Oil and gas well drill string axial vibration severity evaluation and optimization method

Abstract

The invention discloses an oil and gas well drill string axial vibration severity evaluation and optimization method, which comprises the following steps: obtaining drill string structure parameters and power drilling tool parameters, and constructing an oil and gas well drill string axial vibration simulation model; then acquiring necessary parameters for evaluating the axial vibration of the drill stem based on the simulation model, wherein the necessary parameters comprise the minimum axial displacement; based on the relation between the minimum axial displacement and the initial cutting depth, the axial vibration index is calculated in a segmented mode; based on the axial vibration index, evaluating the severity of the axial vibration of the drill stem; and the drilling parameters and the screw model are adjusted, the axial vibration index obtaining process is repeated till the axial vibration index is within the preset interval, the drilling parameters and the screw model which are reasonably matched are obtained, and then the axial vibration of the drill column is optimized. According to the method, the drilling parameters and the use reasonability of the screw drilling tool can be judged, then the parameters are optimized, the drilling strategy is adjusted, it is guaranteed that less axial vibration occurs in the drilling process, and the mechanical drilling speed is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil drilling, and particularly relates to a method for evaluating and optimizing the severity of axial vibration of a drill string in an oil and gas well. Background Art

[0002] Harmful vibrations occurring during drilling endanger drilling safety and reduce drilling efficiency and the rate of penetration (ROP). Axial vibration is a type of harmful vibration of the drill string. When the vibration is severe, the axial vibration shows a phenomenon of bit bounce. Severe axial vibration can lead to abnormal wear of the bit and axial spalling of the cutting teeth, and exacerbate the damage of downhole power tools. Therefore, controlling axial vibration has important practical significance for improving drilling efficiency and controlling drilling costs.

[0003] For the control of axial vibration, one is to prevent it during the drilling design before drilling, and the other is to adjust the drilling parameters in real time during drilling to suppress the vibration. In the currently published literature, most of the evaluation indicators for axial vibration use axial acceleration for quantification. For example, Baker Hughes INTEQ divides different vibration levels according to the root mean square value of axial acceleration. However, in actual analysis, the magnitude of axial vibration under different working conditions and drill string combinations is not the same, and it is unreasonable to only use acceleration to quantify vibration. In theoretical research, when analyzing vibration, the velocity or displacement in the corresponding dimension is often considered. However, this qualitative analysis method can only be used as a basis for judging the occurrence of bit bounce and cannot quantitatively analyze the intensity of axial vibration.

[0004] Recent patents and research mainly focus on the evaluation and optimization methods of bit stick-slip vibration, while the evaluation and optimization methods for axial vibration remain to be further studied and developed. For example, Patent CN115324554B proposes a method for evaluating and optimizing the severity of bit stick-slip vibration. This method adjusts the drilling strategy through a simulation model but does not consider axial vibration. Patent CN102575516B discloses a method for estimating the amplitude of downhole drilling vibration based on surface measurement, which is applicable to vibration monitoring during drilling but cannot optimize drilling parameters and drill string models. The conference paper SPE 177950 proposes an evaluation index for the severity of stick-slip vibration, which is only applicable to stick-slip vibration and not to axial vibration. The conference paper SPE 163420 proposes an evaluation index for the severity of torsional vibration, which is calculated by the maximum bit rotation speed and the average bit rotation speed. This index is for torsional vibration and does not involve axial vibration.

[0005] In addition, the optimization methods for axial vibration in current research have not fully considered the influence of the main downhole motor - positive displacement motor. For example, Patent CN117272611A proposed a dynamic model of the drill string system considering the positive displacement motor, but mainly focused on stick - slip vibration rather than axial vibration. Patent CN113688482A established a simulation model for stick - slip vibration, but did not include the positive displacement motor and hydraulic parameters. Patent CN116244906A mainly studied the simulation of stick - slip vibration in the horizontal section of a horizontal well and did not involve axial vibration. Patent CN113638729A considered the torque impactor to suppress stick - slip vibration, but the model also did not include the positive displacement motor and did not involve axial vibration

[0006] In summary, there is an urgent need to propose an evaluation and optimization method for the severity of axial vibration of the drill string in oil and gas wells, so as to carry out pre - drilling design, in - drilling optimization, and post - drilling analysis, avoid the occurrence of axial vibration of the drill string, improve the mechanical drilling rate, and reduce the drilling cost. Summary of the Invention

[0007] To solve the above - mentioned technical problems, the present invention proposes an evaluation and optimization method for the severity of axial vibration of the drill string in oil and gas wells, which evaluates the axial vibration of the drill string and prevents the occurrence of axial vibration of the drill string by adjusting drilling parameters or downhole motors, reducing the drilling cost, and solving the problems existing in the above - mentioned prior art.

[0008] To achieve the above object, the present invention provides an evaluation and optimization method for the severity of axial vibration of the drill string in oil and gas wells, including the following steps:

[0009] Obtain the structural parameters of the drill string and the parameters of the downhole motor, and construct a simulation model for the axial vibration of the drill string in oil and gas wells;

[0010] Based on the simulation model, obtain the necessary parameters for evaluating the axial vibration of the drill string, and the necessary parameters include the maximum axial displacement, the minimum axial displacement, the average axial displacement, and the cutting depth;

[0011] Based on the relationship between the minimum axial displacement and the initial cutting depth, calculate the axial vibration index in segments;

[0012] Based on the axial vibration index, evaluate the severity of the axial vibration of the drill string;

[0013] Adjust the drilling parameters and the screw type, and repeat the process of obtaining the axial vibration index until the axial vibration index is within a preset range, obtain reasonable drilling parameters and screw types that match, and then optimize the axial vibration of the drill string.

[0014] Optionally, the simulation model for the axial vibration of the drill string in oil and gas wells is:

[0015]

[0016] In the formula, the subscript r represents the mass block of the rotary table; dp1 to dp(i) represent the mass blocks of the first drill pipe to the i-th drill pipe; dc1 to dc(i) represent the mass blocks of the first drill collar to the i-th drill collar; pb represents the mass block of the screw rotor-bit; J represents the moment of inertia; θ represents angular acceleration, angular velocity, and angular displacement respectively; k kp is the torsional stiffness between the rotary table and the drill pipe; k pp is the torsional stiffness between drill pipes; k pc is the torsional stiffness between the drill pipe and the drill collar; k cc is the torsional stiffness between drill collars; k cb is the torsional stiffness between the upper mass block of the drill collar-screw and the lower mass block of the screw-bit; c rp is the torsional damping between the rotary table and the drill pipe; c pp is the torsional damping between drill pipes; c pc is the torsional damping between the drill pipe and the drill collar; c cc is the torsional damping between drill collars; c cb is the torsional damping between the upper mass block of the drill collar-screw and the lower mass block of the screw-bit; T is the torque input by the driving motor to the rotary table; T fb is the frictional torque at the contact between the bit and the rock; T ar is the loss damping of the drive system; T t is the output torque of the positive displacement motor; M a is the axial equivalent mass of the drill string; C a is the axial equivalent damping of the drill string; K a is the axial equivalent stiffness of the drill string; z a represent the axial acceleration, axial velocity, and axial displacement of the drill string respectively; Wob is the weight on bit; W t is the total axial force of the positive displacement motor; W b is the axial force generated on the drill string under the interaction between the bit and the rock.

[0017] Optionally, the total axial force W of the positive displacement motor t is:

[0018]

[0019] In the formula, W P is the total gravity of the rotor, universal joint shaft, drive shaft, and bit of the positive displacement motor; α is the well inclination angle; W P cosα is the axial component of the total weight; E is the eccentricity; N is the number of motor heads corresponding to the positive displacement motor model; r0 is the equidistant radius coefficient; T is the torque at the bit; i is the ratio of the number of motor heads; D h is the outer diameter of the positive displacement motor housing; P his the distance between the housings of the positive displacement motor.

[0020] Optionally, the process of obtaining the necessary parameters for evaluating the axial vibration of the drill string based on the simulation model includes:

[0021] Obtain different drilling parameters and downhole motor parameters and input them into the simulation model for simulation to obtain the dynamic response parameters of the drill string system; from the dynamic response parameters, obtain the necessary parameters for evaluating the severity of the axial vibration of the drill string; the necessary parameters for evaluating the severity of the axial vibration of the drill string also include the axial velocity, the maximum axial displacement within a certain time range, and the cutting depth corresponding to the time.

[0022] Optionally, when the minimum axial displacement is greater than or equal to the initial cutting depth, the calculation formula for the axial vibration index is:

[0023]

[0024] When the minimum axial displacement is less than the initial cutting depth, the calculation formula for the axial vibration index is:

[0025]

[0026] In the formula, Max z represents the maximum axial displacement, Min z represents the minimum axial displacement, Z i represents the axial displacement corresponding to the time, S i represents the cutting depth corresponding to the time, Avg z represents the average axial displacement.

[0027] Optionally, it further includes establishing an axial velocity phase trajectory curve graph. Taking the initial cutting depth as the boundary, when the axially acquired displacement is greater than the initial cutting depth in real time, a bit bounce phenomenon occurs; when the axially acquired displacement is less than the initial cutting depth in real time, the drill string does not have a bit bounce phenomenon.

[0028] The present invention also provides a computer device, including a memory, a processor, and a computer program stored on the memory, and the steps implemented when the processor executes the computer program.

[0029] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of any of the above-mentioned methods are implemented.

[0030] The present invention also provides a computer program product, including a computer program, and when the computer program is executed by a processor, the steps of the above-mentioned method are implemented.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects:

[0032] The method for evaluating and optimizing the axial vibration severity of an oil and gas well drill string provided by the present invention first obtains the drill string structure parameters and downhole motor parameters, and constructs a simulation model of the axial vibration of the oil and gas well drill string; then obtains the necessary parameters for evaluating the axial vibration of the drill string based on the simulation model, and the necessary parameters include the maximum axial displacement, the minimum axial displacement, the average axial displacement, and the cutting depth; based on the relationship between the minimum axial displacement and the initial cutting depth, the axial vibration index is calculated in segments; based on the axial vibration index, the severity of the axial vibration of the drill string is evaluated; the drilling parameters and the downhole motor model are adjusted, and the process of obtaining the axial vibration index is repeated until the axial vibration index is within a preset range, and reasonable drilling parameters and downhole motor models are obtained, thereby optimizing the axial vibration of the drill string.

[0033] The method for evaluating the severity of the axial vibration of the drill string proposed by the present invention takes into account the influence of the cutting depth and torsional vibration, quantifies the severity of the axial vibration of the drill string, and the established coupled simulation model takes into account the influence of the downhole motor. The axial force of the downhole motor takes into account the influence of factors such as drill string size, formation pressure drop, and pump pressure. According to the simulation model and the evaluation method, the rationality of the drilling parameters and the use of the downhole motor can be judged, and then the parameters can be optimized and the drilling strategy can be adjusted. Finally, appropriate weight on bit, rotary speed, pump pressure, displacement, downhole motor, etc. are proposed to ensure less axial vibration during the drilling process, improve the mechanical drilling rate, and achieve safe and fast drilling. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0035] Figure 1 is a flow chart of the method for evaluating and optimizing the axial vibration severity of the drill string according to the embodiment of the present invention;

[0036] Figure 2 is a curve graph of the axial velocity phase trajectory divided by the initial cutting depth according to the embodiment of the present invention;

[0037] Figure 3 is a curve graph of the axial velocity time history response according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail this application.

[0039] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0040] Embodiment 1

[0041] As Figures 1 - 3 shown, in this embodiment, a method for evaluating and optimizing the axial severity of an oil and gas well drill string is provided. Considering the use of a positive displacement motor, the axial vibration severity of the drill string is evaluated, and the parameters and drilling tools are optimized, which can avoid the occurrence of axial vibration of the drill string and improve the mechanical drilling rate.

[0042] The method for evaluating and optimizing the axial severity of the drill string includes:

[0043] Step 101: Calculate the structural parameters of the drill string and the parameters of the downhole motor, and establish a simulation model for the axial vibration of the oil and gas well drill string;

[0044] Implementable, the simulation model for the axial vibration of the oil and gas well drill string is:

[0045]

[0046] In the formula, the subscript r—the mass block of the rotary table; dp1~dp(i)—the mass blocks of the first drill pipe to the i-th drill pipe; dc1~dc(i)—the mass blocks of the first drill collar to the i-th drill collar; pb—the mass block of the positive displacement motor- bit; J—the moment of inertia; θ—the angular acceleration, angular velocity, angular displacement; k kp —the torsional stiffness between the rotary table and the drill pipe; k pp —the torsional stiffness between drill pipes; k pc —the torsional stiffness between the drill pipe and the drill collar; k cc —the torsional stiffness between drill collars; k cb —the torsional stiffness between the upper mass block of the drill collar-positive displacement motor and the lower mass block of the positive displacement motor-bit; c rp —the torsional damping between the rotary table and the drill pipe; c pp —the torsional damping between drill pipes; c pc —the torsional damping between the drill pipe and the drill collar; c cc —the torsional damping between drill collars; c cb —the torsional damping between the upper mass block of the drill collar-positive displacement motor and the lower mass block of the positive displacement motor-bit; T—the torque input by the driving motor to the rotary table; T fb —the frictional torque between the bit and the rock; T ar —the loss damping of the drive system; T t —the output torque of the positive displacement motor; Ma — Axial equivalent mass of the drill string; C a — Axial equivalent damping of the drill string; K a — Axial equivalent stiffness of the drill string; z a — Axial acceleration, axial velocity, and axial displacement of the drill string; Wob — Weight on bit.

[0047] Furthermore, the total axial force W of the positive displacement motor t is:

[0048]

[0049] In the formula, W P — Total gravity of the rotor, universal shaft, drive shaft, and bit of the positive displacement motor; α — Well deviation angle; W P cosα — Axial component of the total weight; pl — Pressure drop; E — Eccentricity; N — Number of motor heads corresponding to the positive displacement motor model; r0 — Equispaced radius coefficient; The pressure drop pl is affected by the torque, T — Dynamic torque at the bit, which consists of the top drive torque and the output torque of the positive displacement motor; i — Ratio of the number of motor heads; D h — Outer diameter of the positive displacement motor housing.

[0050] Step 102: Input drilling parameters, downhole motor parameters, etc., conduct simulation and obtain the dynamic response parameters of the drill string system; From the dynamic response parameters, obtain the necessary parameters for evaluating the severity of the axial vibration of the drill string; The parameters include: axial velocity, maximum axial displacement, minimum axial displacement, average axial displacement, and corresponding cutting depth within a certain time range;

[0051] Step 103: Establish an axial velocity phase trajectory curve graph, and judge the axial movement state of the bit within this time range with the initial cutting depth as the boundary; When the axial displacement is greater than the initial cutting depth, a bit bounce phenomenon occurs; When the axial displacement is less than the initial cutting depth, it indicates that the drill string has not experienced a bit bounce phenomenon;

[0052] Step 104: Calculate the axial vibration index AVS in segments according to the minimum axial displacement within a certain time range;

[0053] The method for calculating the axial vibration index AVS is as follows:

[0054] When the minimum axial displacement Min z is greater than or equal to the initial cutting depth S0, the calculation formula is:

[0055]

[0056] In the formula, Max z represents the maximum axial displacement, Z i represents the axial displacement corresponding to time, S iRepresents the cutting depth corresponding to time, Avg z Represents the average axial displacement;

[0057] When the minimum axial displacement Min z Is less than the initial cutting depth S0, the calculation formula is:

[0058]

[0059] In the formula, Min z Represents the minimum axial displacement, Z i Represents the axial displacement corresponding to time, S i Represents the cutting depth corresponding to time; Avg z Represents the average axial displacement.

[0060] Step 105: According to the calculated axial vibration index AVS, taking 0 as the boundary, AVS less than 0 represents that the drill string has severe axial vibration - bit bounce. The smaller AVS is, the greater the intensity of axial vibration. AVS greater than 0 represents that there is no bit bounce phenomenon. The closer AVS is to 0, the smoother the axial movement of the drill string. The greater AVS is, the more severe the non-bit bounce axial vibration is;

[0061] Step 106: Adjust different bit weights, rotational speeds, pump pressures, displacements, and positive displacement motor models for simulation to obtain AVS under different conditions. Repeat the above steps until AVS is within a reasonable range;

[0062] In a specific implementation, if AVS is less than 0, adjust the bit weight, rotational speed, displacement, pump pressure, and positive displacement motor model, and repeat steps 102 - 106 until AVS is greater than 0 and less than 1. Then it is considered that the drilling parameters and positive displacement motor model at this time are reasonably matched.

[0063] Example Two

[0064] This example combines the drilling data of a 5000m deep well in an oilfield site to specifically introduce the implementation and application of the evaluation and optimization method for the axial severity of the drill string in oil and gas wells as follows:

[0065] The selected drill string parameters are from a deep well in the Shunbei block of the Tarim Oilfield, drilled to a well depth of 5000m.

[0066] Step 1: According to the drill string structure used in the drilling site, based on the spring - lumped mass principle, establish the motion differential equation of the drill string system.

[0067] Special treatment is taken for the positive displacement motor. In the torsional direction, the upper part connecting the positive displacement motor and the drill collar is established as a mass block with the same moment of inertia as the drill collar. The rotational speeds and external forces of the two are the same. The lower part connecting the positive displacement motor and the drill bit is established as a mass block with the same moment of inertia as the drill bit, indicating that the output of the positive displacement motor acts on the drill bit. The middle part is established as the connection body between the two mass blocks, with independent torsional stiffness and torsional damping. In the axial direction, since the length of the positive displacement motor is relatively short, generally 8m - 12m, if the modeling method in the torsional direction is adopted, the axial stiffness and axial damping of the connection body between the mass blocks are relatively large, and it is very likely to cause the simulation results to be distorted. Therefore, the axial direction is simplified to one degree of freedom, and the coupled vibration model considering the multi-degree-of-freedom torsion - single-degree-of-freedom axial of the positive displacement motor is established as follows:

[0068]

[0069] In the formula, the subscript r represents the rotary table mass block; dp1 to dp(i) represent the mass blocks of the first drill pipe to the i-th drill pipe; dc1 to dc(i) represent the mass blocks of the first drill collar to the i-th drill collar; pb represents the positive displacement motor - drill bit mass block; J represents the moment of inertia; θ represents angular acceleration, angular velocity, and angular displacement; k kp — represents the torsional stiffness between the rotary table and the drill pipe; k pp — represents the torsional stiffness between drill pipes; k pc — represents the torsional stiffness between the drill pipe and the drill collar; k cc — represents the torsional stiffness between drill collars; k cb — represents the torsional stiffness between the drill collar - upper part of the positive displacement motor mass block and the lower part of the positive displacement motor - drill bit mass block; c rp — represents the torsional damping between the rotary table and the drill pipe; c pp — represents the torsional damping between drill pipes; c pc — represents the torsional damping between the drill pipe and the drill collar; c cc — represents the torsional damping between drill collars; c cb — represents the torsional damping between the drill collar - upper part of the positive displacement motor mass block and the lower part of the positive displacement motor - drill bit mass block; T represents the torque input by the driving motor to the rotary table; T fb — represents the frictional torque between the drill bit and the rock; T ar — represents the loss damping of the drive system; T t — represents the output torque of the positive displacement motor; M a — represents the axial equivalent mass of the drill string; C a — represents the axial equivalent damping of the drill string; K a — represents the axial equivalent stiffness of the drill string; z a — represents the axial acceleration, axial velocity, and axial displacement of the drill string; Wob represents the weight on bit; T fb The expression is as shown in the following formula:

[0070]

[0071] where k f is the formation contact stiffness, z a is the axial displacement, s0 is the initial cutting depth, n bit is a coefficient related to the bit type, θ b is the angular displacement of the bit, λ is a very small positive integer used to describe the variable in the transition stage, R b is the bit radius, is a dimensionless factor related to the cutting force. The coefficient of friction μ b between rocks is:

[0072]

[0073] where is the angular velocity of the bit, μ sb , μ cb are the static and dynamic coefficients of friction, c1 and c2 are dimensionless coefficients. y c is the average cutting depth:

[0074]

[0075] where ω d is the set rotational speed of the rotary table, ROP is the average rate of penetration, which is related to the weight on bit and the rotational speed, and its empirical expression is:

[0076]

[0077] is the effective radius of the bit:

[0078]

[0079] W b — the axial force on the drill string due to the interaction between the bit and the rock:

[0080]

[0081] W t — the total axial force of the positive displacement motor:

[0082]

[0083] where W P — the total gravity of the rotor, universal joint shaft, drive shaft and bit of the positive displacement motor; α is the well deviation angle; W Pcosα — Axial component of the total weight; pl — Pressure drop; E — Eccentricity; N — Number of motor heads corresponding to the type of positive displacement motor; r0 — Equispaced radius coefficient; The pressure drop pl is affected by the torque, T — Driving torque at the bit, which is composed of the top drive torque and the output torque of the positive displacement motor; i — Ratio of the number of motor heads; D h — Outer diameter of the positive displacement motor housing. When considering the number of stages of the positive displacement motor, according to the design principle of the positive displacement motor, the maximum total pressure drop of the motor generally does not exceed 0.8 times the number of stages of the motor. Therefore, when calculating the output parameters according to the specific type of positive displacement motor, the maximum pressure drop should be limited by the number of stages of the motor.

[0084] The moment of inertia of the drill string is:

[0085]

[0086] In the formula, J dp 、J dc 、J pb — Moments of inertia of the drill pipe, drill collar, and bit; ρ — Density of the drill string material; D p 、d p — Outer and inner diameters of the drill pipe; D c 、d c — Outer and inner diameters of the drill collar; L p — Length of the drill pipe; L c — Length of the drill collar.

[0087] The equivalent torsional stiffness k of the drill string is:

[0088]

[0089] In the formula, G — Shear modulus; L — Length; D — Outer diameter; d — Inner diameter.

[0090]

[0091] In the formula, M — Mass matrix; K — Torsional stiffness matrix; α, β — Rayleigh damping coefficients.

[0092] The equivalent mass M of the drill string is:

[0093]

[0094] In the formula, ρ is the density of the drill string material, L is the length of the drill string, D is the outer diameter of the drill string, and d is the inner diameter of the drill string.

[0095] The equivalent stiffness K a of the drill string is:

[0096]

[0097] In the formula, E is the elastic modulus of the drill string, L is the length of the drill string, D is the outer diameter of the drill string, and d is the inner diameter of the drill string.

[0098] The mass of the drilling fluid is:

[0099]

[0100] In the formula, ρ l is the density of the drilling fluid, L c is the length of the drill collar, c a is the additional mass coefficient of the drilling fluid, D c is the outer diameter of the drill collar, d c is the inner diameter of the drill collar.

[0101] The equivalent damping C of the drill string a is:

[0102]

[0103] In the formula, K is the equivalent stiffness matrix, and a and b are damping coefficients.

[0104] Based on the above formulas, the structural parameters of the drill string in the motion differential equation of the drill string system are calculated, and then the Runge-Kutta 4-5 order method can be used to iteratively solve this non-linear differential equation system.

[0105] Step 2: Input the drilling parameters and the power drill parameters, as shown in Table 1:

[0106] Table 1

[0107]

[0108]

[0109] And calculate the structural parameters of the drill string as: J dp = 42.2852 kg·m 2 ; J dc = 90.568 kg·m 2 ; J pb = 111.71 kg·m 2 ; k rp = 4764 N·m / rad; k pp = 4764 N·m / rad; k pc = 187420 N·m / rad; k cc = 187420 N·m / rad; k cb = 216570 N·m / rad; c rp = 477 N·m·s / rad; c pp = 477 N·m·s / rad; c pc = 919.87 N·m·s / rad; c cc= 919.87 N·m·s / rad; c cb = 239.54 N·m·s / rad; M a = 101240 kg; K a = 187110 N / m; C a = 4935.3 N·s / m.

[0110] The drilling parameters are as follows: the weight on bit is 120 kN, the rotary speed is 75 r / min, the pump pressure is 27 MPa, and the displacement is 38 L / s.

[0111] Step 3: Establish the axial velocity phase trajectory curve graph. As shown, taking the initial cutting depth of -0.001 m as the boundary, judge the axial movement state of the drill bit within this time range: when the axial displacement is greater than the initial cutting depth, drill string jumping occurs; when the axial displacement is less than the initial cutting depth, it indicates that the drill string does not have drill string jumping. Figure 2 As shown, taking the initial cutting depth of -0.001 m as the boundary, judge the axial movement state of the drill bit within this time range: when the axial displacement is greater than the initial cutting depth, drill string jumping occurs; when the axial displacement is less than the initial cutting depth, it indicates that the drill string does not have drill string jumping.

[0112] Under this drill string assembly and parameters, the axial displacement exceeds the initial cutting depth at some moments, indicating that drill string jumping has occurred in the system.

[0113] Step 4: Select the axial displacement and cutting depth of the drill string in the time range of 100 s to 300 s, find the minimum value of the axial displacement, and calculate the axial vibration index AVS (Axial Torsional Severity) in segments;

[0114]

[0115] In the formula, Z i and S i represent the axial displacement and cutting depth corresponding to this moment respectively, Max Z and Min Z represent the maximum and minimum axial displacements respectively, Avg Z represents the average axial displacement, and S0 represents the initial cutting depth.

[0116] The calculated axial vibration index AVS is -3.2843, indicating that drill string jumping has occurred in the drill string and the axial vibration is severe.

[0117] Step 5: Adjust different weights on bit, rotary speeds, pump pressures, displacements, and the types of positive displacement motors for simulation, obtain the AVS under different conditions, and repeat the above steps until the AVS is within a reasonable range;

[0118] Adjust the weight on bit to 180 kN, the rotational speed to 60 r / min, the pump pressure to 25 MPa, and the displacement to 36 L / s. Select the screw drill model as H7LZ216X7.0 - 4G. Repeat the above steps and calculate the AVS to be -1.9215. Then continue to adjust the weight on bit to 200 kN, the rotational speed to 45 r / min, keep the pump pressure unchanged, adjust the displacement to 34 L / s, and keep the screw drill model unchanged. Repeat the above steps and calculate the AVS to be 0.083. Compared with before, the axial vibration has been greatly alleviated, and these parameters can be used as the drilling parameters during actual drilling.

[0119] The method for evaluating the severity of drill string axial vibration proposed in this embodiment takes into account the influence of cutting depth and torsional vibration, quantifies the severity of drill string axial vibration, and establishes an axial-torsional coupling simulation model that considers the influence of the positive displacement motor. The axial force of the positive displacement motor takes into account the influence of factors such as drill string size, hydraulic pressure drop, and pump pressure. According to the simulation model and evaluation method, it is possible to judge the rationality of drilling parameters and the use of the positive displacement motor, and then optimize the parameters and adjust the drilling strategy. Finally, appropriate weight on bit, rotational speed, pump pressure, displacement, positive displacement motor, etc. are proposed to ensure less axial vibration during the drilling process and achieve safe and fast drilling.

[0120] Embodiment III

[0121] The present invention also provides a computer device, including a memory, a processor, and a computer program stored on the memory, and the processor executes the computer program to implement the steps.

[0122] Embodiment IV

[0123] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the steps of any one of the above methods.

[0124] Embodiment V

[0125] The present invention also provides a computer program product, including a computer program, and when the computer program is executed by a processor, it implements the steps of the above method.

[0126] The above is only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for evaluating and optimizing the severity of axial vibration of a drill string in an oil and gas well, characterized in that: The following steps are involved: Obtain drill string structural parameters and power drilling tool parameters, and build a simulation model of axial vibration of oil and gas well drill string; Obtaining necessary parameters for evaluating the axial vibration of the drill string based on the simulation model, wherein the necessary parameters include maximum axial displacement, minimum axial displacement, average axial displacement and cutting depth; Based on the relationship between the minimum axial displacement and the initial cutting depth, calculating the axial vibration index in sections; Based on the axial vibration index, evaluating the severity of the axial vibration of the drill string; The drilling parameters and screw model are adjusted, and the process of obtaining the axial vibration index is repeated until the axial vibration index is within a preset range, and reasonable matching drilling parameters and screw model are obtained, thereby optimizing the axial vibration of the drill string.

2. The method according to claim 1, characterized in that The simulation model of the axial vibration of the oil and gas well drill string is: Wherein, subscript r is the turntable mass block; dp1~dp(i) is the mass block from the first drill pipe to the i-th drill pipe; dc1~dc(i) is the mass block from the first drill collar to the i-th drill collar; pb is the screw rotor-drill bit mass block; J is the moment of inertia; θ are angular acceleration, angular velocity, and angular displacement respectively; k kp is the torsional stiffness between the rotary table and the drill pipe; k pp is the torsional stiffness between the drill pipes; k pc is the torsional stiffness between the drill pipe and the drill collar; k cc is the torsional stiffness between drill collars; k cb is the torsional stiffness between the drill collar-upper screw mass block and the lower screw-drill bit mass block; c rp is the torsional damping between the rotary table and the drill pipe; c pp is the torsional damping between the drill pipes; c pc is the torsional damping between the drill pipe and the drill collar; c cc is the torsional damping between drill collars; c cb is the torsional damping between the drill collar-upper mass block of the screw and the lower part of the screw-drill bit mass block; T is the torque input to the rotary table by the drive motor; T fb is the friction torque between the drill bit and the rock; T ar is the loss damping of the drive system; T t is the output torque of the screw drill; M a is the equivalent axial mass of the drill string; C a is the equivalent axial damping of the drill string; K a is the equivalent axial stiffness of the drill string; z a are the axial acceleration, axial velocity and axial displacement of the drill string respectively; Wob is the bit pressure; W t is the total axial force of the screw drill; W b It is the axial force exerted on the drill string by the interaction between the drill bit and the rock.

3. The method according to claim 2, characterized in that The total axial force W of the screw drill t for: Where W P is the total weight of the screw drilling tool rotor, universal shaft, transmission shaft and drill bit; α is the well inclination angle; W P cosα is the axial component of the total weight; E is the eccentricity; N is the number of motor heads corresponding to the screw drill model; r0 is the equidistant radius coefficient; T is the dynamic torque at the drill bit; i is the ratio of motor heads; D h P is the diameter of the screw drill housing; h is the distance between the screw drill bit housing.

4. The method according to claim 1, characterized in that: The process of obtaining the necessary parameters for evaluating the axial vibration of the drill string based on the simulation model includes: Different drilling parameters and power drill tool parameters are obtained and input into the simulation model for simulation to obtain dynamic response parameters of the drill string system; from the dynamic response parameters, necessary parameters for evaluating the severity of the axial vibration of the drill string are obtained; the necessary parameters for evaluating the severity of the axial vibration of the drill string also include maximum axial displacement, minimum axial displacement, average axial displacement and cutting depth.

5. The method according to claim 4, characterized in that When the minimum axial displacement is greater than or equal to the initial cutting depth, the calculation formula for the axial vibration index is: When the minimum axial displacement is less than the initial cutting depth, the calculation formula for the axial vibration index is: Where Max z Indicates the maximum axial displacement, Min z Indicates the minimum axial displacement, Z i represents the axial displacement corresponding to time, S i Indicates the cutting depth corresponding to time, Avg z represents the average axial displacement.

6. The method according to claim 1, characterized in that It also includes establishing an axial velocity phase trajectory curve diagram, with the initial cutting depth as the boundary. When the real-time axial displacement is greater than the initial cutting depth, drill jumping occurs; when the real-time axial displacement is less than the initial cutting depth, the drill string does not experience drill jumping.

7. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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