Three-dimensional horizontal well dynamic friction coefficient testing method and friction torque simulation calculation method

Abstract

The present application relates to oil and gas exploration and development technical field, particularly to three-dimensional horizontal well dynamic friction coefficient testing method and friction torque simulation calculation method, the dynamic friction coefficient testing method includes: with the contact width of drill string and well wall under actual conditions and under experimental conditions is equal as the premise, determine the size specification of experimental simulation drill string and simulation well wall; carry out sliding friction experiment under the contact condition of simulation drill string and simulation well wall, calculate the sliding friction coefficient in the sliding friction process, generate the sliding friction coefficient response curve with time; on the basis of the sliding friction coefficient response curve in the stable stage of sliding friction, take the average value as the sliding friction coefficient corresponding to the sliding speed, draw the change curve of sliding friction coefficient with sliding speed. Through the dynamic friction coefficient testing method and the friction torque simulation calculation method, real-time accurate calculation, horizontal well drilling parameter design and optimization can be provided for three-dimensional horizontal well drilling process scientific basis and decision support.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development technology, and in particular to a method for testing the dynamic friction coefficient of three-dimensional horizontal wells and a method for simulating and calculating friction torque. Background Technology

[0002] Horizontal wells are a key technology for the effective development of unconventional, low-permeability oil and gas resources such as shale oil and gas. However, due to limitations in the development level and economics of directional drilling tools, sliding drilling, consisting of downhole power drilling tools and a measurement-while-drilling (MWD) system, remains the primary directional drilling method. During horizontal well sliding drilling, because the drill string does not rotate throughout the well, the frictional resistance generated by the interaction between the drill string and the wellbore increases sharply as the horizontal section extends, leading to severe "pressure build-up" during sliding drilling, difficulties in tool face adjustment, and low mechanical drilling rates. Accurately predicting frictional torque and optimizing drilling parameters accordingly is crucial to maximizing the capabilities of conventional directional drilling technology.

[0003] Traditional horizontal well drill string friction torque prediction methods generally employ soft rod models, rigid rod models, and combinations of soft rod and rigid rod models, all based on the Coulomb friction model. However, numerous studies have shown a close relationship between the friction coefficient and the sliding velocity (manifested as the mechanical drilling rate during drilling). Especially with the increasing number of large-offset 3D horizontal wells, the contact behavior between the drill string and the wellbore becomes more complex, leading to a decrease in the accuracy of traditional friction torque prediction models based on Coulomb friction, which can no longer fully meet the needs of 3D horizontal well friction torque prediction. Furthermore, the nonlinear sliding friction characteristics between the drill string and the wellbore under different lithological conditions are still unclear, and a mathematical model characterizing these nonlinear friction characteristics is lacking. Therefore, a 3D horizontal well friction torque prediction method based on a nonlinear sliding friction model has not yet been established. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for testing the dynamic friction coefficient of three-dimensional horizontal wells and a method for simulating and calculating friction torque. This method can provide a scientific basis and decision support for real-time and accurate calculations, design and optimization of horizontal well drilling parameters during the drilling process of three-dimensional horizontal wells.

[0005] This invention is achieved by adopting the following technical solution:

[0006] The method for testing the dynamic friction coefficient of a three-dimensional horizontal well includes the following steps:

[0007] S 11 Assuming that the contact width between the drill string and the well wall is equal under both actual and experimental conditions, determine the dimensions and specifications of the simulated drill string and the simulated well wall for the experiment.

[0008] S 12Sliding friction experiments were conducted under simulated drill string and simulated well wall contact conditions at different sliding speeds. During the experiments, the curves of friction force and normal load change with time were recorded, and the sliding friction coefficient was calculated to generate the sliding friction coefficient response curve over time.

[0009] S 13 Based on the sliding friction coefficient response curve during the stable phase of sliding friction, the average value is taken as the sliding friction coefficient corresponding to that sliding speed, and the curve of the sliding friction coefficient changing with the sliding speed is plotted.

[0010] Step S 11 The method for determining the contact width between the drill string and the wellbore is as follows:

[0011]

[0012] In the formula, b represents the contact width between the drill string and the well wall, F represents the contact normal pressure between the drill string and the well wall, l represents the length of the micro-element drill string, R1 represents the outer radius of the drill string, R2 represents the inner radius of the wellbore, E1 and E2 represent the elastic modulus of the drill string and the formation rock material, respectively, and μ1 and μ2 represent the Poisson's ratio of the drill string and the formation rock material, respectively.

[0013] The method for simulating and calculating frictional torque in a three-dimensional horizontal well includes the following steps:

[0014] S 21 Based on the curve of sliding friction coefficient as a function of sliding speed, a dynamic friction model is selected to describe the friction response characteristics, and the undetermined parameters of the dynamic friction model are determined based on experimental results.

[0015] S 22 Establish a conventional three-dimensional horizontal well drill string friction prediction model; combine the corresponding initial and boundary conditions to calculate the drill string normal load, axial force, torque and friction during the conventional drilling process;

[0016] S 23 Based on the stratigraphic data, the lithology is determined. Based on the lithology determination results, the dynamic friction model between the drill string and the well wall in the corresponding well section is selected. The corresponding dynamic friction model is then substituted into the rigid rod model of the conventional three-dimensional horizontal well drill string friction prediction model to establish a three-dimensional horizontal well friction torque prediction method based on the nonlinear sliding friction model.

[0017] S 24 Based on the actual well drilling parameters, calculate the distribution characteristics of drill string friction torque during horizontal well sliding drilling.

[0018] The dynamic friction model is specifically a velocity-state friction model:

[0019]

[0020] In the formula, μ * The velocity is represented by V. * The coefficient of sliding friction under steady-state conditions; |v| represents the sliding velocity; a, b, c, and ε represent empirical constants related to the experiment.

[0021] Establishing a conventional three-dimensional horizontal well drill string friction prediction model specifically refers to establishing a three-dimensional horizontal well drill string friction prediction model that does not consider the effects of hydraulic oscillators and torsional drilling systems.

[0022] The conventional three-dimensional horizontal well drill string friction prediction model is as follows:

[0023]

[0024] in,

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] In the formula, N represents the normal pressure between the drill string and the wellbore; N n N represents the contact force between the drill string along its principal normal direction and the wellbore wall. b μ represents the contact force between the drill string and the wellbore along the normal direction; μ represents the coefficient of sliding friction between the drill string and the wellbore. a μ represents the axial friction coefficient component. t f represents the tangential friction coefficient component; λ ν represents the viscous resistance of the drill string; v represents the axial velocity of the drill string; ω represents the angular velocity of the drill string rotation; τ represents the shear stress of the drilling fluid; η represents the dynamic viscosity of the drilling fluid; R represents the outer diameter of the drill string; D w Indicates the wellbore diameter; T e M represents the axial force of the drill string. t The torque of the drill string is represented by k; the wellbore curvature is represented by q. m ρ represents the buoyant weight per unit length of drill string; i ρ0 represents the density of the drilling fluid inside the drill string; ρ0 represents the density of the drilling fluid outside the drill string; A i A represents the inner cross-sectional area of ​​the drill string; A0 represents the outer cross-sectional area of ​​the drill string; E represents the elastic modulus of the drill string; I represents the moment of inertia of the drill string; k α k φα represents the well inclination rate and azimuth rate, respectively; α represents the well inclination angle; Ψ represents the azimuth angle; and ds represents the drill string element length.

[0031] Step S 22 The initial and boundary conditions are as follows:

[0032] T e (0) = WOB

[0033] M t (0) = TOB

[0034] In the formula, WOB represents drilling pressure; TOB represents drill bit torque.

[0035] The normal load on the drill string during conventional drilling is calculated using the finite difference method.

[0036] The method for calculating the axial force is as follows:

[0037]

[0038]

[0039] In the formula, ΔT r α1 represents the axial force increment; N represents the normal pressure between the drill string and the wellbore; WOB represents the drilling pressure; μ represents the sliding friction coefficient between the drill string and the wellbore; W represents the weight of the drill string in the micro-element segment; α1 and α2 represent the well inclination angles corresponding to the two ends of the drill string micro-element.

[0040] The method for calculating the torque is as follows:

[0041]

[0042] In the formula, M t M0 represents the drill string torque; μ represents the drill bit reverse torque. t The component represents the tangential friction coefficient; N represents the normal pressure between the drill string and the wellbore; and r represents the radius of the drill string in the micro-element segment.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] 1. This invention employs a dynamic friction coefficient testing method, using water-based drilling fluid as the lubricating medium. Other experimental parameters, including sliding speed and normal load, are determined based on the principle of similarity. The parameter settings during the experiment are all determined according to actual drilling parameters, meaning the experimental sliding speed matches the actual drilling speed, and the applied normal pressure matches the contact force between the drill string and the wellbore during actual drilling. Therefore, the dynamic friction coefficient testing method used in this invention is more consistent with actual conditions. The experiment records the curves of friction force and normal load changing over time, thereby calculating the sliding friction coefficient during the sliding friction process, making the calculation method more accurate.

[0045] Conventional friction experiments typically employ ball-disc or pin-disc friction pairs. However, in actual drilling, the contact state between the drill string and the wellbore is a typical internal cylindrical friction pair, but the actual contact width is very limited. Therefore, this invention limits the contact width to be equal, effectively preventing the friction pair surface from potentially exhibiting a line contact state or insufficient contact during the experiment, thus avoiding affecting the accuracy and reliability of the experimental results.

[0046] 2. Traditional rigid bar models for predicting frictional torque typically set the sliding friction coefficient to a constant value. However, in reality, the sliding friction coefficient is strongly correlated with the sliding velocity (represented as the mechanical drilling rate during actual drilling), and the mechanical drilling rate is constantly changing during actual drilling. Therefore, the prediction accuracy of traditional models is low. This invention fills the gap in traditional horizontal well frictional torque prediction, which does not consider the dynamic changes in the friction coefficient. The system considers the response characteristics of the sliding friction coefficient of different lithological formations as a function of the sliding velocity (represented as the mechanical drilling rate during actual drilling). This method can provide a scientific basis and decision support for the real-time accurate calculation of frictional torque, and the design and optimization of horizontal well drilling parameters during three-dimensional horizontal well drilling. Attached Figure Description

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein:

[0048] Figure 1 This is a schematic diagram of the contact friction between the drill string and the well wall in any tiny well section in this invention;

[0049] Figure 2 This is a schematic diagram illustrating the experimental principle and sample size specifications in this invention;

[0050] Figure 3 The results of the friction experiment at a sliding speed of 1.2 mm / s in this invention are shown.

[0051] Figure 4 This is the curve showing the variation of the sliding friction coefficient with sliding speed in this invention;

[0052] Figure 5 This is a schematic diagram of the X-1 wellbore structure in this invention;

[0053] Figure 6 This is a schematic diagram of the actual drilling trajectory of well X-1 in this invention;

[0054] Figure 7 This is a schematic diagram of the lateral force distribution in well X-1 in this invention;

[0055] Figure 8 This is a schematic diagram of the axial force distribution in well X-1 in this invention. Detailed Implementation

[0056] Example 1

[0057] As a basic embodiment of the present invention, the present invention includes a method for testing the dynamic friction coefficient of a three-dimensional horizontal well, comprising the following steps:

[0058] S 11 Based on the premise that the contact width between the drill string and the well wall is equal under both actual and experimental conditions, the size specifications of the simulated drill string and the simulated well wall for the experiment are determined.

[0059] S 12 Sliding friction experiments were conducted under simulated drill string and simulated well wall contact conditions at different sliding speeds. During the experiments, the curves of friction force and normal load change with time were recorded, and then the sliding friction coefficient was calculated to generate the sliding friction coefficient response curve over time.

[0060] S 13 Based on the sliding friction coefficient response curve during the stable phase of sliding friction, the average value is taken as the sliding friction coefficient corresponding to that sliding speed, and the curve of the sliding friction coefficient changing with the sliding speed is plotted.

[0061] Example 2

[0062] As a preferred embodiment of the present invention, the present invention includes a method for testing the dynamic friction coefficient of a three-dimensional horizontal well, comprising the following steps:

[0063] S 11 Based on the premise that the contact width between the drill string and the well wall is equal under both actual and experimental conditions, the size specifications of the simulated drill string and the simulated well wall for the experiment are determined.

[0064] The method for determining the contact width between the drill string and the well wall is as follows:

[0065]

[0066] In the formula, b represents the contact width between the drill string and the well wall, F represents the contact normal pressure between the drill string and the well wall, l represents the length of the micro-element drill string, R1 represents the outer radius of the drill string, R2 represents the inner radius of the wellbore, E1 and E2 represent the elastic modulus of the drill string and the formation rock material, respectively, and μ1 and μ2 represent the Poisson's ratio of the drill string and the formation rock material, respectively.

[0067] S 12Sliding friction experiments were conducted under simulated drill string-wellbore contact conditions at different sliding speeds. Water-based drilling fluid was used as the lubricating medium during the experiments; other experimental parameters, including sliding speed and normal load, were determined based on the principle of similarity. The changes in friction force and normal load over time were recorded during the experiments, and the sliding friction coefficient was calculated to generate a sliding friction coefficient response curve over time.

[0068] S 13 Based on the sliding friction coefficient response curve, taking the sliding friction coefficient response curve in the stable stage of sliding friction as the basis, take its average value as the sliding friction coefficient corresponding to the sliding speed, and plot the curve of the sliding friction coefficient changing with the sliding speed.

[0069] Example 3

[0070] As a preferred embodiment of the present invention, the present invention includes a three-dimensional horizontal well friction torque simulation calculation method, comprising the following steps:

[0071] S 21 Based on the curve of the sliding friction coefficient versus sliding speed calculated using conventional methods, a dynamic friction model is selected to describe the friction response characteristics, and the undetermined parameters of the dynamic friction model are determined based on experimental results. Commonly used dynamic friction models in engineering include the rate-state friction model, the LuGre model, the Leuven model, and the Hsieh friction model.

[0072] S 22 Considering the effects of wellbore trajectory, drill string assembly structure, drilling fluid viscous resistance, and drill string buckling, a conventional three-dimensional horizontal well drill string friction prediction model is established. Based on the corresponding initial and boundary conditions, the drill string normal load, axial force, torque, and friction during the conventional drilling process are calculated.

[0073] S 23 Based on the stratigraphic data, the lithology is determined. Based on the lithology determination results, the dynamic friction model between the drill string and the well wall in the corresponding well section is selected. The corresponding dynamic friction model is then substituted into the rigid rod model of the conventional three-dimensional horizontal well drill string friction prediction model to establish a three-dimensional horizontal well friction torque prediction method based on the nonlinear sliding friction model.

[0074] S 24 Based on the actual well drilling parameters, calculate the distribution characteristics of drill string friction torque during horizontal well sliding drilling.

[0075] Example 4

[0076] As the preferred embodiment of the present invention, the present invention includes a method for testing the dynamic friction coefficient of a three-dimensional horizontal well, and a method for simulating and calculating friction torque based on the dynamic friction coefficient testing method. Specifically, it includes the following steps:

[0077] S1. Complete the test of the dynamic friction coefficient of the three-dimensional horizontal well. This includes the following steps:

[0078] S 11 In actual drilling operations, the contact friction between the drill string and the wellbore in any minute section can be equivalent to the friction described in the instruction manual. Figure 1 The physical model is shown. Based on Hertzian contact theory, and assuming that the contact width between the drill string and the wellbore is equal under both actual and experimental conditions, the dimensions of the experimental samples are determined, taking into account the structural characteristics of the UMT friction and wear testing machine. The determined dimensions of the experimental samples are shown in the appendix to the instruction manual. Figure 2 As shown.

[0079] The methods for determining the contact width between the drill string and the wellbore, as well as the maximum contact stress, are as follows:

[0080]

[0081]

[0082] In the formula, σ Hmax denoted by , b represents the contact width between the drill string and the wellbore, F represents the normal contact pressure between the drill string and the wellbore (N); l represents the length of the drill string segment (m); R1 represents the outer radius of the drill string (m); R2 represents the inner radius of the wellbore (m); E1 and E2 represent the elastic modulus of the drill string and the formation rock material (MPa), respectively; μ1 and μ2 represent the Poisson's ratio of the drill string and the formation rock material (dimensionless).

[0083] S 12 Sliding friction experiments were conducted under simulated drill string-wellbore contact conditions with different parameter combinations. Water-based drilling fluid was used as the lubricating medium. Other experimental parameters, including sliding velocity and normal load, were determined based on the principle of similarity. Specifically, the drilling fluid density was 1.35 g / cm³. 3 The sliding speeds were set to 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, and 2.1 mm / s, respectively, and the normal load was set to 40 N.

[0084] During the experiment, the curves of frictional force and normal load changing with time were recorded, and then the coefficient of sliding friction was calculated to generate a sliding friction coefficient response curve over time. The sliding friction experimental curve at a sliding speed of 1.2 mm / s is shown in the attached instruction manual. Figure 3 As shown, the average coefficient of sliding friction during this sliding friction process is 0.273.

[0085] S 13 Based on the sliding friction coefficient response curve, taking the average value of the sliding friction coefficient response curve during the stable phase of sliding friction as the basis, we obtain the sliding friction coefficient corresponding to that sliding speed. Furthermore, the test results of the sliding friction coefficient at different sliding speeds are plotted as a curve showing the change of sliding friction coefficient with sliding speed, as shown in the appendix to the instruction manual. Figure 4 As shown, it can be seen that with the increase of sliding speed, the coefficient of sliding friction gradually decreases and exhibits obvious nonlinear variation characteristics.

[0086] Specifically, the sliding friction stabilization stage refers to: as per the appendix of the instruction manual. Figure 3 As shown, before the sliding friction begins, there is a friction initiation stage, during which both the normal force and frictional force show a gradual increasing trend, after which the friction process tends to stabilize. Furthermore, the frictional force rapidly changes from -20N to 20N in the figure; this is due to the change in the sliding direction of the sample and does not affect the test results for the coefficient of friction.

[0087] S2. Complete the three-dimensional horizontal well friction torque simulation calculation. This includes the following steps:

[0088] S 21 According to step S 13 The obtained curves showing the change in sliding friction coefficient with sliding speed were used to describe the friction response characteristics using a dynamic friction model. Commonly used dynamic friction models in engineering include the rate-state friction model, the LuGre model, the Leuven model, and the Hsieh friction model. Among these, the rate-state friction model was chosen as the characterization model for sliding friction experiments because it has fewer parameters to be estimated and can describe the velocity response characteristics during the sliding friction process. The rate-state friction model can be expressed as:

[0089]

[0090] Where: μ * The velocity is represented by V. * The coefficient of sliding friction under steady-state conditions is dimensionless; |v| represents the sliding velocity, mm / s; a, b, c, and ε represent empirical constants related to the experiment.

[0091] Based on the experimental results of sandstone-steel sliding friction, the undetermined parameters of the velocity-state friction model are determined. The specific expression for the velocity-state friction model is then:

[0092]

[0093] S 22Considering the effects of wellbore trajectory, drill string assembly structure, drilling fluid viscous resistance, and drill string buckling, a conventional three-dimensional horizontal well drill string friction prediction model is established. This model does not consider the effects of the hydraulic oscillator and torsional drilling system. Based on the appropriate initial and boundary conditions, the drill string normal load, axial force, torque, and friction during conventional drilling are calculated.

[0094] The conventional three-dimensional horizontal well drill string friction prediction model is as follows:

[0095]

[0096] in,

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103] In the formula, N represents the normal pressure between the drill string and the wellbore, N; N n The contact force between the drill string and the wellbore along the principal normal direction is expressed in N; N b denoted by , μ represents the contact force between the drill string and the wellbore along the normal direction, in N; μ represents the coefficient of sliding friction between the drill string and the wellbore, dimensionless. a μ represents the axial friction coefficient component, which is dimensionless. t f represents the tangential friction coefficient component, which is dimensionless; λ ν represents the viscous resistance of the drill string, N; v represents the axial velocity of the drill string, m / s; ω represents the angular velocity of the drill string rotation, rad / s; τ represents the shear stress of the drilling fluid, Pa; η represents the dynamic viscosity of the drilling fluid, Pa·s; R represents the outer diameter of the drill string, m; D w T represents the wellbore diameter, in meters (m); e The axial force of the drill string is expressed in N; M. t The torque of the drill string is represented in N·m; k represents the wellbore curvature in rad / m; q m ρ represents the buoyant weight per unit length of drill string, in N / m. i This indicates the density of the drilling fluid inside the drill string, in kg / m³. 3 ρ0 represents the density of the drilling fluid outside the drill string, in kg / m³. 3 A i The cross-sectional area of ​​the drill string is expressed in meters (m²). 2A0 represents the outer cross-sectional area of ​​the drill string, in meters. 2 E represents the drill string's elastic modulus, in Pa; I represents the drill string's moment of inertia, in meters. 4 ;k α k φ α represents the inclination rate and azimuth rate, respectively, in rad / m; α represents the inclination angle, in rad; Ψ represents the azimuth angle, in rad; ds represents the length of the drill string element, in m.

[0104] As a preferred option, step S 22 In this context, the initial and boundary conditions are:

[0105] T e (0) = WOB (12)

[0106] M t (0) = TOB (13)

[0107] In the formula, WOB represents drilling pressure in N; TOB represents drill bit torque in N·m.

[0108] As a preferred option, step S 22 In conventional drilling, the normal load on the drill string can be obtained using the finite difference method. Furthermore, the axial force and torque can be calculated using the following formula:

[0109]

[0110]

[0111]

[0112] In the formula, ΔT r α1 represents the axial force increment, N; N represents the normal force between the drill string and the wellbore, N; WOB represents the drilling pressure; μ represents the sliding friction coefficient between the drill string and the wellbore, dimensionless; W represents the weight of the drill string in the micro-element segment; α1 and α2 represent the well inclination angles corresponding to the two ends of the drill string micro-element; M t M0 represents the drill string torque (N·m); M0 represents the drill bit reverse torque (N·m); μ t denoted by tangential friction coefficient component, dimensionless; r represents the radius of the drill string in the micro-element segment.

[0113] S 23Based on the stratigraphic data, the lithology is determined. Based on the lithology determination, a dynamic friction model between the drill string and the wellbore is selected for the corresponding well section. This dynamic friction model is then substituted into the rigid rod model of the conventional three-dimensional horizontal well drill string friction prediction model to establish a three-dimensional horizontal well friction torque prediction method based on a nonlinear sliding friction model. For example, if the drilled formation is determined to be sandstone, equation (4) is selected to describe the friction coefficient response characteristics during drilling. Substituting this into equation (5) establishes a three-dimensional horizontal well friction torque prediction method based on a nonlinear sliding friction model.

[0114] S 24 Based on the actual well drilling parameters, calculate the distribution characteristics of drill string friction torque during horizontal well sliding drilling.

[0115] Example 5

[0116] As another preferred embodiment of the present invention, taking the X-1 shale gas horizontal well as an example, the drag reduction effect is evaluated using the calculation method described in this invention. The wellbore structure is shown in the appendix to the specification. Figure 5 As shown, the drill string assembly used during the actual drilling process was a Φ215.9mm PDC drill bit + a 1.25° single-bend screw rod + Φ127mm heavy-duty drill pipe × 27m + Φ127mm drill pipe × 108m + Φ127mm heavy-duty drill pipe × 108m + Φ127mm drill pipe × 5212m. Other basic parameters of this well are shown in Table 1 below.

[0117] Table 1X-1 Basic Parameters of Shale Gas Horizontal Wells

[0118] Parameter name Value unit Parameter name Value unit Drill string elastic modulus 206 GPa Drilling fluid density 1350 kg / m 3 ]]> Drill string density 7850 kg / m 3 ]] Drilling fluid dynamic viscosity 54 mPa·s drill string shear modulus 79 GPa Drilling fluid shear stress 7 Pa drill string outer diameter 127 mm Drill bit reverse torque 2500 N·m Drill string inner diameter 108.6 mm Wellbore diameter 215.9 mm Buoyancy per unit length of drill string 284.58 N / m Drilling pressure 80000 N Increase the outer diameter of the drill pipe 127 mm Increase the inner diameter of the drill pipe 76.2 mm Buoyancy of drill pipe per unit length 720.3 N / m

[0119] Instruction manual attached Figure 6 The figure shows the actual drilling trajectory data for well X-1. As can be seen from the figure, this well is a three-dimensional horizontal well with a maximum inclination angle of 93° and a horizontal section length of 2795m.

[0120] Instruction manual attached Figure 7 The diagram shows the lateral force distribution during the sliding drilling process of well X-1. It can be seen that the contact force between the drill string and the well wall is relatively high in the upper pre-deflection section and the high-angle section, which is the root cause of the high friction problem in sliding drilling.

[0121] Instruction manual attached Figure 8 The diagram shows the axial force distribution during the sliding drilling process of well X-1. It can be seen that the maximum axial force at the wellhead is 207.2 kN, and the maximum axial pressure on the drill string is 211.67 kN, corresponding to a well depth of 2633.48 m.

[0122] As can be seen from the above, the present invention systematically considers the response characteristics of the sliding friction coefficient of different lithological formations as a function of sliding speed (which is manifested as mechanical drilling speed in actual drilling process). This method can provide a scientific basis and decision support for the real-time and accurate calculation of friction torque, and the design and optimization of horizontal well drilling parameters during three-dimensional horizontal well drilling.

[0123] In summary, any other corresponding modifications made by those skilled in the art after reading this invention document, without requiring creative mental effort, based on the technical solutions and concepts of this invention, are all within the scope of protection of this invention.

Claims

1. A method for testing the dynamic friction coefficient of a three-dimensional horizontal well, characterized in that: Includes the following steps: S 11 Assuming that the contact width between the drill string and the well wall is equal under both actual and experimental conditions, determine the dimensions and specifications of the simulated drill string and the simulated well wall for the experiment. S 12 Sliding friction experiments were conducted under simulated drill string and simulated well wall contact conditions at different sliding speeds. During the experiments, the curves of friction force and normal load change with time were recorded, and the sliding friction coefficient was calculated to generate the sliding friction coefficient response curve over time. S 13 Based on the sliding friction coefficient response curve during the stable phase of sliding friction, the average value is taken as the sliding friction coefficient corresponding to that sliding speed, and the curve of the sliding friction coefficient changing with the sliding speed is plotted.

2. The method for testing the dynamic friction coefficient of a three-dimensional horizontal well according to claim 1, characterized in that: Step S 11 The method for determining the contact width between the drill string and the wellbore is as follows: In the formula, b represents the contact width between the drill string and the well wall, F represents the contact normal pressure between the drill string and the well wall, l represents the length of the micro-element drill string, R1 represents the outer radius of the drill string, R2 represents the inner radius of the wellbore, E1 and E2 represent the elastic modulus of the drill string and the formation rock material, respectively, and μ1 and μ2 represent the Poisson's ratio of the drill string and the formation rock material, respectively.

3. A three-dimensional horizontal well friction torque simulation calculation method, characterized in that: Includes the following steps: S 21 According to the curve of the sliding friction coefficient as a function of sliding speed obtained according to claim 1 or 2, a dynamic friction model is selected to describe the friction response characteristics, and the undetermined parameters of the dynamic friction model are determined based on the experimental results; S 22 Establish a conventional three-dimensional horizontal well drill string friction prediction model; combine the corresponding initial and boundary conditions to calculate the drill string normal load, axial force, torque and friction during the conventional drilling process; S 23 Based on stratigraphic data, lithology is determined. A dynamic friction model between the drill string and wellbore is selected for the corresponding well section based on the lithology determination results. This dynamic friction model is then substituted into the rigid rod model of a conventional three-dimensional horizontal well drill string friction prediction model to establish a three-dimensional horizontal well friction torque prediction method based on a nonlinear sliding friction model. 24 Based on the actual well drilling parameters, calculate the distribution characteristics of drill string friction torque during horizontal well sliding drilling.

4. The three-dimensional horizontal well friction torque simulation calculation method according to claim 3, characterized in that: The dynamic friction model is specifically a velocity-state friction model: In the formula, μ * The velocity is represented by V. * The coefficient of sliding friction under steady-state conditions; |v| represents the sliding velocity; a, b, c, and ε represent empirical constants related to the experiment.

5. The three-dimensional horizontal well friction torque simulation calculation method according to claim 3, characterized in that: Establishing a conventional three-dimensional horizontal well drill string friction prediction model specifically refers to establishing a three-dimensional horizontal well drill string friction prediction model that does not consider the effects of hydraulic oscillators and torsional drilling systems.

6. The three-dimensional horizontal well friction torque simulation calculation method according to claim 5, characterized in that: The conventional three-dimensional horizontal well drill string friction prediction model is as follows: In the formula, N represents the normal pressure between the drill string and the wellbore; N n N represents the contact force between the drill string along its principal normal direction and the wellbore wall. b μ represents the contact force between the drill string and the wellbore along the normal direction; μ represents the coefficient of sliding friction between the drill string and the wellbore. a μ represents the axial friction coefficient component. t f represents the tangential friction coefficient component; λ ν represents the viscous resistance of the drill string; v represents the axial velocity of the drill string; ω represents the angular velocity of the drill string rotation; τ represents the shear stress of the drilling fluid; η represents the dynamic viscosity of the drilling fluid; R represents the outer diameter of the drill string; D w Indicates the wellbore diameter; T e M represents the axial force of the drill string. t The torque of the drill string is represented by k; the wellbore curvature is represented by q. m ρ represents the buoyant weight per unit length of drill string; i ρ0 represents the density of the drilling fluid inside the drill string; ρ0 represents the density of the drilling fluid outside the drill string; A i A represents the inner cross-sectional area of ​​the drill string; A0 represents the outer cross-sectional area of ​​the drill string; E represents the elastic modulus of the drill string; I represents the moment of inertia of the drill string; k α k φ α represents the well inclination rate and azimuth rate, respectively; α represents the well inclination angle; Ψ represents the azimuth angle; and ds represents the drill string element length.

7. The three-dimensional horizontal well friction torque simulation calculation method according to claim 6, characterized in that: Step S 22 Initial and boundary conditions are expressed as follows: T e (0)<WOB M t (0)=TOB In the formula, WOB represents drilling pressure; TOB represents drill bit torque.

8. The three-dimensional horizontal well friction torque simulation calculation method according to claim 7, characterized in that: The normal load on the drill string during conventional drilling is calculated using the finite difference method.

9. The three-dimensional horizontal well friction torque simulation calculation method according to claim 7, characterized in that: The method for calculating the axial force is as follows: In the formula, ΔT r α1 represents the axial force increment; N represents the normal pressure between the drill string and the wellbore; WOB represents the drilling pressure; μ represents the sliding friction coefficient between the drill string and the wellbore; W represents the weight of the drill string in the micro-element segment; α1 and α2 represent the well inclination angles corresponding to the two ends of the drill string micro-element.

10. The three-dimensional horizontal well friction torque simulation calculation method according to claim 7, characterized in that: The method for calculating the torque is as follows: In the formula, M t M0 represents the drill string torque; μ represents the drill bit reverse torque. t The component represents the tangential friction coefficient; N represents the normal pressure between the drill string and the wellbore; and r represents the radius of the drill string in the micro-element segment.

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