U.S. patent application number 12/420675 was filed with the patent office on 2010-10-14 for system and method for drill string vibration control.
This patent application is currently assigned to King Saud University. Invention is credited to Osama J. Aldraihem, Amr M. Baz.
Application Number | 20100258352 12/420675 |
Document ID | / |
Family ID | 42933448 |
Filed Date | 2010-10-14 |
United States Patent
Application |
20100258352 |
Kind Code |
A1 |
Aldraihem; Osama J. ; et
al. |
October 14, 2010 |
System And Method For Drill String Vibration Control
Abstract
A drilling assembly includes a derrick, a swivel assembly
coupled to the derrick, and a drill string coupled to the swivel
assembly. The drill string includes a plurality of pipe sections,
each having an insert providing a material and/or geometrical
discontinuity in the pipe section, the plurality of pipe sections
forming periodic cells collectively operative to selectively block
propagation of vibrations in the drill string.
Inventors: |
Aldraihem; Osama J.;
(Riyadh, SA) ; Baz; Amr M.; (Rockville,
MD) |
Correspondence
Address: |
Nixon Peabody LLP
P.O. Box 60610
Palo Alto
CA
94306
US
|
Assignee: |
King Saud University
Riyadh
SA
|
Family ID: |
42933448 |
Appl. No.: |
12/420675 |
Filed: |
April 8, 2009 |
Current U.S.
Class: |
175/57 ;
175/320 |
Current CPC
Class: |
E21B 17/07 20130101;
E21B 44/005 20130101; E21B 17/00 20130101 |
Class at
Publication: |
175/57 ;
175/320 |
International
Class: |
E21B 17/07 20060101
E21B017/07; E21B 17/00 20060101 E21B017/00; E21B 7/00 20060101
E21B007/00 |
Claims
1. A drill string comprising: a plurality of pipe sections, each
having an insert providing a material and/or geometrical
discontinuity in the pipe section, the plurality of pipe sections
forming periodic cells collectively operative to selectively block
propagation of vibrations in the drill string.
2. The drill string of claim 1, wherein said blocking is a function
of vibrational frequency.
3. The drill string of claim 1, wherein said inserts are
passive.
4. The drill string of claim 1, wherein said inserts are
active.
5. The drill string of claim 4, wherein the inserts comprise
piezoelectric devices.
6. The drill string of claim 4, wherein the inserts comprise shape
memory devices.
7. The drill string of claim 1, wherein said inserts are provided
over substantially the entire length of the drill string.
8. The drill string of claim 1, wherein said inserts are clustered
over one or more portions of the drill string.
9. A drilling assembly comprising: a derrick; a swivel assembly
coupled to the derrick; a drill string coupled to the swivel
assembly, the drill string comprising: a plurality of pipe
sections, each having an insert providing a material and/or
geometrical discontinuity in the pipe section, the plurality of
pipe sections forming periodic cells collectively operative to
selectively block propagation of vibrations in the drill
string.
10. The drilling assembly of claim 9, wherein said blocking is a
function of vibrational frequency.
11. The drilling assembly of claim 9, wherein said inserts are
passive.
12. The drilling assembly of claim 9, wherein said inserts are
active.
13. The drilling assembly of claim 12, wherein the inserts comprise
piezoelectric devices.
14. The drilling assembly of claim 12, wherein the inserts comprise
shape memory devices.
15. The drilling assembly of claim 9, wherein said inserts are
provided over substantially the entire length of the drill
string.
16. The drilling assembly of claim 9, wherein said inserts are
clustered over one or more portions of the drill string.
17. A method for suppressing vibrations in drill string comprising:
providing a plurality of periodic inserts along a portion of the
drill string.
18. The method of claim 17, wherein said suppression is a function
of vibrational frequency.
19. The method of claim 17, wherein said inserts are passive.
20. The method of claim 17, wherein said inserts are active.
21. The method of claim 20, wherein the inserts comprise
piezoelectric devices.
22. The method of claim 20, wherein the inserts comprise shape
memory devices.
23. The method of claim 17, wherein said inserts are provided over
substantially the entire length of the drill string.
24. The method of claim 17, wherein said inserts are clustered over
one or more portions of the drill string.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to drill strings
used in underground drilling such as for gas or oil extraction or
for geothermal exploration and activity.
BACKGROUND
[0002] Underground drilling, such as for gas, oil, or geothermal
research and the like, generally involves drilling a bore through a
formation deep in the earth. Such bores are formed by connecting a
drill bit to long sections of pipe, referred to as a "drill pipe,"
so as to form an assembly commonly referred to as a "drill string."
The drill string extends from the surface to the bottom of the
bore.
[0003] FIG. 1 shows a drilling assembly 100 as described above.
Drilling assembly 100 includes a derrick 102 for providing physical
support, a swivel assembly 104 for interfacing a drill string 106
to the derrick, and a bottom-hole assembly (BHA) 108 containing the
drill bit (not shown) for drilling into the earth to form the bore
110. Drill string 106 is typically comprised of multiple sections
or drill pipes 106a, 106b, etc. A computer 112 or similar device
provides control and monitoring capabilities by way of cables
114.
[0004] In rotary drilling, the drill bit is rotated by rotating the
drill string 106 at the surface--that is, at the swivel assembly
104. In addition, piston-operated pumps (not shown) on the surface
pump high-pressure fluid, referred to as "drilling mud," through an
internal passage in the drill string and out through the drill bit.
The drilling mud lubricates the drill bit, and flushes cuttings
from the path of the drill bit. The drilling mud then flows to the
surface through an annular passage formed between the drill string
and the surface of the bore.
[0005] The drilling environment, and especially hard rock drilling,
can induce substantial vibration and shock into the drill string.
Vibration also can be introduced by factors such as rotation of the
drill bit, the motors used to rotate the drill string, pumping
drilling mud, imbalance in the drill string, and so forth. Such
vibration can result in premature failure of the various components
of the drill string. Substantial vibration also can reduce the rate
of penetration of the drill bit into the drilling surface and, in
extreme cases, can cause a loss of contact between the drill bit
and the drilling surface.
[0006] The dynamical behavior of drill strings used in the oil or
gas industry is very complex and needs to be effectively controlled
to avoid undesirable destructive potential. The complexity stems
from the fact that typical drill strings have diameter-to-length
ratios in the order of 10.sup.-5, which is less than that of the
average human hair. Furthermore, such very slender drill strings
are subjected to complex vibrational phenomena that include:
torsional relaxation oscillations induced by non-linear
"slip-stick" frictional torques between the drill-bit at the rock
surface, axial vibrations that induce "bit-bounce" which cause the
drill-bit to intermittently lose contact with the rock surface, and
whirling motion of the drill string and the motion of the bit in
the Bottom-Hole Assembly "bit in BHA."
[0007] A summary of the different modes of vibrations encountered
by the drill strings and the associated physical mechanisms
contributing to such modes is given by Spanos et al (2003) and
Table 1 lists these modes and the corresponding mechanisms as
reported by Besaisow and Payne (1988).
TABLE-US-00001 TABLE 1 Drill-string excitation mechanisms Physical
Mechanism Primary Excitation Secondary Excitation Mass imbalance
Lateral Axial-torsional-lateral Misalignment Lateral Axial
Three-cone bit Axial Torsional-lateral Loose drill-string
Axial-torsional-lateral Rotational walk Lateral Axial-torsional
Asynchronous walk or Lateral Axial-torsional whirl Drill-string
whip Lateral Axial-torsional
[0008] Extensive efforts have been expended during the past decades
to understand the underlying physical phenomena governing such
complex vibration behavior of the drill strings in order to develop
appropriate means for mitigating the resulting destructive effects.
These efforts include mathematical modeling, simulation, and/or
experimental investigation. Examples of these efforts include the
work of Aarrested et al. (1986), Jansen (1991), Chen and Geradin
(1995), Yigit and Christoforou (1996-2000), Christoforou and Yigit
(1997-2003), Leine et al (2002), Al-Hiddabi et al. (2003), Spanos
et al, (2003), Khulief and Al-Nasr (2005), and MihajloviC et al.
(2006).
[0009] In 1986, Aarrested et al. presented the first theoretical
and experimental investigation of the vibration of full-scale
drilling rig. In 1991, Jansen modeled the bottom-hole assembly
(BHA) to study the nonlinearities due to the interaction between
the drill string and the outer shell. Chen and Geradin (1995)
presented a finite element model of transverse vibration of drill
strings under axial loading. A linear finite element model has been
developed by Khulief and Al-Naser, (2005), to predict the buckling
loads and critical rotational speeds of drill strings. In 1996 and
1998, Yigit and Christoforou developed finite element models to
study the coupled torsional and bending vibration as well as the
axial and transverse vibrations of passive drill strings. In 2000
and 2003, their models were extended to simulate the dynamics of
drill strings with active control capabilities. Similar attempts
have been reported by Al-Hiddabi et al (2003) to control the
nonlinearly coupled torsional and bending vibration of drill
strings. The effect of interaction with the bore hole has been
analyzed theoretically by Christoforou and Yigit (1997) and both
theoretically and experimentally by Melakhessou et al (2003).
[0010] The effect of stick-slip and whirl vibrations on the
stability and bifurcation of drill strings were studied by Leine et
al (2002) using a two degrees-of-freedom model. In 2006, Mihajlovic
et al presented an extensive study of the limit cycles of torsional
vibrations of drillstrings subjected to constant input torque.
Also, the equilibrium points are determined and related stability
properties are discussed. In 2007, Khulief et al. extended their
finite element model to study the dynamics of drill string system
in the presence of stick-slip excitations.
[0011] In all the above-mentioned studies, emphasis has been placed
on conventional drill strings of uniform cross sections. No attempt
has been made to considering radically different designs such as
periodic drill strings in spite of the potential of this class of
drill strings in minimizing the vibration transmission.
Overview
[0012] As described therein, a drill string includes a plurality of
pipe sections, each having an insert providing a material and/or
geometrical discontinuity in the pipe section, the plurality of
pipe sections forming periodic cells collectively operative to
selectively block propagation of vibrations in the drill
string.
[0013] Also as described herein, a drilling assembly includes a
derrick, a swivel assembly coupled to the derrick, and a drill
string coupled to the swivel assembly. The drill string includes a
plurality of pipe sections, each having an insert providing a
material and/or geometrical discontinuity in the pipe section, the
plurality of pipe sections forming periodic cells collectively
operative to selectively block propagation of vibrations in the
drill string.
[0014] Also as described herein, a method for suppressing
vibrations in a drill string includes providing a plurality of
periodic inserts along a portion of the drill string.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated into and
constitute a part of this specification, illustrate one or more
examples of embodiments and, together with the description of
example embodiments, serve to explain the principles and
implementations of the embodiments.
[0016] In the drawings:
[0017] FIG. 1 is a schematic diagram of a prior art drilling
assembly;
[0018] FIG. 2 is a schematic diagram of a periodic structures based
on geometrical and material discontinuities;
[0019] FIG. 3 is a plot showing the filtering characteristics of
period passive and active struts;
[0020] FIG. 4 shows vibration contour plots for plain, passive
periodic, and active periodic struts at different excitation
frequencies; and
[0021] FIG. 5 is a diagram illustrating to the concept of the
periodic drill string in which schematic (a) depicts a
conventional, non-periodic, drill string 502, while schematics (b)
and (c) depict novel periodic drill strings 504, 506, having
passive (508p) and active (508a) inserts, respectively.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[0022] Example embodiments are described herein in the context of a
system and method for drill string vibration control. Those of
ordinary skill in the art will realize that the following
description is illustrative only and is not intended to be in any
way limiting. Other embodiments will readily suggest themselves to
such skilled persons having the benefit of this disclosure.
Reference will now be made in detail to implementations of the
example embodiments as illustrated in the accompanying drawings.
The same reference indicators will be used to the extent possible
throughout the drawings and the following description to refer to
the same or like items.
[0023] In the interest of clarity, not all of the routine features
of the implementations described herein are shown and described. It
will, of course, be appreciated that in the development of any such
actual implementation, numerous implementation-specific decisions
must be made in order to achieve the developer's specific goals,
such as compliance with application- and business-related
constraints, and that these specific goals will vary from one
implementation to another and from one developer to another.
Moreover, it will be appreciated that such a development effort
might be complex and time-consuming, but would nevertheless be a
routine undertaking of engineering for those of ordinary skill in
the art having the benefit of this disclosure.
[0024] The vibration of drillstrings is, in general, detrimental to
the drilling process and may induce premature wear and damage of
the drilling equipment which eventually results in fatigue
failures. As disclosed herein, a new design of drill strings is
proposed for mitigating such undesirable vibrations in an attempt
to avoid wear and premature failures. In the new design, the drill
string is provided with optimally-designed and -placed periodic
inserts which can be either passive or active. The inserts make the
drill string act as a mechanical filter for vibration transmission.
As a result, vibration can propagate along the periodic drill
string only within specific frequency bands called the "pass bands"
and the vibration will be substantially or completely blocked
within other frequency bands called the "stop bands." The spectral
width of these bands can be tuned actively according to the nature
of the external excitation which can be either passive or active.
The inserts introduce impedance mismatch zones along the vibration
transmission path to impede the propagation of vibration along the
string. The design and the location of the inserts is optimized to
confine the dominant modes of vibration of the drill string within
the stop bands generated by the periodic arrangement of the inserts
in order to substantially or completely block the propagation of
the vibration.
[0025] The theory governing the operation of this new class of
drill string as disclosed herein is developed to describe the
complex nature of the vibration encountered during drilling
operations. The developed model accounts for the bending,
torsional, and axial vibrations of the drill string while operating
under the influence of "slip-stick" frictional torques between the
drill-bit at the rock surface, "bit-bounce" which make the
drill-bit intermittently lose contact with the rock surface, and
the motion of the bit in the Bottom-Hole Assembly "bit in BHA." The
disclosure herein provides invaluable analytical and experimental
tools for the design of a class of drill strings that exhibits
unique vibration mitigation characteristics, low wear, long service
life, and improved drilling quality.
[0026] A. General Period Structures
[0027] Periodic structures, whether passive or active, are
structures that consist of identical substructures, or cells,
connected in an identical manner. The periodicity can be introduced
either by geometrical or material discontinuities as shown in FIG.
2. In (a), the discontinuity is geometrical and the structure and
the discontinuity are made of the same material A. In (b), the
discontinuity is material--the structure is made of material B,
while the discontinuity is made of material C. Because of the
periodicity, these periodic structures exhibit unique dynamic
characteristics that make them act as mechanical filters for wave
propagation. As a result, waves can propagate along the periodic
structures only within specific frequency bands called the pass
bands and wave propagation is substantially or completely blocked
within other frequency bands called the stop bands. The spectral
width of these bands can be tuned actively according to the nature
of the external excitation.
[0028] The finite element equations of a typical periodic structure
can be rewritten as:
{ u L F L } k + 1 = [ t 11 t 12 t 21 t 22 ] { u L F L } k or S k +
1 = [ T k ] S k ( 1 ) ##EQU00001##
where S and [T.sub.k] denote the state vector ={u.sub.L
F.sub.L}.sup.T and the transfer matrix of the k.sup.th cell. Note
that the transfer matrix relates the state vector at the left end
of k+1.sup.th cell to that at the left end of the k.sup.th cell.
Also, note that u.sub.L and F.sub.L define the deflection and force
vectors.
[0029] Equation (1) can also be written as:
S.sub.k+1=.lamda.S.sub.k (2)
indicating that the eigenvalue A of the matrix [T] is the ratio
between the state vectors at two consecutive cells. Therefore, one
can draw the following conclusions:
[0030] i. If |.lamda.|=1, then S.sub.k+1=S.sub.k and the state
vector propagates along the structure as is. This condition defines
a pass band condition;
[0031] ii. If |.lamda.|<1, then S.sub.k+1<S.sub.k and the
state vector is attenuated as it propagates along the structure.
This condition defines a stop band condition.
[0032] A further explanation of the physical meaning of the
eigenvalue .lamda. can be extracted by rewriting it as:
.lamda.=e.sup..mu.=e.sup..alpha.+i.beta.
where .mu. is defined as the propagation constant which has a real
part (.alpha.)=the logarithmic decay and imaginary part
(.beta.)=the phase difference between the adjacent cells. Plain
struts (rods) can act as wave guides that not only transmit
completely the vibration from one end to the other but also can
amplify the vibration at the structural resonances as seen in FIG.
3 by the bold solid lines. Using passive periodic struts results in
blocking completely the transmission of vibration above 600 Hz as
indicated by the plain solid line in FIG. 3. This range is extended
to almost 0 Hz when the periodic strut is provided with active
control capabilities as shown by the broken lines in FIG. 3. The
displayed characteristics indicate that the periodic strut behaves
as a low pass mechanical filter. Also, the periodic struts generate
a non-zero apparent damping, throughout the stop band, which is
quantified by the parameter a shown in the lower diagram for plain,
passive periodic, and active periodic struts. For plain struts,
a=0, suggesting that all the vibration will be transmitted while a
is high for passive periodic struts and much higher and broader for
the active periodic struts.
[0033] Such unique characteristics can be further emphasized by
considering the vibration contour plots shown in FIG. 4 for plain,
passive periodic, and active periodic struts at different frequency
of excitation.
[0034] From the above, it can be seen that vibration transmission
can be effectively blocked by introducing periodicity along the
structure. The systems and methods disclosed herein apply these
concepts to drill strings, minimizing their vibrations and
extending their service life by reducing premature wear and failure
due to excessive and undesirable vibrations.
[0035] B. Periodic Drill Strings
[0036] The concept of the periodic drill string can best be
understood by considering the schematic drawings shown in FIG. 5,
in which schematic (a) depicts a conventional, non-periodic, drill
string 502, while schematics (b) and (c) depict novel periodic
drill strings 504, 506, having passive (508p) and active (508a)
inserts, respectively. The inserts, referred to collectively as
508, are optimally designed and placed in the drill strings 504,
506, and, together with the pipe or rod section 512 with which they
are associated, form periodic cells 514 in the drill string. The
inserts 508 can be provided over substantially the entire length of
the drill string 504, 506, or they can be clustered in one or more
portions of the drill string, depending on the operating
characteristics. In each of the drill strings 504 or 506, the
inserts can be of the geometrical or the material discontinuity
type, or a combination of geometrical and material discontinuity
type. The passive inserts 508p introduce zones of impedance
mismatch along the vibration transmission path to impede the
propagation through geometrical or material discontinuities. On the
other hand, the active inserts 508a can be computer-controlled
(computer 510) to tune the mechanical filtering characteristics of
the drill string 506. It will be appreciated that the "active"
nature of the inserts 508a in one embodiment derives from their
ability to generate controllable in-plane force along the
longitudinal axis of the drill string 506, making the drill string
stiffer or softer as necessary. Other types of forces and
adjustment can be imparted to the drill string 506, and all of
these can be realized by using for example electromagnetic,
piezoelectric, or shape memory materials in the inserts. In either
the passive or active periodic drill strings 504, 506, the design
and the location of the inserts is optimized to confine the
dominant modes of vibration of the drill string within the stop
bands generated by the periodic arrangement of the inserts 508a,
508p. In the case of the passive material discontinuity type of
inserts, the material of the inserts can be selected from steel or
aluminum. In the case of the active material discontinuity type of
inserts, the material of the inserts can be selected from
piezoelectric or shape memory materials.
[0037] As disclosed herein, a new class of drill strings that
enables fast drilling with minimal down time due to premature
failures because of excessive vibration is provided. The concept of
periodic drill strings is a viable solution to mitigating the
catastrophic problems that arise from excessive vibrations. With
such a new class of drill strings, the interaction between the
drill collars and the bore hole can be minimized, the whirling
effect can be reduced, and the effect of the drill bounce can be
decreased. It should be noted that the manufacturing of the passive
periodic drill string in particular requires minimal modification
of the designs of conventional drill strings as the periodic
inserts can be manufactured as an integral part of each drill pipe
section. For even better performance, however, these inserts can be
provided with active capabilities to attenuate the vibration over
wide frequency bands. The concept can also be effective for
horizontal drilling. Furthermore, the concept can be equally
effective for direct application in all the drill strings for
offshore platforms where lateral vibrations due to fluid loading
can also be effectively minimized by the periodicity arrangement of
the drill strings. The outline merits and the potential application
spectrum of the new class of periodic drill strings are envisioned
to be beneficial to improving the quality and the state-of-the-art
of drilling operations both in land and in sea.
[0038] While embodiments and applications have been shown and
described, it would be apparent to those skilled in the art having
the benefit of this disclosure that many more modifications than
mentioned above are possible without departing from the inventive
concepts disclosed herein. The invention, therefore, is not to be
restricted except in the spirit of the appended claims.
* * * * *