Dynamic design method for personalized drill bit for complex difficult-to-drill formation

Abstract

A design method for a personalized drill bit for a complex difficult-to-drill formation includes: S1, acquiring rock drillability indexes of a drilled formation; S2, performing digital simulation analysis of rock breaking of bit teeth and a composite rock breaking experiment of a ring gear and a drill bit, and establishing a mechanical model of the rock interaction at the bottom of a well; S3, establishing an integrated dynamics model of drill string-drill bit-rock system coupling; S4, designing a tooth shape, a tooth distribution density, a crown shape and a gauge protection structure for rock mechanics properties of a complex difficult-to-drill formation; S5, optimizing bit nozzle and hydraulic structure parameters by using the computational fluid dynamics theory and the numerical simulation method; S6. optimizing a manufacturing process of the drill bit by using the tooth material decarburization strengthening technology, the high-strength bit body material technology and the special tooth-shaped tooth technology.

Claims

1. A dynamic design method for a personalized drill bit for a complex difficult-to-drill formation, comprising the following steps: S1, simulating a high temperature and high pressure environment under a well, performing a rock mechanics property test and analysis on the complex difficult-to-drill formation, acquiring rock drillability indexes of a drilled formation, and performing a rock drillability analysis based on a rock debris microhardness experiment and logging data; S2, performing a digital simulation analysis of rock breaking of bit teeth by conducting a composite rock breaking experiment for a ring gear and a drill bit, and establishing a mechanical model of different bit structures, non-uniform tooth distribution methods, tooth sizes, and different downhole rock interactions; S3, discretizing a drill string into a unit by using a finite element method and an energy method, in consideration of influences of parameters of a drill string structure, a drill string vibration, a well depth, and a hole diameter on a bit-rock interaction, and establishing a coupled integrated dynamics model of a drill string-drill bit-rock system by taking the drill bit as one unit at a bottommost end of the drill string; S4, designing a tooth shape, a tooth distribution density, a crown shape, and a gauge protection structure based on different shapes of the bit teeth and the non-uniform tooth distribution methods for impacting, scraping, and gauge protection functions of different parts of the bit teeth, wherein the different tooth shapes include a conical shape, a spherical shape, and a wedged shape, and the non-uniform tooth distribution methods include an unequally-spaced distribution method, a twisted distribution method, and a spiral tooth distribution method; S5, analyzing a flow field distribution of the drill bit under different drilling pressures, rotation speeds, and mud flows by using a computational fluid dynamics theory and a numerical simulation method, and optimizing parameters of a bit nozzle and a hydraulic structure; S6, forming the personalized drill bit by optimizing a manufacturing process of the drill bit by using a tooth material decarburization strengthening technology, a high-strength bit body material technology, and a special tooth-shaped tooth technology based on the rock drillability analysis in S1, the mechanical model in S2, the coupled integrated dynamics model in S3, the tooth shape, the tooth distribution density, the crown shape, and the gauge protection structure in S4, and the parameters of the bit nozzle and the hydraulic structure in S5.

2. The dynamic design method for the personalized drill bit for the complex difficult-to-drill formation according to claim 1, wherein when the rock drillability analysis is performed based on the rock debris microhardness experiment in the step S1, rock debris is collected in different well sections, a microhardness test is performed, and a drillable profile of an analyzed well section is established by using a relationship model of the a rock drillability and the microhardness; the rock mechanics analysis of a whole well section and a difficulty of drilling are judged according to the logging data, and the drillable profile of a whole well is established.

3. The dynamic design method for the personalized drill bit for the complex difficult-to-drill formation according to claim 1, wherein the mechanical model in the step S2 is as follows: $F_z\left(t\right)=\underset{i,j,k}{.Math.}{F}_{\mathrm{vijk}\left(t\right)}^{*}{F}_{\mathrm{lx}}\left(t\right)=\underset{i,j,k}{.Math.}{F}_{\mathrm{lijk}\left(t\right)}^{*}\cos \left(\pi +{\alpha }_{\mathrm{ijk}\left(t\right)}\right)F_{\mathrm{ly}}\left(t\right)=\underset{i,j,k}{.Math.}{F}_{\mathrm{lijk}\left(t\right)}^{*}\sin \left(\pi +{\alpha }_{\mathrm{ijk}\left(t\right)}\right)M_R\left(t\right)=\underset{i,j,k}{.Math.}{l}_{\mathrm{xijk}\left(t\right)}{f}_{\mathrm{lxijk}\left(t\right)}^{*}+\underset{i,j,k}{.Math.}{l}_{\mathrm{yijk}\left(t\right)}{f}_{\mathrm{lyijk}\left(t\right)}^{*}$ where F.sub.z(t) is a longitudinal reaction force of the rock received by the drill bit at any time, in a unit of N; F*.sub.vijk(t) is a longitudinal reaction force received by the bit teeth of the drill bit at the time of reaching a bottom, in a unit of N; F.sub.lx(t) is a decomposition of a transverse force received by the drill bit at any time in an X direction, in a unit of N; F.sub.ly(t) is a decomposition of a transverse force received by the drill bit at any time in a Y direction, in a unit of N; F*.sub.lijk(t) is a transverse force received by the bit teeth of the drill bit at the time of reaching the bottom, in a unit of N; α.sub.ijk(t) is a working angle of the bit teeth of the drill bit at the time of reaching the bottom, in a unit of degree; M.sub.R(t) is a torsional time of the drill bit interacting with the rock at any time, in a unit of N.Math.m; f*.sub.lxijk(t) is a decomposition of a transverse force received by the bit teeth of the drill bit at any time of reaching the bottom in the X direction, in a unit of N; f*.sub.lyijk(t) is a decomposition of a transverse force received by the bit teeth of the drill bit at any time of reaching the bottom in the Y direction, in a unit of N; l.sub.xijk(t) is a distance between the bit teeth of the drill bit at the time of reaching the bottom and the X direction, in a unit of m; l.sub.yijk(t) is a distance between the bit teeth of the drill bit at the time of reaching the bottom and the Y direction, in a unit of m.

4. The dynamic design method for the personalized drill bit for the complex difficult-to-drill formation according to claim 1, wherein the coupled integrated dynamics model of the drill string-drill bit-rock system in the step S3 is as follows: $M^e{U}^{e^{″}}+C^e{U}^{e^{\prime }}+K_L^e{U}^e+K_N^e{U}^e=F^e{C}^e=C_D^e+C_N^e{K}^e=K_L^e+K_N^e$ After assembling a unit model, an integrated dynamic model of the drill string-drill bit-rock system is: MU″+CU′+KU=F, where, M.sup.e is a unit mass matrix; C.sup.e is a unit damping matrix; C.sub.D.sup.e is a unit dissipative damping matrix; C.sub.N.sup.e is a unit non-dissipative property damping matrix; K.sup.e is a unit stiffness matrix; K.sub.L.sup.e is a linear part of the unit stiffness matrix; K.sub.N.sup.e is a non-linear part of the unit stiffness matrix; F.sup.e is a unit load array; U.sup.e″ is a unit acceleration array; U.sup.e′ is a unit speed array; U.sup.e is a unit displacement array; M is an integrated mass matrix; C is an integrated damping matrix; K is an integrated stiffness matrix; F is an integrated load array; U″ is an acceleration array of the drill string-drill bit-rock system; U′ is a speed array of the drill string-drill bit-rock system; U is a displacement array of the drill string-drill bit-rock system.

5. The dynamic design method for the personalized drill bit for the complex difficult-to-drill formation according to claim 1, wherein the rock drillability indexes in the step S1 include a rock hardness, a strength, a Poisson's ratio, and a ground stress.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a design flow of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(2) The present invention will be further described below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the followings. As shown in FIG. 1, a dynamic design method for a personalized drill bit for a complex difficult-to-drill formation comprises the following steps:

(3) S1, simulating a high temperature and high pressure environment under the shaft, performing rock mechanics property testing and analysis on the complex difficult-to-drill formation, acquiring rock drillability indexes of the drilled formation, and meanwhile performing rock drillability analysis based on a debris microhardness experiment and logging data;

(4) S2, performing digital simulation analysis of rock breaking of bit teeth and a composite rock breaking experiment of a ring gear and a drill bit, and establishing a mechanical model of different bit structures, tooth distribution methods, tooth sizes and different downhole rock interactions;

(5) S3, discretizing a drill string into n unit by using a finite element method and an energy method, in consideration of the influences of the drill string structure, drill string vibration, well depth and hole diameter parameters on the bit-rock interaction, and establishing a coupled integrated dynamics model of drill string-drill bit-rock system by taking the drill bit as one unit at the bottommost end of the drill string;

(6) S4, designing a tooth shape, a tooth distribution density, a crown shape and a gauge protection structure for rock mechanics properties of the complex difficult-to-drill formation according to impacting, scraping and gauge protection functions of teeth in different parts of the drill bit, by using teeth of different tooth shapes, i.e., a conical shape, a spherical shape and a wedged shape and non-uniform tooth distribution methods, i.e., unequally-spaced, twisted, and spiral tooth distribution methods;

(7) S5, analyzing the flow field distribution of the drill bit under different drilling pressures, rotation speeds and mud flows by using the computational fluid dynamics theory and the numerical simulation method, and optimizing bit nozzle and hydraulic structure parameters;

(8) S6, optimizing a manufacturing process of the drill bit by using the tooth material decarburization strengthening technology, the high-strength bit body material technology and the special tooth-shaped tooth technology;

(9) S7, forming the personalized drill bit for the complex difficult-to-drill formation.

(10) Further, when the rock drillability analysis is performed based on the rock debris microhardness experiment in the step S1, the rock debris is collected in different well sections, the microhardness test is performed, and a drillable profile of the analyzed well section is established by using a relationship model of the rock drillability and the microhardness; the rock mechanics analysis of the whole well section and the difficulty of drilling are judged according to logging data, and the drillable profile of the whole well is established.

(11) Further, the mechanical model in the step S2 is as follows:

(12) $F_z\left(t\right)=\underset{i,j,k}{.Math.}{F}_{\mathrm{vijk}\left(t\right)}^{*}{F}_{\mathrm{lx}}\left(t\right)=\underset{i,j,k}{.Math.}{F}_{\mathrm{lijk}\left(t\right)}^{*}\cos \left(\pi +{\alpha }_{\mathrm{ijk}\left(t\right)}\right)F_{\mathrm{ly}}\left(t\right)=\underset{i,j,k}{.Math.}{F}_{\mathrm{lijk}\left(t\right)}^{*}\sin \left(\pi +{\alpha }_{\mathrm{ijk}\left(t\right)}\right)M_R\left(t\right)=\underset{i,j,k}{.Math.}{l}_{\mathrm{xijk}\left(t\right)}{f}_{\mathrm{lxijk}\left(t\right)}^{*}+\underset{i,j,k}{.Math.}{l}_{\mathrm{yijk}\left(t\right)}{f}_{\mathrm{lyijk}\left(t\right)}^{*}$

(13) in which, F.sub.z(t) is a longitudinal reaction force of the rock received by the drill bit at any time, in a unit of N; F*.sub.vijk(t) is the longitudinal reaction force received by the tooth of the drill bit at the time of reaching the bottom, in a unit of N; F.sub.lx(t) is the decomposition of a transverse force received by the drill bit at any time in an X direction, in a unit of N; F.sub.ly(t) is the decomposition of a transverse force received by the drill bit at any time in a Y direction, in a unit of N; F*.sub.lijk(t) is a transverse force received by the tooth of the drill bit at the time of reaching the bottom, in a unit of N; α.sub.ijk(t) is a working angle of the tooth of the drill bit at the time of reaching the bottom, in a unit of (°); M.sub.R(t) torsional time of the drill bit interacting with the rock at any time, in a unit of N.Math.m; f*.sub.lxijk(t) is the decomposition of a transverse force received by the tooth of the drill bit at any time of reaching the bottom in a X direction, in a unit of N; f*.sub.lyijk(t) is the decomposition of a transverse force received by the tooth of the drill bit at any time of reaching the bottom in a Y direction, in a unit of N; l.sub.xijk(t) is a distance between the tooth of the drill bit at the time of reaching the bottom and the X axis, in a unit of m; l.sub.yijk(t) is a distance between the tooth of the drill bit at the time of reaching the bottom and the Y axis, in a unit of m.

(14) Further, the coupled integrated dynamics model of drill string-drill bit-rock system is as follows:

(15) $M^e{U}^{e^{″}}+C^e{U}^{e^{\prime }}+K_L^e{U}^e+K_N^e{U}^e=F^e{M}^e=\left[\begin{array}{cc}{M}_{11\left(6\times 6\right)}^e& M_{12\left(6\times 6\right)}^e\\ M_{21\left(6\times 6\right)}^e& M_{22\left(6\times 6\right)}^e\end{array}\right]C^e=C_D^e+C_N^e{K}^e=K_L^e+K_N^e{F}^e=\left[\begin{array}{cc}{f}_{1\left(1\times 6\right)}^e& f_{2\left(1\times 6\right)}^e\end{array}\right]$

(16) After assembling a unit model, an integrated dynamic model of the system is obtained: MU″+CU′+KU=F,

(17) in which, M.sup.e is a unit mass matrix; C.sup.e is a unit damping matrix; C.sub.D.sup.e is a unit dissipative damping matrix; C.sub.N.sup.e is a unit non-dissipative property damping matrix; K.sup.e is a unit stiffness matrix; K.sub.L.sup.e is a linear part of the stiffness matrix; K.sub.N.sup.e is a non-linear part of the stiffness matrix; F.sup.e is a unit load array; U.sup.e″ is a unit acceleration array; U.sup.e′ is a unit speed array; U.sup.e is a unit displacement array; M is an integrated mass matrix; C is an integrated damping matrix; K is an integrated stiffness matrix; F is an integrated load array; U″ is an acceleration array of the system; U′ is a speed array of the system; U is a displacement array of the system.

(18) The above content is only a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention by using the above-mentioned technical contents, or modify the technical solutions as equivalent embodiments of equivalent changes without departing from the scope of the technical solutions of the present invention. Therefore, any modifications, equivalent changes, and modifications made to the above embodiments in accordance with the techniques of the present invention are within the protection scope of the present technical solutions.