CN108708710B - Method for reducing probability of drill bit burying caused by well wall dropping block - Google Patents
Method for reducing probability of drill bit burying caused by well wall dropping block Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 238000005553 drilling Methods 0.000 claims abstract description 105
- 238000009434 installation Methods 0.000 claims description 53
- 238000013016 damping Methods 0.000 claims description 44
- 239000006096 absorbing agent Substances 0.000 claims description 37
- 239000011435 rock Substances 0.000 claims description 36
- 238000010521 absorption reaction Methods 0.000 claims description 32
- 238000004088 simulation Methods 0.000 claims description 32
- 238000004364 calculation method Methods 0.000 claims description 21
- 230000009467 reduction Effects 0.000 claims description 18
- 238000009933 burial Methods 0.000 claims description 11
- 238000005094 computer simulation Methods 0.000 claims description 4
- 230000005540 biological transmission Effects 0.000 abstract description 13
- 238000009966 trimming Methods 0.000 abstract description 4
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- 238000006243 chemical reaction Methods 0.000 description 7
- 238000011160 research Methods 0.000 description 6
- 230000036571 hydration Effects 0.000 description 5
- 230000001687 destabilization Effects 0.000 description 4
- 230000003116 impacting effect Effects 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000006073 displacement reaction Methods 0.000 description 3
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 210000002445 nipple Anatomy 0.000 description 2
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- 238000004901 spalling Methods 0.000 description 2
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- 230000009286 beneficial effect Effects 0.000 description 1
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B44/00—Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
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- E—FIXED CONSTRUCTIONS
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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Abstract
The invention discloses a method for reducing the probability of drill bit burying caused by well wall dropping, and provides a method for reducing the vibration strength of a lower drilling tool by installing a special vibration-reducing and vibration-absorbing tool and obtaining a uniform well diameter by reducing the well diameter expansion rate by using a well wall trimming reamer from the novel view point of drill string vibration and well wall flatness. The method combining the two measures can effectively reduce the fatal influence on the stability of the well wall caused by the fact that the drill string collides the well wall due to the vibration of the drill string, relieve the difficult problem of drill bit burying caused by the falling of the well wall block and reduce the occurrence probability of the problem, and simultaneously can reduce friction resistance, promote the transmission of drilling pressure, lower a sleeve and the like. The method is an effective measure for multiple purposes, and can provide important guarantee for safe and efficient exploitation of oil and gas reservoirs.
Description
Technical Field
The invention relates to the technical field of petroleum and natural gas drilling, in particular to a method for reducing the probability of drill bit burying caused by well wall dropping under the drilling working condition that the vibration of a drill string reaches a medium or strong level.
Background
The condition that the drilling tool is buried by rock debris or buried by borehole wall collapses, quicksand and the like in a borehole and cannot rotate and lift, and drilling fluid cannot circulate is called buried drilling. The buried drilling is one of serious accidents in the drilling engineering, the buried drilling accident can bring great economic loss to the drilling engineering, and if the buried drilling is not treated properly, the buried drilling also has the risk of losing drilling tools and scrapping well bores; therefore, the occurrence of a buried drilling accident should be avoided as much as possible.
The buried drilling accident is mainly caused by the collapse of the well wall, and the reason for the collapse of the well wall can be mainly summarized into two aspects: firstly, hydration reaction, in particular physical and chemical reaction between the shale and the drilling fluid; and the other is mechanical factors including the impact of the drill string on the well wall, the difference of the mechanical properties of the rock, the redistribution of the stress around the well hole and the like. The hydration reaction of rock is the key point of long-term concern of the well wall stability problem research, most scholars consider that the rock water swelling is the main factor causing the destabilization and collapse of the well wall, and a great deal of related research is carried out in this respect, and the destabilization problem of the well wall is mainly controlled by adjusting the density and the composition of the drilling fluid.
In the drilling process, the vibration of the drill string can reach a medium or strong level, so that the drill string impacting against the well wall caused by the vibration of the drill string is an important factor causing the well wall instability or the well diameter expansion to be not negligible, but no effective prevention method aiming at the well wall instability caused by the drill string impacting against the well wall caused by the vibration of the drill string exists at present.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for reducing the probability of drill bit burial caused by well wall dropping, and from the novel perspective of drill string vibration and well wall flatness, aiming at the condition that the vibration of a drill string reaches a medium or strong grade, the method provides the optimized design of a downhole drill string, installs a special vibration reduction and vibration absorber to reduce the vibration strength of a lower drilling tool, reduces a well wall trimming reamer to obtain a uniform well diameter, and relieves the problem of drill bit burial caused by the well wall dropping.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for reducing the incidence of bit burial due to wall sloughing, the method comprising the steps of:
the method comprises the following steps: establishing a dynamic simulation model of a whole-well drill column system to be drilled according to drilling parameters, a drilling tool assembly, drill bit structural parameters and rock parameters to be drilled;
step two: adding a vibration reduction and absorption tool into the drilling tool assembly of the simulation model;
step three: in the simulation model, adjusting the installation position and the working parameters of the vibration-damping and vibration-absorbing tool, respectively carrying out simulation calculation aiming at different installation positions and working parameters, taking the vibration intensity of the lower drilling tool as an index, and carrying out comparison and selection on the calculation result, wherein when the vibration intensity is minimum, the corresponding installation position and the working parameters of the vibration-damping and vibration-absorbing tool are the optimal installation position and the optimal working parameters;
step four: carrying out actual drilling tool assembly installation according to the optimal installation position and working parameters of the vibration reduction and absorption tool calculated in the third step, and simultaneously connecting a reamer above the drill bit to obtain an actual drilling tool assembly;
step five: and (5) performing drilling operation on the well to be drilled according to the actual drilling tool combination to finish drilling.
Because the underreamer is used for trimming the well wall, the underreamer is directly connected and installed on the drill bit, and the installation position is fixed, so that the open hole well wall can be trimmed in the most timely mode. Because if a drill string is also connected between the underreamer and the drill bit, this drill string will always be in the untrimmed section of the wellbore, which has a relatively high risk of wall clashing. In addition, in the simulation calculation, the direct influence on the vibration itself is not large compared with when the vibration reduction and absorption tool is selected, and therefore, the reamer may not be added in the simulation.
Further, in the first step, CAD software is adopted to establish a geometric model comprising a drill string, a drill bit and rock, and CAE software is adopted to establish a simulation model.
Further, the simulation calculation uses the Abaqus/Explicit software.
Further, the underreamer is coupled to the drill bit and positioned above the drill bit. The reamer can be used for reaming and repairing the well wall together with the drill bit in the drilling process, so that the problem that the well wall is unstable due to the fact that the well wall is irregular and is easy to collide with a drill column is avoided. The reamer can be an eccentric reamer, a bicentric reamer, a concentric reamer and the like.
Further, the vibration-damping and vibration-absorbing tool is a combination of a vibration damper, a vibration-absorbing short section and a centralizer. The vibration condition of the simulation drill string can be freely combined, for example, a vibration absorber and a centralizer are selected, a vibration absorbing short section and the centralizer are selected, and the vibration absorber, the vibration absorbing short section and the centralizer are combined. The vibration reduction and absorption tool can reduce the vibration of the drill string during drilling as much as possible, and reduce the possibility of drilling-drop accidents caused by the instability of the well wall due to the collision of the drill string with the well wall caused by vibration.
The vibration-damping and vibration-absorbing tool comprises a vibration damper and a centralizer, the position of the centralizer is set to be unchanged during simulation calculation, comparison and selection are performed according to the installation positions and working parameters of different vibration dampers, and the position and the working parameters of the vibration damper when the drill string vibrates minimally are determined to be the optimal installation position and the optimal working parameters of the vibration damper. The centralizer is generally positioned above the reamer and connected with the reamer, and the optimal installation position and the optimal working parameters of the vibration damper can ensure that the vibration damping effect is better and the transmission of the drilling burying accident can be controlled to the greatest extent.
Further, on the basis of determining the optimal installation position and the optimal working parameters of the vibration absorber, the positions of the centralizer and the vibration absorber are set to be unchanged, comparison and selection are performed according to the installation positions and the working parameters of different vibration absorbing short sections, and the position and the working parameters of the vibration absorbing short section when the drill string vibrates minimally are determined to be the optimal installation position and the optimal working parameters of the vibration absorbing short section. The vibration absorption effect is increased on the basis of vibration absorption, so that the vibration of the drill string is smaller, and the transmission probability of the buried drilling accident is lower.
Further, the vibration reduction and absorption tool comprises a combination of the vibration absorption short section and the centralizer, during simulation calculation, the position of the centralizer is set to be unchanged, comparison and selection are carried out according to the installation position and the working parameters of different vibration absorption short sections, and the vibration absorption short section position and the working parameters are determined to be the best installation position and the best working parameters of the vibration absorption short section when the drill string vibrates minimally. The centralizer is generally located reamer top, and is connected with the reamer, and the best mounting position of inhaling the nipple joint and best working parameter can make to inhale the shock effect better, the most possible control transmission of buried drilling accident.
Further, on the basis of determining the optimal installation position and the optimal working parameters of the vibration absorbing short section, the positions of the centralizer and the vibration absorbing short section are set to be unchanged, comparison and selection are performed according to the installation positions and the working parameters of different vibration absorbers, and the position and the working parameters of the vibration absorber when the drill string vibrates minimally are determined to be the optimal installation position and the optimal working parameters of the vibration absorber. The vibration reduction effect is increased on the basis of vibration absorption, so that the vibration of the drill string is smaller, and the transmission probability of the buried drilling accident is lower.
Further, the working parameters of the vibration absorber and the vibration absorbing short joint comprise rigidity and damping.
The theoretical derivation of the method of the invention is as follows:
in the well drilling field, the buried drilling accident is mainly caused by the collapse of the well wall, and the reason for causing the collapse of the well wall can be mainly summarized into two aspects: firstly, hydration reaction, in particular physical and chemical reaction between the shale and the drilling fluid; and the other is mechanical factors including the impact of the drill string on the well wall, the difference of the mechanical properties of the rock, the redistribution of the stress around the well hole and the like. The hydration reaction of rock is the key point of long-term concern of the well wall stability problem research, most scholars consider that the rock water swelling is the main factor causing the destabilization and collapse of the well wall, and a great deal of related research is carried out in this respect, and the destabilization problem of the well wall is mainly controlled by adjusting the density and the composition of the drilling fluid.
However, the existing research directions neglect some problems, the hydration expansion of the rock may be only an inducing factor (if the hydration expansion of the rock is a main factor, the rock will cause the large-area collapse of the well wall of the same stratum, because the lithology of the same stratum is basically consistent, and the hydration degree is basically the same), and the impact of the drill string on the well wall caused by the vibration of the drill string during the drilling process may be the factor which can cause fatal influence on the instability of the well wall. The vibration acceleration of the vertical well drill string is measured by a measurement while drilling method, and the following findings are found: under the condition of good drilling condition, the measured transverse vibration acceleration of the drill string is generally between 20g and 30g, and the measured transverse vibration acceleration of the drill string generally exceeds 70g, and some transverse vibration acceleration of the drill string even reaches 80g under the condition of severe drilling condition; due to the difference of the weight on bit, the rotation speed and the rock properties, the transverse vibration acceleration of the drill string is also different, and the transverse vibration acceleration of the drill string is generally above 20g and can reach 200g at most, as shown in fig. 1. The large drill string lateral vibration acceleration is sufficient to cause the borehole wall rock to be irreparably damaged by the drill string impact.
The company divides the lateral and axial vibration levels into 7 levels according to the vibration intensity level classification of Baker Hughes ineq, and the corresponding acceleration values of different levels are shown in table 1, in which the vibration levels are measured as multiples of the gravity acceleration g, and are statistical indexes RMS (Root mean square) based on actual measurement results. The company stipulates that the axial vibration is 0-1 grade as a safety grade, and the underground drilling tool is in a safe and good operation environment; the grade 2-3 is a medium vibration grade, at this time, the underground vibration is shown to be in a high level, and at this time, although the drilling can be continued, the tracking of the underground working condition is required to be enhanced; grade 4-7 is a severe vibration grade, and the company stipulates that once the tool vibration reaches grade 4-7, vibration reduction measures must be taken to eliminate the severe vibration and then drilling can be continued.
TABLE 1 drill string vibration Strength rating
In addition, the vibration characteristics of the lower drilling tool are researched, and the vibration condition of the lower drilling tool is analyzed by establishing a dynamic simulation model of a full-well drill string system mainly through a large-scale commercial software ABAQUS. At present, there are two main numerical models reflecting the dynamic characteristics of the lower drill string: firstly, assuming that an underground drill string is a homogeneous elastic rod, establishing an underground drill string wave equation, and solving by adopting a separation variable method; and on the basis of the multi-degree-of-freedom system vibration theory, dispersing the underground drill string into n spring-mass-damping micro elements, and solving by adopting a finite element method. Regardless of the analytical model, its study of downhole drill string dynamics consists of two aspects: one is the boundary condition, especially the excitation condition at the drill bit; secondly, the dynamic response of the drill string system under the boundary condition is mainly determined by the inherent characteristics of the drill string system. The dynamics of the drill bit and the lower drill string as a whole are coupled with each other and mutually affect: on one hand, rock breaking by the drill bit is a main vibration source of underground drill string vibration, and on the other hand, the drill string vibration has a feedback effect on the interaction of the drill bit and the rock. After a system model of a drill string, a well wall, a drill bit and a rock is calculated, the fact that the system is huge, the calculation time of a CPU is long, the output result is not many, more than 30 hours are spent on simulation calculation for 10s, and the motion rule of the drill string cannot be well represented by the first 10s of simulation. Thus, the interaction of the drill bit with the rock is reduced to a sinusoidal displacement excitation for a computation time of 500s, as shown in fig. 2. In the model, a tensile force F and a rotating speed omega are applied to the top end of a drill string, a reaction torque M and a displacement excitation u are applied to the lower end of the drill string, the bit pressure is applied by the gravity of a drill collar, and a well wall is a rigid body.
A node on a drill collar close to the drill bit is taken to obtain the transverse vibration characteristic of the drill collar as shown in figure 3, and the transverse vibration strength of the lower drill string is generally between 15g and 25g and is close to 60g as large as the transverse vibration characteristic. Due to the difference of the bit pressure, the rotating speed and the rock property, the transverse vibration acceleration of the drill string is different, and the transverse vibration acceleration of the drill string is generally over 20g and can reach 200g at most. The simulation calculation result further shows that the vibration characteristic of the lower drilling tool is very severe and is an important influence factor for researching the borehole wall instability condition.
In addition, in the process of forming a well wall by crushing rock at the bottom of the well by the drill bit, the transverse movement of the drill bit in the drilling process or the transverse impact on the well wall can be caused by the transverse stress imbalance of the drill bit, so that the drill bit does not always follow a fixed central line in the drilling process, and the formed well wall is uneven and has uneven well diameter; in addition, the formation of the well wall breaks the stress balance of the original stratum, and the well wall can form a stress concentration phenomenon around the well wall under the disturbance of all-directional stress (including ground stress, mud pressure and the like), so that the instability and the block dropping of the well wall can be caused, and the well diameter is enlarged. The phenomenon of hole enlargement does occur in the actual drilling process and is sometimes particularly severe. Due to the fact that the hole diameters of different well hole sections are different in expansion rate, the formed well wall surface is uneven and presents concave surfaces and convex surfaces in different degrees, the concave surfaces represent positions with larger hole diameter expansion rate, and the convex surfaces represent positions with smaller hole diameter expansion rate relative to the concave surfaces. When the drill string contacts and collides with the concave surfaces and the convex surfaces on the well wall, the well wall is more prone to collapse and fall blocks, the instability degree of the well wall due to the collision of the drill string is increased, and the occurrence of buried drilling accidents is caused. Therefore, it is very important to obtain a well wall with a regular diameter and a smooth wall surface.
However, there is currently little research regarding borehole wall buckling or borehole diameter enlargement due to impact with the drill string. Researchers generally believe that the most main cause of borehole wall instability is the physicochemical reaction between borehole wall rocks (particularly shale) and drilling fluid, and neglects the influence of the drill string impacting the borehole wall caused by the drill string vibration on borehole wall instability or borehole diameter expansion, which easily leads the wrong recognition of the real cause of borehole wall instability by the researchers. Not all borehole wall stability problems are in fact caused by the physicochemical reactions between borehole wall rock and drilling fluid, and in many cases the drill string impact against the borehole wall caused by drill string vibration is the leading cause of borehole wall instability. In order to obtain the influence relation between the vibration of a drill column and the stability of a well wall, three wells in the Amazon area are measured; by monitoring the vibration of the drill string through the measurement of four parameters of hook load, drill string rotation speed, torque and drill string tension, and analyzing the vibration of the drill string and the hole diameter curve (as shown in a, b and c in fig. 4), the hole diameter curves of A, B have great difference although the lithology of the two wells is basically the same: in the well A, when the drill string vibrates severely, the well wall can have the phenomenon of well diameter expansion in many places to cause instability of the well wall, and the curve is shown as a in figure 4; on the contrary, in the well B, when the vibration of the drill string is relatively slight, the expansion degree of the well diameter is not large, the well wall is relatively stable, and the curve is shown as B in fig. 4; it can be seen that drill string vibration has a significant effect on borehole wall stability. As further shown in fig. 4C, in well C, even if water-based drilling fluid is used, the damage degree of shale layer is not the most serious in the well, but on the contrary, the damage degree of diabase is very high, which indicates that the most main factor causing the instability of well wall in the present case is not the physicochemical reaction between well wall rock and drilling fluid but is likely to be the vibration of drill string, which indicates that the impact of drill string impact caused by the vibration of drill string has non-negligible effect on the stability of well wall. In addition, the hole diameter is greatly enlarged when the drill encounters diabase relative to other rock formations, and the reason for enlarging the diabase layer hole diameter is probably the unstable spalling of the well wall rock caused by the drill string impacting the well wall due to the transverse vibration of the drill string, and should not be attributed to the hydration of the drilling fluid and the well wall rock, and Santos also points out that the well wall stability is more affected by the vibration of the drill string especially in hard rock formations.
The damage caused by the fact that a drill string collides with a well wall to the instability of the well wall can be clearly and briefly described according to the following simple calculation:
taking a 7-inch drill collar as an example, the mass of the drill collar of one meter is as follows:
m＝164kg×1m＝164kg
from newton's second law:
F＝ma＝164kg×20×9.81m/s2＝32800N＝3.28ton
namely, when the drill collar impacts the well wall at the acceleration of 20g, a force of 3.28 tons can be generated, the impact can certainly cause a large number of crack areas and even spalling of the well wall rock, and particularly, the impact on the concave-convex surface of the well wall after hydration expansion by the drilling tool can cause more serious results. The drill string impacts the well wall caused by the vibration of the drill string not once but repeatedly and uninterruptedly, so that the vibration of the drill string poses a serious threat to the buried drilling accident caused by the unstable collapse of the well wall, as shown in fig. 5.
The invention has the beneficial effects that:
the vibration reduction and vibration absorption tool can weaken the vibration intensity of the lower drilling tool, prolong the service life of the lower drilling tool, improve the drilling efficiency, reduce the risk of instability and collapse of the well wall due to collision of the drilling tool and reduce the probability of buried drilling accidents. The technology can relieve the problem of instability of the borehole wall caused by factors such as stress concentration and drilling fluid scouring, reduce the probability of impact of a drilling tool and the uneven wall surface, and simultaneously reduce friction resistance, promote the transmission of drilling pressure and the running of a casing pipe and the like. Aiming at the condition that the vibration intensity is in a medium or strong level, the buried drilling accident caused by the collapse of the well wall can be effectively relieved by 20-40% through the matching use of the two technologies, the drilling efficiency can be greatly improved, and the drilling cost can be reduced.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings.
FIG. 1 is a cross-directional vibration characteristic of a lower drill string tested in the field;
FIG. 2 is a schematic view of a finite element model of a drill string vibration system;
FIG. 3 is a theoretical calculated lateral vibration characteristic of the lower drill string;
FIG. 4 is a graph showing the relationship between the vibration of a three-hole drilling string and the hole diameter expansion rate in Amazon;
FIG. 5 is a schematic view of the borehole wall destabilized by impact of the drill string;
FIG. 6 shows the longitudinal vibration characteristics of the lower drill at a distance of 10m from the drill bit for the vibration damper according to the embodiment of the present invention;
FIG. 7 shows the longitudinal vibration characteristics of the lower drill at a distance of 19m from the drill bit for the vibration damper according to the embodiment of the present invention;
FIG. 8 shows the longitudinal vibration characteristics of the lower drill at a distance of 28m from the drill bit for the vibration damper according to the embodiment of the present invention;
FIG. 9 illustrates a damping effect curve for dampers of varying stiffness according to embodiments of the present invention;
FIG. 10 is a graph showing the damping effect of different damping absorbers in the embodiment of the present invention;
FIG. 11 is a schematic flow chart of the method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear, the present invention is further illustrated with reference to the following examples, but not to limit the scope of the present invention.
A method for reducing the incidence of bit burial due to wall sloughing, the method comprising the steps of:
the method comprises the following steps: establishing a dynamic simulation model of a whole-well drill column system to be drilled according to drilling parameters, a drilling tool assembly, drill bit structural parameters and rock parameters to be drilled;
step two: adding a vibration reduction and absorption tool into the drilling tool assembly of the simulation model;
step three: in the simulation model, adjusting the installation position and the working parameters of the vibration-damping and vibration-absorbing tool, respectively carrying out simulation calculation aiming at different installation positions and working parameters, taking the vibration intensity of the lower drilling tool as an index, and carrying out comparison and selection on the calculation result, wherein when the vibration intensity is minimum, the corresponding installation position and the working parameters of the vibration-damping and vibration-absorbing tool are the optimal installation position and the optimal working parameters;
step four: carrying out actual drilling tool assembly installation according to the optimal installation position and working parameters of the vibration reduction and absorption tool calculated in the third step, and simultaneously connecting a reamer above the drill bit to obtain an actual drilling tool assembly;
step five: and (5) performing drilling operation on the well to be drilled according to the actual drilling tool combination to finish drilling.
Because the underreamer is used for trimming the well wall, the underreamer is directly connected and installed on the drill bit, and the installation position is fixed, so that the open hole well wall can be trimmed in the most timely mode. Because if a drill string is also connected between the underreamer and the drill bit, this drill string will always be in the untrimmed section of the wellbore, which has a relatively high risk of wall clashing. In addition, in the simulation calculation, the direct influence on the vibration itself is not large compared with when the vibration reduction and absorption tool is selected, and therefore, the reamer may not be added in the simulation.
In the first step, a geometric model comprising a drill string, a drill bit and rock is established by adopting CAD software, and then a simulation model is established by adopting CAE software.
The simulation calculation was performed using the Abaqus/Explicit software.
The reamer is connected with the drill bit and is positioned above the drill bit. The reamer can be used for reaming and repairing the well wall together with the drill bit in the drilling process, so that the problem that the well wall is unstable due to the fact that the well wall is irregular and is easy to collide with a drill column is avoided. The reamer can be an eccentric reamer, a bicentric reamer, a concentric reamer and the like.
Preferably, the vibration-damping and vibration-absorbing tool is a combination of a vibration damper, a vibration-absorbing short joint and a centralizer. The vibration condition of the simulation drill string can be freely combined, for example, a vibration absorber and a centralizer are selected, a vibration absorbing short section and the centralizer are selected, and the vibration absorber, the vibration absorbing short section and the centralizer are combined. The vibration reduction and absorption tool can reduce the vibration of the drill string during drilling as much as possible, and reduce the possibility of drilling-drop accidents caused by the instability of the well wall due to the collision of the drill string with the well wall caused by vibration.
As a preferred scheme, the vibration-damping and vibration-absorbing tool comprises a vibration damper and a centralizer, during simulation calculation, the position of the centralizer is set to be unchanged, comparison and selection are performed according to the installation positions and the working parameters of different vibration dampers, and the position and the working parameters of the vibration damper when the vibration of the drill string is minimum are determined to be the optimal installation position and the optimal working parameters of the vibration damper. The centralizer is generally positioned above the reamer and connected with the reamer, and the optimal installation position and the optimal working parameters of the vibration damper can ensure that the vibration damping effect is better and the transmission of the drilling burying accident can be controlled to the greatest extent.
As a preferred scheme, on the basis of determining the optimal installation position and the optimal working parameters of the vibration absorber, the positions of the centralizer and the vibration absorber are set to be unchanged, comparison and selection are performed according to the installation positions and the working parameters of different vibration absorbing short sections, and the position and the working parameters of the vibration absorbing short section when the vibration of the drill string is minimum are determined to be the optimal installation position and the optimal working parameters of the vibration absorbing short section. The vibration absorption effect is increased on the basis of vibration absorption, so that the vibration of the drill string is smaller, and the transmission probability of the buried drilling accident is lower.
As a preferred scheme, the vibration-damping and vibration-absorbing tool comprises a combination of a vibration-absorbing short section and a centralizer, during simulation calculation, the position of the centralizer is set to be unchanged, comparison and selection are performed according to the installation positions and working parameters of different vibration-absorbing short sections, and the vibration-absorbing short section position and the working parameter which are determined when the vibration of the drill string is minimum are the optimal installation position and the optimal working parameter of the vibration-absorbing short section. The centralizer is generally located reamer top, and is connected with the reamer, and the best mounting position of inhaling the nipple joint and best working parameter can make to inhale the shock effect better, the most possible control transmission of buried drilling accident.
As a preferred scheme, on the basis of determining the optimal installation position and the optimal working parameter of the vibration absorption short section, the positions of the centralizer and the vibration absorption short section are set to be unchanged, comparison and selection are performed according to the installation positions and the working parameters of different vibration absorbers, and the position and the working parameter of the vibration absorber when the vibration of the drill string is minimum are determined to be the optimal installation position and the optimal working parameter of the vibration absorber. The vibration reduction effect is increased on the basis of vibration absorption, so that the vibration of the drill string is smaller, and the transmission probability of the buried drilling accident is lower.
The working parameters of the vibration absorber and the vibration absorbing short joint comprise rigidity and damping.
This is further illustrated by a specific example.
In this embodiment, the vibration-damping and vibration-absorbing tool includes a vibration damper and a centralizer, and the centralizer is connected to and located above the drill bit. The method comprises the following specific steps:
the simulation parameters are divided into four parts. Drilling parameters are as follows: the rotating speed VR is 80r/min, the bit pressure T is 60kN, the drilling fluid is air, and the gas density is 24kg/m3Viscosity 2.0X 10-5Pa.s. Drilling tool combination: tricone bit + phi 215mm centralizer × 1.45m + phi 178mm drill collar × 27.35m + phi 159mm drill collar × 44.35m + phi 127mm drill rod × 20 m. The main structural parameters of the drill bit are as follows: the outer diameter phi is 216mm, the journal angle is 57 degrees, the shift distance is 7mm, and the c value of the drill bit is 86.3. The main parameters of the rock are as follows: the elastic modulus is 51500MPa, the Poisson ratio is 0.33, the compressive strength is 120MPa, the shear expansion angle is 44.47 degrees, and the internal friction angle is 30.16 degrees.
Firstly, a three-dimensional model of a drill string, a tricone bit and a rock is respectively established by utilizing CAD software, and CAE software is introduced for grid division to obtain a system simulation model shown in figure 2.
Then, the optimal mounting position of the damper is determined: the longitudinal vibration characteristics of the lower drill were analyzed when the dampers were spaced apart from the drill bits by 10m, 19m and 28m, respectively, as shown in fig. 6, 7 and 8, respectively. As can be seen, when the vibration dampers are spaced from the drill bits by 10m, 19m and 28m, the average fluctuation amounts of the drill bit weight of the drill bits are respectively 11.1kN, 15.8kN and 17.9kN, and the average fluctuation amounts of the longitudinal force of the drill string at the upper ends of the vibration dampers are respectively 2.8kN, 2.9kN and 3.2 kN. It can be seen that as the distance between the vibration damper and the drill increases, the vibration damping effect on the drill is greatly reduced, and therefore, the installation position of the vibration damper is selected to be 10m away from the drill in the present embodiment.
Then, the operating parameters of the shock absorber are determined:
when the rigidity of the vibration damper is 3.5kN/mm, 4kN/mm and 6.5kN/mm, the average fluctuation quantity of the bit weight of the drill bit is 3.9kN, 4kN and 4.6kN respectively, and the average fluctuation quantity of the longitudinal force of the drill string is 2.6kN, 2.8kN and 3.8kN respectively. The curve of the damping effect of the damper with different rigidity is shown in fig. 4, the larger the rigidity of the damper is, the larger the rock reaction force received by the drill bit for breaking rock is, the poorer the vibration damping capacity of the damper is, when the rigidity of the damper is increased from 3.5kN/mm to 6.5kN/mm, the damping coefficient is increased from 0.21 to 0.25, and the force transmission coefficient is increased from 0.67 to 0.83. Therefore, the shock absorber with smaller rigidity has better shock absorption effect, but the rigidity of the shock absorber cannot be infinitely small due to the limitation of the working stroke of the shock absorber, because the movement displacement of the shock absorber under longitudinal load is inevitably overlarge due to the overlarge rigidity, the reliability of the structure of the shock absorber is influenced, the production and processing difficulty of the shock absorber is increased, and the run-out of a drill bit at the bottom of a well can be accelerated. In the drilling engineering, the selection of the rigidity of the shock absorber needs to comprehensively consider the longitudinal load (weight on bit) and the shock absorbing capacity of the shock absorber, under the normal condition, when the weight on bit is smaller, the shock absorber with lower rigidity is selected, and when the weight on bit is larger, the shock absorber with higher rigidity is preferably selected.
When the damping of the shock absorber is respectively 20 Ns/mm, 40 Ns/mm, 60 Ns/mm, 120 Ns/mm and 200 Ns/mm, the average fluctuation amount of the drill bit weight of the drill bit is respectively 6.6kN, 5.1kN, 4.1kN, 4.5kN and 5.3kN, and the average fluctuation amount of the longitudinal force of the drill string is respectively 4.7kN, 3.2kN, 2.5kN, 3.7kN and 4.6 kN. The curves of the vibration damping effect of different damping vibration dampers are shown in FIG. 10, when the damping of the vibration damper is less than 60 N.s/mm, the vibration damping effect of the vibration damper on the drill bit and the drill string is increased along with the increase of the damping of the vibration damper, when the damping of the vibration damper is increased from 20 N.s/mm to 60 N.s/mm, the vibration damping coefficient is reduced from 0.36 to 0.22, the force transmission coefficient is reduced from 0.71 to 0.61, when the damping of the vibration damper is less than 40 N.s/mm, the longitudinal force response curve of the drill bit and the drill string has a plurality of large peak values, and the maximum value is 9.8 kN; when the damper damping is more than 60 N.s/mm, the longitudinal vibration characteristic curves of the drill bit and the drill string are relatively gentle, the damping effect of the damper on the drill bit and the drill string is reduced along with the increase of the damping, when the damper damping is increased from 60 N.s/mm to 200 N.s/mm, the damping coefficient is increased from 0.22 to 0.29, and the force transmission coefficient is increased from 0.61 to 0.87. Therefore, from the vibration damping point of view, the damping of the vibration damper has an optimal value, and the vibration damping effect is the best when the damping of the vibration damper is 60 N.s/mm for the drilling tool assembly and the drilling parameters selected in the embodiment.
And according to the simulated parameters, the actual drill string combination is carried out, and the drilling is completed, so that the probability of the drilling accident sending by the current drilling can be reduced by 30%.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. A method for reducing the incidence of bit burial due to wall sloughing, comprising the steps of:
the method comprises the following steps: establishing a dynamic simulation model of a whole-well drill column system to be drilled according to drilling parameters, a drilling tool assembly, drill bit structural parameters and rock parameters to be drilled;
step two: adding a vibration reduction and absorption tool into the drilling tool combination of the simulation model, wherein the vibration reduction and absorption tool is a combination of a vibration absorber, a vibration absorption short section and a centralizer;
step three: in the simulation model, adjusting the installation position and the working parameters of the vibration-damping and vibration-absorbing tool, respectively carrying out simulation calculation aiming at different installation positions and working parameters, taking the vibration intensity of the lower drilling tool as an index, and carrying out comparison and selection on the calculation result, wherein when the vibration intensity is minimum, the corresponding installation position and the working parameters of the vibration-damping and vibration-absorbing tool are the optimal installation position and the optimal working parameters;
the vibration-damping and vibration-absorbing tool comprises a vibration damper and a centralizer, the position of the centralizer is set to be unchanged during simulation calculation, comparison and selection are carried out according to the installation positions and working parameters of different vibration dampers, and the position and the working parameters of the vibration damper when the drill string vibrates minimally are determined to be the optimal installation position and the optimal working parameters of the vibration damper;
the vibration reduction and absorption tool comprises a combination of a vibration absorption short section and a centralizer, the position of the centralizer is set to be unchanged during simulation calculation, comparison and selection are carried out according to the installation positions and working parameters of different vibration absorption short sections, and the vibration absorption short section position and the working parameter when the drill string vibrates minimally are determined to be the optimal installation position and the optimal working parameter of the vibration absorption short section;
step four: carrying out actual drilling tool assembly installation according to the optimal installation position and working parameters of the vibration reduction and absorption tool calculated in the third step, and simultaneously connecting a reamer above the drill bit to obtain an actual drilling tool assembly;
step five: and (5) performing drilling operation on the well to be drilled according to the actual drilling tool combination to finish drilling.
2. The method for reducing the incidence of bit burial caused by wall sloughing according to claim 1, wherein: in the first step, a geometric model comprising a drill string, a drill bit and rock is established by adopting CAD software, and then a simulation model is established by adopting CAE software.
3. The method for reducing the incidence of bit burial caused by wall sloughing according to claim 1, wherein: the simulation calculation was performed using the Abaqus/Explicit software.
4. The method for reducing the incidence of bit burial caused by wall sloughing according to claim 1, wherein: the reamer is connected with the drill bit and is positioned above the drill bit.
5. The method for reducing the incidence of bit burial caused by wall sloughing according to claim 1, wherein: on the basis of determining the optimal installation position and the optimal working parameters of the vibration absorber, the positions of the centralizer and the vibration absorber are set to be unchanged, comparison and selection are performed according to the installation positions and the working parameters of different vibration absorbing short sections, and the position and the working parameters of the vibration absorbing short section when the drill string vibrates minimally are determined to be the optimal installation position and the optimal working parameters of the vibration absorbing short section.
6. The method for reducing the incidence of bit burial caused by wall sloughing according to claim 1, wherein: on the basis of determining the optimal installation position and the optimal working parameter of the vibration absorbing short section, the positions of the centralizer and the vibration absorbing short section are set to be unchanged, comparison and selection are performed according to the installation positions and the working parameters of different vibration absorbers, and the position and the working parameter of the vibration absorber when the drill string vibrates minimally are determined to be the optimal installation position and the optimal working parameter of the vibration absorber.
7. A method for reducing the incidence of bit burial due to wall sloughing according to claim 5 or 6, wherein: the working parameters of the vibration absorber and the vibration absorbing short joint comprise rigidity and damping.
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