Hydraulic impact drilling mechanical specific energy calculation method based on stress wave theory

Abstract

A method for calculating mechanical specific energy of hydraulic percussion drilling based on a stress wave theory relates to the technical field of drilling engineering and comprises the following steps: acquiring working parameters of a hydraulic percussion drilling system, calculating actual speed of a hydraulic drill bit and actual stress acting on rocks during working by combining energy conversion of acting of an impactor and drilling fluid influence, and calculating the mechanical specific energy of the hydraulic percussion drilling system according to the actual speed and the actual stress. The actual stress acting on the rock is considered, a calculation model of the total specific energy consumed by the rock in unit volume is established, and the total specific energy in the whole drilling process is accurately evaluated through the calculation model and is applied to real-time optimization control of drilling parameters. According to the high-frequency hydraulic impactor drilling mechanical specific energy calculation method provided based on the stress wave theory, a drilling fluid-piston-drill bit-rock stress wave propagation model considering the drilling fluid influence is established, and the calculation precision of the MSE under the drilling fluid-related impact drilling working condition is improved; and a more reliable data basis is provided for MSE-based drilling parameter optimization, drilling tool state monitoring and lithology identification.

Description

Technical Field

[0001] This invention relates to the field of drilling engineering technology, specifically to a method for calculating the specific energy of hydraulic impact drilling machinery based on stress wave theory. Background Technology

[0002] As oil drilling technology expands into deeper, ultra-deep, and unconventional resource areas, the challenges are also increasing. Deep and ultra-deep formations contain harder rocks, and their strength increases significantly under high confining pressure. Meanwhile, traditional rotary drilling methods suffer from low drilling rates and severe drill bit wear. Against this backdrop, percussion drilling technology has demonstrated excellent adaptability in drilling operations in deep formations. Percussion drilling can provide greater rock-breaking energy, thereby significantly improving drilling rates.

[0003] Mechanical specific energy (MSE), a key indicator for assessing drill string load transfer efficiency, reflects the real-time mechanical energy consumption during drilling. Analyzing changes in MSE helps engineers adjust drilling strategies promptly to improve drilling efficiency. Currently, most MSE calculations use the Teale method; however, this method has limitations. The Teale method ignores the influence of impact loads in percussion drilling, considering only torque and drilling pressure, failing to accurately reflect the instantaneous stress on the drill bit during impact. Therefore, in high-frequency, high-energy percussion drilling, its calculation results often contain significant errors. Summary of the Invention

[0004] In view of this, this invention proposes a method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory. Through a detailed analysis of the entire impact drilling process, from the force exerted by the piston on the drill bit to the impact between the drill bit and the rock, and combining the impact stress wave theory, a new method for calculating the mechanical specific energy of impact drilling is proposed. This method considers the stress wave propagation process in the drill string and incorporates relevant factors of the drilling fluid, reflecting phenomena such as energy dissipation (damping attenuation) and reflection, thus improving the accuracy of the calculation.

[0005] To solve at least one of the above-mentioned technical problems, the present invention provides a method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory, comprising the following steps: Step S1: Obtain the operating parameters of the hydraulic impact drilling system; Step S2: Considering the energy conversion of the work done by the impactor and the influence of drilling fluid, calculate the actual speed of the hydraulic drill bit and the actual stress acting on the rock during operation; Step S3: Considering the actual stress acting on the rock, establish a calculation model for the total specific energy consumed per unit volume of rock; Step S4: Accurately evaluate the total specific energy of the entire drilling process through a calculation model and apply it to the real-time optimization and control of drilling parameters.

[0006] The technical effects achieved by this invention are: This invention presents a method for calculating the specific energy (MSE) of drilling machinery using high-frequency hydraulic impactors based on stress wave theory. By analyzing the energy transferred from the drilling fluid to the impactor, a stress wave propagation model considering the influence of the drilling fluid on the drilling fluid-piston-drill bit-rock process is established. In operation, the MSE is divided into axial, tangential, and impact components, improving the calculation accuracy of the MSE under impact drilling conditions involving drilling fluid. This more accurately reflects downhole rock breaking efficiency and provides a more reliable data foundation for MSE-based drilling parameter optimization, drill string condition monitoring, and lithology identification. Furthermore, the method has a clear principle and can be integrated into downhole real-time processing systems as well as used for post-processing analysis in surface drilling software. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced 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 from these drawings without creative effort.

[0008] Figure 1 This is an overall flowchart of the present invention; Figure 2 The result of MSE calculation in this embodiment of the invention. Detailed Implementation

[0009] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0010] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0011] See Figure 1 A method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory includes the following steps: Step S1: Obtain the operating parameters of the hydraulic impact drilling system; The working parameters include the loading frequency of the impactor, piston mass, drill bit mass, drill bit density, drill bit wave velocity, number of drill bit teeth, drill bit diameter, drill tooth radius of curvature, rock sample density, and rock sample wave velocity. These parameters can be obtained through indoor tests or field extraction.

[0012] Step S2: Considering the energy conversion of the work done by the impactor and the influence of drilling fluid, calculate the actual speed of the hydraulic drill bit and the actual stress acting on the rock during operation; In high-frequency, high-energy hydraulic impact drilling, the interaction between the piston, drill bit, and rock is the transmission of one-dimensional impact stress waves. During the interaction between the drill bit and the rock, stress wave reflection and transmission occur, and the transmitted stress wave is the energy absorbed by the rock.

[0013] Based on this, the actual operating speed of the hydraulic drill bit is calculated using the following formula: In the formula, v 20 This indicates the initial velocity of the hydraulic drill bit; E impact This represents the impact energy generated on the drill bit by a single movement of the impactor piston. or 1 indicates the energy efficiency of the impactor piston impacting the drill bit in a single motion; m 2 indicates the drill bit quality; The working principle of the impactor is that the piston is pushed by the drilling fluid to do work, and then the piston moves to hit the drill bit, and finally the drill bit impacts the rock. Therefore, the propagation of stress waves needs to be calculated from the impact work of the piston.

[0014] The impact energy generated by a single movement of the impactor piston on the drill bit E impact The calculation method is shown in the following formula: in, m 1 represents the piston mass; v 1 represents the speed of a single piston movement; Energy efficiency of the impactor piston during a single stroke impacting the drill bit or The calculation method for 1 is shown in the following formula: When the piston performs its action, it will be subject to the resistance and compression of the drilling fluid. Considering the piston's own weight, the piston's single-stroke velocity... v The calculation method for 1 is shown in the following formula: In the formula, r Indicates the density of the drilling fluid;Q Indicates flow rate; C d Indicates the pressure coefficient; A d Indicates the flow channel area; g Represents gravitational acceleration; f Indicates the loading frequency; The calculation method for the actual stress exerted on the rock by the hydraulic drill bit is shown in the following formula: In the formula, F This represents the actual stress exerted on the rock by the hydraulic drill bit; N Indicates the number of drill teeth; R 1 represents the radius of curvature of the drill tooth; s T This represents the transmitted stress exerted on the rock by the hydraulic drill bit; The incident stress from the drill bit impact on the rock is transmitted and reflected through the rock. The transmitted and reflected stresses are related to the wave impedance of the material. Therefore, the transmitted stress exerted on the rock by the hydraulic drill bit can be calculated from the impact energy of the drill bit. s T The calculation method is shown in the following formula: In the formula, r rock Indicates the density of the rock; c rock The wave velocity of a rock represents the speed at which mechanical waves propagate in that type of rock within that stratum. r bit Indicates the density of the drill bit; c bit The wave velocity of the drill bit represents the speed at which mechanical waves propagate within the drill bit. s bit This indicates the incident stress exerted by the drill bit on the rock; r bit c bit This is the wave impedance of the drill bit.

[0015] According to Newton's second law, the stress at a single point of contact between the drill bit and the rock... s bit The calculation method is shown in the following formula: Step S3: Considering the actual stress acting on the rock, establish a calculation model for the total specific energy consumed per unit volume of rock; The calculation model for the total specific energy consumed per unit volume of rock is shown in the following formula: In the formula, MSE corrected This represents the total specific energy consumed per unit volume of rock at the current well depth; WOB represents the drilling pressure at the current well depth; ROP represents the mechanical drilling rate at the current well depth; RPM represents the rotational speed at the current well depth; and T represents the drill bit torque at the current well depth.

[0016] Drill bit cutting area A b The calculation method is shown in the following formula: In the formula, D represents the diameter of the drill bit.

[0017] The mechanical specific energy of high-frequency, high-energy hydraulic impact drilling can be divided into the crushing work provided by the drill string's drilling pressure, the shearing work provided by the drill bit's rotary cutting, and the impact work provided by the high-frequency, high-energy hydraulic impactor. Therefore, the formula for calculating the mechanical specific energy of high-frequency hydraulic impact drilling is derived as follows: MSE corrected = MSE WOB + MSE TQ + MSE impact The crushing work is calculated according to the following formula: For shearing work, we have: The formula for calculating impact energy is: Adding the three together, we get the above formula for calculating the mechanical specific energy of high-frequency hydraulic impact drilling.

[0018] Step S4: Accurately evaluate the total specific energy of the entire drilling process through a calculation model and apply it to the real-time optimization and control of drilling parameters.

[0019] According to the MSE calculation formula, the parameters can be changed to make the MSE variable. The main optimization methods are to change the drilling fluid density and flow rate, change the drilling pressure and rotation speed, and change the number of drill bit teeth and radius of curvature, so as to further adjust the MSE corresponding to the actual working conditions to a better state.

[0020] Example The above method was used to calculate the total specific energy (MSE) consumed per unit volume of rock during drilling in a well in an oil field. The following data were collected for the calculation: The flow channel area of ​​the impactor is 18.38 cm². 2 The loading frequency is 20Hz, the pressure coefficient is 0.1, the piston mass is 40kg, the drill bit mass is 50kg, the drill bit wave velocity is 6546m / s, and the density is 14950kg / cm³. 3The drill bit has a radius of curvature of 6 mm, 24 drill teeth, a rock wave velocity of 4497 ​​m / s, and a density of 2620 kg / cm³. 3 The drilling fluid density is 2100 kg / cm³. 3 Displacement 30L / s.

[0021] Substituting the data into the formula above, we obtain the following calculation results: 6.16m / s Based on this, during the drilling process, parameters such as well depth, drilling pressure, rotational speed, drilling fluid displacement, drilling fluid density, and mechanical drilling speed can be collected from logging data. Then, the calculation results of these parameters are substituted into the total specific energy calculation model for the total specific energy consumed per unit volume of rock to calculate the relationship between total specific energy and well depth, such as... Figure 2 As shown, the method in this invention can accurately determine the variation of MSE with well depth, providing higher quality data for drilling parameter optimization and drill string condition monitoring.

[0022] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory, characterized in that, Includes the following steps: Step S1: Obtain the operating parameters of the hydraulic impact drilling system; Step S2: Considering the energy conversion of the work done by the impactor and the influence of drilling fluid, calculate the actual speed of the hydraulic drill bit and the actual stress acting on the rock during operation; Step S3: Considering the actual stress acting on the rock, establish a calculation model for the total specific energy consumed per unit volume of rock; Step S4: Accurately evaluate the total specific energy of the entire drilling process through a calculation model and apply it to the real-time optimization and control of drilling parameters.

2. The method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory according to claim 1, characterized in that: The operating parameters of the hydraulic impact drilling system include the impactor loading frequency, flow channel area, piston mass, drill bit mass, drill bit density, drill bit wave velocity, number of drill bit teeth, drill bit diameter, drill tooth curvature radius, rock sample density, and rock sample wave velocity.

3. The method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory according to claim 1, characterized in that: The actual speed calculation method for the hydraulic drill bit in step S2 is shown in the following formula: In the formula, v 20 This indicates the initial velocity of the hydraulic drill bit; E impact This represents the impact energy generated on the drill bit by a single movement of the impactor piston. η 1 indicates the energy efficiency of the impactor piston impacting the drill bit in a single motion; m 2 indicates the drill bit quality; The impact energy generated by a single movement of the impactor piston on the drill bit E impact The calculation method is shown in the following formula: in, m 1 represents the piston mass; v 1 represents the speed of a single piston movement; Energy efficiency of the impactor piston during a single stroke impacting the drill bit η The calculation method for 1 is shown in the following formula: Piston's single-stroke speed v The calculation method for 1 is shown in the following formula: In the formula, ρ Indicates the density of the drilling fluid; Q Indicates flow rate; C d Indicates the pressure coefficient; A d Indicates the flow channel area; g Represents gravitational acceleration; f Indicates the loading frequency.

4. The method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory according to claim 3, characterized in that: The calculation method for the actual stress exerted on the rock by the hydraulic drill bit in step S2 is shown in the following formula: In the formula, F This represents the actual stress exerted on the rock by the hydraulic drill bit; N Indicates the number of drill teeth; R 1 represents the radius of curvature of the drill tooth; σ T This represents the transmitted stress exerted on the rock by the hydraulic drill bit; Among them, the transmitted stress exerted on the rock by the hydraulic drill bit σ T The calculation method is shown in the following formula: In the formula, ρ rock Indicates the density of the rock; c rock Indicates the wave velocity of the rock; ρ bit Indicates the density of the drill bit; c bit Indicates the wave velocity of the drill bit; σ bit This indicates the incident stress exerted by the drill bit on the rock; Stress at a single point of contact between the drill bit and the rock σ bit The calculation method is shown in the following formula: 。 5. The method for calculating the mechanical specific energy of hydraulic impact drilling based on stress wave theory according to claim 4, characterized in that: The calculation model for the total specific energy consumed per unit volume of rock in step S3 is shown in the following formula: In the formula, MSE corrected This represents the total specific energy consumed per unit volume of rock at the current well depth; WOB represents the weight of drill bit at the current well depth; ROP represents the rate of drilling at the current well depth; RPM represents the rotational speed at the current well depth; and T represents the bit torque at the current well depth. Drill bit cutting area A b The calculation method is shown in the following formula: In the formula, D represents the diameter of the drill bit.

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