High-steel-grade large-drift-diameter heat insulation drill rod and preparation method thereof

Abstract

The invention discloses a high-steel-grade large-drift-diameter heat insulation drill rod and a preparation method thereof, and relates to the technical field of drilling tools. The high-steel-grade large-drift-diameter heat insulation drill rod comprises a pipe body; the inner wall of the drill rod is coated with a heat insulation layer, the thickness of the heat insulation layer is 1.0-3.0 mm, and the heat insulation layer is made of modified fluorosilicone resin; the modified fluorosilicone resin is uniformly coated and cured on the inner wall of the drill rod, so that the overall heat conductivity coefficient of the drill rod is effectively reduced, the transmission speed of the formation temperature to the interior of the drill rod is reduced, the underground environment temperature is reduced, the use requirements of underground electronic instruments and the like are met, and the performance of drilling fluid is guaranteed; meanwhile, an inner hole of the drill rod is large, the inner diameter of the drill rod is not changed greatly after the drill rod is coated with a heat insulation coating with a certain thickness, large pumping resistance cannot be generated, and the requirement that a logging tool is tripped into a well bottom through the interior of the drill rod can be met.

Description

Technical Field

[0001] The invention relates to the technical field of drilling tools, and in particular to a high-steel-grade, large-diameter, heat-insulating drill rod and a preparation method thereof. Background Art

[0002] As oil and gas development gradually enters deep and ultra-deep oil and gas reservoirs, high underground temperatures have become a major obstacle to their development. Specifically, when drilling in high-temperature and ultra-high-temperature formations, the drill pipe, which is the main transmission channel for drilling fluid, is made of carbon steel with high thermal conductivity. The heat in the formation will be transferred from the outer wall of the drill pipe to the drill pipe to heat the mud, making the temperature in the wellbore consistent with the formation temperature. The drilling fluid cannot effectively cool the bottom hole assembly (BHA) and sensitive electronic equipment (such as rotary steering, logging instruments, etc.), causing their performance to degrade, fail or be damaged, resulting in the suspension of drilling operations. At the same time, excessively high mud temperature also greatly reduces the rock carrying capacity, which can easily cause serious underground accidents such as drill stuck, seriously restricting the development of deep and ultra-deep oil and gas reservoirs.

[0003] At present, there are different types of heat-insulating drill pipe products on the market, such as lined heat-insulating drill pipe, heat-insulating drill pipe wrapped with heat-insulating materials, etc., which play a role in heat insulation within a certain range, but their disadvantages are also obvious. Although foreign drilling tool manufacturers such as Halliburton and Weatherford have also developed some high-temperature resistant drilling electronic equipment and drilling tools, they have not been widely promoted in oil fields due to their high fees.

[0004] For example, the invention patent with application number 202010450022.3 discloses a method for manufacturing an insulated drill pipe, a drill tool, and an insulated drill pipe, comprising an outer pipe and an inner liner pipe sleeved in the outer pipe, a cavity between the outer pipe and the inner liner pipe, the cavity is filled with an insulating material, and the outer pipe has an injection hole connected to the cavity, wherein the insulating material is sand and gravel particles. This invention patent uses sand and gravel particles as insulating materials, and injects them into the annular space formed by the inner wall of the drill pipe and the outer wall of the inner liner pipe, thereby forming an insulating layer to reduce the temperature of the drilling fluid in the drill pipe during the drilling of high-temperature oil and gas reservoirs. However, the following problems exist in the insulated drill pipe of this structure: 1. The addition of a liner inside the drill pipe compresses the inner diameter of the drill pipe, resulting in a decrease in mud displacement, an increase in pumping resistance, and affecting the effective operation of screw drill bits and rotary guides; at the same time, some conventional logging instruments cannot pass through the inner hole of the drill pipe to the bottom of the well for operation; 2. The unit weight of the insulated drill pipe of this structure is large, and the excessive hanging weight of the drill string will limit its application in ultra-deep wells and ultra-long horizontal wells; 3. During the drilling process, the drill pipe is always affected by harsh working conditions such as tension, compression, torsion, internal pressure, external pressure and medium corrosion. If the liner inside the drill pipe of this structure is not installed securely, it is easy to cause problems such as falling off, resulting in downhole accidents.

[0005] For another example, the utility model patent with application number 202323562766.2 discloses a drill pipe for underground high temperature, including a hollow drill pipe body, one end of the drill pipe body having a female joint, the other end of the drill pipe body having a male joint, the inner wall of the drill pipe body being coated with an inner thermal insulation coating, the outer wall of the drill pipe body being provided with a plurality of wear-resistant ribs in the axial direction, and the plurality of wear-resistant ribs being arranged at intervals in the circumferential direction, the outer wall of the drill pipe body between adjacent wear-resistant ribs being coated with an outer thermal insulation coating, and the circumferential diameter of the outer thermal insulation coating being smaller than the circumferential diameter of the wear-resistant ribs. Although the heat-insulating drill pipe of this structure increases the heat insulation effect of the drill pipe through the cooperation of the inner thermal insulation coating and the outer thermal insulation coating, the drill pipe of this structure has a complex structure, and a plurality of wear-resistant ribs need to be welded on the outer wall of the drill pipe. Such welding is very likely to produce welding cracks in the drill pipe body, causing the drill pipe to be scrapped, and the drill pipe is affected by various complex working conditions and corrosive media at the bottom of the well, and the external coating and wear-resistant ribs are very likely to fail, causing objects to fall down the well, affecting drilling safety.

[0006] Therefore, developing a new type of heat-insulating drill pipe with simple structure, safety and reliability is of great significance to meet the development of high-temperature and ultra-high-temperature wells and reduce their development costs. Summary of the invention

[0007] In view of the above deficiencies in the prior art, the object of the present invention is to provide a high-steel-grade, large-diameter, insulated drill pipe and a preparation method thereof, which can solve the above technical problems.

[0008] In order to achieve the above object, the present invention provides the following technical solutions: A high-grade, large-diameter, heat-insulating drill pipe comprises a pipe body, with external threaded joints and internal threaded joints respectively provided at two ends of the pipe body; an insulation layer is coated on the inner wall of the drill pipe, and the thickness of the insulation layer is 1.0-3.0 mm.

[0009] Preferably, the thermal insulation layer is made of modified fluorosilicone resin.

[0010] Preferably, the external thread joint and the internal thread joint are connected to the pipe body by friction welding.

[0011] A method for preparing a high-grade, large-diameter, heat-insulated drill pipe comprises the following steps: Step 1: Place the drill pipe in a heating furnace and heat it to 380±10℃ for 2 hours to burn the grease and organic matter in the pipe into dry ash; Step 2: In an environment where the air humidity is less than 60%, the inner surface of the drill pipe is sandblasted and cleaned to control the surface anchor grain to 40-60μm; Step 3: Evenly apply the modified fluorosilicone resin on the inner surface of the drill rod, and rotate the drill rod for 10 minutes to allow the modified fluorosilicone resin to level and shape; Step 4: Place the sprayed drill pipe indoors and cure it at room temperature for 24 hours; Step 5: Place the naturally cured drill pipe in a box furnace for heat curing, heat the drill pipe body to 150°C, keep it warm for 4 hours, and take it out of the furnace after the pipe body cools to 80°C; Step 6: Test the coating quality according to SY / T 0544-2016 standard, and only leave the factory after passing the test.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. By evenly coating and curing the modified fluorosilicone resin on the inner wall of the drill pipe, the overall thermal conductivity of the drill pipe is effectively reduced, the speed at which the formation temperature is transmitted to the inside of the drill pipe is reduced, the bottom hole ambient temperature is reduced, the use requirements of downhole electronic instruments are met, and the performance of the drilling fluid is guaranteed.

[0013] 2. The coating has the advantages of good thermal stability, wear resistance and corrosion resistance, and can replace conventional phenolic epoxy coated drill pipes to meet drilling requirements in different geological environments.

[0014] 3. The high-grade steel and large-diameter drill pipe structure is adopted. With less increase in the purchase cost of drilling tools, the drill pipe with thermal insulation coating has higher mechanical properties and meets the development requirements of unconventional oil and gas wells such as deep wells and ultra-deep wells.

[0015] 4. The inner hole of the drill pipe of this structure is relatively large. After coating with a certain thickness of thermal insulation coating, the inner diameter of the drill pipe does not change much, and will not produce a large pumping resistance. It can also meet the requirements of the logging tool being lowered into the bottom of the well through the inside of the drill pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0018] Description of reference numerals: 1-external thread joint, 2-tube body, 3-insulation layer, 4-internal thread joint. DETAILED DESCRIPTION

[0019] The following is a detailed description of the invention by way of examples in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, rather than all of the embodiments.

[0020] Embodiment 1 like Figure 1 As shown, the present invention discloses a high-grade steel-grade large-diameter heat-insulating drill pipe, including a pipe body 2, wherein both ends of the pipe body 2 are provided with an external threaded joint 1 and an internal threaded joint 4, wherein both the external threaded joint 1 and the internal threaded joint 4 are high-torsion-resistant double-shoulder joints, and both the external threaded joint 1 and the internal threaded joint 4 are connected to the pipe body 2 by friction welding; the inner wall of the drill pipe is coated with a heat-insulating layer 3, wherein the heat-insulating layer 3 is made of modified fluorosilicone resin, and its thermal conductivity is 0.07W / (mK), and after sintering and curing, the heat-insulating layer is firmly attached to the inner surface of the drill pipe, forming a dense heat-insulating layer with a thickness of 1.0-3.0mm, and the speed of formation heat conduction to the inside of the drill pipe is reduced by reducing the overall thermal conductivity of the drill pipe, thereby achieving the purpose of reducing the wellbore temperature. Compared with the existing technology, the advantages are: the drill pipe of the present invention has a simple structure, a simple preparation process, and a good heat-insulating effect.

[0021] Embodiment 2 The present invention also discloses a method for preparing a high-grade steel and large-diameter heat-insulating drill pipe, comprising the following steps: Step 1: Place the drill pipe in a heating furnace, heat it to 380±10℃ and keep it warm for 2 hours to burn the grease and organic matter in the pipe body 2 into dry ash.

[0022] Step 2: In an environment where the air humidity is less than 60%, the inner surface of the drill pipe is sandblasted and cleaned, and the surface anchor texture is controlled to 40-60μm.

[0023] Step 3: Evenly apply the modified fluorosilicone resin on the inner surface of the drill pipe, and rotate the drill pipe for 10 minutes to allow the modified fluorosilicone resin to level and shape; during spraying, the modified fluorosilicone resin is transported to the bell of the spray gun head through a pipeline, the sieve holes are evenly distributed on the wall of the bell, and the bell rotates at a high speed of more than 15,000 rpm to evenly apply the modified fluorosilicone resin on the inner wall of the drill pipe.

[0024] Step 4: Place the sprayed drill pipe indoors and cure it at room temperature for 24 hours.

[0025] Step 5: Place the naturally cured drill pipe into a box-type furnace for heat curing, heat the drill pipe body to 150°C, keep it warm for 4 hours, and take it out of the furnace after the pipe body cools to 80°C.

[0026] Step 6: Test the coating quality according to SY / T 0544-2016 standard, and only leave the factory after passing the test.

[0027] When used, in deep well drilling operations over 6,000 meters, a total of about 2,000 meters of insulated drill pipes were used. After testing, the formation temperature was 180°C and the drilling fluid temperature in the drill pipe was 149°C. The temperature of the drilling fluid was nearly 30°C lower than that of ordinary drill pipes, achieving the goal of reducing the wellbore temperature.

[0028] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and application concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A high-grade, large-diameter, heat-insulating drill pipe, comprising a pipe body (2), wherein both ends of the pipe body (2) are respectively provided with an external threaded joint (1) and an internal threaded joint (4); characterized in that: The inner wall of the drill rod is coated with a heat insulation layer (3), and the thickness of the heat insulation layer (3) is 1.0-3.0 mm.

2. A high-grade, large-diameter, heat-insulated drill pipe as claimed in claim 1, characterized in that: The material of the heat insulation layer (3) is modified fluorosilicone resin.

3. A high-grade, large-diameter, heat-insulated drill pipe as claimed in claim 1, characterized in that: The external thread joint (1) and the internal thread joint (4) are both connected to the pipe body (2) by means of friction welding.

4. A method for preparing a high-grade, large-diameter, heat-insulated drill pipe as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Place the drill pipe in a heating furnace and heat it to 380±10°C for 2 hours to burn the grease and organic matter in the pipe body (2) into dry ash; Step 2: In an environment where the air humidity is less than 60%, the inner surface of the drill pipe is sandblasted and cleaned to control the surface anchor grain to 40-60μm; Step 3: Evenly apply the modified fluorosilicone resin on the inner surface of the drill rod, and rotate the drill rod for 10 minutes to allow the modified fluorosilicone resin to level and shape; Step 4: Place the sprayed drill pipe indoors and cure it at room temperature for 24 hours; Step 5: Place the naturally cured drill pipe in a box furnace for heat curing, heat the drill pipe body to 150°C, keep it warm for 4 hours, and take it out of the furnace after the pipe body cools to 80°C; Step 6: Test the coating quality according to SY / T 0544-2016 standard, and only leave the factory after passing the test.

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