Drilling fluid heat storage phase change microcapsule and preparation method thereof

Abstract

The invention relates to the technical field of drilling fluid cooling, and discloses a drilling fluid heat storage phase change microcapsule and a preparation method thereof.The drilling fluid heat storage phase change microcapsule comprises a core material and a wall material wrapping the outer surface of the core material, the wall material further contains an optional wall material enhancer, the core material is selected from one or more of dodecanol and octanoic acid, and the wall material is selected from one or more of dodecanol and octanoic acid. The wall material is polyether sulfone containing nano-graphite. According to the phase-change constant-temperature microcapsule material and the preparation method thereof, the phase-change temperature and the phase-change latent heat of the phase-change heat-storage microcapsule material suitable for cooling the drilling fluid prepared in the embodiment 1 are tested through a differential scanning calorimeter, and the particle size distribution of the phase-change heat-storage microcapsule material is tested through a laser particle analyzer. The invention further provides a high-temperature drilling fluid system based on the phase-change constant-temperature microcapsule material, the characteristic that the phase-change constant-temperature material absorbs a large amount of heat and keeps constant temperature in the phase change process is utilized, the effect of actively cooling the high-temperature drilling fluid is achieved, and the purposes of stabilizing the performance of the drilling fluid and reducing the drilling cost are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of drilling fluid cooling, and in particular to a drilling fluid heat storage phase change microcapsule and a preparation method thereof. Background Art

[0002] Natural gas hydrate resources are extremely abundant and are considered to be the most promising alternative energy source in the future. More than 90% of natural gas hydrate resources are found in seabed sediments. Although natural gas hydrate is a new type of high-efficiency energy, oil exploration is currently facing a situation of "low, deep, hidden and difficult". "Low" means that the target layer is mostly a low-porosity and low-permeability reservoir, "deep" means that the burial depth of oil and gas in the target layer is very large, "hidden" means that the oil and gas reservoirs are hidden and difficult to discover, and "difficult" means that the exploration difficulty is becoming more and more difficult. Field practice has shown that in deep oil and gas drilling and development, drilling is facing more and more high temperatures, and the bottom hole temperature is generally between 180-260°C. In such a high temperature environment, it is difficult for the various components of the drilling fluid to resist the high temperature for normal drilling operations, which will seriously affect the performance of the drilling fluid. The components of the well fluid undergo dispersion and degradation, resulting in drastic changes in rheological and filtration properties, making drilling operations difficult. Not only that, drilling tools, measurement while drilling, logging and other instruments and equipment will also be severely affected in the face of high and ultra-high temperature environments. Their service life is greatly shortened and the drilling cost expenditure is increased. In addition, with the development of geothermal resources and the implementation of deep scientific drilling projects in my country, more and more high-temperature formations are encountered. The bottom hole temperature of hot dry rock high-temperature wells is mostly above 200°C, and even exceeds 300°C. Therefore, the extremely harsh environment of high temperature and high pressure such as deep oil and gas, hot dry rock, etc. has put forward severe tests on drilling fluid technology and downhole instruments and equipment, limiting the efficient drilling and development of deep oil and gas and geothermal clean resources. However, changes in its occurrence state during drilling projects can cause serious engineering problems.

[0003] In order to overcome the high temperature and ultra-high temperature problems encountered by drilling fluid during deep well resource development, various studies have been carried out on cooling the drilling fluid. However, the current cooling methods are mostly ground cooling methods, which only indirectly reduce the circulating temperature of the drilling fluid in the wellbore by lowering the temperature at the drilling fluid inlet. The equipment investment is large and the efficiency is not high, which makes it difficult to meet the cooling needs of deep well high-temperature drilling.

[0004] In the drilling of natural gas hydrate formations, the drilling fluid is in direct contact with the hydrate formation and is the technical carrier for controlling the downhole temperature and pressure. Its temperature, liquid column pressure and physical and chemical properties are the key factors in maintaining the stability of the hydrate formation. In theory, the stability of hydrates can be maintained by lowering the drilling fluid temperature and increasing the density. However, increasing the density will aggravate the invasion of the drilling fluid into the formation. Simply lowering the drilling fluid temperature is difficult to completely inhibit the decomposition of hydrates. The equipment conditions, energy consumption and efficiency of cooling also need to be considered. Moreover, the drilling fluid can only be kept at a low temperature at the drilling platform, and it is no longer controllable once it enters the wellbore.

[0005] To this end, we propose a drilling fluid heat storage phase change microcapsule and a preparation method thereof. Summary of the invention

[0006] The present invention mainly solves the technical problems existing in the above-mentioned prior art and provides a drilling fluid heat storage phase change microcapsule and a preparation method thereof.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a drilling fluid heat storage phase change microcapsule, comprising a core material, a composite polymer wall material on the outer surface of the core material, and the wall material also containing an optional wall material strengthener, the core material is selected from one or more of dodecanol and octanoic acid, and the composite polymer wall material is polyethersulfone containing nanographite and modified polyethylene graphite.

[0008] Preferably, the modified polyethylene graphite is prepared by heating and melting graphite and mixing and stirring with a proper amount of polyethylene.

[0009] Preferably, the composite high molecular polymer wall material has good chemical stability and thermal stability, can effectively protect the core material and prevent it from leaking, and can also improve the mechanical strength and durability of the microcapsule.

[0010] Preferably, the graphite is heated to melt, and the temperature of the heated liquid wax reaches 110-150°C; appropriate amounts of polyethylene and copolymer solution are added to the molten graphite and stirred, wherein the modified polyethylene graphite has a phase change temperature between 100 and 120°C, an average particle size between 3 and 10 μm, the copolymer is styrene-butene-styrene, the average molecular weight of the copolymer is 100,000-110,000, accounting for 4-15% of the mass of the modified polyethylene graphite, and the molecular weight of the modified polyethylene graphite is between 2,000 and 8,000.

[0011] A drilling fluid heat storage phase change microcapsule and a preparation method thereof, comprising the above-mentioned drilling fluid cooling multi-layer shell phase change microcapsule, specifically comprising the following steps:

[0012] S1: heating graphite, adding appropriate amount of polyethylene and copolymer solution into graphite and stirring at high speed to obtain modified polyethylene graphite;

[0013] S2: Dissolve 30 g of polyethersulfone in 100 mL of organic solvent as the oil phase, and dissolve 20 g of polyethylene graphite in 100 ml of deionized water as the internal water phase;

[0014] S3: After the internal water phase and the oil phase are mixed in a ratio of 1:4, 0.075 g of graphite is added, and then 3 g of sodium sulfate is added;

[0015] S4: taking 5 parts of urea and 5 parts of formaldehyde and reacting them at a constant temperature for 1 hour under alkaline conditions with a pH value of 10 to obtain a urea-formaldehyde resin prepolymer, and mixing the modified polyethylene graphite with the urea-formaldehyde resin prepolymer to obtain a phase change microcapsule;

[0016] S5: Put the phase change microcapsules into a stirring container, add sodium bentonite while stirring, continue stirring, and seal and cure for more than 24 hours to obtain a prehydrated bentonite slurry. Under high-speed stirring at a speed of 10,000 rpm, add phase change constant temperature microcapsules, filtrate reducer, and lubricant to the prehydrated bentonite slurry in proportion, stir for 30 minutes, and finally add a weighting agent to obtain a high-temperature drilling fluid.

[0017] Preferably, the urea-formaldehyde resin prepolymer obtained in S4 is mixed with the modified polyethylene graphite and stirred in a dry environment, during which hydrochloric acid is slowly added to control the pH value of the solution to 3. After the reaction is completed, the unreacted matter is washed away to obtain phase change microcapsules.

[0018] Preferably, the drying process should be carried out in a low temperature and low humidity environment to prevent thermal deformation and moisture absorption of the microcapsules, and the sieving process is carried out according to the particle size distribution of the desired microcapsules to obtain a phase change microcapsule product that meets the use requirements.

[0019] Beneficial Effects

[0020] The present invention provides a drilling fluid heat storage phase change microcapsule and a preparation method thereof. It has the following beneficial effects:

[0021] (1) A drilling fluid heat storage phase change microcapsule and a preparation method thereof. The phase change temperature and phase change latent heat of a phase change heat storage microcapsule material suitable for cooling drilling fluid prepared in Example 1 are tested by a differential scanning calorimeter, and its particle size distribution is tested by a laser particle size analyzer. The present invention provides a phase change constant temperature microcapsule material and a preparation method thereof, and provides a high-temperature drilling fluid system based on the phase change constant temperature microcapsule material. The phase change constant temperature material absorbs a large amount of heat and maintains a constant temperature during the phase change process, thereby achieving the effect of actively cooling the high-temperature drilling fluid, thereby achieving the purpose of stabilizing the drilling fluid performance and reducing the drilling cost.

[0022] (2) The drilling fluid heat storage phase change microcapsule and its preparation method test the influence of energy storage phase change materials on drilling fluid temperature, compare the effects of different materials on cooling, explore the influence law and mechanism of energy storage phase change materials on drilling fluid cooling, and systematically analyze the influence characteristics of phase change materials on temperature, construct a new method for cooling drilling fluid, achieve the purpose of underground temperature suitable for construction and measurement, achieve the goal of reducing drilling costs and improving drilling efficiency, and form a technology for cooling drilling fluid with energy storage phase change materials.

[0023] (3) A drilling fluid heat storage phase change microcapsule and a preparation method thereof. The phase change temperature of the phase change microcapsule of the present invention is such that the phase change material is transformed from a liquid state to a solid state to achieve cold storage. During the drilling process, once the drilling fluid temperature is higher than the phase change temperature, the phase change material is transformed from a solid state to a liquid state, releasing cold energy, so that the drilling fluid is kept at a low temperature for a long time, inhibiting the decomposition of hydrates and avoiding the collapse of the wellbore wall caused by the decomposition of hydrates. When the drilling fluid circulates again to the low-temperature section of the mud line, the temperature is reduced again, and the microcapsule is transformed from a liquid state to a solid state to achieve cold storage, and the cycle is repeated.

[0024] (4) The drilling fluid heat storage phase change microcapsule and its preparation method. The present invention utilizes the characteristics of phase change material, that is, large phase change latent heat and constant temperature during the heat absorption process, to provide a phase change heat storage microcapsule material suitable for cooling the drilling fluid and its preparation method. The method can play a role when the drilling fluid is heated to a certain temperature during drilling into a high-temperature formation, absorb heat and cool the drilling fluid, thereby achieving the effect of stabilizing the performance of the drilling fluid, ensuring the normal progress of drilling, and achieving drilling while drilling. It is a drilling fluid additive that does not affect the performance of the drilling fluid while achieving the effect of cooling the drilling fluid.

Claims

1. A drilling fluid heat storage phase change microcapsule, comprising a core material, a composite polymer wall material on the outer surface of the core material, and the wall material further containing an optional wall material strengthener, characterized in that: The core material is selected from one or more of dodecanol and octanoic acid, and the composite high molecular polymer wall material is polyethersulfone containing nanographite and modified polyethylene graphite.

2. The drilling fluid heat storage phase change microcapsule according to claim 1, characterized in that: The modified polyethylene graphite is prepared by heating and melting graphite and mixing and stirring the graphite with appropriate amounts of polyethylene and copolymer.

3. The drilling fluid heat storage phase change microcapsule according to claim 1, characterized in that: The composite high molecular polymer wall material has good chemical stability and thermal stability, can effectively protect the core material and prevent it from leaking, and can also improve the mechanical strength and durability of the microcapsule.

4. The drilling fluid heat storage phase change microcapsule according to claim 1, characterized in that: The graphite is heated to melt, and the temperature of the heated liquid wax reaches 110-150°C; appropriate amounts of polyethylene and copolymer solution are added to the molten graphite and stirred, wherein the modified polyethylene graphite has a phase change temperature between 100-120°C, an average particle size between 3-10 μm, the copolymer is styrene-butene-styrene, the average molecular weight of the copolymer is 100000-110000, accounting for 4-15% of the mass of the modified polyethylene graphite, and the molecular weight of the modified polyethylene graphite is between 2000-8000.

5. A drilling fluid heat storage phase change microcapsule and a preparation method thereof, characterized in that: The method comprises the drilling fluid cooling multi-layer shell phase change microcapsules according to any one of claims 1 to 4, and is specifically divided into the following steps: S1: heating graphite, adding appropriate amount of polyethylene and copolymer solution into graphite and stirring at high speed to obtain modified polyethylene graphite; S2: Dissolve 30 g of polyethersulfone in 100 mL of organic solvent as the oil phase, and dissolve 20 g of polyethylene graphite in 100 ml of deionized water as the internal water phase; S3: After the internal water phase and the oil phase are mixed in a ratio of 1:4, 0.075 g of graphite is added, and then 3 g of sodium sulfate is added; S4: taking 5 parts of urea and 5 parts of formaldehyde and reacting them at a constant temperature for 1 hour under alkaline conditions with a pH value of 10 to obtain a urea-formaldehyde resin prepolymer, and mixing the modified polyethylene graphite with the urea-formaldehyde resin prepolymer to obtain a phase change microcapsule; S5: Put the phase change microcapsules into a stirring container, add sodium bentonite while stirring, continue stirring, and seal and cure for more than 24 hours to obtain a prehydrated bentonite slurry. Under high-speed stirring at a speed of 10,000 rpm, add phase change constant temperature microcapsules, filtrate reducer, and lubricant to the prehydrated bentonite slurry in proportion, stir for 30 minutes, and finally add a weighting agent to obtain a high-temperature drilling fluid.

6. A drilling fluid heat storage phase change microcapsule and a preparation method thereof according to claim 5, characterized in that: The urea-formaldehyde resin prepolymer obtained in S4 is mixed with the modified polyethylene graphite and stirred in a dry environment, during which hydrochloric acid is slowly added dropwise to control the pH value of the solution to 3. After the reaction is completed, the unreacted matter is washed away to obtain phase change microcapsules.

7. A drilling fluid heat storage phase change microcapsule and a preparation method thereof according to claim 6, characterized in that: The drying process should be carried out in a low temperature and low humidity environment to prevent thermal deformation and moisture absorption of the microcapsules. The screening process is carried out according to the particle size distribution of the required microcapsules to obtain a phase change microcapsule product that meets the use requirements.