U.S. patent application number 13/998925 was filed with the patent office on 2015-06-25 for downhole assembly.
The applicant listed for this patent is Stephen John McLoughlin, George Swietlik. Invention is credited to Stephen John McLoughlin, George Swietlik.
Application Number | 20150176344 13/998925 |
Document ID | / |
Family ID | 53399448 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150176344 |
Kind Code |
A1 |
McLoughlin; Stephen John ;
et al. |
June 25, 2015 |
Downhole assembly
Abstract
A piezo electric control system for use in a downhole assembly
which is inserted into a borehole comprising an articulated
mandrel, a passive and an active damping mechanism operating on
said mandrel for exercising control over torsional stick-slip in
which said piezo electric system exercises control.
Inventors: |
McLoughlin; Stephen John;
(Apse Heath, GB) ; Swietlik; George; (Oulton
Broad/Lowestoft, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
McLoughlin; Stephen John
Swietlik; George |
Apse Heath
Oulton Broad/Lowestoft |
|
GB
GB |
|
|
Family ID: |
53399448 |
Appl. No.: |
13/998925 |
Filed: |
December 23, 2013 |
Current U.S.
Class: |
175/24 |
Current CPC
Class: |
E21B 17/1078 20130101;
G01V 2210/1429 20130101; E21B 17/07 20130101; E21B 17/076 20130101;
E21B 47/01 20130101; G01H 1/00 20130101 |
International
Class: |
E21B 17/10 20060101
E21B017/10; E21B 17/07 20060101 E21B017/07; E21B 7/00 20060101
E21B007/00; E21B 12/00 20060101 E21B012/00 |
Claims
1. A downhole assembly comprising piezo electric members configured
to output an electrical signal in response to vibration of the
assembly and controlling means for controlling an aspect of said
downhole assembly, wherein the assembly is configured to provide a
proportional control voltage for the controlling means from the
magnitude of the electric signal outputted from the piezo electric
members.
2. The assembly according to claim 1, wherein said control voltage
is provided by the electric signal outputted from the piezo
electric members.
3. The assembly according to claim 1, wherein said control means
comprises means to damp vibrations in the downhole assembly.
4. The assembly of claim 3, comprising a primary passive damping
means and an independently operating secondary, active, damping
control means.
5. The assembly of claim 1 incorporating piezo electric members
which are configured as transducers which are responsive to motion,
vibration and compression and which recover waste mechanical energy
from the assembly, converting said energy into electrical power,
resulting in an electrical signal output responds proportionally to
vibration imparted to the assembly during operation.
6. The assembly of claim 1 where the piezo electric members
comprise piezo electric fibres.
7. The assembly of claim 1 configured to harvest electrical energy
from the piezo electric members and where said output energy is
used as means to measure vibration within distal elements of the
downhole assembly.
8. The assembly of claim 4 configured to harvest electrical energy
from the piezo electric members to provide a proportional control
voltage from an electric signal outputted from the piezo electric
members for controlling an aspect of the active damping
mechanism.
9. The assembly of claim 1 wherein the piezo electric members are
located in proximity to the distal end of the downhole
assembly,
10. The assembly of claim 1, wherein the piezo electric members are
embedded in an elastomeric matrix.
11. A method for harvesting vibration energy from a piezo electric
control system for electrical control during a drilling operation,
which method comprises use of a downhole assembly according to
claim 1.
12. The method of claim 11, wherein the downhole assembly comprises
a primary passive closed cell elastomeric damping means and an
independently operating secondary, active, damping means, a lower
assembly and an upper assembly, incorporating piezo electric
members configured within a lower sub-assembly, to output an
electrical signal which is proportional in response to vibration
imparted to the lower assembly and secondary piezo electric members
configured within an upper sub-assembly to output an electrical
signal response which is proportional to the vibration imparted to
the upper assembly.
13. The method of claim 12, wherein a comparison is made between
said output electrical signal generated within the lower sub
assembly and said output electrical signal generated within the
upper sub assembly.
14. The method of claim 12, wherein active damping is applied which
is proportional to the differential between the electrical response
of the piezo electric member in the lower sub assembly and the
electrical response of the piezo-electric member in the upper sub
assembly.
15. The method of claim 11, incorporating piezo electric fibres
into the downhole assembly for the purpose of generating a
proportional electrical output in response to the magnitude of
vibration imparted to the assembly.
16. The method of claim 15, wherein said electrical output from the
piezo electric fibres is a signal.
17. The method of claim 15, wherein said electrical output from the
piezo electric fibres is a control voltage.
18. The method of claim 15, wherein said electrical output is used
instantly.
19. The method of claim 15, wherein said electrical output is
stored for later usage.
20. The method of claim 15, wherein said electrical output is used
to control viscosity of magneto-rheological fluids.
21. The method of claim 15, wherein said electrical output is used
to control at least one hydraulic damping valve mechanism.
22. The method of claim 15, where said magnitude of vibration can
be segregated into components in order to better comprehend motion
of the drilling assembly.
23. The method of claim 12, wherein said damping is continuous.
24. The method of claim 12, wherein intermittent or sporadic active
damping is applied.
Description
[0001] This is a divisional application of U.S. patent application
Ser. No. 12/733,480 filed on Mar. 3, 2010 further claiming priority
from U.S. Provisional Application 60/967,307 filed on Sep. 4,
2007.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to the field of rotary
drilling tools.
BACKGROUND ART
[0003] In the field of rotary drilling the drillstring, obeying
Hooke's Law is perceived, to act as a spring. The lower component
of the drillstring, however, reacts differently to the drillpipe
section of the drillstring as it has a very high torsional
stiffness combined with a high modulus of elasticity. As a result
of having these two major elements incorporated into the
drillstring and adding bit and drill collar torsional resonance the
drillstring undergoes harmonic oscillations which, at best,
represent inefficiencies in the drilling process and at worst can
cause drillstring failure with the added expense and
unpredictability of remedial work.
[0004] Warren and Oster in "Improved ROP in Hard and Abrasive
Formations" conclude that drill-collar torsional resonance in hard
rock environments is responsible for PDC cutter damage and that
reverse rotation of the drilling assembly is one of the more
damaging elements of this particular drilling environment. The
instant device seeks to identify such damaging conditions and
improve the drilling process through active damping applied to the
near-bit sub and distal components of the drilling assembly.
[0005] Perhaps the best single definition of stick-slip is given by
John Dominick who provides a succinct description of the anomalies
of drillstring behaviour in his [U.S. Pat. No. 6,065,332] "METHOD
AND APPARATUS FOR SENSING AND DISPLAYING TORSIONAL VIBRATION."
[0006] "During drilling operations, a drillstring is subjected to
axial, lateral and torsional loads stemming from a variety of
sources. In the context of a rotating drill string, torsional loads
are imparted to the drill string by the rotary table, which rotates
the drill string, and by the interference between the drill string
and the wellbore. Axial loads act on the drill string as a result
of the successive impacts of the drill bit on the cutting face, and
as a result of irregular vertical feed rate of the drill string by
the driller. The result of this multitude of forces applied to the
drill string is a plurality of vibrations introduced into the drill
string. The particular mode of vibration will depend on the type of
load applied. For example, variations in the torque applied to the
drill string will result in a torsional vibration in the drill
string.
[0007] At the surface, torsional vibration in the drill string
appears as a regular, periodic cycling of the rotary table torque.
The torsional oscillations usually occur at a frequency that is
close to a fundamental torsional mode of the drill string, which
depends primarily on drill pipe length and size and the mass of the
bottom hole assembly (BHA). The amplitude of the torsional
vibrations depends upon the nature of the frictional torque applied
to the drill string downhole, as well as the properties of the
rotary table. Torsional vibrations propagating in the drill string
are significant in that they are ordinarily accompanied by
acceleration and deceleration of the BHA and bit, as well as
repeated twisting of the drill pipe section of the drill
string."
[0008] The magnitude of these torsional and lateral characteristics
represents a reduction in efficiency in the drilling process: thus,
removal or reduction of these destructive elements would,
naturally, constitute an improvement to drilling efficiency.
[0009] As can be inferred, "stick-slip" is a chaotic issue. In the
environs of the bit and the bottom-hole-assembly some or all of the
following characteristics may be present: drag, stick-slip--which
at a maximum may cause the BHA to spin backwards, torque shocks
(torsional vibration), BHA and bit whirl, drillpipe buckling,
bit-bounce (axial shock loading of the BHA components) and lateral
vibration. Warren et al comment that once whirl begins it is
self-sustaining as the centrifugal force maintains the effect and
that stopping rotation is the only effective way to stop whirl.
Generally speaking, "stick-slip" represents an extreme of the
condition referred to as "drilling vibration" or "harmonic
vibration".
[0010] When, however, the bit is "off-bottom" it is evident that
stick-slip decreases. Unfortunately having the bit off bottom also
compromises the efficiency and economics of the drilling process.
Thus, a primary mechanism in the creation of stick slip is bit to
formation interaction. Confirmation of the bit as one of the root
causes of stick-slip generation is found when drilling with a
positive displacement motor (PDM). PDMs represent a form of
Moineaux screw assembly, with internal rotor and external stator.
Widely used for directional and performance drilling purposes PDMs
reduce bit generated stick-slip as the rotor to stator interaction
acts as a de-coupler between the torsionally rigid collars and the
bit. Recently, high-torque output motors have removed some of this
damping effect, until, in some cases, there is little visible
difference in torque characteristics between drilling with a
positive-displacement-motor and conventional rotary drilling.
[0011] Grosso, (SPE 16,660, September, 1987) concluded; "Downhole
measurements of forces and accelerations within the BHA have shown
that the vibrations at the bit have large quasi-random components
for axial and rotational movements . . . probably due to unevenness
of formation strength, random breakage or rock and amplification of
these effects by mode coupling . . . " Grosso also concluded in
(U.S. Pat. No. 4,878,206) METHOD AND APPARATUS FOR FILTERING NOISE
FROM DATA SIGNALS, that stick-slip action was a combination of
torsional and axial movements and that torsional and axial
stick-slip measurement should be considered separately.
[0012] However, for the purposes of remedial action it is
insufficient merely to measure quantities of shock and vibration.
Other drillstring attributes need to be considered in order to be
meaningful.
[0013] Prior art in the domain of vibration measurement and control
is plentiful, yet, to date, there has been little success in
creating a panacea for stick-slip or success in diminishing
drillstring harmonics and thereby deriving improvements to the
drilling process.
[0014] The major identified sources of harmonic vibration are the
rotary drive system above the rotary table, the drillstring, the
torsionally rigid element of the BHA component of the drillstring
and the bit to formation interaction. Each has a varying degree of
influence in the total system vibration and adding further
complexity, each has an interactive effect on the other. Thus
variations in bit generated torque will reflect in drillstring
torque which feeds back into the rotary drive system: the system is
complex, iterative and constantly changing.
[0015] Prior art in this domain largely reflects two separate
schools of thought; harmonic reduction through surface control
means or by downhole control means. However, historically, neither
the selection of a surface nor a downhole approach to harmonic
damping, has achieved success across a wide range of geological
formations. In certain environments and circumstances, however,
both approaches have achieved limited success.
[0016] The first approach asserts that stick-slip can be diminished
through more precise control over the surface drive mechanism. As
this represents the variable means of torque input into the
drilling system, the premise of this group of industry studies and
intellectual property is that by oscillating the drillstring at
surface proportionally to the observed harmonic frequency of the
drilling assembly and in particular the drillstring, that
drillstring downhole torque can be controlled and harmonic
vibrations and in particular stick-slip reduced to within
acceptable limits. Practical applications of this theory have
proved effective in some situations.
[0017] Worrall, (U.S. Pat. No. 5,117,926) METHOD AND SYSTEM FOR
CONTROLLING VIBRATIONS IN BOREHOLE EQUIPMENT provided for control
of the energy flow through the borehole equipment by defining
"across" and "through" variables "wherein fluctuations in one
variable are measured and the energy flow is controlled by
adjusting the other variable in response to the measured
fluctuations in said one variable."
[0018] Van Den Steen (U.S. Pat. No. 6,166,654) DRILLING ASSEMBLY
WITH REDUCED STICK-SLIP TENDENCY acknowledging the influence of
topdrive and above rotary table harmonics proposes the addition of
surface mounted torsional viscous damper sub-systems to the
drilling assembly with the aim of introducing a lower rotational
resonant frequency into the drilling assembly by negating harmonic
influences induced by the rotating equipment located above the
rotary table.
[0019] Keultjes et al (U.S. Pat. No. 6,327,539) METHOD OF
DETERMINING DRILL STRING STIFFNESS proposes the determination of
the rotational stiffness of a drill string and in particular
determining the moment of inertia of the BHA for optimizing energy
within the drilling assembly so as to reduce stick-slip
effects.
[0020] The second school of thought asserts that downhole
measurements and associated downhole mechanisms are the preferred
route to controlling stick-slip in the bottom-hole assembly.
[0021] Prior art in the domain of passive damping devices for
rotary drilling has been deployed for over half a century.
Generically they are referred to as "shock-subs". Typically these
devices have a splined, telescopic shaft axially co-located within
a hollow cylindrical housing. When subjected to axial shock these
devices perform a controlled telescopic translation along the
principle axis of the borehole until the entirety of the shock has
been absorbed. Internal damping mechanisms vary, but are
predominantly Belleville spring, fluid compression, ring spring or
gas charged. These devices have some degree of effectiveness, but
are constrained by having their own internal natural frequency,
which, at some stage will compound the existing wellbore harmonic.
Additionally, shock subs are, largely, incompatible with
directional drilling processes, directional wells and also
relatively ineffective when dealing with high magnitude harmonic
vibrations.
[0022] These devices also have inherent natural frequencies of
their own which are not field tuneable to provide damping
capability Across wider ranges of harmonic vibration. In summary,
they individually provide a single solution which attempts to suit
the entire range of harmonic vibration conditions. The instant
device constitutes an improvement over prior art in that although
it has an inherent primary damping natural frequency, it
preferentially also provides for selective damping across a
plurality of alternative or secondary frequencies which exist in
the distal environment.
[0023] Early prior art focussed on the measurement of vibrations in
the bottom-hole assembly, with the objective of quantifying
accelerational characteristics although downhole sampling and
processor speeds prevented analysis across the wider range of
harmonics.
[0024] As an alternative to damping bit generated vibration across
the entire frequency spectrum, prior art corrective procedures have
generally either focussed on the practical measures of predicting
and avoiding critical rotary speeds, although chaotic rotary
vibration rendered this approach problematic: SPE Publication,
16675-MS "CASE STUDIES OF BHA VIBRATION FAILURE" by R. F. Mitchell
and M. B. Allen, September, 1987 included the following
commentary:
[0025] "Speeds that might result in destructive lateral vibrations
are addressed with equations 9.11 and 9.12 of API RP 7G. A recent
study has shown that these equations, even when modified to account
for fluid added mass and precessional forces, do not accurately
predict critical rotating speeds and do not correspond well with
field experience."
[0026] By 1990 the aforementioned formulae had been removed from
API RP7G, which publication added as a comment:
[0027] "Numerous field cases have indicated that previous
formulations given in Section 9.1 of API RP 7G, 12.sup.th Edition
(May 1, 1987) did not accurately predict critical rotary speeds and
thus have been removed. Presently no generally accepted method
exists to accurately predict critical rotary speeds."
[0028] Once accurate measurements were made of acceleration and
vibration which could be reconstructed to quantify downhole
harmonic vibration these were conveyed back to the surface of the
earth using any of a variety of commercially available telemetry
methods or recorded in the downhole environment and reserved for
post-well analysis. At surface "BHA Modelling" took place. BHA
modelling, largely using finite-element analysis techniques sought
to avoid specific resonant vibrations which were incompatible with
a specific configuration of BHA, drill bit and rock formation
configuration. However, even slight hole enlargement reduces
pre-well BHA Modelling effectiveness as it alters the natural
frequency of the BHA. The degree of hole enlargement is,
additionally, unquantifiable until the well is in progress.
[0029] Research has shown that the main causes of premature bit and
BHA damage in any one drilling scenario are, largely, confined to
one or two major frequencies with single "sidebands". The abstract
of MacPherson (U.S. Pat. No. 5,321,981) "METHODS FOR ANALYSIS OF
DRILLSTRING VIBRATION USING TORSIONALLY INDUCED FREQUENCY
MODULATION" informs:
[0030] "Torsional oscillations of the drillstring will lead to
frequency modulation (FM) of the signal from a vibratory source
(e.g. the bit). This results, in the frequency domain, in sidebands
being present around a detected excitation frequency. In accordance
with the present invention, it has been discovered that these
sidebands may be used in advantageous methods for optimizing
drillstring and drilling performance. In a first embodiment of this
invention, these sidebands are used to discriminate between
downhole and surface vibrational sources."
[0031] Mason, (U.S. Pat. No. 5,448,911) METHOD AND APPARATUS FOR
DETECTING IMPENDING STICKING OF A DRILLSTRING utilized a
comparative method which identified impeding downhole sticking
conditions and compared them to observed surface conditions. The
objective being to identify surface condition parameters which were
to be avoided.
[0032] Wassell (U.S. Pat. No. 5,226,332) VIBRATION MONITORING
SYSTEM FOR DRILLSTRING proposed an alternate configuration for
downhole sensors which allowed for enhanced accuracy in measurement
of lateral and torsional vibration.
[0033] Pavone (U.S. Pat. No. 5,721,376) METHOD AND SYSTEM FOR
PREDICTING THE APPEARANCE OF A DYSFUNCTION DURING DRILLING focused
on the creation of a drilling model constructed from measurements
taken from sensors located in the drillstring.
[0034] Later art in the field of vibration damping through
application of downhole assemblies and mechanisms has focussed on
intelligent networks and processes which utilize the integration of
multiple sensor inputs with logic control either encompassed within
a downhole device or, alternatively transferred back to surface in
order for the operator to make corrective actions.
[0035] The importance of completeness of data is revealed by, among
others, Warren and Oster "Improved ROP in Hard and Abrasive
Formations" who, in a detailed discussion on bit wear, make the
following observations:
[0036] "Whether or not a cutter moves backwards depends on the
amplitude of the accelerations, the frequency of the accelerations
and the average rotary speed. FIG. 47 shows the amplitude/frequency
regions for 60 rpm and 120 rpm where backwards rotation can occur.
In general for a typical frequency of 20 Hz, any accelerations over
3.5G for 60 rpm and 6.5G for 120 rpm result in reverse rotation.
These conditions are often observed on the D(rilling) D(ynamics)
S(ub) data.
[0037] The implication of this is that without, at a minimum, the
amplitude, frequency and average rotary speed of a drilling
assembly, active, adaptive, vibration damping cannot take place.
Unfortunately, not all of these inputs can be measured in the
downhole environment.
[0038] Dubinsky et al (U.S. Pat. No. 6,021,377) DRILLING SYSTEM
UTILIZING DOWNHOLE DYSFUNCTIONS FOR DETERMINING CORRECTIVE ACTIONS
AND SIMULATING DRILLING CONDITIONS, provides for a "closed-loop"
system where downhole dysfunctions are quantified by sensors and
the results telemetered to surface where a surface control unit
determines the severity of dysfunction and the operator provides
corrective action which is required to alleviate the dysfunction at
surface.
[0039] MacDonald et al (U.S. Pat. No. 6,732,052) METHOD AND
APPARATUS FOR PREDICTION CONTROL IN DRILLING DYNAMICS USING NEURAL
NETWORKS proposes:
[0040] "A drilling system that utilizes a neural network for
predictive control of drilling operations. A downhole processor
controls the operation of devices in a bottom hole assembly to
effect changes to drilling parameters [and drilling direction] to
autonomously optimize the drilling effectiveness. The neural
network iteratively updates a prediction model of the drilling
operations and provides recommendations for drilling corrections to
a drilling operator."
[0041] This approach has achieved some recent success; however, its
objective is the avoidance of BHA/well specific destructive RPM
ranges through operator intervention at surface. Using these
methods may reduce harmonic vibration, yet compromise rate of
penetration as a result of the selection of sub-optimal drilling
RPM ranges. Once destructive harmonics have been identified, they
are avoided, rather than corrected for and negated.
[0042] Prior art in the field of downhole mechanical bit vibration
damping revealed in DEFOURNY et al (U.S. Pat. No. 6,945,338)
DRILLING BIT ASSEMBLY AND APPARATUS proposes a fixed cutter bit
with isolative damping capability particularly between bit cutters
and bit body. Several formats are introduced within the scope of
the Defourny patent, all of which have the intention of isolating
the bit from the destructive properties associated with drill
collar whirl and BHA induced vibration.
[0043] Defourny and Abbassian explain the practical advantages of
their system further in SPE Paper 30475 "Flexible Bit: A New
Anti-Vibration PDC Bit Concept":
[0044] "Due to the rigid connection between the bit and the BHA,
vibration events originated in the BHA can influence the dynamic
motion of the bit and vice versa. As a consequence of this dynamic
coupling, a given vibration mechanism, which involves the bit, can
trigger one involving the BHA. For example, extreme bit slip-stick
torsional vibrations have been observed to cause BHA lateral
instability which can in turn trigger whirl as a result of
increased BHA/Wellbore interaction. Conversely, BHA whirl can
induce lateral bit instability"
[0045] The instant invention initially proposes improvement over
Defourny in that it is stabilized within the borehole. The
stabilizer element advantageously confines the radial motion of the
tool within the borehole, providing limitations to the internal
attitudinal motion and constraint to lateral and torsional degrees
of freedom conferred thereby. Additionally, the stabilization means
conveys potentially destructive energy from the drilling assembly
to the borehole wall. Furthermore, prior art relies upon the
"resiliently deformable spacer" for the effective transfer of
torque from the first member of the drilling assembly to the second
member of the drilling assembly [Claim 1], whereas the invention
disclosed herein provides for direct, compliant, metal-to-metal
torque transfer between first and second member yet without loss of
intra-device articulation. Additionally, prior art was constrained
to a single natural frequency, whereas the instant device offers
improvement over prior art in that it is adaptive, adjustable in
the downhole environment, and provides damping across a wider range
of drilling conditions without the requirement to reconfigure or
trip the device to surface.
[0046] Given the frequency of harmonic vibrations associated with
the drilling process and the requirement for timely corrective
action, hydraulic system response times may prove to be inadequate
for active damping control mechanism purposes. This is particularly
evident where the bit generated vibration frequency is relatively
high in both frequency and amplitude and a proportionately rapid
damping response is required. A more timely damping response time
may be obtained by electro-mechanical or, preferentially,
electro-hydraulic control means which are proposed as an integral
inventive step of the instant device.
[0047] More recent prior art by Raymond et al (U.S. Pat. No.
7,036,612) CONTROLLABLE MAGNETO RHEOLOGICAL FLUID BASED DAMPERS FOR
DRILLING sought to overcome the limitations inherent in a purely
hydraulic damping mechanism by proposing a controllable damping
apparatus for the downhole reduction of harmonic vibration. This
device, which utilizes a traditional shock absorber format,
incorporates restrictive valves which have magneto rheological
fluid ("MR Fluids") housed within a chamber with an orifice between
two sections of the chamber. An electromagnetic coil "employed
proximate the orifice" controls the flow of fluid between the two
sections.
[0048] M R Fluids ("MRF") are fluids which have an initial state
and a second state and whose material properties are altered
through the presence of a magnetic field. The first lower viscosity
state is the natural state of the fluid, whereas the second,
high-viscosity state is induced through the application of magnetic
field to the fluid. The magnetic field may be induced by
application of real-earth magnets, or, alternatively through the
application of electro magnetic field. The magnetic field may also
be permanent or temporary in nature without detriment to the
characteristics of the fluid. Additionally, it may also be
configured to be a bi-state, binary operator, temporary or pulsed,
thus making it almost infinitely adjustable across a range of
values.
[0049] Magneto Rheological materials encompass materials with both
fluid and solid properties. Although MRE ("Magneto Rheological
Elastomers") are, from certain material property standpoints,
preferable to the fluid properties which are encountered with
magneto rheological fluids, energy consumption demands which are
inherent in MRE deployment make it preferable to utilize MRF. From
a comparative perspective, it appears from manufacturers'
specifications, that energizing an MRE takes approximately 2.5
times the power draw of energizing an MR Fluid. Thus, the instant
device may incorporate by reference MRE, but preferentially use MRF
as an active element in its adaptive actuation mechanism.
[0050] Advantageously, the "activation-time" between states is
relatively rapid. The Lord Corporation, manufacturers of fluids
with MR properties quote activation times of 0.07 seconds. This
corresponds to a frequency of 14.25 Hz, placing it within the upper
range of vibrations encountered in harsh drilling conditions.
[0051] The Raymond mechanism claims means for "providing frictional
properties that are alterable while the drillstring is in use; and
controlling the frictional properties based upon changing ambient
conditions encountered by the bit. The invention preferably dampens
longitudinal vibrations and preferably additionally dampens
rotational vibrations. Two damping mechanisms in series may be
employed."
[0052] The axial and torsional vibration damping mechanisms in the
Raymond invention are physically separate in the Raymond invention,
leading to a device which is substantially longer and more flexible
than the one proposed in the instant invention. Thus the instant
invention incorporating both axial and torsional damping means
within a single, truncated element presents improvements over prior
art in that it is shorter, approximately one-quarter the length]
less flexible and thus has a more predictable modulus of elasticity
which is operationally advantageous. The instant invention
advantageously claims the benefit of lateral vibration damping
control, which ability is outside the scope of the Raymond
device.
[0053] The Raymond device was configured with mechanical spring
mechanisms as its basis. Various configurations having natural
frequencies which were reported as 32.39 Hz, 26.45 Hz and 12.83 Hz
respectively were used. Despite the use of mechanical damping means
with various natural frequencies in combination with MR damping
mechanisms, the experiments which were carried out and reported in
Raymond showed that some spring configurations were less beneficial
than others. Thus, the performance of MR damping means in Raymond
was contingent on the natural frequency of the mechanical spring
mechanisms.
[0054] "The importance of choosing the correct spring stiffness for
the shock sub is shown in FIG. 12 for a 1500 lb WOB and 180 RPM in
SWG ("Sierra White Granite"). This figure compares the effect of
using 32.39, 26.45 and 12.83 Hz shock subs, with comparable damping
levels to a rigid system. The 12.83 Hz shock sub performs best.
[0055] Background materials in Raymond suggest that while the 12.83
Hz shock sub may perform best with the bit size and cutter
configuration selected in the undertaking the field experiments,
that this particular frequency is not, of itself, a panacea. Nor is
it evident that a sprung system with a lower natural frequency is
ultimately more successful across a range of drilling conditions
than one with a higher natural frequency.
[0056] The construction of the instant invention is such that it
has no internal spring mechanism and additionally, that there is no
causal relationship between the closed cell elastomeric material
which acts as the primary damping mechanism and the secondary,
active damping mechanism. This advantageous construction, having no
constraining natural frequency, means that the active MR damping
means is functionally independent. This, therefore, constitutes a
significant improvement over prior art. Additionally, as will be
shown, magneto-rheological damping means will be employed which
will enable adaptive damping to suit changing drilling conditions.
Further, the MR damping capability will be capable of being
continuously, discontinuously, intermittently or sporadically
activated on command and in conjunction with pre-determined sensor
and logic means in order to arrive at damping whose effectiveness
is energy efficient.
[0057] The Raymond device incorporates a mud powered turbine
generator with which to generate electrical power for the downhole
device. The turbine generator adds significant additional length to
the device and, were the Raymond device to be deployed in the near
bit position, would place additional distance between the bit
surveying devices located proximate the bit.
[0058] An improvement over the Raymond device is disclosed in U.S.
Pat. No. 7,219,752 to Wassell et al SYSTEM AND METHOD FOR DAMPING
VIBRATION IN A DRILLSTRING in which the valve mechanisms
incorporated within the damping device receive particular
attention. As with Raymond, the Wassell device also has its basis
in traditional shock absorber mechanism construction with a stroke
length which is several inches in length. The Wassell device
features an axial damping spring assembly and torsional bearing
assembly which are individually configured and separated by a valve
assembly with the objective of diminishing bit and drillstring
generated vibration.
[0059] The instant device claims advantage over both Raymond and
Wassell in that it is constructed specifically to diminish bit
generated vibration, has no stroke length, providing for a shorter
more rigid construction for incorporation into the BHA which is not
influenced by internally generated displacement related
harmonics.
[0060] Additionally, the instant device features a combined and
integrated axial and torsional and lateral damping element which
favourably provides for insertion of the invention in the near-bit
stabilizer position This mechanical construction, in combination
with active and secondary damping elements which are unique to the
instant device acknowledges that the amplitude of bit generated
harmonic vibration typically requires a damping mechanism with a
relatively short stroke.
[0061] A further improvement over Wassell, which will be explained
later, is the ability to provide adaptive damping response by
informing the instant device of alterations to relevant surface and
downhole parameters through use of a downlink protocol.
[0062] In a further improvement over prior art, the a device in
accordance with an embodiment of the present invention proposes the
use of simplified, commercially available magneto-rheological
control mechanisms such as those described in Ivers et al (U.S.
Pat. No. 6,158,470) TWO WAY MAGNETORHEOLOGICAL FLUID VALVE ASSEMBLY
AND DEVICES USING SAME. These valve configurations enable
simplified hydraulic circuitry and control means to be deployed in
conjunction with electro-magnetic coil elements and MR fluid which
may advantageously be utilized within the instant invention.
[0063] The instant device, which will be described later, may
effectively also utilize piezo-electric fibre technology as a means
for measuring vibration. Additionally, the instant device may use
piezo-electric fibre technology for the purposes of generating
power as an integral component of the mechanism.
[0064] Therefore, as the generated electrical power is proportional
to the amount of vibration encountered in the downhole environment,
piezo electric fibre ["PE Fibre"] technology may advantageously be
used both as a measurement and a control and activation means. The
utility of the PE Fibre technology can be put is dependent on its
generation, which is, in turn, dependent on the amount of vibration
encountered in the distal elements of the BHA.
[0065] The inventors believe that the partial successes of prior
art and the body of information accumulated to date indicate that
it is insufficient to obtain sensor data from a single source of
harmonics and that an integrated closed loop, adaptive approach is
required. Notwithstanding sensor measurements made within the
instant device, without information pertaining to wider
environmental conditions and at a minimum surface RPM, the downhole
device has insufficient information to be able to determine the
appropriate frequency of corrective actions. This will provide for
versatility and adaptability to changing drilling conditions.
Additionally it allows for real time adjustments to be made to the
downhole device without compromising the efficiency and
effectiveness of the drilling process. Thus, the instant device
claims improvement over prior art through the incorporation of both
surface and downhole data in its approach to the control of
harmonic vibration within the single, instant, device. In addition
to surface parameters, the downlinked data may incorporate, data
derived from measurement-while-drilling "MWD" telemetry and which
may further communicate component measurements pertaining to the
real-time downhole vibrational state from sensors located in other
components of the BHA to the instant device, via the surface of the
earth. The information which is transmitted may be raw, processed
or encoded sensor data. At the surface the uplinked information is
additionally utilized in order to preferentially modify surface
RPM, thus optimizing the environment for operation of the downlink
protocol.
[0066] In order to achieve this, a downlink communications protocol
is required. Downlinking refers to the ability to send data from
the surface of the earth to a downhole device. Used in conjunction
with industry standard "uplink" protocols, the combination of
systems is frequently referred to within the industry as
"closed-loop".
[0067] Although "closed-loop" is referred to in several prior art
publications, and most recently in particular with regard to
providing instructions for 3-dimensional rotary steerable systems
("3D-RSS") its utility as a element with which to reduce harmonic
vibration has, largely, gone un-remarked.
[0068] Hay et al (U.S. Pat. No. 6,948,572), COMMAND METHOD FOR A
ROTARY STEERABLE DEVICE, restricts the application of its downlink
protocol to usage with a 3D-RSS:
[0069] Claim 1: In a drilling system of the type comprising a
rotatable drilling string, a drilling string communication system
and a drilling direction control device connected with the drilling
string, a method for issuing one or more commands to the drilling
direction control device . . . . "
[0070] Alternatively, Finke et al (U.S. Pat. No. 6,920,085),
"DOWNLINK TELEMETRY SYSTEM" using timed fluctuations in the
drilling fluid pressure, provides for instruction via pressure
pulses to a downhole assembly. In this case the designated
receiving tool is a "Pressure While Drilling" tool.
[0071] McLoughlin (U.S. Pat. No. 6,847,304) "APPARATUS AND METHOD
FOR TRANSMITTING INFORMATION TO. AND COMMUNICATING WITH A DOWNHOLE
DEVICE" proposed a discontinuous method for communicating between
surface and a 3D-RSS device configured about a non-rotating
stabilizer format and utilizing variations in the rotary speed of
the drilling assembly. Principally, this method allowed for periods
of reduced or null rotary speed as components in the communications
protocol.
[0072] It may be noted that all downlink prior art protocols,
unless using customized, hard-wired drillpipe, for example, such as
those proposed in Hall (U.S. Pat. No. 6,670,880) "DOWNHOLE DATA
TRANSMISSION SYSTEM and Hall (U.S. Pat. No. 6,392,317) "ANNULAR
WIRE HARNESS FOR USE IN DRILL PIPE, in some way compromise the
integrity of drilling operations.
[0073] A device in accordance with an embodiment of the present
invention claims improvement over prior art through the
incorporation of a methodology for communicating information from
the surface of the earth to a downhole device on a semi-continuous
or continuous basis without utilizing customized drill-pipe, or
compromising the drilling operation, which method constitutes an
improvement over claims made by prior art.
[0074] A downlink communications protocol method, systems and
apparatus which may fulfil the desired criteria without
compromising drilling operations is disclosed as U.S. Pat. No.
7,540,337 to McLoughlin & Variava, ADAPTIVE APPARATUS, SYSTEM,
AND METHOD FOR COMMUNICATING WITH A DOWNHOLE DEVICE which proposes
a downlink protocol which uses the optimized surface drilling RPM
as a baseline for a real-time adjustable communications protocol.
Advantageously, the system is capable of adaptive recalibration to
accommodate alterations to the baseline RPM, without compromising
drilling performance. At surface minor alterations to the frequency
of the baseline drilling RPM are made in accordance with
pre-determined timing intervals with the objective of conveying
information to a device or multiple devices located at the distal
end of the drilling assembly. As previously commented, the downhole
device is instrumented such that rotational velocity can be
determined by any of a number of well understood means, in order to
be able to identify alterations to rotational speed in the distal
environment.
[0075] Thus a significant improvement which an embodiment of the
present invention claims over prior art is the closing of the
communications loop between the surface of the earth and the
instant downhole device, supplying data for the purposes of
enabling adaptive damping means and without detriment to the
drilling process.
SUMMARY OF THE INVENTION
[0076] In a first aspect, the present invention provides an
adaptive system, method and apparatus for active vibration damping
and control of downhole systems.
[0077] In an embodiment, the invention comprises a system and
apparatus and method of controlling and adjusting the attitude of
drill-collars with respect to the drill-bit in the rotary drilling
process, the advantage of which, via means of a ball joint torque
transfer mechanism, allows for relative lateral motion
therebetween. Advantageously, the attitude control mechanism
provides for reduced lateral vibration which substantially
diminishes bit radial force and mass imbalances, resulting in an
improvement to the rate-of-penetration. The attitude adjustment is
intrinsic to the device, system and apparatus.
[0078] According to an embodiment, the invention exercises control
over torsional stick-slip and additionally proposes improvement
over prior art in the construction of a mechanism which diminishes
lateral shock.
[0079] Preferentially, the system, method and apparatus for
substantially reducing or eliminating bit and drill collar induced
drilling vibration comprises a near-bit device which is equipped
with stabilization which centres it within the borehole. The device
additionally constitutes an improvement over prior art in that it
claims the benefit of having a natural frequency which is alterable
in the downhole location which advantageously provides for
compliance across the entire range of drilling vibrations.
[0080] The device, although functionally autonomous, may
preferentially work in collaboration with a surface downlink
protocol which is responsible for transferring information
pertaining to drilling parameters and conditions from the surface
of the earth. Such a protocol is described in U.S. Pat. No.
7,540,377 to McLoughlin & Variava, ADAPTIVE APPARATUS, SYSTEM
AND METHOD FOR COMMUNICATING WITH A DOWNHOLE DEVICE. The surface
downlinked information is communicated to electronics, logic and
control systems within the downhole assembly, thus closing the loop
between surface and downhole and allowing the downhole assembly to
be functionality adaptive to real-time drilling conditions.
Advantageously, the device profits from the vibration inherent in
the distal component of the downhole environment in order to
harvest electrical energy through the integration of materials
which have piezo-electric properties. Primary damping capability
within the instant invention is derived from closed cell
elastomeric material. The device also confers hydraulic damping
capability across a range of frequencies and is equipped with
appropriate hydraulic circuitry. Preferentially, the hydraulic
circuitry of the device may be configured advantageously to utilize
the variable rheological properties inherent in magneto-rheological
fluids to achieve a damping across a wider range of frequencies or
in controlling the tool's operation.
[0081] The instant device and downlink protocol may also
preferentially work in conjunction with a TORSION SUB, which is
advisably located in the drilling assembly proximately in relation
to the surface of the earth. The objective of the Torsion Sub is to
provide damping to the BHA, inhibiting drillstring induced axial
and torsional vibrations. The Torsion Sub is the subject of a
Co-pending U.S. Provisional Patent Application, Ser. No. 60/967,306
entitled "ADAPTIVE, COMBINED AXIAL AND TORSIONAL COMPENSATION
SYSTEM, METHOD AND APPARATUS for ACTIVE VIBRATION DAMPING," filed
on Sep. 4, 2007 and published as WO 2009/030926 A2/A3 under the
title "A Downhole Device."
[0082] In a further aspect, the present invention provides control
over downhole system and apparatus by which control is exercised
over an articulated mandrel by hydraulic fluid transfer means and
preferentially whereby axial, torsional and lateral shock damping
means is enabled; wherein, the fluid is preferably transferred
between piston means of equal volumes.
[0083] The above method an apparatus is preferably equipped with
stabilizer means for the purposes of centering the device within
the borehole and for providing energy dissipation thereby and
wherein an articulatable torque transfer mechanism may provide for
degrees of freedom between structural elements of the device in
which a resilient fluid passageway may be provided which provides
intra-structural support, additionally serving to isolate the
torque transfer mechanism and active vibration element means from
drilling fluids.
[0084] The damping means may be passive. The damping means may be
active and adjustable within the apparatus. The active damping
means may utilize variations in rheological fluids. The damping
capability may be modifiable in frequency and amplitude, responsive
to harmonic vibration encountered in the environs of the drill bit.
The damping means may preferentially incorporate electro-mechanical
or electro-hydraulic valve means. Hydraulic actuation capability
may be proportional, continuous, discontinuous, intermittent or
sporadic, responsive to harmonic vibration encountered in the
environs of the drill bit. The apparatus may be informed of events
pertaining to alternate physical locations within the drilling
assembly.
[0085] Piezo-electric (fibre) structures may be utilized for
measurement, as a means of quantifying forces to be applied or as
actuation motive means within the device.
[0086] In a further aspect, the present invention provides a
downhole system, method and apparatus with adaptive, active,
multi-frequency damping which is functionally adjustable in the
downhole location in response to changing drilling harmonics, and
which may also be a control mechanism for downhole systems,
BRIEF DESCRIPTION OF THE DRAWINGS
[0087] The present invention will now be described with reference
to the following preferred, non-limiting embodiments, in which:
[0088] FIG. 1: is a longitudinal cross-sectional view of the
instant invention.
[0089] FIG. 2: is an enlarged, partial, longitudinal
cross-sectional view of the active damping mechanism housed within
the stabilizer contact area.
[0090] FIG. 3: is a three dimensional rendering representation of
FIG. 1.
[0091] FIG. 4: is a cross sectional view of the invention
illustrating a four-bladed configuration of the instant device.
[0092] FIG. 5: is an enlarged, partial, longitudinal
cross-sectional view highlighting secondary damping piston means
and associated fluid transfer mechanism equispaced about the
rotational centre of the device.
[0093] FIG. 6: is an enlarged partial, longitudinal cross-sectional
view highlighting secondary damping piston means and associated
fluid transfer mechanism differentially spaced about the rotational
centre of the device so as to achieve a mechanical advantage.
[0094] FIG. 7: is an enlarged, partial, longitudinal
cross-sectional view highlighting the electro-magnetic coil means
radially configured about a single fluid passageway.
[0095] FIG. 8: is an enlarged partial longitudinal cross-sectional
view highlighting alternate electro-magnetic coil means radially
configured about damping piston means.
[0096] FIG. 9: is an enlarged partial longitudinal cross-sectional
view of the seal-carrier sub-assembly, piezo-electric fibre
sections and wiring conduits.
[0097] FIG. 10: is an exploded rendered, three-dimensional view of
the removable electro-magnetic control and valve housing.
MODES FOR CARRYING OUT THE INVENTION
Including a Functional Explanation
[0098] The device will first be discussed in general terms in order
to explain embodiments of the invention. It will be described in
several forms, all of which have similar objectives and which have
varying degrees of technical complexity. Principally, this device
differs from prior art in the field of downhole vibration damping
in that it provides damping for rotational, longitudinal and
lateral vibrations, it is responsive to information conveyed to it
in real time from the surface of the Earth, that it is constructed
with an inherently variable natural frequency and that,
advantageously, it seeks to harvest energy from the downhole
environment.
[0099] Referring to FIG. 1: The instant stabilized mechanism
comprises a stabilizer sleeve element [1] which is radially
co-located about a bi-partite internal mandrel sub-assembly [2],
[3]. The stabilizer may be equipped with any of a variety of well
understood stabilization means [4] which formats may include
straight, spiral or ring blades. Stabilization means may be
selected and deployed in preferential fulfilment of geographic
regionally dictated operating parameters.
[0100] The mandrel element comprises an upper[2], and lower element
[3], which are appropriately equipped with rotary threaded
connections. The upper mandrel is equipped with a box
connection[5], and the lower mandrel is preferentially also
provided with a box connection [6], it being the intention to place
the device at the near-bit location within the drillstring. Should
the device be positioned at an alternate location within the
drillstring an alternate pin connection may equally be provided for
the lower member [3].
[0101] Torque transfer within the bi-partite mandrel configuration
allows for torque transfer between mandrel elements by means of a
compliant metal-to-metal torque transfer mechanism [7] having
ball-joint functionality or any similar structure which allows for
relative articulation and compliant structural rigidity between the
upper and lower mandrel sub-assemblies [2],[3]. The lower mandrel
assembly [3] is held in torsional rigidity relative to the
stabilizer sleeve element [1] allowing for relative motion only
between upper mandrel [2] and the stabilizer sleeve element
[1].
[0102] Significant benefits of the compliant vibration damping
configuration of the invention are on-centred drill bit alignment,
reduction of micro-tortuosity of the borehole, consistent, rather
than irregular instantaneous force being applied to the bit cutting
structure resulting in reduction to wear of the cutting elements.
When the instant invention is utilized with rock-bits, the bearings
contained therein are less likely to be damaged by fluctuations in
bearing loading. Additionally, the instant device is more likely to
result in the drilling of a gauge hole, and less likely to result
in "out of round" or "lobed" hole profiles.
[0103] The advantageous compliance resulting from the installation
of the instant device within the bottom-hole-assembly decouples the
torsionally stiff drill collar elements from the bit while still
allowing for effective weight transfer from the BHA to the bit
cutting structure.
[0104] The mandrel [2] [3] articulation is facilitated by upper
contact ring [11] and lower contact ring [8] sub assemblies which
emulate ball joint functionality. The off bottom contact ring [11]
is deployed in conjunction with a locking ring sub-assembly [12],
preventing disengagement of the mandrel elements when the assembly
is being tripped in or out of the hole. Significant primary axial,
rotational and lateral damping capability is added through the
inclusion of an upper anti-vibration ring assembly [19]. Drilling
fluid passes through a flexible flow tube [13] which has a proximal
end [14] which is suspended or locked into a counterbore [15]
located in the internal diameter of the proximal mandrel
sub-assembly box connection[5]. The flow tube [13] has a distal end
[16] which traverses a lower anti-vibration ring [17], and is
co-located within that same mechanism wherein it is axially secured
by means of a lock ring [18]. The flow tube [13] bridges the
flexible area between upper[2] and lower mandrel [3] elements and
contributes significantly to the structural rigidity of the device.
Additionally the flow-tube [13] provides means for preventing
drilling fluid from contaminating the hydraulic reservoir elements
of the instant invention.
[0105] The seal carrier [38] and lower anti-vibration ring [17],
being in the vicinity of the highest amplitude bit vibration, may
also preferentially incorporate, piezo electric fibre harvesting
elements [37].
[0106] Primary passive damping capability within the device is
provided by an upper anti-vibration ring [19] which is axially
located between the upper mandrel [2] and sleeve elements [1] and
which is radially locked into place through the identical locking
ring sub assembly [12] which serves as axial retainer for the
off-bottom contact ring [11]. The upper anti-vibration ring [19] is
composed of closed cell elastomeric material which is placed under
compression and suitably dimensioned for the purposes of damping
bit generated radial, axial and torsional and lateral shocks.
[0107] The properties of the elastomeric materials are selected to
achieve damping across a range of frequencies typically associated
with rotary drill bits, which properties are suitable for service
in a wide range of drilling environments. The upper anti-vibration
damping ring [19] is additionally responsible for the stabilization
of the upper mandrel [2] and for the effective transfer of unwanted
harmonics to the stabilizer sleeve contact area [4] and thence to
the borehole wall. The closed cell elastomeric material is,
however, constrained in that it has a natural frequency which, in
certain scenarios will provide insufficient or ineffective harmonic
damping. Alternate configurations using laminated elastomers with
different natural frequency properties or dimensional
characteristics may be utilized without departing from the spirit
of the invention. Any inherent weakness in the passive damping
mechanism is compensated for in a scenario which is detailed
below.
[0108] Referring now to FIGS. 2 and 3: Additional damping
capability within the instant device is accomplished through a
plurality of damping piston[24] means constrained between upper
mandrel sub-assembly [2] and stabilizer body sub assembly [1].
FIGS. 2 and 3 are intended to be illustrative of the concept and
represent a quadripartite symmetry which has been selected for ease
of description: these Figures are illustrative of the active
vibration damping elements and should not be taken as limiting the
invention.
[0109] Likewise, each set of piston sub-assemblies in the
illustrations incorporates paired piston sub-assemblies,
representing an ideal configuration. In smaller diameter
constructions it may be preferred to construct the invention with a
single piston per blade and effect secondary damping by means of
inter-blade fluid transfer--as opposed to intra-blade fluid
transfer. Each of these methodologies is considered to be within
the scope of the instant device.
[0110] In one, exemplary configuration, each borehole contact blade
or contact point of the stabilizer with the formation[4]
sub-assembly is equipped with, at a minimum, two damping piston[24]
sub assemblies, Wherever functional distinction is required in the
specification, for ease of reference these will be referred to as
[24-D] "distal" and [24-P], "proximal."
[0111] The pistons [24] are located radially within cylindrical
means [28], preferentially integrated into the blade housing [4],
[28] and oriented perpendicularly with respect to the principal
axis of the borehole, although other orientations made be made
without departing from the spirit of the instant device. Each
piston[24] is equipped with appropriate sealing means [25] which
seals the piston within the blade housing [28]. Thus equipped with
seals, the piston[24] sub-divides into inboard chamber [26] and
outboard chamber [27] elements. The piston is preferentially biased
towards the mandrel [2] by use of compression springs [29] inserted
between the piston and the piston cover plug [30] which is retained
within the stabilizer housing body by threaded means [31] or by
other methods which are well understood within the industry.
Preferentially an additional locking mechanism such as a snap-ring
[32] is utilized for additional security.
[0112] Returning to the chambers [26], [27], which are created by
the piston sub assemblies [24], the inboard chamber [26]
preferentially contains hydraulic fluid or other lubricating means
for the gear assembly [7]. At a radial location outboard of the
piston seal sub assemblies [25] the outboard chamber [27] contains
magneto-rheological fluid "MR Fluids".
[0113] In its simplest configuration, each blade sub-assembly
contains within it, a bored passageway [33] which connects the
outboard chambers [27] created by piston sub-assemblies
[24-P],[24-D], although cross linking between any blade
sub-assemblies is also considered within the scope of the instant
device. For example, as illustrated in FIG. 4: it may be
advantageous to take an input harmonic vibration force from Blade
1, proximal piston sub-assembly [24-P] and apply a restoring
damping force to Blade 3 distal piston sub-assembly [24-D].
[0114] Control over fluid flow between the outboard chambers [27]
may be achieved by means of a low power electro-mechanical valve
[34]. It will be evident that the flow of fluid across the valve
surfaces is proportional to the relative torsional and lateral
motion between upper mandrel [2] and sleeve [1] sub-assemblies.
Volumetric fluid flow characteristics may be altered through
changes to the relative diameters of cylindrical bores within the
stabilizer housing [28] and the through bore [33]. The greater the
ratio of diameters, the larger the displacement of fluid within the
through bore [33] and the more finely tuned may be the degree of
damping control.
[0115] Although control over the volume of fluid which is displaced
as a result of piston movement and the resulting inter-piston fluid
flow will confer secondary damping capability to the distal
elements of the BHA, it is envisaged that additional damping
capability across a range of frequencies is derived through the
alteration of the fluid properties inherent in MR Fluids.
[0116] Referring now to FIGS. 5 and 6, it will further be apparent
that the damping capability of the piston means [24-P], [24-D] is
such that mechanical advantage may be claimed by adjusting the
axial position of the pistons relative to the torque transfer bevel
gear [7] between upper mandrel [2] and stabilizer sub assembly
[1].
[0117] The motion of the pistons [24] may be described as
perpendicular-radial with respect to the principal axis of the
mechanism although this should not be taken as a constraint on the
piston configuration. Thus, irrespective of the relative position
of the pistons [24] and the mechanical benefit conferred, thereby,
the instant device claims as an inventive step, the transfer of an
equal volume of fluid between proximal and distal elements of the
bored passageway [33].
[0118] FIGS. 5 and 6 also introduce the downhole harvesting of
electrical power through the use of piezo-electric technology.
[0119] Thus, for example, the optimal position for the location of
piezo electric generation is in the region of the lower anti
vibration ring and seal carrier sub assembly[17] although any other
alternative locations for its installation may be considered within
the scope of the instant invention. The selected location is
beneficial as it is subject to rotational compression, lateral,
torsional and axial vibration. The instant device therefore
proposes the generation of electrical power using materials with
piezo-electric properties which are integrated into the lower
sub-assembly. Piezo-electric fibrous materials are embedded in a
matrix and configured as transducers which are responsive to
motion, vibration and compression and which recover [waste]
mechanical energy from the lower sub-assembly, converting it to
electrical power.
[0120] The inherent system symmetry within the instant invention is
such that the electrical energy output is in proportion to input
vibration. Preferentially, the PE material[42] may be configured in
radial nodes within the seal carrier and lower anti-vibration ring
[17]. In this configuration non-continuous off-axis vibration can
be quantified as a function of generated power. FIG. 9 provides an
enlargement of the preferred embodiment of the PE Harvesting sub
assembly. The electrical energy is harvested as a by-product of the
bit generated vibration which is experienced within the stabilizer
body [1] and lower sub assembly, [3] and seal carrier [17] in
particular. This sub-assembly, being directly coupled to the bit is
subject to maximal axial, lateral and torsional bit vibration, thus
realizing peak energy generation capability. A collector ring [37]
and associated wiring conduits [38] serve to transfer the harvested
power throughout the device.
[0121] A further benefit of utilizing piezo-electric fibres [37]
within the instant device is that, in addition to its electrical
generating capability, it can be used as a relatively accurate
indicator of downhole vibration, obviating the requirement for
sophisticated sensor arrays. Thus, as PE electrical generating
capability is proportional to vibration, if the instrumentation
contained within the downhole device is equipped to monitor PE
generation levels in conjunction with a clock-timing board, it is
able to relate the generated PE electrical charge to vibrational
levels.
[0122] Contingent on the internal sample rate, the use of PE fibres
[37] as sensor may confer the ability to distinguish between
vibrational sources, which functionality may be utilized to
determine when and where to apply intermittent or sporadic damping
capabilities to the magneto-rheological, [36] active vibration
damping element of the device.
[0123] Additional and alternative locations for incorporating the
PE materials [37] may include the upper-anti-vibration ring [19]
where the output, measured relative to the output of PE materials
incorporated into distal elements of the device may be utilized as
a measurement of the damping efficiency of the instant invention.
Thus, relative, successive qualitative measurements may serve to
indicate internal efficiency of damping mechanism of the instant
device and iterative improvements to the active damping mechanism
made thereby.
[0124] In summary, the PE material[37] capability may be used as an
initial condition sensor, when measured against time, and it may be
used as a relative measurement of harmonic damping improvement.
[0125] Alternatively it may be used as one or more power means for
the control of the internal hydraulic circuitry, either for both or
each of the MR fluid means or the valve actuation means.
[0126] Referring now to FIGS. 7 and 8: In furtherance of the aim of
variable control over secondary damping means therefore, a
preferred embodiment of the instant device is preferentially
equipped with electro-magnetic coils [35]. From the perspective of
energy efficiency and power conservation[36] it is preferable to
configure the coils to be arranged circumferentially about the
bored passageway [33]. However, from the perspective of ease of
construction, in an alternate embodiment, the coils [35] may be
configured circumferentially about the piston means [24] giving
rise to differential damping capability and the possibility of
damping across multiple frequencies within a single blade
sub-assembly. From the perspective of ease of assembly, FIG. 9
illustrates one method of constructing the damping control means
whereby the electro-magnetic control and valve housing [46] are
bolted [47] into the blade sub-assemblies [4], although any means
of retention may equally be utilized.
[0127] The configuration of FIG. 7 through to 9 incorporates
auxiliary power in the form of lithium cells [23], which
illustrated number is not intended to be a constraint upon the
invention. An electronic control mechanism in the form of a PCB
mechanism [21] and associated sensors [22] are contained in a
pressure vessel within the housing [46] and sealed therein by
sealing caps [44] which are equipped with sealing means [not shown]
which are well understood by those practiced in the art. Valve
means [34] preferentially of electro-mechanical construction is
also sealed into the housing in such a manner as to intersect the
bored passageway [33] between proximal outboard chamber [27P] and
distal outboard chamber [27D] which chambers are preferentially
filled with hydraulic fluids which have magneto-rheological
properties. [36].
[0128] Electro magnetic coil assemblies [35] are inserted into the
housing [46], providing fluid connection means between proximal
outboard chamber [27P] and distal outboard chamber [27D] and
sealing the fluid mechanism within the housing [46] and the
stabilizer sub-assembly [1], with the objective of affecting
changes to the viscous properties of the magneto-rheological fluid
[36] contained therein.
[0129] Recent commercial developments in simplified MR Valve
control mechanisms per Ivers, U.S. Pat. No. 6,158,470 may be
employed in furtherance of this arrangement.
[0130] The instrumentation assembly [21] which is incorporated into
the device in order to acquire sensor data and information from
both surface and downhole locations, acts as power distributor,
logic gate, comparator of sensor outputs and facilitates actuation
timing of the active components of the damping piston
sub-assemblies. The instrumentation is equipped with a PCB [21] and
may be equipped with sensor inputs [22]. Downhole memory is a
further function of the instrumentation.
[0131] As the instrumentation[21] package is likely to require
stable and continuous power supply, parasitic current drain is
preferentially to be provided for by high temperature batteries
[23] which are frequently deployed and well understood in the
industry.
[0132] Sensors [22] which may be deployed may include
accelerometers, magnetometers, inertial devices, strain gauges or
any other sensors which are capable of measuring shock, vibration,
acceleration, rotation or other relevant measurements without
departing from the spirit of the invention. Sensors of this type
are well understood in the industry. Low mass, low power devices
may preferentially be deployed, such as MEMS accelerometers.
[0133] For the comparative purposes of relative internal
measurement within the instant device, a primary, distal, group of
sensors [22-D] may preferentially be located within the collective
lower mandrel [3] and sleeve sub assemblies [1] with a secondary,
proximal[22-P] group of sensors being located within the upper
mandrel sub-assembly [2].
[0134] Without departing from the spirit of the instant invention,
the distal and proximal sensors may be of identical configuration
and construction, or alternate means of construction. Additionally,
they may be radially indexed for the purposes of obtaining
relationally comparative harmonic measurements, or, alternatively,
for ease of construction, they may be physically radially offset
with temporal or geometrical sensor offsets being applied as
required. The number, type, and placement of sensors should not be
taken as a limiting factor in the construction of the instant
device.
[0135] The instant device provides for improvements over prior art
insofar as it proposes constructive utilization of the
characteristics of the drilling process itself and thus a preferred
configuration of the device provides for in situ generation and use
of harvested electrical power by means of piezo electric fibre
[42].
[0136] Typical stable electrical power means incorporated into
prior art includes either lithium cells [23] or turbine alternator
devices [not illustrated]. The turbine method of electrical power
generation is constrained to the provision of power during periods
when drilling fluid is being pumped through the drilling assembly.
Typically, even when turbines are deployed, battery elements [23]
are utilized which can provide continuous current for parasitic
devices such as instrumentation[21], clock-timing boards and
sensors [22]. Batteries require pressure vessels--in this case the
EMC and valve housing--to protect them from the ambient pressure
and represent considerable packaging constraints on the design of
downhole devices.
[0137] Restated, the magnitude of electrical energy which is
generated by the piezo-electric materials [42] is thus perceived as
having proportionality to the magnitude of bit vibration. It will
be appreciated by those skilled in the art that this electrical
energy is intermittent in nature and is unlikely to be generated
and consumed in the same instant. Therefore, although the PE [37]
generated energy may be measured instantaneously as sensor means,
it is preferentially stored for later use. Storage for the
electrical power is provided in the form of high temperature
capacitors which are well known to those versed in the art of
downhole electronics construction and are hereby schematically
included as being incorporated within the PCB means [21]
A Functional Description
[0138] A description will now be made of the idealized
functionality of an embodiment of the invention. The description is
not intended to provide constraints, but is intended to provide
exemplary description of the key elements of the design.
[0139] At surface the device is coupled to the bit and lower
elements of the BHA; preferentially it is installed in the position
of near-bit stabilizer. Functionally, the device is run in the hole
and drilling commences using drilling parameters optimized for the
particular bit type and formation properties. As bit generated
harmonic vibration commences, the passive elastomeric component of
the upper anti vibration damping sub assembly prevents the transfer
of some of the vibration from the lower mandrel and stabilizer sub
assembly to the upper mandrel assembly.
[0140] The passive damping mechanism is augmented by the active
anti-vibration sub-assembly which comprises a plurality--although
probably no less than three in number--of essentially radially
configured hydraulic damping piston assemblies. Each damping piston
sub-assembly constitutes a plurality of damping piston
sub-assemblies which are interconnected by means of passageways or
tubular means which are preferably installed within the stabilizer
blade sub-assemblies.
[0141] At the distal end of the instant device, on making contact
with the rock formation, the bit typically generates low frequency
vibration which is transferred to PE elements contained
preferentially within the seal carriage sub-assembly. The PE
elements are subject to stresses resulting from vibration inherent
in the near-bit drilling environment and generate electricity which
passes through a voltage conditioning circuit and is then stored in
capacitors located within the electronics sub assembly. The
electrical output of the PE material may be monitored as
pseudo-sensor means, indicative of the vibration condition present
in the environs of the seal carrier sub assembly. Timing circuitry
and logic systems build into the PCB sub-assembly may be made in
order to further benefit from the inherent system symmetry where
electricity generated is proportional to input harmonic amplitude
and frequency.
[0142] The capacitors used for storing the PE generated electrical
power may be segregated such that they are related to specific
radial constructional nodes of PE material and indexed to provide
preferential circumferential damping, or charged sequentially or
cumulatively for general damping across the entire active vibration
damping area.
[0143] It will be apparent to those skilled in the art that the
intrinsic functional symmetry of the device is such that when peak
vibration is at its highest then the electricity which is generated
will also be at a maximum and can be applied to the active damping
process. Correspondingly, when vibration is at a minimum then
active damping requirements are also at a minimum.
[0144] In summary, piezo electric generation is always proportional
to distal vibration amplitude and frequency.
[0145] Thus, a preferred configuration of the instant device relies
on symmetrical and proportional application of electrical power
derived from vibration to generate an electro-magnetic field which
may preferentially be applied to the magneto rheological fluids
whose properties have been broadly described earlier in this
application. The PE utility may be confined to actuation means,
i.e. valve control, where primary electrical power used to alter
the MR Fluid properties is provided by lithium cells encapsulated
within the instant device and the vibration derived electrical
power is utilized to control the valve mechanisms. Alternatively
the PE output power may be utilized to alter the MR fluid
properties and lithium cell derived electrical power to provide
motive force for the low power valve mechanisms. In yet another
alternative configuration, the vibration generated electrical power
may be used to increment battery power, acting as both input and
output, thus quantifying vibration and delivering damping
capability.
[0146] In a preferred configuration of the instant device the
damping piston assemblies are configured with narrow by-pass
apertures around which coils are configured to apply an
electro-magnetic field to magneto-rheological fluids. The fluid
viscosity is altered by applying varying amounts of current and by
altering the phase and duration of the current timing in order to
create an adaptive and adjustable level of shock damping. The
smaller the amount of MR Fluid which requires energizing, the more
efficient the instant device will be: thus smaller diameter fluid
channels which are circumscribed by EM coils will require less
power in order to effect changes to the apparent fluid properties
of the MR fluid. This translates into greater mechanical
efficiency.
[0147] The instant invention may be configured to be sophisticated
or relatively simple in format. The overall timing of damping
piston strokes and valve actuations is generically under the
control of the downhole instrumentation. Utilizing the downlink
command protocol increases the information at the disposal of the
downhole instrumentation, but, preferably does not override the
logic control which the on-board instrumentation exercises.
[0148] Damping piston strokes may be preferentially envisaged as
being proportional, rather than binary in nature, although in the
case of simple harmonic vibration a pure binary damping mechanism
may prove adequate. Thus the degree of damping can be controlled
with precision by the downhole electronics.
[0149] This does not remove the possibility of applying equal
damping to all piston assemblies simultaneously, but leaves open
the capability of differential and proportional damping
stabilization of the assembly through the application of damping to
one or more pistons sequentially, discontinuously or continuously,
depending on the environment and damping requirement.
[0150] In an embodiment of the instant device which was equipped
with an limitless energy budget, it may be envisaged that harmonic
vibration may be continuously damped with each revolution of the
bit, however it is within the scope of the instant device for the
active vibration damping mechanism to operate intermittently and
disruptively in order to prevent cumulative and incrementing
harmonic vibration effects.
[0151] It is also within the scope of the instrumentation of the
instant invention to phase shift the valve actuation timing in
order to minimize transference of bit vibration from the lower
sub-assembly to the proximal bottom hole assembly.
[0152] At its most simple, a configuration which instantaneously
delivers proportional hydraulic damping via vibration generated
electrical power, may be used irrespective of whether bit generated
vibration is high or low as the generation of electricity and
subsequent alteration of the magneto rheological fluid properties
is proportional to input system vibration. Thus, when vibration is
high, PE generation capability and active damping capability is
proportionately high: when vibration is low, PE generation is also
low, but there is little or no requirement for active damping.
[0153] Alternatively, the trigger for releasing the energy may be
simply configured such that a device equipped with capacitors or
capacitance banks discharges its energy once the capacitors are
fully charged. In this configuration, when the capacitors
discharge, a damping pulse is transmitted to one or several of the
damping piston assemblies. This would represent the least
sophisticated method of delivering active vibration damping, but
one which could be honed through iterative procedures. It will be
noted that this method requires very little in the way of sensors
in able to function.
[0154] In a preferred simple embodiment, measurements of PE
generation, whether quantitative or qualitative in nature, are used
as a substitute for sensor measurements. The effectiveness of such
a system is dependent upon the ability to index the measurements to
time and tool rotational position. The underlying vibration
characteristic--measured as a function of electrical
output--establishes the presence or absence of harmonics, the
amplitude and dominant frequency of the harmonic. It also allows
for simple corrective damping to be applied in phase with and
proportionally to the perceived vibration. More sophisticated, out
of phase damping may also be applied using this un-instrumented
embodiment, but requiring additional downhole processor capability
and program algorithms to be developed.
[0155] As previously discussed, measurements of shock and
acceleration may be taken by sensors located within the lower
mandrel. These measurements which are indicative of vibration may
be qualitative or quantitative, calibrated or raw as
appropriate.
[0156] In the first instance the sensor data is gathered for
application within the internal logic of the instant device; in a
second embodiment, the sensor data is gathered for telemetry back
to the surface of the earth using any one of a number of well
understood methods. In yet another embodiment, a second, equivalent
set of sensors in the upper mandrel sub assembly gather comparative
measurements. These measurements are indicative of the efficiency
of the active damping device and allow iterative improvements to be
made during the drilling process. Sensor measurements are taken and
analyzed to determine the input vibrational characteristics and,
through the use of adaptive systems the correct time and piston
selection and damping energy level is selected with which to
achieve optimal damping per available unit of damping energy.
[0157] Thus, in an embodiment of the instant device which provides
the capability of active vibration damping across a more complex
range of harmonic vibration frequencies, sensors take measurements
of the vibration characteristics of distal and proximal elements of
the device; the piezo-electric devices located within the distal
element of the device generate electricity which is then
temporarily stored in capacitors prior to being discharged on
command from the instrumentation in order to energize the magneto
rheological properties of the active vibration device located
between the proximal mandrel element and the sleeve assembly,
conferring the ability to damp multiple frequencies of harmonic
vibration.
[0158] This preferred configuration, while intrinsically more
complex, has the benefit of allowing for more accurate comparative
measurements to be made between the distal and proximal elements of
the instant device and thus for damping adjustments to be made
which are based on comparative, sequential, sensor measurements.
Real-time, iterative adjustments to the actuation timing of the
active damping mechanism are made in order to continue reducing the
vibrational level which is observed by the proximal mandrel
sub-assembly. Ultimately, this leads to an iterative damping
process which minimizes the transfer of harmonic vibration to other
components of the BHA.
[0159] Sensor data may be acquired and retained in the
instrumentation memory. Either analogue or digital sensor outputs
may be acquired and stored. Sensor data may be stored in the short
term for n rotation cycles in order to accurately, quantify, assess
and compensate for the vibrational characteristics, such that large
amounts of downhole memory are not required, Rapid sampling of
sensors may be required either continuously or in bursts in order
to quantify tool vibrational environment and damped response. In
furtherance of continually adaptive improvements, sensor data also
may be subjected to statistical processing or analysis in the
distal environment.
[0160] The sensor data may be semi-permanently recorded and memory
dumped at surface as a record of the environment at the distal and
proximal ends of the device. In this way the data may be used for
post-run performance indicators, advisory or illustrative purposes
or, alternatively, to fine tune the operating characteristics
between successive runs.
[0161] Alternatively, key indicator data may be retained in memory,
such data pertaining to extremes of high level and low level
amplitudes and frequencies of drilling vibrational data.
[0162] In regions where greater stick-slip and higher rotational
velocities are anticipated, such as high inclination intersections
between formation bedding planes of differing hardness, the ability
to apply phase shifting, intermittent or sequential piston
activation to the active vibration damping mechanism may add
significant harmonic frequency damping capability, to the device,
without compromising the power budget.
[0163] Thus, in a preferred embodiment of the device preferably for
usage in high vibration environments it is envisaged that the
electrical output to the active vibration damping located at the
proximal end of the device may be pulsed in such a way as to
disrupt the measured harmonic vibration and achieve optimal
damping. It is envisaged that, in conjunction with tool reference
indexing that this capability may lead to improved directional
control, for example, in zones where "skipping" bedding planes
takes place. Typically this might occur in environments where
relatively hard and soft bedding planes are in juxtaposition.
However, if the internal electrical power capability of the device
was augmented--such as by the installation of a turbine
sub-assembly--the ability to utilize the torque transfer mechanism
between sleeve sub assembly and upper mandrel may result in
three-dimensional borehole trajectory control capability.
* * * * *