U.S. patent number 3,737,843 [Application Number 05/206,367] was granted by the patent office on 1973-06-05 for hydraulically controlled device for modulating the mud.
This patent grant is currently assigned to Societe Anonyme dite: Societe Nationale Des Petroles D'Aquitaine. Invention is credited to Jean-Pierre Le Peuvedic, Claude Quichaud.
United States Patent |
3,737,843 |
Le Peuvedic , et
al. |
June 5, 1973 |
HYDRAULICALLY CONTROLLED DEVICE FOR MODULATING THE MUD
Abstract
A hydraulically controlled device to transmit measurements taken
at the bottom of a well to the surface, in the form of pressure
modulations created by periodical restrictions on the passage of
the drilling fluid, characterized by the use of a servovalve which
operates the drilling fluid flow-restriction system, and the
hydraulic control fluid of which is uniformly related, in quantity
and direction, to the electric intensity passing through its
coil.
Inventors: |
Le Peuvedic; Jean-Pierre (Pau,
FR), Quichaud; Claude (Billere, FR) |
Assignee: |
Societe Anonyme dite: Societe
Nationale Des Petroles D'Aquitaine (Courbevoie,
FR)
|
Family
ID: |
22766063 |
Appl.
No.: |
05/206,367 |
Filed: |
December 9, 1971 |
Current U.S.
Class: |
367/85;
175/45 |
Current CPC
Class: |
E21B
47/24 (20200501); E21B 47/18 (20130101) |
Current International
Class: |
E21B
47/12 (20060101); E21B 47/18 (20060101); G01v
001/40 () |
Field of
Search: |
;340/18NC,18LD
;175/50,40,45 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Feinberg; Samuel
Assistant Examiner: Moskowitz; N.
Claims
What claimed is :
1. In a hydraulically controlled device for transmitting signals
representing measurements taken within a well to the surface in the
form of pressure modulations created by periodical restrictions on
the flow of the drilling fluid, which device comprises
a mechanism for restricting said flow,
means for controlling said mechanism operated by electrical signals
indicative of said measurements,
a hydraulic fluid circuit by means of which said control means
operates the flow-restricting mechanism, and
a turbine driven by the drilling fluid,
the improvement according to which:
said device comprises a hydraulic fluid pressure pump to supply
pressure fluid to said hydraulic circuit and an electrical
generator, both driven by said turbine, and
said control means comprises electrically operated servo valve
means supplied from said generator for controlling the flow of
hydraulic fluid in said circuit in dependence on the quantity and
direction of the electrical signal delivered to the servo valve and
means for regulating the electrical signal to said servo valve at
least in part in dependence on said measurements.
2. A device according to claim 1 in which said flow restriction
mechanism comprises a mobile valve-needle cooperating with a fixed
seat and attached to a double-action hydraulic jack piston mounted
for movement between two positions, one of which corresponds to
maximum opening of the flow-restricting mechanism and is obtained
by passing an electric current in one direction through the servo
valve coil, and the other of which corresponds to minimum opening
of the flow-restricting mechanism and is obtained by passing
current through said coil in the opposite direction.
3. A device according to claim 1 in which said control means
comprises a sensor which emits an electrical signal indicative of a
controlled functional characteristic of said restriction mechanism,
a generator of signals related to said measurement signals, and an
error detector delivering a signal equal to the difference between
the signals emitted by said sensor and generator, and said servo
valve comprises a control coil to which said difference signal is
applied to control said functional characteristic.
4. A device according to claim 3 in which said sensor is responsive
to the position of said flow-restricting mechanism.
5. A device according to claim 3 in which said sensor is a pressure
difference sensor which measures the difference in pressure above
and below said flow-restricting mechanism.
Description
This invention concerns a hydraulic system for transmitting
signals, representing measurements taken at the bottom of a well,
to the surface.
When drilling a well, it is very useful to know a number of
parameters concerning the ground being drilled and the working
conditions of the tool. Such information is generally used to
define and adjust drilling conditions. It is usually transmitted
from the bottom of the well to the surface by means of series of
hydraulic impulses produced in the drilling fluid at the base of
the well, and transmitted to the surface without disturbing the
normal drilling operations.
Many inventors have tried to design simple devices for producing
reliable, high-level hydraulic impulses, despite the unfavourable
conditions prevailing at the bottoms of wells. Hydraulically
controlled devices have attracted particular attention because of
their functional reliability and high power-to-weight ratio. The
applicant, for instance, has designed a device with independent
hydraulic control, in which the hydraulic fluid circuit contains a
pump discharging fluid under pressure, through a control device
such as a slide distributor or electrovalve, on one side or other
of the piston of a double-action hydraulic jack, connected
mechanically to a mechanism which restricts the passage of the
drilling fluid.
This device, like other existing systems involving hydraulic
circuits with separate control fluid, uses a control component
operated by electric impulses related to the measurement signals,
and which may be a slide distributor controlled by one or two coils
or a combination of electro-valves.
This method of controlling the mechanism for restricting the flow
of drilling fluid has many drawbacks, however. The equipment
involved is often too bulky for the confined space available inside
drilling rods. The small flow of fluid produced for a given
exciting power means that the fluid restricting mechanism operates
at reduced speed, limiting the number of signals that can be sent
in one unit of time. Another drawback of existing control systems
is that the amplitude of the pressure impulses obtained by
operating the restricting mechanism varies with the flow and
density of the mud passing through it, which means that when
impulses of uniform level are required, in wells being drilling
with varying mud flows and densities, a correction system has to be
used every time the composition of the drilling fluid is
changed.
The aim of this invention is to offer a hydraulic system for rapid
operation of the restriction mechanism. Another aim is to provide a
hydraulic servo-device which can operate the restriction mechanism
at pre-set amplitudes, and which can be regulated independently of
drilling fluid circulating conditions. The invention also concerns
a method of producing modulations in the total mud flow, at
selected frequencies ranging from several tenths of a Hertz to
several tens of Hertzes. The system according to this invention
allows a considerable amount of data to be transmitted easily,
using modulation frequencies that are quite distinct from the
unwanted ones often produced by drilling mud pumps.
The present invention concerns a hydraulically controlled system to
transmit signals representing measurements taken at the bottom of a
well to the surface, in the form of pressure modulations created by
periodical restrictions on the flow of the drilling fluid, and
consists of a mechanism for restricting this flow, a device for
controlling the mechanism, operated by electrical signals related
to the measurement signals, a hydraulic fluid circuit by means of
which the controlling device operates the flow-restriction device,
a turbine driven by the drilling fluid and a hydraulic fluid
pressure pump on the same shaft, being characterized by the fact
that the device to control the periodical restrictions on the flow
of drilling fluid consists of a servovalve controlling a hydraulic
fluid, the flow of which is uniformly related, in quantity and
direction, to the electrical intensity passing through its
coil.
The restriction mechanism used to impart impulses to the drilling
fluid and transmit signals to the surface in the form of pressure
modulations may be a shutter or needle-valve connected mechanically
to a hydraulic sink such as a jack, hydraulic gear or piston motor
receiving a continuous flow of control fluid.
According to one embodiment, the servo-valve acts through a control
fluid circuit to operate a double-action hydraulic jack, linked
mechanically to a needle-valve attached to its piston, which acts
with a fixed seat. In this embodiment, the movement of the piston
is confined between two positions marked by mechanical stops,
corresponding to minimum and maximum openings of the drilling fluid
flow-restriction mechanism, maximum opening being obtained by
passing an electric current, corresponding to fast displacement of
the jack in the direction of opening of the passage, through the
servovalve coil, while minimum opening is obtained by reversing the
direction of the electric current.
The advantage of this method is the speed with which the
restriction mechanism is operated. When used at the base of a well,
during drilling, to transmit information to the surface, it allows
signals to be sent in the form of rapid pressure variations,
ranging from 5 to 30 bars, and succeeding one another at intervals
of between 1 and 30 seconds, each such signal being obtained by
reversing the electric current passing through the servovalve
coil.
According to another embodiment of the invention, the servovalve is
the device by which a functional characteristic of the restriction
mechanism is controlled by an electrical signal which varies
according to a pre-set pattern. A current representing the
difference between two signals, one from the detector of a
controlled characteristic of the restriction mechanism, and the
other from a generator of electrical signals related to the
measurement signals, is applied to the servovalve coil.
The functional characteristics of the restriction mechanism may be
its position, or the pressure-drop it creates in the drilling fluid
passing through it.
Instantaneous command of the position of the restriction mechanism
by control signals, preferably related to the measurement signals,
allows its functioning to vary in terms of time on the same pattern
as the control signal variations.
Instantaneous command of the pressure-drop in the restriction
mechanism by control signals, preferably related to the measurement
signals, allows it to function, notably as regards the amplitude of
the signals transmitted in the form of pressure modulations,
without being affected by the flow, nature and density of the
drilling fluid used, or the control fluid pressure.
Use of a servovalve to control the functioning of the restriction
mechanism allows the use of a wide range of frequencies, from
several tenths to several tens of Hertz, with a different set of
frequencies for each speed of movement of the mechanism. This range
of frequencies allows a considerable amount of information to be
transmitted easily, using modulation frequencies quite distinct
from the unwanted ones usually produced by drilling pumps.
The controlled hydraulic system according to this invention allows
information to be transmitted by the drilling fluid current, by
means of signals consisting of continuous or intermittent
modulations of the drilling fluid pressure, in the form of
sinusoidal pressure variations at frequencies of from 0.1 to 100
cycles per second. The electrical control voltage, which may be nil
at rest, is formed during transmission of the signals, by
superimposing a sinusoidal alternating voltage with a frequency of
between 0.1 and 100 cycles per second on a direct voltage, making
it possible, by controlling the position of the restriction
mechanism or the pressure-drop it creates, to obtain an average
pressure-drop of between 5 and 15 bars, in the flow of drilling
fluid passing through the mechanism.
The figures described below illustrate some embodiments of the
present invention.
FIG. 1 shows a special drill collar containing the controlled
hydraulic system for modulation of the mud flow. Externally it
resembles components commonly used in drilling operations. In
particular, it has standard API threads at each end, so that it can
be incorporated at any point in the drilling line, preferably near
the tool.
FIG. 2 shows the electrical circuit by which the position of the
hydraulic jack is controlled by any type of electrical signal.
FIG. 3 shows the electrical circuit by which the pressure-drop in
the restriction mechanism is controlled by any type of electrical
signal.
The special drill collar (1) containing the controlled hydraulic
system, in FIG. 1, has standard threaded sections string wide bore
on the female side, compatible with the threads and housing the
internal equipment, which rests on a shoulder (3).
This internal equipment consists of a modulation valve which
occupies the whole upper end of the wide bore, forcing all the
drilling fluid to circulate between the fixed seat (12) and mobile
needle (13). The invention is not confined to use of this type of
valve, and other restriction mechanisms, such as a dome valve or
balanced multi-seat valves, may also be used to modulate the mud
flow.
Beneath the modulating valve is a watertight cylinder (15),
containing the hydraulic valve-control system, electrical control
circuits, measurement-sensing devices (not shown) and an
independent electricity supply system.
The lower end of this cylinder is connected to a turbine (16)
supplying energy from the mud flow. The drilling fluid can pass
from the modulating valve (11) to the turbine (16), along the
annular space between the bore of the drill collar (1) and the
cylinder (15). The fixed (17) and mobile (18) blades of this
turbine, which is of standard type, are held by nuts (19 and 20)
against shoulders provided inside the turbine casing and on the
shaft (14). The drilling fluid penetrates into the fixed blading
through a series of apertures (21) at the top of the turbine
casing, and leaves the turbine through the bottom, round the shaft,
going on to irrigate the drilling tool in the usual way. The shaft
(14), with the mobile blades (18), is suspended from a bearing (22)
inside the watertight cylinder (15). The shaft passes from the
turbine casing into the cylinder through a sealing system (23),
which may be a conventional stuffing-box held in position by a nut
(24). The role of the bearing (22) is also to absorb the axial
hydraulic thrust on the mobile blades. The advantage of having this
bearing inside the cylinder is the ease with which it can be
lubricated by the fluid with which the watertight cylinder is
filled; this may be a mineral oil, which can withstand the
pressures and temperatures encountered at the bottoms of drilling
wells.
A device not shown in the figure allows the static pressure of the
drilling fluid to be applied to the filling and control fluids
inside the cylinder (15).
Pressure differences on each side of the sealing system (23) thus
remain slight, making it easier to design and maintain in good
condition.
The shaft (14) drives an alternator (5), which supplies
electricity, and a regulated hydraulic pressure generator (7), not
shown in detail in the figure.
The type of regulated pressure generator chosen is of little
importance. It may consist of a fixed-cylinder pump, regulator and
tank accumulating oil under pressure, or of a self-regulating
variable-cylinder pump and pressure tank.
The invention is in no way confined to use of these types of
pressure generator: any other regulated pump and tank containing
oil under pressure, providing sufficient instant flow at uniform
pressure to operate the restriction mechanism energetically may be
used, without departing from the context of the present invention,
provided that their size is compatible with the space available
inside the watertight cylinder (15).
Above the pressure generator (7) is the servovalve (50), the
function of which is to modulate the control fluid delivered at
uniform pressure by the generator. It does this by receiving the
fluid under pressure through an intake pipe (49) and returning it
without pressure to the generator, through a discharge pipe (48).
On the other side, the servovalve (50) is connected with the two
sides of a piston (56), by pipes (51 and 52). This piston forms the
main part of a double-acting jack connected mechanically with the
restriction mechanism. It moves inside a cylindrical space (55),
operating a rod (57) connected to the mobile valve-pin (13), which
acts with the fixed seat (12) to modulate the flow of drilling
fluid. The piston (56) can move upwards or downwards, depending on
whether the fluid under pressure is directed to the upward side
along one pipe (51), or to the downward side along the other pipe
(52).
The control sensors and electronic circuits regulating the
electricity and controlling the servovalve (50) are placed in a
compartment (35) in the upper part of the watertight cylinder (15),
round the rod (57).
In some cases, measurement sensors supplying signals representing
drilling parameters may also be housed in this compartment.
Passages separate from the hydraulic circuit are provided in the
cylindrical space (55) and generator (7), for electrical conductors
(58 and 6), which link the servovalve (50) and alternator (5) with
the circuits inside the special compartment (35).
The servovalve contains a control coil or winding through which
passes an electric current supplied by these circuits.
When there is no exciting current, no hydraulic communication
exists, and the piston (56) cannot move. The special peculiarity of
the servovalve is that it can produce any degree of such
communication, from complete closure to direct communication
between the oil under pressure and one side of the jack piston
(56), when an electric current of appropriate direction and
intensity is applied to its control coil. In other words, the flow
of fluid controlled by a servovalve is uniformly related, in
direction and quantity, to the electric intensity passing through
its control coil.
The control sensors are instruments detecting some functional
characteristic of the restriction mechanism. Their applications are
illustrated in FIGS. 2 and 3.
The method of control by position illustrated in FIG. 2 involves a
position sensor (33), the rod (32) of which is connected with the
rod (57) between the jack piston (56), and the valve-needle. The
position of this rod (57) is controlled by an electrical signal,
which is fixed or variable in time, so that a restriction, fixed or
varying in time, is produced.
FIG. 2 provides a diagrammatical illustration of how this principle
is applied.
A position sensor (33), connected mechanically with the jack rod
(57), supplies an electrical signal representing the position of
the valve-needle (13), in accordance with a continuous, uniform
pattern. The coder (59) supplies a reference or control signal,
fixed or varying according to a pattern preferably related to
measurements taken at the bottom of the well, and designed to
produce a pressure variation of pre-determined form in the drilling
fluid. These two signals are compared in an error detector (60),
which is also an amplifier. The difference between the two signals
is applied to the servovalve coil by conductors (58). Because of
the operating principle of the servovalve, the piston (56) will
move in the direction which tends to reduce the difference. When
the reference signal is fixed, the piston (56) comes to rest in a
position dictated solely by the value of the reference signal, and
unaffected by oil pressure, drilling fluid, speed and flow, etc. If
the reference signal varies in time, the piston position will also
vary in accordance with the same pattern. In this way, position of
the needle of the valve modulating the flow of drilling fluid is
controlled by a reference signal, which may, for instance,
represent successive measurements, coded or uncoded, taken at the
bottom of a well during drilling.
The electric power needed to operate the measurement and control
sensors and the electronic circuits (59 and 60) is supplied from
the alternator (5), by a power-supply unit (31), which is also
housed in the compartment (35).
FIG. 3 shows one interesting possibility offered by the controlled
hydraulic device. FIG. 2 illustrated how the position of the
modulating valve needle (13) could be controlled by a fixed or
variable reference signal. When the flow or density of the drilling
fluid vary, however, a fixed position of the modulating valve
needle will not ensure a pre-determined difference in pressure on
each side of the restriction point. For a given restriction, the
pressure-drop varies depending on the density, and is proportional
to the square of the flow. The system illustrated diagrammatically
in FIG. 3 overcomes this drawback, offering a way of controlling
the restriction so as to ensure, within a certain range of flows, a
pressure-difference that either remains uniform or varies in
accordance with a predetermind pattern, without being affected by
the flow.
This is done by a pressure differential sensor (36), which detects
the pressure above the valve by means of one pipe (38), and the
pressure below it by means of another pipe (37), and supplies an
electrical signal representing the difference in pressure, in other
words the pressure-drop created by the modulating valve.
This signal is compared with a reference signal supplied by a coder
(59), in an error-detector amplifier (60).
The difference between the two signals is applied, in the form of
an electrical error signal, to the servovalve (50) coil, by
conductors (58). When the reference signal is fixed, the
pressure-drop will also remain steady, at a level determined solely
by this reference signal; the signal representing the difference in
pressures above and below the restriction point will then
correspond exactly to the reference signal.
In this way, the pressure-difference created by the modulating
valve depends on a given reference signal, regardless of the
viscosity, density or flow of the drilling fluid. If the reference
signal is made to vary in time, according to a pattern related to
the drilling parameter measurements to be transmitted, pressure
variations can also be created easily in the column of drilling
fluid, matching the same time pattern, and thus providing
transmission signals. In particular, the process can be used to
obtain variable-frequency modulations related to the parameter
being measured at the bottom of the well, with a high
information-transmission capacity.
* * * * *