A drill pipe and method for reducing drilling fluid circulating temperature

Abstract

To solve the technical problem of high bottom hole drilling fluid circulating temperature affecting oil and gas well exploitation operation in the prior art, the embodiment of the present application provides a drill pipe and method for reducing the drilling fluid circulating temperature, which comprises a drill pipe; the inner wall of the drill pipe is coated with a heat insulation material; the method comprises the following steps: S1, lowering a drill tool combination comprising the drill pipe into a bottom hole; S2, preparing a plurality of drilling fluids with different density gradients according to a fixed density difference based on a low limit density p1 of the drilling fluid meeting the well wall stability and a high limit density p2 of the drilling fluid meeting the well control requirement; S3, drilling with the drilling fluid and monitoring the bottom hole drilling fluid circulating temperature; S4, judging whether the density of the drilling fluid in the step S3 is p1, if not, executing S5; S5, judging whether the bottom hole drilling fluid circulating temperature is greater than a preset value, if yes, selecting a drilling fluid with a lower density to return to S3. The embodiment of the present application overcomes the defect of high bottom hole drilling fluid circulating temperature affecting oil and gas well exploitation operation in the prior art.

Description

Technical Field

[0001] This invention relates to a drill pipe and a method for reducing the circulating temperature of drilling fluid. Background Technology

[0002] The impact of bottomhole circulating temperature on downhole tools during deep and ultra-deep well drilling is becoming increasingly significant. High temperatures lead to frequent tool failures, hindering drilling efficiency. Bottomhole drilling fluid circulating temperature is influenced by multiple factors, including geothermal gradient, lithological characteristics, surface temperature, and drilling parameters. Currently, in the Gaoshiti-Moxi block of the Sichuan Basin and the Luzhou deep shale gas block, bottomhole drilling fluid circulating temperatures exceeding 150°C have been observed to varying degrees. This results in frequent signal loss for directional tools, making it impossible to determine the wellbore's azimuth and inclination. Consequently, multiple trips have been required for the reservoir section, with a maximum of 21 trips for the horizontal section, severely restricting the drilling period for oil and gas wells and increasing the intensity of manual operations and operating costs. Summary of the Invention

[0003] To address the technical problem of excessively high bottom hole drilling fluid circulation temperature affecting oil and gas well production operations in existing technologies, this invention provides a drill pipe and method for reducing drilling fluid circulation temperature.

[0004] The embodiments of the present invention are achieved through the following technical solutions:

[0005] In a first aspect, embodiments of the present invention provide a drill pipe for reducing the circulating temperature of drilling fluid, comprising a drill pipe; the inner wall of the drill pipe is covered with a heat-insulating material.

[0006] Furthermore, the thermal conductivity of the insulation material is k = 1.

[0007] Furthermore, the thickness of the thermal insulation material is 0.05-0.15 mm.

[0008] Furthermore, the thickness of the thermal insulation material is 0.1 mm.

[0009] Furthermore, the drill pipe is a standard drill pipe.

[0010] Secondly, embodiments of the present invention provide a method for reducing the circulating temperature of drilling fluid, comprising:

[0011] S1. Lower the drill string assembly, including the drill pipe, to the bottom of the well;

[0012] S2. Based on the lower limit density ρ1 of the drilling fluid that satisfies wellbore stability and the upper limit density ρ2 of the drilling fluid that satisfies well control requirements, drilling fluids with different density gradients between ρ1 and ρ2 are prepared according to a fixed density difference.

[0013] S3. Drill with drilling fluid and monitor the bottom hole drilling fluid circulation temperature;

[0014] S4. Determine whether the density of the drilling fluid in step S3 is ρ1; otherwise, proceed to S5.

[0015] S5. Determine if the bottom hole drilling fluid circulation temperature is greater than the preset value. If so, select a lower density drilling fluid and return to S3.

[0016] Furthermore, step S5 includes: S5. Determining whether the bottom hole drilling fluid circulation temperature is greater than a preset value; if so, selecting a drilling fluid with a lower fixed density difference and returning to S3.

[0017] Furthermore, the fixed density difference is 0.1 g / cm³. 3 .

[0018] Furthermore, it also includes:

[0019] Determine the drilling fluid system based on the formation lithology;

[0020] Based on the formation lithology and the complex drilling conditions of adjacent wells, determine the minimum drilling fluid density that is sufficient to maintain wellbore stability.

[0021] Based on the formation pressure coefficient and oil and gas reservoir development of the well to be drilled, determine the upper limit density of the drilling fluid that meets the well control requirements.

[0022] Furthermore, the density of the initial drilling fluid in step S3 is ρ2.

[0023] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects:

[0024] This invention discloses a drill pipe and method for reducing the circulating temperature of drilling fluid. By using a drill pipe with an inner wall covered with heat-insulating material, the thermal conductivity of the drill string is changed to indirectly alter the circulating temperature of the drilling fluid. By employing a gradient selection of drilling fluids with different densities, the circulating temperature of the drilling fluid is reduced. Thus, this invention overcomes the defect in the prior art where excessively high bottom hole drilling fluid circulating temperature affects oil and gas well production operations. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram showing the transfer of heat from drilling fluid to the annulus through the drilling tools.

[0027] Figure 2This is a flowchart illustrating a method for reducing the circulating temperature of drilling fluid. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0029] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0030] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] In the description of this invention, the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0032] Example 1

[0033] To address the technical problem of excessively high bottom hole drilling fluid circulation temperature affecting oil and gas well production operations in existing technologies, this invention provides a drill pipe for reducing drilling fluid circulation temperature.

[0034] In a first aspect, embodiments of the present invention provide a drill pipe for reducing the circulating temperature of drilling fluid, comprising a drill pipe; the inner wall of the drill pipe is covered with a heat-insulating material.

[0035] The following analysis examines the temperature propagation mechanism of drilling fluid in drill pipe:

[0036] During normal drilling, drilling fluid is injected into the wellbore from the drill string wellhead. After being heated by the formation in the lower part of the wellbore, it returns to the annulus and exits from the annulus wellhead. During its flow from the annulus to the wellhead, it heats the formation surrounding the wellbore. Drilling fluid is the primary carrier of heat transfer. Assuming the wellbore and drilling fluid are considered as a single unit, a schematic diagram illustrating the heat transfer from the drilling fluid to the annulus via the drill string is provided. Figure 1 As shown.

[0037] The propagation of heat conduction in a three-dimensional, unidirectional homogeneous medium can be expressed by the following equation:

[0038]

[0039] Where k is the thermal conductivity.

[0040] Therefore, assuming the drilling tool meets API standards and uses a steel medium, its thermal conductivity remains constant. This can be mitigated by applying an insulating material to the inner wall of the drilling tool, with a theoretical selection coefficient of k1-k. n The reasonable range is proposed to be k.

[0041] However, the media and working conditions encountered during the drilling process are complex, and considering only a single influencing factor cannot effectively guide the on-site drilling operation. In the oil and gas drilling process, the drilling circulation temperature is mainly affected by (1) wellbore conditions (2) drill string conditions (3) drilling fluid conditions: drilling fluid system, drilling fluid density, viscosity, dynamic shear force; (4) specific heat capacity and thermal conductivity of the wellbore medium.

[0042] When the drilling fluid temperature is constant, the heat propagation is positively correlated with the thermal conductivity. Therefore, we can start by considering the thermal conductivity, which affects the temperature propagation, in the above formula.

[0043] This invention identifies a key factor affecting drilling fluid circulation temperature: thermal conductivity. The drilling fluid system is then determined based on formation lithology. Furthermore, considering the formation lithology and the complexity of drilling adjacent wells, a minimum drilling fluid density sufficient for wellbore stability is determined. An upper limit drilling fluid density sufficient for well control is determined based on the formation pressure coefficient and oil / gas reservoir development of the well to be drilled. The drilling fluid density is then progressively reduced to lower the circulation temperature. Field tests have yielded the expected results.

[0044] Therefore, the embodiments of the present invention indirectly change the drilling fluid circulation temperature by altering the thermal conductivity of the drill string through the drilling pipe with heat-insulating material on its inner wall. By using a gradient selection of drilling fluids of different densities, the drilling fluid circulation temperature is reduced. Thus, the embodiments of the present invention overcome the defect in the prior art where excessively high bottom hole drilling fluid circulation temperature affects oil and gas well production operations.

[0045] Furthermore, the thermal conductivity of the insulation material is k = 1.

[0046] Using insulation materials with a thermal conductivity of 1 can meet the insulation requirements of the drill pipe.

[0047] Furthermore, the thickness of the thermal insulation material is 0.05-0.15 mm. Optionally, the thickness of the thermal insulation material is 0.1 mm. The thickness of the thermal insulation material can be selected according to different materials, as long as it meets the thermal conductivity requirements. Generally, the thickness of the thermal insulation material can be 0.05, 0.08, or 0.12 mm.

[0048] Furthermore, the thickness of the thermal insulation material is 0.1 mm.

[0049] Furthermore, the drill pipe is a standard drill pipe.

[0050] Example 2

[0051] To address the technical problem of excessively high bottom hole drilling fluid circulation temperature affecting oil and gas well production operations in existing technologies, embodiments of the present invention provide a drill pipe and method for reducing drilling fluid circulation temperature.

[0052] In a first aspect, embodiments of the present invention provide a drill pipe for reducing the circulating temperature of drilling fluid, comprising a drill pipe; the inner wall of the drill pipe is covered with a heat-insulating material.

[0053] The following analysis examines the temperature propagation mechanism of drilling fluid in the drill pipe:

[0054] During normal drilling, drilling fluid is injected into the wellbore from the drill string wellhead. After being heated by the formation in the lower part of the wellbore, it returns to the annulus and exits from the annulus wellhead. During its flow from the annulus to the wellhead, it heats the formation surrounding the wellbore. Drilling fluid is the primary carrier of heat transfer. Assuming the wellbore and drilling fluid are considered as a single unit, a schematic diagram illustrating the heat transfer from the drilling fluid to the annulus via the drill string is provided. Figure 1 As shown.

[0055] The propagation of heat conduction in a three-dimensional, unidirectional homogeneous medium can be expressed by the following equation:

[0056]

[0057] Where k is the thermal conductivity.

[0058] Therefore, assuming the drilling tool meets API standards and uses a steel medium, its thermal conductivity remains constant. This can be mitigated by applying an insulating material to the inner wall of the drilling tool, with a theoretical selection coefficient of k1-k. n The reasonable range is proposed to be k.

[0059] However, the media and working conditions encountered during the drilling process are complex, and considering only a single influencing factor cannot effectively guide the on-site drilling operation. In the oil and gas drilling process, the drilling circulation temperature is mainly affected by (1) wellbore conditions (2) drill string conditions (3) drilling fluid conditions: drilling fluid system, drilling fluid density, viscosity, dynamic shear force; (4) specific heat capacity and thermal conductivity of the wellbore medium.

[0060] When the drilling fluid temperature is constant, the heat propagation is positively correlated with the thermal conductivity. Therefore, we can start by considering the thermal conductivity, which affects the temperature propagation, in the above formula.

[0061] This invention identifies a key factor affecting drilling fluid circulation temperature: thermal conductivity. The drilling fluid system is then determined based on formation lithology. Furthermore, considering the formation lithology and the complexity of drilling adjacent wells, a minimum drilling fluid density sufficient for wellbore stability is determined. An upper limit drilling fluid density sufficient for well control is determined based on the formation pressure coefficient and oil / gas reservoir development of the well to be drilled. The drilling fluid density is then progressively reduced to lower the circulation temperature. Field tests have yielded the expected results.

[0062] Therefore, the embodiments of the present invention indirectly change the drilling fluid circulation temperature by altering the thermal conductivity of the drill string through the drilling pipe with heat-insulating material on its inner wall. By using a gradient selection of drilling fluids of different densities, the drilling fluid circulation temperature is reduced. Thus, the embodiments of the present invention overcome the defect in the prior art where excessively high bottom hole drilling fluid circulation temperature affects oil and gas well production operations.

[0063] Furthermore, the thermal conductivity of the insulation material is k = 1.

[0064] Using insulation materials with a thermal conductivity of 1 can meet the insulation requirements of the drill pipe.

[0065] Furthermore, the thickness of the thermal insulation material is 0.05-0.15 mm. Optionally, the thickness of the thermal insulation material is 0.1 mm. The thickness of the thermal insulation material can be selected according to different materials, as long as it meets the thermal conductivity requirements. Generally, the thickness of the thermal insulation material can be 0.05, 0.08, or 0.12 mm.

[0066] Furthermore, the drill pipe is a standard drill pipe.

[0067] Secondly, embodiments of the present invention provide a method for reducing the circulating temperature of drilling fluid, referring to... Figure 2 As shown, it includes:

[0068] S1. Lower the drill string assembly, including the drill pipe, to the bottom of the well;

[0069] After connecting the drill pipe to the drill string assembly, it is lowered to the bottom of the well;

[0070] S2. Based on the lower limit density ρ1 of the drilling fluid that satisfies wellbore stability and the upper limit density ρ2 of the drilling fluid that satisfies well control requirements, drilling fluids with different density gradients between ρ1 and ρ2 are prepared according to a fixed density difference.

[0071] S2 uses a fixed density difference, i.e., a fixed density interval, to produce a series of drilling fluids with different densities, which makes it easier to change the circulating temperature of the drilling fluid in the formation by controlling the density of the drilling fluid; of course, drilling fluids with non-fixed density differences can also be selected to achieve the above purpose.

[0072] S3. Drill with drilling fluid and monitor the bottom hole drilling fluid circulation temperature;

[0073] After drilling begins, drilling can start from the highest density ρ2 of the drilling fluid. At the same time, the bottom-hole directional tool records the bottom-hole drilling fluid circulation temperature and monitors the bottom-hole drilling fluid circulation temperature.

[0074] S4. Determine whether the density of the drilling fluid in step S3 is ρ1; otherwise, proceed to S5.

[0075] S5. Determine if the bottom hole drilling fluid circulation temperature is greater than the preset value. If so, select a lower density drilling fluid and return to S3.

[0076] The preset value can be determined according to the actual situation. The preset value can be a temperature of about 135℃.

[0077] Furthermore, step S5 includes: S5. Determining whether the bottom hole drilling fluid circulation temperature is greater than a preset value; if so, selecting a drilling fluid with a lower fixed density difference and returning to S3.

[0078] For example, when drilling fluid S3 is used, if the density of S3 is A + a fixed density difference, and the bottom hole drilling fluid circulation temperature is higher than a preset value, then drilling fluid S3 will be replaced with drilling fluid of density A, and so on. Thus, drilling fluids with different density gradients can be adjusted in descending order of density to reduce the bottom hole drilling fluid circulation temperature.

[0079] Optionally, the fixed density difference is 0.05-0.2 g / cm³. 3 The fixed density difference can be selected as 0.05 g / cm³ based on the actual situation. 3 0.08g / cm 3 Or 0.15g / cm 3 Furthermore, the fixed density difference is 0.1 g / cm³. 3 .

[0080] Furthermore, it also includes:

[0081] Determine the drilling fluid system based on the formation lithology;

[0082] Based on the formation lithology and the complex drilling conditions of adjacent wells, determine the minimum drilling fluid density that is sufficient to maintain wellbore stability.

[0083] Based on the formation pressure coefficient and oil and gas reservoir development of the well to be drilled, determine the upper limit density of the drilling fluid that meets the well control requirements.

[0084] The drilling fluid system can be selected based on the formation lithology, and the minimum drilling fluid density that meets wellbore stability can be determined based on the formation lithology and the complexity of drilling adjacent wells; the maximum drilling fluid density that meets well control requirements can be determined based on the formation pressure coefficient and oil and gas reservoir development of the well to be drilled; thus, the minimum and maximum drilling fluid densities are more in line with actual drilling needs.

[0085] Furthermore, the density of the initial drilling fluid in step S3 is ρ2.

[0086] Specifically, a method for reducing the temperature of circulating drilling fluid includes the following steps:

[0087] (1) API standard drill pipe with diameter φ127mm and φ139.7mm is required, and the wall thickness is not limited;

[0088] (2) Thermal insulation materials with a thermal conductivity of k=1 are required;

[0089] (3) Lay the heat insulation material in (2) on the inner wall of the drill pipe prepared in (1) with a thickness of 0.1 mm;

[0090] (4) After the drill pipe is connected to the drill string assembly, it is lowered to the bottom of the well;

[0091] (5) The minimum drilling fluid density ρ1 that satisfies wellbore stability and the maximum drilling fluid density ρ2 that satisfies well control requirements are adjusted according to 0.1 g / cm³. 3 The density difference is divided into multiple density gradients;

[0092] (6) The well site is equipped with precision pressure-controlled drilling equipment;

[0093] (7) After drilling begins, drilling starts from the highest density ρ2, and the bottom hole directional tool records the bottom hole circulation temperature at the same time;

[0094] (8) If the circulating temperature is high (around 142℃), use precision pressure-controlled drilling equipment and coordinate with the surface drilling fluid engineer to adjust the drilling fluid density to 0.1 g / cm³. 3 The gradient decreases sequentially.

[0095] (9) Repeat steps (7) to (8) to record the circulating temperature and the drilling fluid density decreasing sequentially;

[0096] (10) Stop reducing the density until the drilling fluid temperature drops to around 135°C, or the drilling fluid density drops to the minimum drilling fluid density ρ1 that is sufficient for wellbore stability.

[0097] Therefore, this embodiment of the invention indirectly changes the drilling fluid circulation temperature by altering the thermal conductivity of the drill string through the application of heat-insulating material to the inner wall of the drill string. By applying heat-insulating material to the inner wall of the drill string, the heat insulation performance of the drill string is changed, thereby altering the heat insulation performance of the drill string. Furthermore, by employing a gradient selection of drilling fluids with different densities, the drilling fluid circulation temperature is reduced. Thus, this embodiment of the invention overcomes the defect in the prior art where excessively high bottom hole drilling fluid circulation temperature affects oil and gas well production operations.

[0098] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for reducing the circulating temperature of drilling fluid, characterized in that, include: S1. Lower the drill string assembly, including the drill pipe with heat-insulating material on its inner wall, to the bottom of the well; S2. Based on the lower limit density ρ1 of the drilling fluid that satisfies wellbore stability and the upper limit density ρ2 of the drilling fluid that satisfies well control requirements, drilling fluids with different density gradients between ρ1 and ρ2 are prepared according to a fixed density difference. S3. Drill with drilling fluid and monitor the bottom hole drilling fluid circulation temperature; S4. Determine whether the density of the drilling fluid in step S3 is ρ1; otherwise, proceed to S5. S5. Determine whether the bottom hole drilling fluid circulation temperature is greater than the upper limit of the normal operating temperature of the downhole tools. If so, under the condition of keeping other drilling parameters unchanged, select a drilling fluid with a lower fixed density difference and return to S3.

2. The method according to claim 1, characterized in that, The fixed density difference is 0.1 g / cm³.

3. The method according to claim 1, characterized in that, Also includes: Determine the drilling fluid system based on the formation lithology; Based on the formation lithology and the complex drilling conditions of adjacent wells, determine the minimum drilling fluid density that is sufficient to maintain wellbore stability. Based on the formation pressure coefficient and oil and gas reservoir development of the well to be drilled, determine the upper limit density of the drilling fluid that meets the well control requirements.

4. The method according to claim 1, characterized in that, The density of the initial drilling fluid in step S3 is ρ2.

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