Hydrovibrator for Vibro-Rotary Well Drilling
One of the most promising ways of hard-rock
drilling is vibratory-rotary drilling. Its essence consists in that
high-frequency and high-amplitude longitudinal vibration accelerations are
imparted to the rock cutting tool. The advantage of this method consists in the
fact that it combines the merits of vibratory drilling and rotary drilling. In
combined drilling methods of this kind, the rock is acted upon not only by
static forces, but also by intermittent dynamic loads (short shock pulses).
Under the action of these forces, the rock is not only broken and chipped off
under the rock cutting tool at the instant a blow is given thereto, but also cut
off or chipped off when acted upon by the static load during the rotation of the
rock cutting tool.
At present, the world’s practice to set up
dynamic loads on the rock cutting tool is to use vibrators and vibrohammers.
However, existing vibrators and vibrohammers cannot be used as downhole devices.
Because of this, they are used in drilling short holes with diameters larger
than 250 mm. The studies conducted at the Exploration Engineering Chair of
Tomsk Polytechnic Institute have shown that vibratory-rotary drilling offers a
2–3-fold increase in penetration speed. With a magnetostriction vibrator, the
cutting speed of vibratory-rotary roller-bit drilling is 3.2 to 4.3 times as
high as that of rotary drilling. The published results on rock cutting tool wear
show that in vibratory-rotary drilling the first-sharpening bit life is 5 to 8
times longer in comparison with rotary drilling. However, magnetostriction sonic
borers can be used to the best advantage only in drilling holes with diameters
of 250-300 mm and larger. This is due, among other things, to their large
overall dimensions. Besides, such vibrators call for electric power supply
through the whole depth of the hole. Thus at present it is impossible do drill
deep holes with diameters smaller than 250 mm using vibratory drilling.
Over a period of
years, self-oscillation regimes in hydraulic systems with cavitating devices
have been studied at the Institute of Technical Mechanics (ITM) of the National
Academy of Sciences of Ukraine and the National Space Agency of Ukraine under
the direction of Prof. Victor V. Pilipenko, Academician of the National Academy
of Sciences of Ukraine.
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Fig.1 Schematic of vibratory-rotary drilling using high-frequency
cavitation hydrovibrator |
Based on the
results of the study of cavity flows in hydraulic systems with different restrictors, a
high-frequency cavitation hydrovibrator of radically new design without any
moving or rotating parts has been proposed (see its schematic diagram in Fig.1).
The cavitation hydrovibrator 7 imparts high-frequency longitudinal vibration
accelerations to the rock cutting tool 1 using part of the stream energy of the
drilling mud 2 pumped to the borehole 3 to evacuate the cuttings 4 of the rock
5. The hydrovibrator 7 is a part of the drilling assembly 8, and its specially
shaped inner passage 6 provides the regime of periodically detached cavitation
in the drilling mud flow. The hydrovibrator can be mounted immediately ahead of
the rock cutting tool 1 or some distance therefrom (for example, over the core
barrel), and it transforms the steady drilling mud flow into a pulsating flow.
Part of the pulsatory energy of the drilling mud will be transferred to the
drilling assembly structure 8 between the hydrovibrator and the rock cutting
tool. This gives rise to the longitudinal vibrations of the rock cutting tool.
In the specially
shaped passage 6 of the hydrovibrator 7, the periodic process of growth and
detachment of cavities 9 occurs. As soon as the cavity 9 reaches its maximum
size that is governed by the flow regime, its diffuser part detaches. The
detached part 10 of the cavity 9 is carried downstream and collapses in the
pressure zone. When the detached part 10 of the cavity 9 whose volume is
comparatively large collapses, an anomalously high pressure is produced in the
drilling mud flow. The pressure wave from the collapse center runs downstream to
a distance as long as several meters with little or no damping, while the
pressure wave that runs upstream is suppressed by the new cavity 9 that has
grown by that time as evidenced by the absence of pressure pulsation at the
hydrovibrator inlet. However, the backward wave is
involved in initiating backward flows and contributes to the detachment
of the next cavity. Thus the self-regulated periodic process of cavity
detachment and collapse is set up in the flow passage of the hydrovibrator. |
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Fig. 2 Fragment of an oscillogram of the pressure P2 at
the outlet of preprototype hydrovibrator E6.G.2001.01.00.00 at inlet
pressure P1 =101 bar and cavitation parameter t = 0.16
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As an illustration, Fig.2 shows a hydrovibrator outlet pressure oscillogram. As
the hole depth is increased, the regime of periodically detached cavitation is
kept by keeping the requisite pressure at the hydrovibrator inlet. Because the
drilling mud pressure oscillations generated in the regime of periodically
detached cavitation do not run upstream, the hydraulic system of the mud pump
will not be subjected to any dynamic loads. Thus the proposed hydrovibrator is
expected to avoid the disadvantages typical of existing hydraulic hammers and
vibrators.
Selected patents
1. USSR
Inventor’s Certificate No
505444, IPC В
06 В
1/18 Generator of Water Pressure Oscillations/ Pilipenko V.V., Zadontsev
V.A., Man'ko I.K, Dovgot’ko N.I., Drozd V.A., Publ.. 05.02.1976. Bul.
.No9. (in Russian).
2. Patent
of Ukraine No 4624,
IPC
В
06 В
1/28 Method and Means to Produce Liquid Pressure Pulses/ Pilipenko V.V, Zadontsev V.A.,
Man'ko I.K., Severin V.P., Tomchakov N.L. Publ. 28.12.1994. Bul. No. 37-1. (in
Ukrainian).
3.
USSR Inventor’s Certificate No
1496351, IPC E 21
В
10/18 Method and Means to Drill Wells/ Pilipenko V.V., Gavrilenko N.M.,
Zadontsev V.A., Man'ko I.K, Dzoz N.A., Davidenko A.N., Drozd V.A, Shepel
A.I., Sologub S.Ya., Kiselev A.T., Yu.A.Melamed. Publ. 05.02.1987. Bul.
No9. (in Russian). |
The 'Development of a Hydrovibrator for
Vibro-rotary
Well Drilling' project
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To verify the chosen line of R&D, an ITM
research team prepared and submitted to the Science and Technology Center in
Ukraine a project proposal, “Development of a hydrovibrator for vibro-rotary
well drilling” (registration number 1132). The proposal was approved, and
the project started in February 2001 and was completed in September 2004.
The project manager was
Ivan K. Man’ko,
Ph.D., Senior Researcher.
Contact
Coordinates
Dr. Ivan Man'ko
Department of Hydromechanical Systems
Institute of Technical Mechanics of NANU and NSAU
15, Leshko-Popel, Dniepropetrovsk, 49005 Ukraine
imanko@a-teleport.com
tel : 38 0562 471235
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Dr.
Ivan K. Man’ko with
hydrovibrator at the Institute's hydraulic laboratory.
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The main results of the project
Design documentation for three preprototype
hydrovibrators that differ in the throat diameter of the converging-diverging
section of the flow passage thus providing different fluid flow rates at the
same inlet pressure has been drawn up, and these preprototypes have been made.
In the inlet pressure range 11 to 301 bar, the three preprototype
hydrovibrators provide drilling mud flow rates of 30 to 157 dm3/min,
67 to 354 dm3/min and 120 to 629 dm3/min, respectively.
These drilling mud flow rates are required in the hard-rock diamond drilling of
boreholes of diameter 36 to 76 mm, 93 to 150 mm and 151 to 250 mm,
respectively. The preprototype hydrovibrators are required to make sure,
under bench conditions, that the chosen hydrovibrator layout and basic
dimensions of the hydrovibrator flow passages are such that the regime of
periodically detached cavitation does occur in above-mentioned drilling mud flow
rate ranges. A hydraulic bench has been developed and made to characterize the
high-frequency drilling hydrovibrators without any moving or rotating parts in
accordance with the “Requirements Specification for the Project” and “Basic
Requirements for Experimental Prototype Hydrovibrators”. “Hydrovibrator Water
Bench Characterization Program and Procedure” and “Measurement and Measuring
Data Processing Procedure” have been developed. It has been established
by experiment that in the inlet pressure range 11 to 301 bar the hydrovibrators
without any rotating or moving parts developed in the project are capable of
generating fluid pressure oscillations at the outlet in the cavitation parameter
range 0.05 to 0.8 (the cavitation parameter approximates the hydrovibrator
outlet/inlet pressure ratio). In this cavitation parameter range, the frequency
of the oscillations generated in the regime of periodically detached cavitation
varies from 74 to 7,300 Hz depending on the hydrovibrator inlet pressure. At a
fixed inlet pressure, the frequency increases with cavitation parameter nearly
linearly, and at a fixed cavitation parameter the frequency increases with
hydrovibrator inlet pressure. Depending on the inlet pressure, the maximum
peak-to-valley amplitude of the hydrovibrator outlet pressure is 1.2 to 2.72
times as high as the hydrovibrator inlet pressure. As an illustration, Fig.3 and
Fig.4 show the pressure oscillation frequency and peak-to-valley amplitude,
respectively, versus cavitation parameter
t
at different inlet pressures P1.
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Fig. 3. Frequency
f of cavitation oscillations of the fluid pressure P2
at the outlet of preprototype hydrovibrator E5.G.2001.01.00.00 versus
cavitation parameter t
at different values of the inlet pressure P1
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Fig. 4.
Peak-to-valley amplitude Dp2
of the pressure at the outlet of preprototype hydrovibrator
E5.G.2001.01.00.00 versus cavitation parameter t
at
different values of the inlet pressure P1
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Based on the generalization of the results of the tests of the
preprototype hydrovibrators, design documentation for three experimental
prototype high-frequency drilling hydrovibrators without any rotating or moving
parts has been drawn up. The experimental prototype hydrovibrators were tested
at steady inlet pressures of 11, 21, 31, 41, 51, 101, 151 and 201 bar in the cavitation parameter range 0.01 to 0.71.
In this cavitation parameter range, the frequency of the
oscillations generated in the regime of periodically detached cavitation lies in
the range 73 to 5,900 Hz depending on the inlet pressure. The maximum
peak-to-valley amplitude of the outlet pressure is about 2.00 to 3.75 times as
high as the hydrovibrator inlet pressure depending on the inlet pressure and the
throat diameter of the converging-diverging flow passage of the experimental
prototype hydrovibrator.
Experimental dependences of the frequency and peak-to-peak amplitude of the
longitudinal shock vibration accelerations at the hydrovibrator outlet and on
the drilling subs on the cavitation parameter have been obtained for the first
time. The shock vibration acceleration frequency coincides with the frequency of
the fluid pressure oscillations in the hydrovibrator flow passage. The behavior
of the cavitation parameter dependence of the peak-to-peak vibration
acceleration is similar to that of the cavitation parameter dependence of the
peak-to-valley pressure in the hydrovibrator flow passage. In the inlet pressure
range 11 to 201 bar, the measured peak-to-peak longitudinal shock vibration
acceleration at the outlet of the experimental prototype hydrovibrators lies in
the range 60 g to 33,680 g where g is the gravitational acceleration. The
peak-to-peak shock vibration acceleration on the sub downstream of the hydrovibrator is somewhat lower than on the hydrovibrator body. At the same
time, the peak-to-peak shock vibration acceleration on the sub at the
hydrovibrator inlet is nearly an order of magnitude lower than on the
hydrovibrator body.
The
mechanism whereby the high-frequency fluid pressure oscillations in the drilling
assembly flow passage are transformed into the longitudinal vibration
accelerations of the rock cutting tool has been studied theoretically for the
first time. The study has shown that this mechanism is due to the presence of
the longitudinal forces that reflect the force action of the oscillating fluid
on the whole structure of the drilling assembly with the hydrovibrator. These
forces are due to the longitudinal projections of the pressure forces acting on
the structural components of the drilling assembly, the inertia of the fluid
medium (stemming from the acceleration of the drilling assembly structure) and
the fluid medium oscillations caused by the vibratory motion of the variable
flow area components of the drilling assembly. Besides, the longitudinal
vibration accelerations of the drilling assembly structure may also be
responsible for the Poisson interaction between the fluid and the drilling
assembly structure.
The pioneer mathematical model of the longitudinal vibrations of
a high-frequency cavitation hydrovibrator-equipped drilling assembly provides
not only qualitative, but also quantitative agreement between the calculated and
the experimental parameters of the fluid pressure oscillations and the
longitudinal vibration accelerations of the structure at different drilling
assembly sections. According to this mathematical model, the vibratory motion of
a drilling assembly equipped with a high-frequency cavitation hydrovibrator
without any rotating or moving parts is due to its dynamic interaction with the
fluid flowing in its flow passage. In this mathematical model, the dynamic
interaction between the structural components of the drilling assembly and the
corresponding fluid elements in its flow passage is included by entering into
the drilling assembly motion equations the force exerted by the oscillating
fluid on the drilling assembly walls and the inertia force of the moving fluid
caused by the accelerated motion of the drilling assembly. The force acting on a
structural component consists of the forces that are the product of the area
times the fluid pressure at the end sections of the structural component and the
fluid inertia forces caused by the drilling assembly acceleration and fluid mass
flow oscillations in the drilling assembly flow passage.
Design documentation for four preprototype core and noncore
drilling assemblies equipped with a high-frequency cavitation hydrovibrator
without any rotating or moving parts has been drawn up, and they have been made
to this documentation.
A preprototype noncore drilling assembly with
a high-frequency cavitation hydrovibrator and two preprototype core drilling
assemblies with the same hydrovibrator have been tested. The preprototype core
drilling assemblies differ in core barrel length. The tests of the preprototype
drilling assemblies were conducted in the hydrovibrator inlet pressure range 11
to 101 bars. Based on the test results, dependences of the frequency and
peak-to-peak amplitude of the shock vibration acceleration of the rock cutting
tool on the hydrovibrator inlet/outlet pressure ratio for each steady inlet
pressure have been obtained for the first time. It has been found that at a
fixed value of this ratio, the peak-to-peak shock vibration acceleration of the
rock cutting tool increases with inlet pressure. For the preprototype that
models a core drilling assembly with a core barrel of length 1,500 mm, in the
above-mentioned hydrovibrator inlet pressure range the peak-to-peak shock
vibration acceleration of the rock cutting tool ranges between 50 g and
5,700 g. For a core barrel of length 2,240 mm, this peak-to-peak shock
vibration acceleration ranges between 60 g and 5,180 g. For the
preprototype that models a noncore drilling assembly, under the same conditions
this peak-to-peak shock vibration acceleration ranges between 7 g and
10,480 g.
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Fig.5 Dependences of the peak-to-peak shock
vibration acceleration
Dnz5
of the drill bit simulator on the cavitation parameter
t
obtained when testing preprototype drilling assembly
E17.B.2003.01.00.00 at different values of the hydrovibrator inlet
pressure p1 . |
As an illustration, Fig.5 shows the
peak-to-peak shock vibration acceleration of the rock cutting tool versus
cavitation parameter at different hydrovibrator inlet pressures.
Recommendations on designing an
experimental prototype drilling assembly equipped with a high-frequency
cavitation hydrovibrator without any rotating or moving parts have been
worked out. These recommendations have been formulated based on the
analysis of the results of the theoretical study of the effect of the
hydrovibrator-equipped drilling assembly design factors and the
hydrovibrator operating conditions on the peak-to-peak longitudinal
shock vibration acceleration of the rock cutting tool. The
recommendations reflect the effect of the following parameters on the
shock vibration acceleration frequency and peak-to-peak amplitude: the
linear stiffness of the drilling assembly structure, the drilling mud
density, the lumped mass of the rock cutting tool at the end of the
drilling assembly, the drilling mud sound speed, the vibration damping
factor of the threaded joints of the drilling assembly and the length of
the core barrel downstream of the hydrovibrator.
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The proposed high-frequency hydrovibrator
differs from conventional ones in that it doesn’t have any rotating or moving
parts and doesn’t use any energy sources other than the stream energy of the
drilling mud pumped to the borehole for bottomhole cleaning. This simplifies its
design and servicing and offers far higher reliability and smaller mass and
dimensions. All these advantages will make it possible to develop and introduce
a technique for the vibratory-rotary flush drilling of deep holes 36 to 250 mm
in diameter.
Our further
work along this line will be aimed at determining the effect of the
high-frequency shock vibration acceleration frequency and peak-to-peak amplitude
on the process of destruction of various rocks and the life of the rock cutting
tool, at verifying the serviceability of the hydrovibrators in deep drilling and
at the scientific substantiation and development of a technique of application
of the high-frequency cavitation hydrovibrator as a part of core and noncore
drilling assemblies for rocks of different strength.
Selected Recent Publications
1. V.V.Pilipenko, I.К.Man’ko,
S.I.Dolgopolov, O.D.Nikolayev. Effect of liquid flowrate on longitudinal
vibration acceleration parameters of a cavitation hydrovibrator (in Russian)// Naukovy
Vistnyk NDU. – 2006. – No 2. – Dniepropetrovsk, National Mining University
Publishers. – pp.36-39 .
2. V.V.Pilipenko, I.К.Man’ko,
S.I.Dolgopolov, O.D.Nikolayev. Characteristics of a high-frequency cavitation
hydrovibrator for setting up dynamic loads on the rock cutting tool of a
drilling assembly (in Russian)// Naukovy Vistnyk NDU. – 2005. – No 1. – Dniepropetrovsk,
National Mining University Publishers. – pp.66-70 .
3. I.К.Man’ko, O.D.Nikolayev.
Mathematical modeling of the longitudinal vibrations of a drilling assembly with
a high-frequency cavitation hydrovibrator (in
Russian)// Naukovy Vistnyk NDU.
– 2004. – No 11. – Dniepropetrovsk, National Mining University
Publishers. – pp.65-73 .
4. I.К.Man’ko, O.D.Nikolayev.
Mechanism of transformation of the high-frequency oscillations of the drilling
mud into the longitudinal vibration accelerations of the rock cutting tool of a
cavitation hydrovibrator-equipped drilling assembly (in Russian) // Naukovy
Vistnyk NDU. – 2004. – No 10. – Dniepropetrovsk, National Mining University
Publishers. – pp.56-59 .
Design and maintenance: O.
Nikolayev, M.Gorev , I.Man'ko© 2007
All photographs and text copyright © 2007 ITM NANU and NSAU
Please send comments and suggestions about this page to:
nikolayev@ua.fm
Last Updated: March 12, 2007