Optimization method for one-time drilling of tight gas well

Abstract

The invention discloses a tight gas well one-trip drilling optimization method, which comprises the steps of feasibility analysis: analyzing one-trip drilling big data based on an entropy weight method and a Pearson correlation analysis method, determining the influence degree of different factors on one-trip drilling, and obtaining the range of the influence of each index on the one-trip drilling feasibility difficulty degree; a three-dimensional finite element calculation model of the'one-time drilling 'rotary steering system is established based on a three-dimensional solid modeling method, relevant parameters of all types of rotary steering systems are compared, and a preferable rotary steering system is determined; matching tool analysis: simulating matching tools of the rotary steering system based on three-dimensional simulation software, carrying out a simulation test, comparing simulation use effects of various types of matching tools, and determining a preferred matching tool; and drilling parameter analysis: establishing a drilling speed model based on a preferred rotary steering system and a preferred matching tool, simplifying the drilling speed model into binary processing, and determining preferred drilling parameters. According to the invention, the global or local minimum drilling cost can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of shale gas and tight oil and gas exploitation, and particularly to an optimization method for "one-trip drilling" of tight gas wells. Background Art

[0002] In recent years, with the successive development of shale gas and tight oil and gas resources in China, there has been an urgent need for "one-trip drilling" technology in drilling operations. "One-trip drilling" refers to a drilling technology that uses a single bit and a set of downhole drill string assemblies to complete all the footage of one drilling interval or one well section in one run into the well. It has the advantages of improving the mechanical drilling rate, shortening the drilling cycle, and reducing the drilling cost, which greatly promotes the efficient development of unconventional oil and gas resources.

[0003] For example, in the specific Jinhuajia - Qiulin block in central Sichuan, the tight gas reservoir is a typical braided river deposit with extremely strong heterogeneity, large horizontal and vertical differences in the reservoir, and great difficulty in trajectory control in the reservoir section. The closing distance of well A of the completed well is large, resulting in frequent trajectory adjustment and serious directional drag, which restricts the improvement of drilling speed and efficiency. According to the statistical analysis of the horizontal section length and closing distance of the completed wells, it is found that: the maximum target displacement ahead of the completed well is 1134m, the minimum is 305m, and the average is 540m, while the maximum horizontal section length of the completed well is only 1152m, the minimum is 601m, and the average is 1065m.

[0004] How to organically combine the optimal selection analysis of supporting tools and the optimization of drilling parameters for tight gas wells under the idea of "one-trip drilling" and carry out the feasibility theoretical analysis of the efficient development of tight gas wells is worthy of research and breakthrough. Summary of the Invention

[0005] To solve the above problems, the present invention proposes an optimization method for "one-trip drilling" of tight gas wells. First, conduct a feasibility study on "one-trip drilling" for tight gas. Considering the characteristics of "one-trip drilling" big data, preferentially select the entropy weight method and the Pearson correlation analysis method to clarify the influence degree of different factors on "one-trip drilling", and obtain the range of the difficulty degree of each index affecting the feasibility of "one-trip drilling"; for the key technologies of "one-trip drilling", focus on comparing the inclination building capabilities of various types of rotary steerable systems, and conduct the optimal selection analysis of the rotary steerable system; then, based on the optimal selection result of the rotary steerable system, conduct the simulation optimal selection of the supporting "one-trip drilling" tools; finally, use the optimal relationship equation and the weight-on-bit and rotary speed values of the selected type of bit, combined with the well depth and formation hardness, and adopt the optimal weight-on-bit and rotary speed combination of constant rotary speed and optimal weight-on-bit or constant weight-on-bit and optimal rotary speed, then the global or local minimum drilling cost can be achieved.

[0006] Specifically, the technical solution adopted by the present invention is as follows:

[0007] An optimization method for "one-trip drilling" of tight gas wells, comprising the following steps:

[0008] S1. Feasibility analysis: Analyze the big data of "one - trip drilling" based on the entropy weight method and Pearson correlation analysis method, clarify the influence degree of different factors on "one - trip drilling", and obtain the range of the influence degree of each index on the feasibility and difficulty of "one - trip drilling";

[0009] S2. Rotary steerable system analysis: Establish a three - dimensional finite - element calculation model of the "one - trip drilling" rotary steerable system based on the three - dimensional solid modeling method, compare the relevant parameters of various types of rotary steerable systems, and determine the preferred rotary steerable system;

[0010] S3. Matching tool analysis: Simulate the matching tools of the rotary steerable system based on three - dimensional simulation software and conduct simulation tests, compare the simulation usage effects of various types of matching tools, and determine the preferred matching tools;

[0011] S4. Drilling parameter analysis: Establish a drilling rate model based on the preferred rotary steerable system and the preferred matching tools and simplify it into a binary treatment to determine the preferred drilling parameters.

[0012] Further, step S1 includes the following sub - steps:

[0013] S101. Determine the column mean of the data set:

[0014]

[0015] In the formula: X is the average value of the independent variable attribute, Y is the average value of the dependent variable attribute corresponding to the independent variable attribute, X i is the value of the i - th group of independent variable attributes, Y i is the value of the i - th group of dependent variable attributes, and n is the number of statistically obtained data combinations;

[0016] S102. Calculate the covariance matrix of the sample:

[0017]

[0018] S103. Calculate the Pearson correlation coefficient:

[0019]

[0020] In the formula: S X is the standard deviation belonging to the independent variable X, and S Y is the standard deviation belonging to the dependent variable Y;

[0021] S104. Introduce the entropy weight method to calculate the weights of different factors:

[0022]

[0023] In the formula: X ij is the standard - form expression of the evaluation matrix composed of each evaluation index; e jis the information entropy of any evaluation matrix. The larger the entropy value, the greater the impact on the overall drilling parameter combination, and vice versa; h j is the inverse of information entropy, with a value range from 0 to 1 and dimensionless; w j is the weight occupied by the information entropy of each evaluation matrix.

[0024] Further, in step S2, establishing a three-dimensional finite element calculation model of the "one-trip" rotary steerable system based on the three-dimensional solid modeling method includes: regarding the rotary steerable system as an integral and isotropic continuous homogeneous body, simplifying the stabilizer structure into a cylinder with equal diameter; dividing the mesh units of the three-dimensional finite element calculation model of each type of rotary steerable system, and refining the mesh of the stress concentration part.

[0025] Further, in step S2, the relevant parameters of the rotary steerable system include the build rate parameters, and the build rate parameters include the build rate and the ultimate build rate.

[0026] Further, the calculation method of the build rate of the rotary steerable system includes the three-point circle determination method in the geometric prediction method, and the calculation model of the build rate includes:

[0027]

[0028] In the formula: BUR is the build rate, α is the ultimate bending angle, L1 is the distance from the upper stabilizer to the lower stabilizer, and L2 is the distance from the lower stabilizer to the lower end face of the rotary steerable system.

[0029] Further, the calculation method of the ultimate build rate of the rotary steerable system includes obtaining the relationship between the Young's modulus of the rock and the ultimate build rate based on the fitting method, and the calculation model of the ultimate build rate includes:

[0030] K = 0.805E 0.0447 ×K or

[0031] In the formula: K is the ultimate build rate considering the influence of rock strength, E is the Young's modulus of the rock, and K or is the ultimate build rate in a rigid wellbore.

[0032] Further, in step S3, the supporting tools of the rotary steerable system include a drill bit, a positive displacement motor, and a cuttings bed removal tool. Among them, the analysis method of the positive displacement motor includes: simulating and depicting the three-dimensional rendering of the positive displacement motor based on three-dimensional simulation software, conducting indoor simulation tests, and analyzing the on-site use effects of various types of positive displacement motors in combination with the golden section method to determine the positive displacement motor.

[0033] Further, in step S3, the analysis method of the cuttings bed cleaning tool includes: performing a simulation test on the cuttings bed cleaning process based on CFD simulation, analyzing the effects of cuttings bed cleaning tools with different structural shapes, and thereby determining the preferred cuttings bed cleaning tool.

[0034] Further, in step S4, the drilling parameters include mechanical parameters and hydraulic parameters. The mechanical parameters include the weight on bit and the rotary speed during drilling, and the hydraulic parameters include the pump pressure and the displacement.

[0035] Further, step S4 includes the following sub-steps:

[0036] S401. Under the conditions of full bottomhole purification and near-balanced drilling, simplify the penetration rate model into a binary treatment;

[0037] S402. Select the cost equation as the drilling objective function, obtain the weight on bit and the rotary speed at the lowest cost under unconstrained conditions, match the highest mechanical penetration rate, and obtain the optimal relationship equation of the weight on bit and rotary speed for bit tooth wear and bearing wear;

[0038] S403. Utilize the optimal relationship equation of the weight on bit and rotary speed and the weight on bit and rotary speed values of the selected type of bit, and then according to the well depth, the drillability or hardness of the formation rock, adopt the optimal combination of the weight on bit with a fixed rotary speed or the rotary speed with a fixed weight on bit to achieve the global or local lowest drilling cost.

[0039] The beneficial effects of the present invention are as follows:

[0040] Based on the entropy weight method and the Pearson correlation analysis method, the present invention conducts a feasibility study on the influencing factors of tight gas, obtains the range of the difficulty level of each index affecting the feasibility of "one-trip drilling", and is applicable to the promotion and application in other blocks. At the same time, it summarizes the changing trend of the limit build-up rate of the rotary steerable system under different working conditions with the working conditions, organically combines the optimal selection analysis of the supporting tools with the optimization of the drilling parameters of tight gas wells, and obtains the drilling parameter modeling analysis and strengthening method under the conditions of "one-trip drilling" for tight gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flowchart of an optimization method for "one-trip drilling" of a tight gas well according to an embodiment of the present invention;

[0042] Figure 2 is a schematic diagram of the weights and contribution rates of each influencing factor for "one-trip drilling";

[0043] Figure 3 is a set diagram of the build-up rate prediction method of the "three-point circle method";

[0044] Figure 4 is a comparison diagram of the PDC drillability grade value and the roller bit drillability grade value;

[0045] Figure 5 This is a three-dimensional perspective rendering of the internal structure of the screw drill. DETAILED DESCRIPTION

[0046] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0047] like Figure 1 As shown, this embodiment provides a method for optimizing the "one-trip drilling" of a tight gas well, comprising the following steps:

[0048] S1. Feasibility analysis: Based on the entropy weight method and Pearson correlation analysis method, the big data of "one-trip drilling" is analyzed to clarify the influence of different factors on "one-trip drilling" and obtain the range of each indicator affecting the feasibility of "one-trip drilling";

[0049] S2. Analysis of rotary steerable system: A three-dimensional finite element calculation model of the "one-trip drilling" rotary steerable system was established based on the three-dimensional solid modeling method, and the relevant parameters of various types of rotary steerable systems were compared to determine the optimal rotary steerable system;

[0050] S3. Supporting tool analysis: Simulate the supporting tools of the rotary guide system based on 3D simulation software and conduct simulation tests to compare the simulated use effects of various types of supporting tools and determine the preferred supporting tools;

[0051] S4. Drilling parameter analysis: Based on the preferred rotary steerable system and the preferred supporting tools, a drilling speed model is established and simplified into a binary process to determine the preferred drilling parameters.

[0052] This embodiment now takes the tight gas reservoir in the Jinhua-Qiulin block in central Sichuan as an example to specifically illustrate the implementation steps of the "one-trip drilling" optimization method for tight gas wells in this embodiment.

[0053] 1. Feasibility Analysis

[0054] In order to achieve one-trip drilling, the well site selection comprehensively considers the ground conditions and the distribution of underground rivers, minimizes the distance to the target, reduces the useless footage, shortens the closing distance, reduces the length of the second well section, reduces the footage of one-trip drilling, and improves the success rate of one-trip drilling. Therefore, based on the current status of tight gas well trajectory research, a feasibility study on "one-trip drilling" in the target work area was carried out.

[0055] A further technical solution is that, considering the characteristics of the big data of "one-run drilling" in central Sichuan, such as large dataset dimension, data needing to be recoded, and unclear correlation between parameters, the entropy weight-Pearson (Pearson correlation analysis) method is preferentially selected for the weight analysis of the influencing factors of "one-run drilling" to clarify the influence degree of different factors on "one-run drilling". The specific analysis process is as follows:

[0056] S101. Determine the column mean of the dataset:

[0057]

[0058] In the formula: X is the average value of the independent variable attribute, Y is the average value of the dependent variable attribute corresponding to the independent variable attribute, X i is the value of the independent variable attribute in the i-th group, Y i is the value of the dependent variable attribute in the i-th group, and n is the number of data combinations counted.

[0059] It should be noted that assuming the statistical data of the actual drilling depth at any time as the independent variable, then the mechanical drilling rate corresponding to the actual drilling depth at that time is the dependent variable. Among the actual drilling data statistically collected on-site, there are many data combinations with this corresponding relationship. According to this logical relationship, an independent variable-dependent variable data combination with this corresponding relationship is established, and X and Y are used to represent them respectively.

[0060] S102. Calculate the covariance matrix of the sample:

[0061]

[0062] S103. Calculate the Pearson correlation coefficient:

[0063]

[0064] In the formula: S X is the standard deviation belonging to the independent variable X, S Y is the standard deviation belonging to the dependent variable Y.

[0065] S104. Introduce the entropy weight method to calculate the weights of different factors:

[0066]

[0067] In the formula: X ij is the standard form expression of the evaluation matrix composed of each evaluation index; e j is the information entropy of any evaluation matrix. The larger the entropy value, the greater the influence on the overall drilling parameter combination, and vice versa; h j is the inverse of the information entropy, with a value range from 0 to 1 and dimensionless; w j is the weight occupied by the information entropy of each evaluation matrix.

[0068] It should be noted that in the actual programming and calculation process, the evaluation index can be directly substituted into the calculation result using the Pearson correlation coefficient, or the calculation result can be matrixed, the value of the highest-order sub-determinant can be obtained, and then substituted into the calculation.

[0069] Referring to Table 1 and combining with the actual drilling situation of tight gas in central Sichuan, the main influencing factors of "one-trip drilling" for tight gas in central Sichuan can be clarified by the entropy weight - Pearson big data analysis results: well section length, rotary steerable system, positive displacement motor, and bit.

[0070] Table 1 - Basic situation of completed wells with "one-trip drilling" for tight gas in central Sichuan

[0071]

[0072] From Figure 2 it can be seen that among all the influencing factors of "one-trip drilling", the well section length is the most important for the success of one-trip drilling, with a contribution rate of 39.7%; while for other key tools, such as the rotary steerable system, positive displacement motor, and bit, the contribution rates account for 25.4%, 15.9%, and 9.5% respectively. Based on the entropy weight - Pearson method, a feasibility study on the influencing factors of tight gas in central Sichuan can obtain the range of the difficulty level of each index affecting the feasibility of "one-trip drilling":

[0073] (1) When the closure distance at point A is less than 350 m, the build rate of the rotary steerable system is greater than 10° / 30 m, the working time of the rotary steerable system and the positive displacement motor is greater than 300 h, and the bit footage is greater than 3500 m, one-trip drilling is easy to succeed;

[0074] (2) When the closure distance at point A is in the range of 350 - 700 m, the build rate of the rotary steerable system is in the range of 8 - 10° / 30 m, the working time of the rotary steerable system and the positive displacement motor is in the range of 250 - 300 h, and the bit footage is in the range of 2900 - 3500 m, the difficulty of one-trip drilling is medium;

[0075] (3) When the closure distance at point A is greater than 700 m, the build rate of the rotary steerable system is less than 8° / 30 m, the working time of the rotary steerable system and the positive displacement motor is less than 250 h, and the bit footage is less than 2900 m, one-trip drilling is difficult to succeed.

[0076] II. Analysis of Rotary Steerable System

[0077] The horizontal section length of the completed wells in the tight gas area of central Sichuan is about 1000 m, the longest closure distance at point A in the horizontal section exceeds 1000 m, and the average exceeds 600 m. In order to achieve "one-trip drilling", the well location selection should shorten the closure distance as much as possible, and preferably select the well location with a closure distance at point A less than 350 m and a section length of the second spud less than 2900 m. Therefore, for the key technology of "one-trip drilling", the build-up capabilities of various types of rotary steerable systems are compared, and the optimization analysis of the rotary steerable system is carried out.

[0078] The rotary steerable system mainly consists of a surface monitoring system, a two-way communication system, a measurement-while-drilling system, a rotary steerable tool (i.e., the core of rotary steerable drilling, mainly including a measurement and control mechanism, a bias mechanism, an actuator, etc. According to the control instructions, it guides the drill bit to drill along the planned wellbore trajectory direction), etc. Its basic types are as follows:

[0079] ① Pointing type (the bias mechanism generates a bias according to the "displacement working mode", causing the drill bit to generate an inclination angle relative to the wellbore axis to achieve steering);

[0080] ② Push-the-bit type (under the action of the far-bit fulcrum, the bias mechanism at the near-bit position generates a bias force by pounding the wellbore wall according to the "force working mode" to achieve steering);

[0081] ③ Hybrid type (integrates the "force working mode" and the "displacement working mode" to cause the drill bit to be biased and achieve steering).

[0082] Referring to Table 2, the rotary steerable system can also be classified into a static bias type and a dynamic bias type rotary steerable system according to the working mode of the steering actuator. The so-called static bias type means that during the steering operation, the bias mechanism does not rotate with the drill string and maintains a stable steering force in a certain fixed direction. The so-called dynamic bias type means that during the steering operation, the bias mechanism rotates with the drill string and provides a periodic steering force in a certain fixed direction. Due to the different action principles and working modes of each rotary steerable system, different steering effects and performance characteristics will also be presented.

[0083] Table 2 - Advantages and Disadvantages of Rotary Steering under Different Working Modes

[0084]

[0085]

[0086] A further technical solution is to use the "three-point circle method" in the geometric prediction method to predict the build rate of the rotary steerable system. As Figure 3 shown, its calculation model is as follows:

[0087]

[0088] In the formula: BUR - build rate, (° / 100 ft); α - ultimate bending angle, (°);

[0089] L1 - distance from the upper stabilizer to the lower stabilizer, ft;

[0090] L2 - distance from the lower stabilizer to the lower end face of the rotary steerable system, ft.

[0091] Taking the high-temperature rotary steerable system as the object, a three-dimensional finite element calculation model is established based on three-dimensional solid modeling technology: It is defined that the material of the rotary steerable system is uniformly P550, its elastic modulus is 2.1×10 5 MPa, the Poisson's ratio is 0.3, the yield strength is 965 MPa, the tensile strength is 1035 MPa, and the safety factor including impact and vibration loads generally takes 2.5 - 3.5. For safety considerations, 3.5 can be taken; the allowable stress of the material of the calculated rotary steerable system is 275.7 MPa.

[0092] For the convenience of simplifying the calculation model, the following assumptions are made: ① The rotary steerable system is regarded as a whole; ② The stabilizer structure is simplified to a cylinder with equal diameter; ③ The rotary steerable system is regarded as an isotropic, continuous and homogeneous body. The mesh cells of the three-dimensional finite element model of various types of rotary steerable systems are divided, and the meshes of the stress concentration parts are refined.

[0093] For the convenience of directly establishing the relationship between the Young's modulus of rock and the ultimate build rate of CG STEER, the relationship between the Young's modulus of rock and the ultimate build rate is obtained by fitting as:

[0094] K = 0.805E 0.0447 ×K or

[0095] In the formula: K is the ultimate build rate of the rotary steerable considering the influence of rock strength, ° / 30m; E is the Young's modulus of rock, GPa; K or is the ultimate build rate in a rigid wellbore, ° / 30m.

[0096] According to the changing trend of the ultimate build rate of the rotary steerable system under different working conditions with the working conditions, it is found that the weight on bit and the working torque have a greater impact on the ultimate build rate of the steerable system. When the weight on bit is constant, as the working torque increases, the ultimate build rate gradually decreases; when the working torque is constant, as the weight on bit increases, the ultimate build rate gradually decreases. Considering the influence of the weight on bit and torque, according to the designed curvature of the wellbore, the working condition parameters should be matched with the selected rotary steerable system to ensure that the well deviation meets the requirements. From the simulation results and data analysis, the lower limit of the Young's modulus value at the optimal build point of the existing domestic rotary steerable is 30 GPa.

[0097] Therefore, the preferred results of the existing domestic rotary steerable systems are: It is recommended to give priority to using the dynamic hybrid rotary steerable system, which has a high build rate, up to 15° / 30m, and has low requirements for formation strength; secondly, it is recommended to use the static push - type rotary steerable system, with a build rate of 8 - 10° / 30m, and it is required that the Young's modulus of the formation at the build point is greater than 30 GPa.

[0098] III. Analysis of supporting tools

[0099] In addition to the rotary steerable system, the key tools for "one-trip drilling" of tight gas also involve high-efficiency PDC bits (polycrystalline diamond compact bits), long-life positive displacement motors, swirl sand cleaners, etc. At present, the "one-trip drilling" technology for unconventional oil and gas horizontal wells in China is still in the experimental stage as a whole, and it cannot fully meet the requirements of "one-trip drilling" in terms of the life of key tools and the supporting use of rotary steerable systems. Therefore, it is necessary to carry out the optimization analysis of relevant tools.

[0100] A further technical solution is to classify the rock drillability according to the standard of "SY / T5426-2016 Determination and Classification Method of Rock Drillability", use a rock drillability testing machine to carry out micro-bit drilling tests, evaluate the drillability of the bit on the tight gas reservoir rock (as Figure 4 shown), and optimize the supporting high-efficiency PDC bit.

[0101] Precautions for PDC bit selection: Bits with relatively larger main cutting teeth (preferably 19 mm main cutting teeth), relatively fewer blade wings, and more uniform water eye distribution should be selected.

[0102] A further technical solution is to use software such as SolidWorks to simulate and depict the three-dimensional rendering of the positive displacement motor (as Figure 5 shown), conduct indoor simulation tests, and optimize various types of positive displacement motors based on the on-site use effects in combination with the golden section method.

[0103] The main structure of the positive displacement motor is: bypass valve, anti-drop, positive displacement motor, universal joint and drive shaft assembly. The working principle is: when the positive displacement motor works, the high-pressure drilling fluid flows through the internal closed cavity, applies a force on the internal screw surface, drives the screw to rotate, thereby converting the hydraulic energy of the drilling fluid into mechanical energy, driving the bit to rotate, and completing the rock-breaking drilling.

[0104] According to the analysis results of the use effects of the positive displacement motors in the second open hole section of a certain work area in central Sichuan, more types of positive displacement motors are used in the second open hole section than in the first open hole section. The outer diameter of the second open hole positive displacement motor is 172 mm, and the maximum water pressure drop of the bit is mostly 7.0 MPa. The average drilling speed of all positive displacement motors used in the second open hole section is 14.62 m / h, the maximum drilling speed is 62.07 m / h, the average footage is 644 m, and the maximum single-bit footage is 2158 m. In an oily environment, the stator rubber of conventional positive displacement motors is prone to oil dissolution and high-temperature failure, resulting in low output efficiency and short life of the positive displacement motor. The equal-wall-thickness positive displacement motor is less affected by the internal pressure, and has good compressive capacity and sealing performance.

[0105] Precautions for high-performance positive displacement motor selection: It is preferred to select an equal-wall-thickness positive displacement motor, and select a Φ172 / 165 mm equal-wall-thickness straight positive displacement motor with low speed, large torque, 7 / 8 head large lead, and high-hardness rubber.

[0106] A further technical solution is to use CFD simulation to conduct a simulation test on the process of removing the cuttings bed in order to analyze the effects of cuttings bed removal tools with different structural shapes, and to optimize the supporting swirl sand cleaners.

[0107] According to the simulation results of the annulus flow field of the swirl sand cleaner by CFD, due to the existence of the V-shaped groove, the flow velocity vector of the flow field shows a swirl distribution. The inlet velocity increases rapidly from 2 m / s to 4.3 m / s within a very short axial stroke. When the swirl sand cleaner tool approaches the cuttings bed, the pressure loss at the bottom edge is the largest, so its pressure is the lowest, and the pressure drop at the high edge of the tool is smaller and the pressure is the largest. When the rotating fluid moves along the V-shaped groove, a certain swirl is also generated, which is extremely beneficial for carrying cuttings and cleaning. In actual situations, the swirl sand cleaner has been cumulatively applied 9 well times. After use, there is no thick cuttings bed in the build-up section, the wellbore is cleaned well, and the casing is run in smoothly.

[0108] Precautions for optimizing the swirl sand cleaner: Based on the statistics of the application of the swirl sand cleaner in the work area, it is preferred to install a V-type swirl sand cleaner every 150 - 200 m in the high-angle well section (well inclination angle greater than 45°) and the horizontal section.

[0109] IV. Drilling Parameter Analysis

[0110] Drilling parameters mainly include mechanical parameters and hydraulic parameters. Mechanical parameters refer to the weight on bit and rotary speed during drilling, and hydraulic parameters refer to the pump pressure and displacement. Reasonable mechanical parameters and hydraulic parameters can improve the rock-breaking efficiency and extend the service life of the bit, which play a positive role in efficient and fast drilling.

[0111] A further technical solution is to simplify the drilling rate model into a binary treatment assuming full purification at the bottom of the well and near-balanced drilling conditions. The mechanical parameter equations involved are:

[0112]

[0113] In the formula: V m — Mechanical drilling rate, m / h; W — Weight on bit, KN; N — Rotary speed, rpm;

[0114] d — Weight-on-bit exponent, dimensionless; λ — Rotary-speed exponent, dimensionless; K — Calculation coefficient;

[0115] C t — Tooth wear coefficient; C B — Bearing wear coefficient; D b — Bit size, mm;

[0116] The drilling objective is to seek the highest mechanical drilling rate at the lowest cost, that is, the objective function selects the cost equation:

[0117]

[0118] Where: C—direct cost per meter, yuan / m; B C —bit cost, yuan;

[0119] R C —drill rig operation cost, yuan / h; T b —pure drilling time, h;

[0120] T r —normal tripping, connection and circulation time, h; F—penetration, m.

[0121] Let B C +R C T r =C0, F=V m T b , the objective function mainly based on tooth wear can be obtained:

[0122]

[0123] The objective function mainly based on bearing wear is:

[0124]

[0125] The objective function formula C is a convex function. When other drilling conditions are certain, under unconstrained conditions, the weight on bit and rotary speed for the lowest cost can be obtained, matching the highest rate of penetration, and the optimal relationship equation between the weight on bit and rotary speed for tooth wear and bearing wear can be obtained:

[0126] Soft formation:

[0127] W = 0.0058D b N

[0128] Medium-hard formation:

[0129] W = (0.00710~0.00772)D b N

[0130] Hard formation:

[0131] W = 0.0435D b N

[0132] Using the optimal relationship equation and the W×N value of the selected type of bit, and then according to the well depth and the drillability (or hardness) of the formation rock, adopting the optimal combination of weight on bit and rotary speed with a fixed rotary speed (rotary table gear) to optimize the weight on bit, or a fixed weight on bit to optimize the rotary speed, the global or local lowest drilling cost can be achieved.

[0133] For strongly abrasive formations where PDC bits are used for rock breaking, to enhance hydraulic parameter-assisted rock breaking, it is necessary to increase the jet impact force when the drilling fluid flows through the bit nozzles. For example, when operating at the maximum bit hydraulic power, the pump displacement is approximately 22 L / s, and when operating at the maximum jet impact force, the pump displacement is 28 L / s. Most drilling teams use ZJ40 or ZJ50 drills, and the maximum pump displacement achievable in horizontal wells is 30 L / s to 35 L / s, keeping the bit working under the maximum possible jet impact force.

[0134] Based on the above modeling analysis, the drilling parameters are strengthened as follows: relatively large WOB is used to increase the ROP, and relatively high RPM and pump displacement are used to assist in increasing the ROP. The recommended drill string assemblies and parameters for the second spud are shown in Table 3: For the first run, an imported LWD + near-bit / far-end azimuth gamma + bent screw + hydraulic oscillator are used for drilling; for the second run, a rotary steerable tool + screw + cyclone sand cleaner are used for drilling.

[0135] Table 3 - Drill String Assembly and Parameters for Wellbore (215.9 mm)

[0136]

[0137]

[0138] It should be noted that for the foregoing method embodiments, for the sake of simplicity of description, they are expressed as a series of action combinations. However, those skilled in the art should be aware that the present application is not limited by the described action sequence, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present application.

Claims

1. An optimization method for "one-trip drilling" in tight gas wells, characterized in that, It includes the following steps: S1. Feasibility analysis: Analyze the big data of "one-trip drilling" based on the entropy weight method and Pearson correlation analysis method, clarify the influence degree of different factors on "one-trip drilling", and obtain the range of the influence degree of each index on the feasibility of "one-trip drilling". S2. Rotary steerable system analysis: Establish a three-dimensional finite element calculation model of the "one-trip drilling" rotary steerable system based on the three-dimensional solid modeling method, compare the relevant parameters of various types of rotary steerable systems, and determine the optimal rotary steerable system. S3. Analysis of supporting tools: Simulate the supporting tools of the rotary steerable system based on the three-dimensional simulation software and conduct simulation tests, compare the simulation use effects of various types of supporting tools, and determine the optimal supporting tools. S4. Drilling parameter analysis: Establish a drilling rate model based on the optimal rotary steerable system and the optimal supporting tools and simplify it into binary processing to determine the optimal drilling parameters.

2. The optimization method for "one-trip drilling" in tight gas wells according to claim 1, characterized in that, Step S1 includes the following sub-steps: S101. Determine the column mean of the data set. Wherein: is the average value of the independent variable attributes, is the average value of the dependent variable attributes corresponding to the independent variable attributes, X i is the value of the independent variable attributes of the i-th group, Y i is the value of the dependent variable attributes of the i-th group, and n is the number of data combinations counted; S102. Calculate the covariance matrix of the samples. S103. Calculate the Pearson correlation coefficient. Where: S X is the standard deviation belonging to the independent variable X, and S Y is the standard deviation belonging to the dependent variable Y; S104. Introduce the entropy weight method to calculate the weights of different factors. Where: X ij is the standard form expression of the evaluation matrix composed of each evaluation index; e j is the information entropy of any evaluation matrix. The larger the entropy value, the greater the impact on the overall drilling parameter combination, and vice versa; h j is the inverse of the information entropy, with a value range from 0 to 1 and dimensionless; w j is the weight occupied by the information entropy of each evaluation matrix.

3. The optimization method for "one-trip drilling" in tight gas wells according to claim 1, characterized in that, In step S2, establishing a three-dimensional finite element calculation model of the "one-trip drilling" rotary steerable system based on the three-dimensional solid modeling method includes: regarding the rotary steerable system as an integral and isotropic continuous homogeneous body, simplifying the stabilizer structure into a cylinder with equal diameter; dividing the mesh units of the three-dimensional finite element calculation models of various types of rotary steerable systems, and refining the mesh of the stress concentration part.

4. The optimization method for "one-trip drilling" in tight gas wells according to claim 1, characterized in that, In step S2, the relevant parameters of the rotary steerable system include the build rate parameters, and the build rate parameters include the build rate and the ultimate build rate.

5. The optimization method for "one-trip drilling" in tight gas wells according to claim 4, characterized in that, The calculation method of the build rate of the rotary steerable system includes the three-point circle determination method in the geometric prediction method, and the calculation model of the build rate includes: In the formula: BUR is the build rate, α is the ultimate bending angle, L1 is the distance from the upper stabilizer to the lower stabilizer, and L2 is the distance from the lower stabilizer to the lower end face of the rotary steerable system.

6. The optimization method for "one-trip drilling" in tight gas wells according to claim 4, characterized in that, The calculation method of the ultimate build rate of the rotary steerable system includes obtaining the relationship between the Young's modulus of the rock and the ultimate build rate based on the fitting method, and the calculation model of the ultimate build rate includes: K = 0.805E 0.0447 ×K or Where: K is the ultimate build rate considering the influence of rock strength, E is the Young's modulus of the rock, and K or is the ultimate build rate for a rigid wellbore.

7. The optimization method for "one-trip drilling" in tight gas wells according to claim 1, characterized in that, In step S3, the supporting tools of the rotary steerable system include the bit, the positive displacement motor, and the cuttings bed cleaning tool. Among them, the analysis method of the positive displacement motor includes: simulating and depicting the three-dimensional rendering of the positive displacement motor based on the three-dimensional simulation software, conducting indoor simulation tests, and analyzing the on-site use effects of various types of positive displacement motors in combination with the golden section method to determine the positive displacement motor.

8. The optimization method for "one-trip drilling" in tight gas wells according to claim 7, characterized in that, In step S3, the analysis method of the cuttings bed cleaning tool includes: conducting a simulation test on the cuttings bed cleaning process based on CFD simulation, analyzing the effects of cuttings bed cleaning tools with different structural shapes, and thus determining the optimal cuttings bed cleaning tool.

9. An optimization method for "one-trip drilling" of tight gas wells according to claim 1, characterized in that, In step S4, the drilling parameters include mechanical parameters and hydraulic parameters. The mechanical parameters include the weight on bit and the rotary speed during drilling, and the hydraulic parameters include the pump pressure and the displacement.

10. An optimization method for "one-trip drilling" of tight gas wells according to claim 9, characterized in that, Step S4 includes the following sub-steps: S401. Under the conditions of full bottom hole cleaning and near-balanced drilling, simplify the drilling rate model into binary processing. S402. Select the cost equation as the drilling objective function, obtain the weight on bit and rotary speed at the lowest cost under unconstrained conditions, match the highest rate of penetration, and obtain the optimal relationship equation between the weight on bit and rotary speed for bit tooth wear and bearing wear; S403. Utilize the optimal relationship equation between the weight on bit and rotary speed and the weight on bit and rotary speed values of the selected type of bit, and then, based on the well depth, drillability or hardness of the formation rock, adopt the optimal weight on bit and rotary speed combination of constant rotary speed with optimized weight on bit or constant weight on bit with optimized rotary speed, so as to achieve the global or local lowest drilling cost.

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