Method for obtaining wellbore temperature distribution of drill rod and method for obtaining drill rod

Abstract

The invention belongs to the field of drilling of petroleum, natural gas and geothermal wells, and particularly relates to a method for obtaining shaft temperature distribution of a drill rod and a method for obtaining the drill rod. And solving wellbore temperature distribution of the drill rods in different combinations through a first energy conservation equation of the drilling fluid in the drill rods, a second energy conservation equation of the drill rods, a third energy conservation equation of the drilling fluid in the annulus between the drill rods and the well wall and a fourth energy conservation equation of the well wall. The temperature distribution of the drill rods in different combinations in the shaft is obtained, so that the thermal barrier drill rod meeting the working temperature resistance requirement of an underground instrument is selected, and the method has the advantage of reducing the economic cost of drilling operation.

Description

Technical Field

[0001] The invention belongs to the field of geothermal well drilling for petroleum and natural gas, and in particular relates to a method for obtaining the wellbore temperature distribution of a drill pipe and a method for obtaining the drill pipe. Background Art

[0002] Oil and gas security is an important cornerstone of energy security. With the gradual depletion of conventional oil and gas in shallow layers on land, oil and gas exploration is developing towards ultra-deep and extra-deep areas. Affected by the ground temperature gradient, the deeper the wellbore, the higher the temperature inside the wellbore. Current drilling technology has the following serious problems and technical difficulties under high temperatures: (1) The measurement and control instruments and tools used while drilling fail at high temperatures; (2) The service life of the drill bit is greatly reduced, and the drill bit wear rate is higher due to the high surface temperature of the drill bit; (3) The performance of the drilling fluid changes at high temperatures and cannot meet the drilling process requirements.

[0003] Drill pipe is a consumable industrial product. It is an important component and consumable part of the drill string of oil and gas field drilling wells. High temperature conditions put forward higher requirements on the performance of drill pipe.

[0004] Chinese patent application: CN112096303A discloses a heat-insulating drill pipe for cooling a high-temperature wellbore and a preparation method thereof; however, the patent only provides a heat-insulating drill pipe, and if all drill pipes are used, the cost is increased.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a method for obtaining the wellbore temperature distribution of a drill pipe and a method for obtaining a drill pipe. The method of the present invention can obtain the wellbore temperature distribution of drill pipes of different combinations, so that a drill pipe that meets the temperature resistance requirements of downhole instruments can be selected, which has the advantage of reducing the cost of drilling operations.

[0007] The present invention includes the following technical solutions:

[0008] The present invention provides a method for obtaining a wellbore temperature distribution of a drill pipe, the method comprising the following steps:

[0009] Solving the wellbore temperature distribution of different combinations of drill pipes through the first energy conservation equation of the drilling fluid inside the drill pipe, the second energy conservation equation of the drill pipe, the third energy conservation equation of the drilling fluid in the annulus between the drill pipe and the well wall, and the fourth energy conservation equation of the well wall;

[0010] The drill rods of different combinations are drill rod structures of different combinations connected with drill bits, and the drill rod structures of different combinations are different combination structures of thermal barrier drill rod structures and non-thermal barrier drill rod structures.

[0011] Furthermore, the thermal barrier drill pipe structure includes a thermal insulation material thermal barrier drill pipe structure, a thermal insulation coating thermal barrier drill pipe structure, a thermal insulation material + thermal insulation coating thermal barrier drill pipe structure and a vacuum thermal barrier drill pipe structure.

[0012] Furthermore, the heat-insulating material thermal barrier drill pipe structure comprises an inner tube, an outer tube, an annular space and a heat-insulating material, wherein the inner tube is coaxially arranged in the outer tube, an annular space is formed between the outer tube and the inner tube, and the annular space is filled with a heat-insulating material;

[0013] The thermal barrier drill pipe structure with thermal insulation coating comprises an inner tube, an outer tube, an annular space and a thermal insulation coating, wherein the inner tube is coaxially arranged in the outer tube, an annular space is formed between the outer tube and the inner tube, and a thermal insulation coating is sprayed on the wall surface of the annular space;

[0014] The thermal insulation material + thermal insulation coating thermal barrier drill pipe structure comprises an inner tube, an outer tube, an annular space, a thermal insulation material and a thermal insulation coating, wherein the inner tube is coaxially arranged in the outer tube, and an annular space is formed between the outer tube and the inner tube; the annular space is filled with a thermal insulation material, and the wall surface of the annular space is sprayed with a thermal insulation coating;

[0015] The vacuum thermal barrier drill pipe structure comprises an inner tube, an outer tube, an annular space and a vacuum. The inner tube is coaxially arranged in the outer tube, an annular space is formed between the outer tube and the inner tube, and the annular space is vacuumed.

[0016] Further, when solving the drill pipe structure through a first energy conservation equation of the drilling fluid inside the drill pipe, a second energy conservation equation of the drill pipe, a third energy conservation equation of the drilling fluid in the annulus between the drill pipe and the well wall, and a fourth energy conservation equation of the well wall, the wellbore temperature distribution of the drill pipe of different combinations is obtained by controlling the size parameters and thermal conductivity of the drill pipe structure;

[0017] The size parameters include: the inner radius r of the drilling fluid control body P inside the drill string Pi and the outer radius r of the drill pipe control body P Po ;

[0018] The thermal conductivity coefficient includes: the thermal conductivity k of the drill pipe structural material P ;

[0019] The wellbore temperature distribution includes: the temperature of the drilling fluid inside the drill pipe structure T in and the temperature of the annular drilling fluid T a .

[0020] Furthermore, the drill pipe structure is divided into a plurality of control bodies P, the radius of the drill pipe structure includes the inner radius and the outer radius of the control body P, and the first energy conservation equation includes:

[0021]

[0022] Where superscript 1 and superscript 0 represent two adjacent moments, π represents pi, Δz represents the height of the control volume P inside the drill string, c is the specific heat capacity of the drilling fluid, ρ is the density of the drilling fluid, T Pi is the inner wall temperature of the drill pipe structure, f s is the friction coefficient of the drilling fluid inside the drill pipe structure, Δt represents the time interval, μ represents the viscosity of the drilling fluid, and v i is the drilling fluid flow velocity, h Pi It represents the convection heat transfer coefficient between the inner wall of the drill pipe structure and the drilling fluid inside it. represents the control volume P at time 1 cρT in , represents the control volume P at time 0 cρT in , Represents the control volume from time P0 to time 1 cρv i T in The amount of change, Represents the control volume from time P0 to time 1 cρv i T in The amount of change,

[0023] [h Pi (T in -T Pi )] 0-1 Indicates the control volume from time P0 to time 1 h Pi (T in -T Pi ),

[0024] Indicates the control body from time P0 to time 1 The amount of change.

[0025] Further, the drill rod includes a drill rod structure and a drill bit, and the second energy conservation equation includes a drill rod structure energy conservation equation and a drill bit energy conservation equation, and the drill rod structure energy conservation equation includes:

[0026]

[0027] Among them, c P is the specific heat capacity of the control body P, ρ P is the density of the control volume P, h Po is the convective heat transfer coefficient between the outer wall of the drill pipe structure and the drilling fluid in the annulus, T P is the drill pipe temperature, T s ′ is the lower interface temperature of the drill pipe control body P, T N ' is the upper interface temperature of the drill pipe control body P, represents the TP of the control body P at time 1, represents the TP of the control body P at time 0, [k P (T S ′+T N ′-2T P )] 0-1 Indicates the control volume from time P0 to time k P (T S ′+T N ′-2T P ) changes, [h Po (T a -T P )] 0-1 Indicates the control volume from time P0 to time 1 h Po (T a -T P ) changes, [h Pi (T P -T in )] 0-1 Indicates the control volume from time P0 to time 1 h Pi (T P -T in )

[0028] Furthermore, the drill bit energy conservation equation includes:

[0029]

[0030] Among them, Q rg Indicates the heat generated by friction between the drill bit and the formation.

[0031] Furthermore, the third energy conservation equation includes:

[0032]

[0033] Among them, r ci is the inner radius of the casing, h ci is the convective heat transfer coefficient between the inner wall of the wellbore and the drilling fluid in the annulus, T Po is the temperature of the outer wall of the drill pipe, T ci is the temperature of the inner wall of the well, represents the control volume P at time 1 cρT a , represents the control volume P at time 1 cρT a , Represents the control volume from time P0 to time 1 cρv a T a The amount of change, Represents the control volume from time P0 to time 1 cρv a Ta The amount of change, Indicates the control body from time P0 to time 1 The amount of change.

[0034] Furthermore, the fourth energy conservation equation includes:

[0035]

[0036] Among them, r f is the radius of the formation control body, c f is the formation specific heat capacity, k′ P is the thermal conductivity of the casing, k′ w is the heat transfer coefficient between casing and formation, k′ e is the formation thermal conductivity, ρ f is the density of the surface layer, T N ″ represents the upper interface of the near-annular stratum control body, T S ″ represents the lower interface of the near annular stratum control body, T OFT It is the temperature of the formation outside the control body.

[0037] A second aspect of the present invention provides a method for obtaining a drill pipe, comprising the above-mentioned method for obtaining the wellbore temperature distribution of the drill pipe, and further comprising the following steps:

[0038] The temperature T of the drilling fluid inside the drill pipe structure is selected by combining the temperature distribution of the wellbore with the temperature resistance of the instruments used in actual drilling. in and the temperature of the annular drilling fluid T a The drill pipe whose temperature is lower than and closest to the temperature resistance temperature.

[0039] By adopting the above technical solution, the present invention has the following advantages:

[0040] 1. The method of the present invention can obtain the temperature distribution in the wellbore of drill pipes of different combinations, so that the drill pipe that meets the temperature resistance requirements of downhole instruments can be selected, which has the advantage of reducing the cost of drilling operations.

[0041] 2. The method for obtaining drill pipes of the present invention obtains the temperature distribution of drill pipes of different combinations in the wellbore to select a suitable thermal barrier drill pipe for use, which not only improves the ambient temperature of downhole instruments and avoids damage to downhole instruments, but also has the advantage of low cost.

[0042] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A flow chart of a method for obtaining a wellbore temperature distribution of a drill pipe in an embodiment of the present invention;

[0045] Figure 2 Schematic diagram of the use status of the drill rod in the embodiment of the present invention;

[0046] Figure 3 It is a structural schematic diagram of a thermal barrier drill rod structure in an embodiment of the present invention;

[0047] Figure 4 Schematic diagram of heat transfer of the thermal barrier drill pipe structure in an embodiment of the present invention;

[0048] In the figure, 10 is a thermal barrier drill pipe structure, 11 is an inner tube, 12 is an outer tube, 13 is an annular space, and 20 is a non-thermal barrier drill pipe structure. DETAILED DESCRIPTION

[0049] The following description provides many different embodiments or examples for implementing different features of the present invention. The components and arrangements described in the following specific examples are only used to simplify the present invention and are only used as examples, not to limit the present invention.

[0050] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] A first aspect of the present embodiment provides a method for obtaining a wellbore temperature distribution of a drill pipe, the method comprising the following steps: Figure 1 As shown, the wellbore temperature distribution of the drill pipe of different combinations is solved by the first energy conservation equation of the drilling fluid inside the drill pipe, the second energy conservation equation of the drill pipe, the third energy conservation equation of the drilling fluid in the annulus between the drill pipe and the well wall, and the fourth energy conservation equation of the well wall;

[0052] The drill rods of different combinations are drill rod structures of different combinations connected with drill bits, and the drill rod structures of different combinations are different combinations of thermal barrier drill rod structures 10 and / or non-thermal barrier drill rod structures 20. Figure 2 As shown, the drill pipe is formed by connecting a plurality of thermal barrier drill pipe structures 10, a plurality of non-thermal barrier drill pipe structures 20 and a drill bit. It should be noted that the structure shown in the figure is only a specific structure of the drill pipe and does not represent a limitation on the drill pipe.

[0053] Both axial ends of the thermal barrier drill pipe structure 10 and the non-thermal barrier drill pipe structure 20 are provided with male joints or female joints. In this way, the thermal barrier drill pipe structure 10 and the non-thermal barrier drill pipe structure 20, the thermal barrier drill pipe structure 10 and the thermal barrier drill pipe structure 10, and the non-thermal barrier drill pipe structure 20 and the non-thermal barrier drill pipe structure 20 can be connected by means of male joints or female joints.

[0054] It should be noted that the thermal barrier drill pipe structure 10 is a drill pipe structure that is specially provided with corresponding structures and materials for heat shielding; while the non-thermal barrier drill pipe structure 20 is a drill pipe structure that is not specially provided with heat shielding, and the non-thermal barrier drill pipe structure 20 can be a common drill pipe structure in the prior art. Heat shielding should be understood as: the drill pipe structure has the ability to reduce the radial transfer of wellbore temperature, such as Figure 4 As shown, the heat transfer in the direction of the arrow is reduced.

[0055] Compared with the thermal barrier drill pipe structure 10 and the non-thermal barrier drill pipe structure 20, the thermal barrier drill pipe structure 10 is more complicated to manufacture and uses more materials, so the cost is higher; therefore, if the entire drill pipe adopts the thermal barrier drill pipe structure 10, the cost will be greatly increased; therefore, the present invention selects a combined drill pipe of the thermal barrier drill pipe structure 10 and the non-thermal barrier drill pipe structure 20 that meets the use of the instrument by obtaining the temperature distribution of the thermal barrier drill pipe and the non-thermal barrier drill pipe in the wellbore; it has the advantage of reducing costs.

[0056] Furthermore, the thermal barrier drill pipe structure 10 includes a thermal insulation material thermal barrier drill pipe structure, a thermal insulation coating thermal barrier drill pipe structure, a thermal insulation material + thermal insulation coating thermal barrier drill pipe structure and a vacuum thermal barrier drill pipe structure.

[0057] Furthermore, if Figure 3 As shown, the thermal insulation material thermal barrier drill pipe structure comprises an inner tube 11, an outer tube 12, an annular space 13 and a thermal insulation material, wherein the inner tube 11 is coaxially arranged in the outer tube 12, an annular space 13 is formed between the outer tube 12 and the inner tube 11, and the annular space 13 is filled with a thermal insulation material; for the thermal insulation material filled thermal barrier drill pipe structure, the heat of the high temperature fluid environment in the annular space is transferred to the internal space of the thermal insulation material thermal barrier drill pipe structure, such as Figure 4As shown, it will pass through the outer tube 12, the thermal insulation material, and the inner tube 11 in sequence, and then enter the thermal insulation material thermal barrier drill pipe structure. The comprehensive thermal resistance of this transfer process includes the different thermal resistances of the outer tube 12, the thermal insulation material, and the inner tube 11, among which the thermal resistance of the thermal insulation material is the largest. The comprehensive system composed of the outer tube 12, the thermal insulation material, and the inner tube 11 can effectively prevent the heat transfer through the thermal insulation material thermal barrier drill pipe.

[0058] The thermal barrier drill pipe structure with thermal insulation coating comprises an inner tube 11, an outer tube 12, an annular space 13 and a thermal insulation coating, wherein the inner tube 11 is coaxially arranged in the outer tube 12, an annular space 13 is formed between the outer tube 12 and the inner tube 11, and a thermal insulation coating is sprayed on the wall surface of the annular space 13; in the process of heat being transferred from the high-temperature fluid environment of the annular space of this structure to the internal space of the thermal barrier drill pipe structure with thermal insulation coating, the heat will pass through the outer tube 12, the thermal insulation coating on the inner wall of the outer tube 12, the gas medium (such as air), the thermal insulation coating on the outer wall of the inner tube 11, the inner tube 11 in sequence, and then enter the interior of the thermal barrier drill pipe structure with thermal insulation coating. The comprehensive thermal resistance of the transfer process includes the thermal resistance of the outer tube 12, the thermal insulation coating on the inner wall of the outer tube 12, the gas medium (such as air), the thermal insulation coating on the outer wall of the inner tube 11, and the inner tube 11, among which the thermal resistance of the thermal insulation coating and the gas medium is greater, and the specific size of the thermal resistance of the thermal insulation coating will change according to the different spraying thicknesses; the comprehensive system consisting of the outer tube 12, the thermal insulation coating on the inner wall of the outer tube 12, the gas medium (such as air), the thermal insulation coating on the outer wall of the inner tube 11, and the inner tube 11 can effectively prevent the heat transfer of the drill pipe through the thermal insulation coating thermal barrier.

[0059] The thermal insulation material + thermal insulation coating thermal barrier drill pipe structure comprises an inner tube 11, an outer tube 12, an annular space 13, a thermal insulation material and a thermal insulation coating, wherein the inner tube 11 is coaxially arranged in the outer tube 12, and an annular space 13 is formed between the outer tube 12 and the inner tube 11; the annular space 13 is filled with a thermal insulation material, and a thermal insulation coating is sprayed on the wall surface of the annular space 13; in the process of transferring the heat of the high-temperature fluid environment in the annular space of this structure to the internal space of the thermal insulation material + thermal insulation coating thermal barrier drill pipe structure, the heat of the annular space 13 is successively Through the outer tube 12, the thermal insulation coating on the inner wall of the outer tube 12, the thermal insulation material, the thermal insulation coating on the outer wall of the inner tube 11, and the inner tube 11, and then enter the thermal insulation material + thermal insulation coating thermal barrier drill pipe structure; the comprehensive thermal resistance of the transfer process includes the thermal resistance of the outer tube 12, the thermal insulation coating on the inner wall of the outer tube 12, the thermal insulation material, the thermal insulation coating on the outer wall of the inner tube 11, and the inner tube 11, among which the thermal insulation coating and the thermal insulation material have a larger thermal resistance, and the comprehensive system composed of them can effectively prevent the heat transfer through the thermal insulation material + thermal insulation coating thermal barrier drill pipe structure.

[0060] The vacuum thermal barrier drill pipe structure comprises an inner tube 11, an outer tube 12, an annular space 13 and a vacuum, wherein the inner tube 11 is coaxially arranged in the outer tube 12, an annular space 13 is formed between the outer tube 12 and the inner tube 11, and the annular space 13 is vacuumed. Such a structure mainly reduces heat conduction and heat convection by removing the medium in the annular space 13, and there is no heat conduction between the high-temperature fluid environment and the internal space of the vacuum thermal barrier drill pipe structure due to the vacuum environment, and only a small amount of heat is transferred into the vacuum thermal barrier drill pipe structure by thermal radiation. Preferably, for thermal radiation, the inner wall of the outer tube 12 of the vacuum thermal barrier drill pipe structure and the outer wall of the inner tube 11 are covered with a material with low emissivity (such as silver plating or aluminum plating), thereby reflecting radiant heat and reducing the influence of thermal radiation on the internal temperature of the vacuum thermal barrier drill pipe structure. Preferably, the vacuum thermal barrier drill pipe structure is provided with a valve, and the annular space is vacuumed by the valve, which is more conducive to manufacturing and reduces costs.

[0061] The thermal barrier drill pipe structure of thermal insulation material, the thermal barrier drill pipe structure of thermal insulation coating, the thermal barrier drill pipe structure of thermal insulation material + thermal insulation coating and the thermal barrier drill pipe structure with vacuum have different thermal barrier effects, and the costs of the four drill pipe structures are also different. Therefore, in order to reduce costs, in addition to selecting the thermal barrier drill pipe structure 10 and the non-thermal barrier drill pipe structure 20, further selecting the most suitable type of thermal barrier drill pipe structure 10 has the advantages of improving the thermal barrier effect and reducing costs.

[0062] Furthermore, when solving the drill pipe structure through the first energy conservation equation of the drilling fluid inside the drill pipe, the second energy conservation equation of the drill pipe, the third energy conservation equation of the drilling fluid in the annulus between the drill pipe and the well wall, and the fourth energy conservation equation of the well wall, the wellbore temperature distribution of different combinations of drill pipes is obtained by controlling the dimensional parameters and thermal conductivity of the drill pipe.

[0063] The size parameters include: the inner radius r of the drilling fluid control body P inside the drill string Pi and the outer radius r of the drill pipe control body P Po The thermal conductivity coefficient includes: the thermal conductivity k of the drill pipe structural material P .

[0064] The drill pipe is connected and assembled by a thermal barrier drill pipe structure 10 and / or a non-thermal barrier drill pipe structure 20; therefore, there are many ways of combining, and the size of the drill pipe is also different; therefore, by controlling the inner radius r of the drilling fluid control body P inside the drill string Pi , the outer radius r of the drill pipe control body P Po and the thermal conductivity k of the drill pipe structural material P To get different combinations of drill pipes.

[0065] The wellbore temperature distribution includes: the temperature of the drilling fluid inside the drill pipe structure T in and the temperature of the annular drilling fluid T a .

[0066] Furthermore, the drill pipe is divided into a plurality of control bodies P, and the first energy conservation equation includes:

[0067]

[0068]

[0069] Among them, superscript 1 and superscript 0 represent two adjacent moments, π represents pi, and r Pi represents the inner radius of the control body P, Δz represents the height of the control body P, c is the specific heat capacity of the drilling fluid, ρ is the density of the drilling fluid, T Pi is the inner wall temperature of the drill pipe structure, f s is the friction coefficient of the drilling fluid inside the drill pipe structure, Δt represents the time interval, μ represents the viscosity of the drilling fluid, and v i is the drilling fluid flow velocity, h Pi It represents the convection heat transfer coefficient between the inner wall of the drill pipe structure and the drilling fluid inside it. represents the control volume P at time 1 cρT in , represents the control volume P at time 0 cρT in , Represents the control volume from time P0 to time 1 cρv i T in The amount of change, Represents the control volume from time P0 to time 1 cρv i T in The change in [h Pi (T in -T Pi )] 0-1 Indicates the control volume from time P0 to time 1 h Pi (T in -T Pi ), Indicates the control body from time P0 to time 1 The amount of change.

[0070] Further, the drill rod includes a drill rod structure and a drill bit, and the second energy conservation equation includes a drill rod structure energy conservation equation and a drill bit energy conservation equation, and the drill rod structure energy conservation equation includes:

[0071]

[0072] Among them, r Po represents the outer radius of the control volume P, cP is the specific heat capacity of the control body P, ρ P is the density of the control volume P, T P is the drill pipe structure temperature, k P is the thermal conductivity of the drill pipe structural material, T s ′ is the lower interface temperature of the drill pipe control body P, T N ′ is the upper interface temperature of the drill pipe control body P, h Po is the convective heat transfer coefficient between the outer wall of the drill pipe structure and the drilling fluid in the annulus, represents the TP of the control body P at time 1, Indicates that the control volume P is at time 0 T P ,,

[0073] [k P (T S ′+T N ′-2T P )] 0-1 Indicates the control volume from time P0 to time k P (T S ′+T N ′-2T P ) changes, [h Po (T a -T P )] 0-1 Indicates the control volume from time P0 to time 1 h Po (T a -T P ) changes, [h Pi (T P -T in )] 0-1 Indicates the control volume from time P0 to time 1 h Pi (T P -T in )

[0074] Furthermore, the drill bit energy conservation equation includes:

[0075]

[0076] Among them, Q rg Indicates the heat generated by friction between the drill bit and the formation.

[0077] Furthermore, the third energy conservation equation includes:

[0078]

[0079] Among them, r ci is the inner radius of the casing, h ci is the convective heat transfer coefficient between the inner wall of the wellbore and the drilling fluid in the annulus, TPo is the temperature of the outer wall of the drill pipe structure, T ci is the temperature of the inner wall of the well, represents the control volume P at time 1 cρT a , represents the control volume P at time 1 cρT a , Represents the control volume from time P0 to time 1 cρv a T a The amount of change, Represents the control volume from time P0 to time 1 cρv a T a The amount of change, Indicates the control body from time P0 to time 1 The amount of change.

[0080] Furthermore, the fourth energy conservation equation includes:

[0081]

[0082] Among them, r f is the radius of the formation control body, c f is the formation specific heat capacity, k′ P is the thermal conductivity of the casing, k′ w is the heat transfer coefficient between casing and formation, k′ e is the formation thermal conductivity, ρ f is the density of the surface layer, T N ″ represents the upper interface of the near-annular stratum control body, T S ″ represents the lower interface of the near annular stratum control body, T OFT is the formation temperature outside the control volume, T f To control body temperature, It represents the temperature of the control body P at time 1, represents the temperature of the control body P at time 0, [k′ P (T s ″+T N ″-2T f )] 0-1 Represents the control volume from time P0 to time k' P (T s ″+T N ″-2T f ) changes, [k′ e (T OFT -T f )] 0-1 Represents the control volume from time P0 to time k' e (T OFT -T f ) changes, [k′w (T f -T a )] 0-1 Represents the control volume from time P0 to time k' w (T f -T a )’s change.

[0083] A second aspect of the present embodiment provides a method for obtaining a drill pipe, including the above-mentioned method for obtaining the wellbore temperature distribution of the drill pipe, and further comprising the following steps:

[0084] By combining the wellbore temperature distribution with the temperature resistance of the instruments used in actual drilling, a drill pipe with a wellbore temperature distribution lower than and closest to the temperature resistance is selected.

[0085] A drill pipe is divided into a number of control bodies P, then a drill pipe will at least get P temperatures of the drilling fluid inside the heat-resistant drill pipe structure T in and the temperature of the annular drilling fluid T a By comparing the heat-resistant temperature with the temperature of the drilling fluid inside the heat-resistant drill pipe structure, T in and the temperature of the annular drilling fluid T a By comparison, the temperature T of the drilling fluid inside the heat-resistant drill pipe structure which is lower than the heat-resistant temperature and close to the heat-resistant temperature is obtained. in and the temperature of the annular drilling fluid T a Corresponding drill pipe.

[0086] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for obtaining a wellbore temperature distribution of a drill pipe, characterized in that: The method comprises the following steps: Solving the wellbore temperature distribution of different combinations of drill pipes through the first energy conservation equation of the drilling fluid inside the drill pipe, the second energy conservation equation of the drill pipe, the third energy conservation equation of the drilling fluid in the annulus between the drill pipe and the well wall, and the fourth energy conservation equation of the well wall; The drill rods of different combinations are drill rod structures of different combinations connected with drill bits, and the drill rod structures of different combinations are different combination structures of thermal barrier drill rod structures and non-thermal barrier drill rod structures.

2. A method for obtaining the borehole temperature distribution of a drill pipe according to claim 1, characterized in that: The thermal barrier drill pipe structure includes a thermal insulation material thermal barrier drill pipe structure, a thermal insulation coating thermal barrier drill pipe structure, a thermal insulation material + thermal insulation coating thermal barrier drill pipe structure and a vacuum thermal barrier drill pipe structure.

3. A method for obtaining the borehole temperature distribution of a drill pipe according to claim 2, characterized in that: The heat-insulating material thermal barrier drill pipe structure comprises an inner tube, an outer tube, an annular space and a heat-insulating material, wherein the inner tube is coaxially arranged in the outer tube, an annular space is formed between the outer tube and the inner tube, and the annular space is filled with a heat-insulating material; The thermal barrier drill pipe structure with thermal insulation coating comprises an inner tube, an outer tube, an annular space and a thermal insulation coating, wherein the inner tube is coaxially arranged in the outer tube, an annular space is formed between the outer tube and the inner tube, and a thermal insulation coating is sprayed on the wall surface of the annular space; The thermal insulation material + thermal insulation coating thermal barrier drill pipe structure comprises an inner tube, an outer tube, an annular space, a thermal insulation material and a thermal insulation coating, wherein the inner tube is coaxially arranged in the outer tube, and an annular space is formed between the outer tube and the inner tube; the annular space is filled with a thermal insulation material, and the wall surface of the annular space is sprayed with a thermal insulation coating; The vacuum thermal barrier drill pipe structure comprises an inner tube, an outer tube, an annular space and a vacuum. The inner tube is coaxially arranged in the outer tube, an annular space is formed between the outer tube and the inner tube, and the annular space is vacuumed.

4. A method for obtaining the borehole temperature distribution of a drill pipe according to claim 3, characterized in that: When solving the drill pipe structure through the first energy conservation equation of the drilling fluid inside the drill pipe, the second energy conservation equation of the drill pipe, the third energy conservation equation of the drilling fluid in the annulus between the drill pipe and the well wall, and the fourth energy conservation equation of the well wall, the wellbore temperature distribution of the drill pipe of different combinations is obtained by controlling the size parameters and thermal conductivity of the drill pipe structure; The size parameters include: the inner radius r of the drilling fluid control body P inside the drill string Pi and the outer radius r of the drill pipe control body P Po ; The thermal conductivity coefficient includes: the thermal conductivity k of the drill pipe structural material P ; The wellbore temperature distribution includes: the temperature of the drilling fluid inside the drill pipe structure T in and the temperature of the annular drilling fluid T a .

5. A method for obtaining the borehole temperature distribution of a drill pipe according to claim 4, characterized in that: The drill pipe structure is divided into several control volumes P, and the first energy conservation equation includes: Where superscript 1 and superscript 0 represent two adjacent moments, π represents pi, Δz represents the height of the control volume P inside the drill string, c is the specific heat capacity of the drilling fluid, ρ is the density of the drilling fluid, T Pi is the inner wall temperature of the drill pipe structure, f s is the friction coefficient of the drilling fluid inside the drill pipe structure, Δt represents the time interval, μ represents the viscosity of the drilling fluid, and v i is the drilling fluid flow velocity, h Pi It represents the convection heat transfer coefficient between the inner wall of the drill pipe structure and the drilling fluid inside it. represents the control volume P at time 1 cρT in , represents the control volume P at time 0 cρT in , Represents the control volume from time P0 to time 1 cρv i T in The amount of change, Represents the control volume from time P0 to time 1 cρv i T in The amount of change, [h Pi (T in -T Pi )] 0-1 Indicates the control volume from time P0 to time 1 h Pi (T in -T Pi ), Indicates the control body from time P0 to time 1 The amount of change.

6. A method for obtaining the borehole temperature distribution of a drill pipe according to claim 4, characterized in that: The drill rod includes a drill rod structure and a drill bit, and the second energy conservation equation includes a drill rod structure energy conservation equation and a drill bit energy conservation equation, and the drill rod structure energy conservation equation includes: Among them, c P is the specific heat capacity of the control body P, ρ P is the density of the control volume P, h Po is the convective heat transfer coefficient between the outer wall of the drill pipe structure and the drilling fluid in the annulus, T P is the drill pipe temperature, T s ′ is the lower interface temperature of the drill pipe control body P, T N ′ is the upper interface temperature of the drill pipe control body P, TP1 represents the TP of the control body P at time 1, TP1 represents the TP of the control body P at time 0, [k P (T S ′+T N ′-2T P )] 0-1 Indicates the control volume from time P0 to time 1 k P (T S ′+T N ′-2T P ) changes, [h Po (T a -T P )] 0-1 Indicates the control volume from time P0 to time 1 h Po (T a -T P ) changes, [h Pi (T P -T in )] 0-1 Indicates the control volume from time P0 to time 1 h Pi (T P -T in )’s change.

7. A method for obtaining the borehole temperature distribution of a drill pipe according to claim 6, characterized in that: The drill bit energy conservation equation includes: Among them, Q rg Indicates the heat generated by friction between the drill bit and the formation.

8. A method for obtaining the borehole temperature distribution of a drill pipe according to claim 4, characterized in that: The third energy conservation equation includes: Among them, r ci is the inner radius of the casing, h ci is the convective heat transfer coefficient between the inner wall of the wellbore and the drilling fluid in the annulus, T Po is the temperature of the outer wall of the drill pipe, T ci is the temperature of the inner wall of the well, represents the control volume P at time 1 cρT a , represents the control volume P at time 1 cρT a , Represents the control volume from time P0 to time 1 cρv a T a The amount of change, Represents the control volume from time P0 to time 1 cρv a T a The amount of change, Indicates the control body from time P0 to time 1 The amount of change.

9. A method for obtaining a borehole temperature distribution of a drill pipe according to claim 4, characterized in that: The fourth energy conservation equation includes: Among them, r f is the radius of the formation control body, c f is the formation specific heat capacity, k′ P is the thermal conductivity of the casing, k′ w is the heat transfer coefficient between casing and formation, k′ e is the formation thermal conductivity, ρ f is the density of the surface layer, T N ″ represents the upper interface of the near-annular stratum control body, T S ″ represents the lower interface of the near annular stratum control body, T OFT is the formation temperature outside the control volume, T f To control body temperature, It represents the temperature of the control body P at time 1, represents the temperature of the control body P at time 0, [k′ P (T s ″+T N ″-2T f )] 0-1 Represents the control volume from time P0 to time k' P (T s ″+T N ″-2T f ) changes, [k′ e (T OFT -T f )] 0-1 Represents the control volume from time P0 to time k' e (T OFT -T f ) changes, [k′ w (T f -T a )] 0-1 Represents the control volume from time P0 to time k' w (T f -T a )’s change.

10. A method for obtaining a drill pipe, characterized in that: A method for obtaining a wellbore temperature distribution of a drill pipe as claimed in any one of claims 1 to 9, further comprising the following steps: The temperature T of the drilling fluid inside the drill pipe structure is selected by combining the temperature distribution of the wellbore with the temperature resistance of the instruments used in actual drilling. in and the temperature of the annular drilling fluid T a The drill pipe whose temperature is lower than and closest to the above mentioned temperature resistance.

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