water; adding water into a stirring tank, heating to 50 DEG C or above, adding other raw materials, and uniformly stirring; and controlling the in-well temperature of the anti-emulsification workover fluid for the offshore oilfield to be higher than 50 DEG C. The technical problem to be solved is how to provide the anti-emulsification workover fluid for the offshore oilfield, reduce the damage of the anti-emulsification workover fluid to a reservoir, improve the recovery effect of the oil well yield after well repair and reduce the treatment capacity of oil-water separation of a workover flow-back fluid on an offshore platform, so that the anti-emulsification workover fluid is more practical.