Title: Annulus pressure operated well monitoring
Abstract: A method is provided for monitoring a well. In a described embodiment, the method uses annulus pressure to communicate between a downhole system and a remote location. The method may use intermittent electrical power generated by changes in annulus pressure to power the downhole system. Various sensors and well tools may be monitored and actuated by the downhole system, and acquired data may be transmitted to the remote location.
Patent Number: 7,012,545 Issued on 03/14/2006 to Skinner, et al.
| Inventors:
|
Skinner; Neal G. (Lewisville, TX);
Fripp; Michael L. (Carrollton, TX);
Schultz; Roger L. (Aubrey, TX)
|
| Assignee:
|
Halliburton Energy Services, Inc. (Houston, TX)
|
| Appl. No.:
|
077052 |
| Filed:
|
February 13, 2002 |
| Current U.S. Class: |
340/855.8; 166/65.1; 166/66.5 |
| Current Intern'l Class: |
G01V 3/18 (20060101) |
| Field of Search: |
340/8558,855.4,853.7,854.3
166/651,665
324/333,338,351
367/82
|
References Cited [Referenced By]
U.S. Patent Documents
| 4422506 | Dec., 1983 | Beck.
| |
| 4429748 | Feb., 1984 | Beck.
| |
| 4444267 | Apr., 1984 | Beck.
| |
| 4444268 | Apr., 1984 | Barrington.
| |
| 4515219 | May., 1985 | Beck.
| |
| 4537258 | Aug., 1985 | Beck.
| |
| 4633952 | Jan., 1987 | Ringgenberg.
| |
| 4667743 | May., 1987 | Ringgenberg et al.
| |
| 4711305 | Dec., 1987 | Ringgenberg.
| |
| 4736798 | Apr., 1988 | Zunkel.
| |
| 5839508 | Nov., 1998 | Tubel et al.
| |
| 6747569 | Jun., 2004 | Hill et al.
| |
Primary Examiner: Horabik; Michael
Attorney, Agent or Firm: Smith; Marlin R.
Claims
What is claimed is:
1. A method of communicating between a downhole system and a remote location
using intermittent electrical power, the method comprising the steps of:
receiving in the downhole system a series of spaced apart transmissions of electrical
power, the system being powered by the electrical power transmissions;
setting a first telemetry bit to indicate a first bit value of a first byte of
data in response to a first one of the electrical power transmissions;
communicating the first bit value to the remote location;
setting a second telemetry bit to indicate a second bit value of the first byte
of data in response to a second one of the electrical power transmissions; and
communicating the second bit value to the remote location.
2. The method according to claim 1, wherein the first bit value communicating
step is performed in response to the first one of the electrical power transmissions,
and wherein the second bit value communicating step is performed in response to
the second one of the electrical power transmissions.
3. The method according to claim 2, further comprising the steps of generating
the first one of the electrical power transmissions in response to a first pressure
manipulation, and generating the second one of the electrical power transmissions
in response to a second pressure manipulation.
4. The method according to claim 3, wherein the first electrical power transmission
generating step further comprises performing the first pressure manipulation in
an annulus formed between a tubular string and a wellbore, and wherein the second
electrical power transmission generating step further comprises performing the
second pressure manipulation in the annulus.
5. The method according to claim 1, wherein the first bit value communicating
step is performed in response to a third one of the electrical power transmissions,
and wherein the second bit value communicating step is performed in response to
a fourth one of the electrical power transmissions.
6. The method according to claim 1, further comprising the step of incrementing
a count value in response to each of the electrical power transmissions.
7. The method according to claim 6, further comprising the step of storing the
count value between electrical power transmissions.
8. The method according to claim 7, wherein the storing step further comprises
storing the count value in a nonvolatile memory which is not powered between the
electrical power transmissions.
9. The method according to claim 6, further comprising the step of resetting
the count value when a preselected number of bit values of the first byte are communicated
to the remote location.
10. The method according to claim 9, further comprising the step of communicating
bit values of a second byte of data after the resetting step.
11. The method according to claim 1, wherein the first telemetry bit setting
step further comprises selecting a mode of actuation of a valve device.
12. The method according to claim 11, wherein the first telemetry bit communicating
step further comprises selectively accepting and rejecting fluid flow through the
valve device in response to the mode of actuation selecting step.
13. The method according to claim 12, wherein the selectively accepting and rejecting
fluid flow step further comprises selectively accepting and rejecting fluid flow
between the downhole system and an annulus surrounding the system.
14. The method according to claim 1, further comprising the step of taking a
reading from a downhole sensor to acquire the first byte of data.
15. The method according to claim 14, wherein the reading taking step is performed
in response to a third one of the electrical power transmissions.
16. The method according to claim 1, wherein the first telemetry bit setting
and second telemetry bit setting steps are performed in response to separate ones
of a series of pressure increases.
17. The method according to claim 16, wherein the first bit value communicating
and second bit value communicating steps are performed in response to separate
ones of a series of pressure decreases alternating with the pressure increases.
18. The method according to claim 16, wherein the first telemetry bit setting
and first bit value communicating steps are performed in response to a first one
of the pressure increases, and wherein the second telemetry bit setting and second
bit value communicating steps are performed in response to a second one of the
pressure increases.
19. The method according to claim 1, wherein the first telemetry bit setting
and second telemetry bit setting steps are performed in response to separate ones
of a series of pressure decreases.
20. The method according to claim 19, wherein the first bit value communicating
and second bit value communicating steps are performed in response to separate
ones of a series of pressure increases alternating with the pressure decreases.
21. The method according to claim 19, wherein the first telemetry bit setting
and first bit value communicating steps are performed in response to a first one
of the pressure decreases, and wherein the second telemetry bit setting and second
bit value communicating steps are performed in response to a second one of the
pressure decreases.
Description
BACKGROUND
The present invention relates generally to operations performed in conjunction
with subterranean wells and, in an embodiment described herein, more particularly
provides a method of monitoring a well using annulus pressure manipulations.
Various methods have been used in the past for remotely communicating with
a downhole location. For example, electromagnetic telemetry, acoustic telemetry,
mud pulse telemetry during drilling operations, etc. However, each of these methods
has its drawbacks when used for permanent well monitoring.
Electromagnetic and acoustic telemetry each require a downhole power
source, such as a battery. The downhole power source is needed to power downhole
electronic circuits and sensors. The actual transmission of electromagnetic or
acoustic waves from a downhole location to a remote location, such as the earth's
surface, requires a substantial amount of power.
If this power is supplied by batteries, then they will need to be frequently
refreshed
or recharged. This will necessitate intervention into the well and interruption
of the production flow from the well, each of which is costly. If the power is
supplied by lines extending into the well, the lines are costly to install and
are subject to damage throughout the productive life of the well.
Mud pulse telemetry requires a circulating fluid flow. In a producing well, fluid
typically flows upward through a tubing string, and an annulus surrounding the
tubing string is maintained at a static pressure, with no communication between
the tubing and the annulus. Power to operate the downhole mud pulse telemetry equipment
may be supplied by batteries, by lines extending to the surface, or by the fluid
circulation. However, as discussed above, batteries and lines extending to the
surface have certain drawbacks when used for long term well monitoring, and fluid
circulation is not available.
Therefore, it may be seen that there is a need for a method whereby a
well may be conveniently and economically monitored on a long term basis. Methods
and equipment suitable for this purpose could also be used for other purposes.
SUMMARY
In carrying out the principles of the present invention, in accordance with an
embodiment thereof, a method is provided which permits long term monitoring of
a well. The method described herein does not require the use of electrical lines
to transmit data or electrical power, does not require the use of batteries downhole,
and does not rely on electromagnetic, acoustic or mud pulse telemetry for communication
with a remote location.
In one aspect of the invention, a method is provided for communicating between
a downhole system and a remote location. The method uses intermittent electrical
power in the form of spaced apart transmissions of electrical power. Individual
bits of data bytes are communicated to the remote location when the separate electrical
power transmissions are received in the downhole system. The same or alternating
electrical power transmissions may be used to set the bits for telemetry in the
downhole system.
In another aspect of the invention, a method of communicating between a downhole
system and a remote location includes the steps of generating a spaced apart series
of electrical transmissions in response to a spaced apart series of pressure changes
in a well, acquiring into the downhole system at least one byte of data from a
downhole sensor, and transmitting to the remote location individual bits of the
byte in response to respective separate ones of the series of pressure changes.
In yet another aspect of the invention, a method for communicating between a
downhole
system and a remote location is provided which includes the step of selectively
altering an effective volume in a well, thereby indicating a corresponding bit
of a byte of data to be transmitted. Pressure in the well is changed and the effective
volume of the well is detected, thereby determining the corresponding transmitted
bit. These steps are repeated to transmit each bit of the data byte.
In still another aspect of the invention, a method for communicating between a
remote location and a downhole system is provided which includes the step of selectively
changing pressure in a well to first and second predetermined pressures, thereby
transmitting bit values corresponding to the respective predetermined pressures.
In one described embodiment, the predetermined pressures are applied at the remote
location to an annulus of the well. The annulus pressure is monitored at the downhole system.
When one of the predetermined pressures is detected in the annulus, the downhole
system detects that a corresponding bit value has been transmitted, and the bit
value is stored in a shift register. The bits stored in the shift register are
compared to a series of codes and, if a match is found, a function corresponding
to the code is performed by the downhole system.
These and other features, advantages, benefits and objects of the present invention
will become apparent to one of ordinary skill in the art upon careful consideration
of the detailed description of a representative embodiment of the invention hereinbelow
and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross-sectional view of a method of monitoring a well,
the method embodying principles of the present invention;
FIG. 2 is a schematic block diagram of a method of using intermittent electrical
power which may be part of the method of FIG. 1;
FIG. 3 is a flowchart illustrating steps in a method of monitoring a well and
communicating monitored parameters which may be part of the method of FIG. 1;
FIG. 4 is a schematic quarter-sectional view of a first apparatus which may
be used in the method of FIG. 3;
FIG. 5 is a schematic quarter-sectional view of the first apparatus, wherein
fluid from an annulus has been accepted into the apparatus;
FIG. 6 includes plots of pressure vs. volume in the annulus;
FIG. 7 is a schematic quarter-sectional view of a second apparatus which may
be used in the method of FIG. 3;
FIG. 8 is a schematic quarter-sectional view of the second apparatus, wherein
fluid from the annulus is being rejected from the apparatus;
FIGS. 9-11 are schematic views of alternate actuation methods for the second apparatus;
FIG. 12 is a schematic block diagram of a method of communicating with a downhole
system which may be part of the method of FIG. 1;
FIG. 13 is a flowchart illustrating steps in the method of FIG. 12; and
FIG. 14 is a flowchart illustrating alternate steps in the method of FIG. 12.
DETAILED DESCRIPTION
Representatively illustrated in FIG. 1 is a method
10 which
embodies principles of the present invention. In the following description of the
method
10 and other apparatus and methods described herein, directional
terms, such as "above", "below", "upper", "lower", etc., are used only for convenience
in referring to the accompanying drawings. Additionally, it is to be understood
that the various embodiments of the present invention described herein may be utilized
in various orientations, such as inclined, inverted, horizontal, vertical, etc.,
and in various configurations, without departing from the principles of the present invention.
In the method
10, it is desired to monitor various parameters in a well,
communicate between a downhole system
12 and a remote location, such as
the earth's surface, and perform certain functions in the well. As depicted in
FIG. 1, the downhole system includes a telemetry module
14, a generator
module
16 and a controller module
18. Although these elements are
shown as separate modules
14,
16,
18, they may be combined
into the same apparatus, or they may be otherwise configured.
A downhole power generator which may be used for the generator module
16
is described in a copending application entitled ANNULUS PRESSURE OPERATED ELECTRIC
POWER GENERATOR, having as inventors thereof Neal Skinner, Michael Fripp and Roger
Schultz, and having application no. 10/026,175. The generator described in the
copending application electrical power in response to changes in annulus pressure.
Thus, the generated electrical power is intermittent, consisting of a series of
spaced apart electrical power transmissions. A method of using this intermittent
electrical power in the system
12 is described below.
Of course, other types of generators or other types of power sources may be used
for the generator module
16. In fact, batteries or electrical transmission
lines could be used in place of the generator module
16 if desired. However,
electrical power is preferably generated downhole in the method
10.
The telemetry module
14 is used to transmit data acquired by the system
12 to the remote location. Various embodiments of the telemetry module
14
are described below. The data transmitted by the telemetry module
14 is
acquired by means of sensors, such as sensors
20,
22,
24 positioned
in the well.
Preferably, the sensor
20 is at least a pressure sensor for monitoring
pressure in an annulus
26 formed between a tubing string
28 and a
wellbore
30 of the well. The sensor
20 may also include a temperature
sensor and/or any other type of sensor. The sensors
22,
24 may be
pressure, temperature, flowrate, density, resistivity, water cut, gamma ray, pH,
or any other types of sensors.
The sensors
20,
22,
24 are connected to the controller module
18, which is used for data acquisition and control of other portions of
the system
12. Flow control devices, such as valves
32,
34,
may also be controlled by the controller module
18, for example, by selectively
actuating the valves to regulate production flow from the well. The valves
32,
34 may also include sensors, such as position sensors, so that the position
of each of the valves may be detected by the controller module
18.
A pump
36 is used in the method
10 to apply pressure to the annulus
26 in communicating with the downhole system
12, for example, to
receive data transmitted from the downhole system to the remote location, or to
transmit commands or instructions to the downhole system from the remote location.
As depicted in FIG. 1, the pump
36 is positioned at the remote location
(the earth's surface), and the pump communicates with the annulus
26 via
a wellhead
38. However, it should be clearly understood that the remote
location could be elsewhere, such as a seabed in a subsea well, or within the well
itself, etc., without departing from the principles of the invention.
Pressure applied to the annulus
26 is monitored at the remote location
by a sensor
40. The sensor
40 may also include a flow rate sensor
for monitoring the volume of fluid pumped into the annulus
26 by the pump
36. Alternatively, the pump
36 may itself include a means for sensing
the volume of fluid discharged by the pump. Another sensor
42 may be used
to sense the volume of fluid released from the annulus
26 when pressure
therein is decreased.
The pump
36 and sensors
40,
42 are connected to a computer
44. The computer
44 is used to control operation of the pump
36
and monitor the outputs of the sensors
40,
42. In addition, predetermined
pressures and pressure vs. volume relationships are stored in the computer
44
for purposes that will be explained below.
Referring additionally now to FIG. 2, a schematic block diagram
46
of the controller module
18 is representatively illustrated. The controller
module
18 preferably utilizes intermittent electrical power generated by
the generator module
16 as described above. Continuous electrical power
could be used alternatively, or in addition, in keeping with the principles of
the invention.
An oscillator
48 provides clock signals to a processor
50. An EEPROM
52 or flash memory is connected to the processor
50 for nonvolatile
data storage. This nonvolatile data storage is particularly useful in the periods
between the electrical power transmissions when electrical power is not supplied
to the controller module
18. Of course, if continuous power is available
downhole there is no need for nonvolatile memory and another type of memory may
be used in place of the EEPROM
52.
An analog to digital converter
54 is used to convert analog signals from
the sensors
20,
22,
24 to digital signals usable by the processor
50. Various drivers
56 are used to actuate well tools connected to
the controller module
18, such as the valves
32,
34 shown
in FIG. 1.
Referring additionally now to FIG. 3, a flowchart
58 is representatively
illustrated which includes steps performed in transmitting data from the downhole
system
12 to the remote location in the method
10. The flowchart
58 is depicted as if intermittent electrical power is used in the downhole
system
12, with the steps therein being performed when electrical power
is received at the controller module
18 and prior to the electrical power
ceasing. If continuous electrical power is available downhole, appropriate changes
may be made to the steps in the flowchart
58.
If the annulus power operated generator (described in the incorporated copending
application referred to above) is used for the generator module
16, then
electrical power is generated by the generator and transmitted to the controller
module
18 each time pressure in the annulus
26 is increased or decreased.
The computer
44 may be programmed to operate the pump
36 so that
pressure in the annulus
26 is alternately increased and decreased, thereby
supplying a series of electrical power transmissions to the controller module
18
from the generator module
16.
Electrical power being received at the controller module
18 is
represented by the beginning "power up" step
60 in the flowchart
58.
The step
60 could represent each electrical power transmission received
at the controller module
18, that is, each time pressure in the annulus
26 is increased or decreased. Preferably, however, step
60 represents
only alternate power transmissions received in response to pressure changes in
the annulus
26, that is, due only to pressure increases in the annulus,
or due only to pressure decreases in the annulus.
Thus, the steps in the flowchart
58 are performed in response to alternate
electrical power transmissions received at the controller module
18. It
is further preferred that these alternate power transmissions are due only to pressure
increases in the annulus
26. However, it is to be clearly understood that
this is not necessary in keeping with the principles of the invention. For example,
if continuous electrical power is available, the steps in the flowchart
58
could be performed at any time.
In step
62, the count value of a counter device is compared to zero. The
count value is initially set to zero, so on the first instance of electrical power
being received at the controller module
18, the count value is zero and
steps
64,
66,
68,
70,
72 of the flowchart
58
are performed in succession. On subsequent instances of electrical power being
received at the controller module
18, the count value may be nonzero, in
which case step
76 would next be performed.
Assuming that the count value is zero, the next step is to take a reading
from a sensor connected to the controller module
18, such as any one of
the sensors
20,
22,
24. This step would be performed by the
processor
50 via the analog to digital converter
54 as depicted in
FIG. 2. The reading would typically comprise a byte of data which includes a number
of bits.
In step
66, the reading (comprising the byte of data) is stored in the
memory
52.
In step
68, the count value is incremented, i.e., the count value is increased
by one. Assuming that the count value was previously zero, the count value will
be one upon completion of step
68.
In step
70, a telemetry bit is set so that it corresponds to the data
bit
indicated by the count value. That is, if the count value is one, the first data
bit is used to set the telemetry bit. If the count value is two, the second data
bit is used to set the telemetry bit, etc. Thus, when the count value is nonzero,
it indicates a corresponding one of the data bits which will be used to set the
telemetry bit. The use of the telemetry bit will be described in further detail below.
In step
72, the count value is stored in the memory
52. In this
manner, the count value will be available after electrical power to the controller
module
18 ceases in the "sleep" step
74. On the next "power up" step
60, the stored count value will be retrieved, and step
62 will utilize
the stored count value.
If the stored count value is nonzero in step
62, then in step
76
the count value is compared to a maximum bit number. As discussed above, the count
value corresponds to a particular data bit. Therefore, if the count value is equal
to or greater than the maximum bit number, then all of the data bits have been
previously indicated.
If the count value is less than the maximum bit number in step
76, then
steps
68,
70,
72 are performed in succession. Thus, the telemetry
bit is set for each nonzero count value, from one up to the maximum number of bits.
In this way, the telemetry bit is set corresponding to each of the data bits in succession.
If in step
76 the count value is not less than the maximum number of bits,
then the count value is reset to zero in step
78. This count value is then
stored in step
72. On the next "power up" step
60, the comparison
in step
62 will be affirmative and another reading will be taken and stored
in steps
64,
66.
Therefore, when the count value is zero on power up, a reading is taken
and stored, the count is incremented to one, and the telemetry bit is set to correspond
to the data bit indicated by the incremented count value. If, on power up, the
count value is nonzero but is less than the maximum number of data bits, then the
count value is incremented and the telemetry bit is set to correspond to the data
bit indicated by the incremented count value. If, on power up, the count value
is nonzero but is not less than the maximum number of data bits, then the count
value is reset to zero. In all of these circumstances, the incremented or reset
count value is stored prior to the electrical power transmission to the controller
module
18 ceasing in step
74.
Referring additionally now to FIG. 4, an apparatus
80 which may
be used for the telemetry module
14 in the method
10 is representatively
illustrated. In FIG. 4, the apparatus
80 is depicted as if it is interconnected
in the tubing string
28 with the annulus
26 surrounding the apparatus.
However, it is to be understood that the apparatus
80 may be used in other
methods and may be otherwise positioned and configured, without departing from
the principles of the invention.
The apparatus
80 includes two floating pistons
82,
84 sealingly
and reciprocably received in respective chambers
86,
88. A valve
device
90 selectively permits or prevents fluid communication between the
chambers
86,
88.
The valve device
90 may be any type of device which functions to selectively
permit and prevent flow between the chambers
86,
88. For example,
the valve device
90 may be a conventional solenoid valve. Preferably, the
valve device
90 is of the latching type, that is, once actuated to an open
or closed position, the valve device remains in that position without the need
for continued application of energy to the valve device. In this way, energy is
conserved in the system
12.
A port
92 provides fluid communication between the annulus
26 and
the chamber
86 above the upper piston
82. Thus, when the pump
36
applies pressure to the annulus
26, this pressure is transmitted to the
piston
82, and when pressure is released from the annulus, it is also reduced
on the piston
82.
In the chamber
86 below the upper piston
82 is a fluid, such as
oil. This fluid will flow through the valve
90 to the chamber
88
above the lower piston
84 if the valve is open, and if the pressure in the
upper chamber
86 is greater than the pressure in the lower chamber
88.
If this happens (fluid flows from the upper chamber
86 to the lower chamber
88 through the valve
90), then the upper and lower pistons
82,
84 will displace downwardly. Downward displacement of the upper piston
82
increases the effective volume of the annulus
26, since the chamber
86
volume above the piston
82 (which is in fluid communication with the annulus
via the port
92) increases.
Thus, if the valve
90 is open and pressure is applied to the annulus
26 so that it becomes greater than pressure in the lower chamber
88,
the effective volume of the annulus will be increased due to downward displacement
of the upper piston
82. Therefore, a greater volume of fluid will need to
be pumped into the annulus
26 by the pump
36 to achieve a certain
pressure in the annulus, or a lesser pressure will be achieved for a given volume
of fluid pumped into the annulus.
Likewise, if pressure in the annulus
26 is reduced after the upper
piston
82 has been displaced downward and the effective volume of the annulus
has been thereby increased, a greater volume of fluid will need to be released
from the annulus to reduce the pressure in the annulus to a certain level, or the
pressure in the annulus will be reduced to a lesser extent when a given volume
of fluid is released from the annulus. Therefore, it will be readily appreciated
by one skilled in the art that the open or closed position of the valve
90
may be readily determined at the remote location by merely increasing or decreasing
the pressure in the annulus
26, and correspondingly adding or reducing the
volume of fluid in the annulus.
Downward displacement of the lower piston
84 decreases the volume
of the chamber
88 below the piston
84. Preferably, a compressible
fluid, such as Nitrogen gas, is in the chamber
88 below the piston
84.
The pressure of this fluid is preferably greater than the hydrostatic pressure
in the annulus
26 surrounding the apparatus
80. Thus, when pressure
is applied to the annulus
26 with the valve
90 open, pressure in
the annulus surrounding the apparatus
80 will be increased to a level at
which it exceeds the pressure of the fluid in the chamber
88 below the piston
84 in order for the pistons
82,
84 to displace downwardly
and increase the effective volume of the annulus.
Referring additionally now to FIG. 5, the apparatus
80 is shown
in a configuration in which pressure in the annulus
26 surrounding the apparatus
has been increased to a level exceeding the initial pressure of the fluid in the
chamber
88 below the lower piston
84, with the valve
90 open.
Note that both of the pistons
82,
84 have displaced downwardly as
compared to their respective positions as shown in FIG. 4. Downward displacement
of the upper piston
82 has increased the effective volume of the annulus
26, so that more fluid volume must be pumped into the annulus
26
to achieve this increased pressure in the annulus, or less pressure increase in
the annulus is achieved due to a given volume of fluid being pumped into the annulus.
Of course, if the valve
90 is closed when pressure in the annulus
26
is increased, the effective volume of the annulus will not be increased, even if
the annulus pressure is increased so that it is greater than the fluid pressure
in the chamber
88 below the lower piston
84. Depicted in FIG. 6 are
pressure vs. volume plots showing a comparison between the two situations in which
fluid is either accepted into the upper chamber
86 from the annulus
26
(thereby increasing the effective volume of the annulus), or is rejected from entering
the upper chamber from the annulus.
The vertical axis indicates the pressure in the annulus
26 surrounding
the apparatus
80. The horizontal axis indicates the volume of fluid added
to the annulus
26 by the pump
36. The solid line plot
94 is
characteristic of the situation where the valve
90 is closed, so that fluid
from the annulus
26 is rejected from entering the chamber
86 when
pressure in the annulus is increased. The dashed line plot
96 is characteristic
of the situation where the valve
90 is open, so that fluid from the annulus
26 is accepted into the chamber
86.
Note that the plot
94 is substantially a straight line, illustrating
the well-known linear relationship between fluid pressure and volume in a constant
volume container. The plot
96 is also substantially linear up to a point
98, which occurs at the pressure level in the annulus
26 surrounding
the apparatus
80 which equals the pressure of the fluid in the chamber
88
below the lower piston
84. At this point, additional fluid volume added
to the annulus
26 serves to downwardly displace the pistons
82,
84,
thereby increasing the effective volume of the annulus, without substantially increasing
the annulus pressure.
Increased fluid volume added to the annulus
26 from point
98
to another point
100 does not cause a significant increase in pressure in
the annulus
26, thus the plot
96 is substantially horizontal between
the points
98,
100. At the point
100, the upper piston
82
has been displaced downwardly sufficiently far for it to bottom out (as depicted
in FIG. 5), and the effective volume of the annulus
26 is no longer increased
as fluid is added to the annulus
26. Therefore, the plot
96 again
increases substantially linearly after the point
100.
It may now be fully appreciated how conveniently the position of the valve
90
may be determined at the remote location. For example, pressure in the annulus
26 surrounding the apparatus
80 may be increased to a predetermined
level
102, which is greater than the fluid pressure in the chamber
88
below the lower piston
84. If the volume added to the annulus
26
to achieve this pressure level
102 is as indicated by point
104 on
the plot
94, then the valve
90 is closed. If the volume added to
the annulus
26 is as indicated by point
106 on the plot
96,
then the valve
90 is open.
Alternatively, a predetermined volume
108 of fluid may be added
to the annulus
26 to increase the pressure in the annulus surrounding the
apparatus
80 20 so that it is greater than the fluid pressure in
the chamber
88 below the lower piston
84. If the annulus pressure
resulting from this fluid volume increase is as indicated by point
110 on
the plot
94, then the valve
90 is closed. If the annulus pressure
resulting from this fluid volume increase is as indicated by point
112 on
the plot
96, then the valve
90 is open.
As another alternative, the computer
44 (which monitors the fluid pressure
and volume changes in the annulus
26) may be programmed to search for characteristics
which indicate whether the valve
90 is open or closed. For example, the
computer
44 could easily be programmed to recognize the relatively horizontal
characteristic of the plot
96 between the points
98,
100 as
indicative of the valve
90 being open. The lack of such a characteristic
would be indicative that the valve
90 is closed.
It will also be readily appreciated that, although the above discussion of the
plots
94,
96 depicted in FIG. 6 has been given as though the determination
of the position of the valve
90 is made when pressure is increased in the
annulus
26, such a determination may also be made when pressure is decreased
in the annulus. For example, if pressure in the annulus
26 surrounding the
apparatus
80 is decreased a certain amount so that the pistons
82,
84 displace upwardly, then the amount of fluid released from the annulus
will be indicative of whether the valve
90 is open or closed. Likewise,
if a certain volume of fluid is released from the annulus
26, so that pressure
in the annulus
26 surrounding the apparatus
80 is decreased so that
the pistons
82,
84 displace upwardly, then the amount of pressure
decrease in the annulus will be indicative of whether the valve
90 is open
or closed.
Since fluid volume and pressure changes may be accurately measured at the remote
location to determine the position of the valve
90 in the apparatus
80,
the position of the valve may thus be used to communicate between the downhole
system
12 and the remote location. For example, the closed position of the
valve
90 may be used to represent a "0" value of a data bit, and the open
position of the valve may be used to represent a "1" value of a data bit. Therefore,
by appropriately positioning the valve
90 and changing the fluid volume
and pressure in the annulus
26, data bits may be transmitted from the downhole
system
12 to the remote location.
In the above description of the flowchart
58 depicted in FIG. 3, a telemetry
bit was set in step
70 to correspond to a bit of a data byte. It may now
be seen that the setting of this telemetry bit in step
70 corresponds to
the open or closed position of the valve
90, so that the position of the
valve corresponds to the value of the data bit. A pressure change in the annulus
26 produces an electrical power transmission to the controller module
18
which initially causes a data byte to be received into the controller module. This
initial power transmission also causes the telemetry bit to be set so that it corresponds
to the value of the first data bit. In response, the valve
90 may be actuated
to its corresponding open or closed position (if it is not in the appropriate position
already) during the same power transmission, or the telemetry bit may be stored
in the memory
52 so that the valve is actuated on the next power transmission.
With the valve
90 appropriately actuated and fluid pressure and volume
in the annulus
26 changed, the value of the first data bit may be determined
at the remote location. This process is repeated for each data bit, until the entire
byte of data is received at the remote location. A new data byte may then be read
after the count is reset in step
78 of the flowchart
58, and the
process of transmitting each bit of the new data byte is repeated.
Referring additionally now to FIG. 7, an alternate apparatus
114
which may be used for the telemetry module
14 in the system
12 is
representatively illustrated. Of course, the apparatus
114 may be used in
other systems and in methods other than the method
10 described above, without
departing from the principles of the invention.
The apparatus
114 is similar in many respects to the apparatus
80
described above, and elements of the apparatus
114 which are similar to
those of the apparatus
80 are indicated in FIG. 7 using the same reference
numbers. The apparatus
114 may, however, be differently configured in keeping
with the principles of the invention.
Note that the apparatus
114 does not include the conventional valve
90
of the apparatus
80. Instead, the valve device selectively permitting and
preventing fluid flow between the chambers
86,
88 is a magnetorheological
fluid disposed in a passage
116 interconnecting the chambers. The magnetorheological
fluid takes the place of the fluid, such as oil, below the piston
82 in
the chamber
86 in the apparatus
80, and which is flowed into the
lower chamber
88 when the pistons
82,
84 displace downwardly.
That is, the magnetorheological fluid flows downwardly through the passage
116,
from the upper chamber
86 to the lower chamber
88, when the pistons
82,
84 displace downwardly.
The magnetorheological fluid is normally in a free-flowing liquid state. However,
when a magnetic field having a requisite strength is passed through the fluid,
it solidifies or becomes substantially solid. In the apparatus
114, the
magnetorheological fluid in the passage
116 functions as a valve device
to selectively permit and prevent fluid communication between the chambers
86,
88.
When the magnetorheological fluid in the passage
116 is solidified, fluid
communication between the chambers
86,
88 is not permitted and the
pistons
82,
84 will not displace in response to changes in pressure
in the annulus
26 (similar to the valve
90 being closed in the apparatus
80). When the magnetorheological fluid in the passage
116 is liquid,
fluid communication between the chambers
86,
88 is permitted, so
that the pistons
82,
84 can displace in response to changes in pressure
in the annulus
26 (similar to the valve
90 being open in the apparatus
80).
To selectively control the liquid and solid states of the magnetorheological
fluid
in the passage
116, a magnet
118 is positioned in close proximity
to the passage. As depicted in FIG. 7, the magnet
118 is oriented so that
its poles are substantially parallel to the passage
116, and so only a relatively
weak magnetic field is experienced by the fluid in the passage due to the magnet,
and the fluid remains in a liquid state. As depicted in FIG. 8, the magnet
118
has been rotated so that its poles are oriented perpendicular to the passage
116,
and so a relatively strong magnetic field is experienced by the fluid in the passage,
and the fluid is changed to its solid state.
It will be readily appreciated that the liquid and solid states of the magnetorheological
fluid in the passage
116 may be determined at the remote location in the
same manner as the open and closed positions of the valve
90 of the apparatus
80 may be determined at the remote location. It will also be readily appreciated
that the setting of the telemetry bit in step
70 of the flowchart
58
may correspond to the positioning of the magnet
118 to represent the value
of the corresponding data bit in the same manner as the setting of the telemetry
bit corresponds to the positioning of the valve
90 in the apparatus
80.
Therefore, the apparatus
114 may be used to transmit data from the system
12 to the remote location as pressure in the annulus
26 is changed.
Instead of changing the position of the magnet
118, many other methods
may be used to selectively change the state of the magnetorheological fluid in
the passage
116. FIGS. 9-11 representatively illustrate a few of these alternate
methods. Other methods may be used without departing from the principles of the invention.
In FIG. 9, the magnetic field
120 of a magnet
122 is directed through
the magnetorheological fluid
124 in the passage
116 by means of a
ferrous structure
126 of the type well known in the art. The fluid
124
is solidified by the magnetic field
120 passing therethrough, as indicated
by the cross-hatching of the fluid in the passage
116 as depicted in FIG. 9.
In FIG. 10, another ferrous structure
128 has been positioned in the structure
126. The presence of the structure
128 "short circuits" the magnetic
field
120, so that it is directed through the structure
128, instead
of through the fluid
124 in the passage
116. The fluid
124
is not cross-hatched in FIG. 10 to indicate that it is in its liquid state.
Thus, the positioning of the structure
128 may be used to selectively
permit and prevent fluid communication between the chambers
86,
88.
The setting of the telemetry bit may be used to determine the positioning of the
structure
128, to thereby represent the value of the corresponding data
bit transmitted to the remote location.
In FIG. 11, a portion
130 of the structure
126 has been removed.
The removal of the portion
130 prevents the magnetic field
120 from
being directed to flow through the fluid
124 in the passage
116.
The fluid
124 is not cross-hatched in FIG. 11 to indicate that it is in
its liquid state.
Thus, the presence or absence of the portion
130 may be used to selectively
prevent or permit fluid communication between the chambers
86,
88.
The setting of the telemetry bit may be used to determine the positioning of the
portion
130, to thereby represent the value of the corresponding data bit
transmitted to the remote location.
Several alternate methods have been described above for communicating data
from the downhole system
12 to the remote location using pressure changes
in the annulus
26. These methods permit long term monitoring of well parameters
and, in the method
10 utilizing the annulus pressure operated downhole generator,
this monitoring may be accomplished without the use of batteries or electrical
lines extending to the surface.
However, it may at times be desirable to communicate from the remote location
to the downhole system
12. For example, a command may be issued for the
controller module
18 to select a particular one of the sensors
20,
22,
24 for monitoring, a command may be issued for the controller
module to select a particular valve
32,
34 for actuation thereof,
the processor
50 may be reprogrammed from the remote location, etc.
Since pressure changes in the annulus
26 are used for electrical power
generation and for data communication from the downhole system
12 to the
remote location, it would be convenient for these annulus pressure changes to also
be available for use in communicating from the remote location to the downhole
system. It would not be necessary, however, for the same annulus pressure changes
to be used for all of these purposes or a particular combination of these purposes,
although the use of the same annulus pressure changes for all of these purposes
or any desired combination of these purposes is made possible by the principles
of the invention described herein.
Referring additionally now to FIG. 12, a schematic block diagram
132
is representatively illustrated for communication from the remote location to the
downhole system
12. The block diagram
132 includes several of the
elements of the block diagram
46 shown in FIG. 2 for communication from
the downhole system
12 to the remote location.
A pressure transducer, such as the sensor
20, is used to monitor pressure
in the annulus
26. The sensor's output is connected via the analog to digital
converter
54 to the processor
50. The processor
50 is programmed
to monitor the output of the sensor and detect when a change in annulus pressure
indicates a lo value of a communication bit. A flowchart
134 illustrating
this programming is illustrated in FIG. 13 and is described below.
When the processor
50 determines that a change in annulus pressure indicates
a value of a communication bit, the bit value is stored in the nonvolatile memory
52. Specifically, the memory
52 includes a shift register
136.
The shift register
136 has a predetermined number of places corresponding
to the number of bits in a communication byte.
When a new bit value is stored in the shift register
136 (indicated by
arrow
138 in FIG. 12), the oldest bit value stored in the shift register
is discarded (indicated by arrow
140 in FIG. 12), and each of the remaining
bit values are shifted over one place in the shift register (indicated by arrows
142 in FIG. 12). This manner of operation of a shift register is well known
to those skilled in the art.
Thus, the byte indicated by the stored bit values in the shift register
136
changes as each new bit value is stored therein. To send a desired communication
byte from the remote location to the downhole system
12, the appropriate
annulus pressure changes are made at the remote location so that the processor
50 thereby detects a corresponding succession of bit values, which are stored
in succession in the shift register
136. When the processor
50 recognizes
that an appropriate communication byte has been stored in the shift register
136,
the processor performs a corresponding programmed function, executes a command,
records an instruction, etc.
Referring additionally now to FIG. 13, the flowchart
134 shows representatively
how annulus pressure changes may be used to communicate from the remote location
to the downhole system
12. As with the "power up" step
60 in the
flowchart
58 shown in FIG. 2, a "power up" step
144 is used in the
flowchart
134 to indicate that a transmission of electrical power is received
at the controller module
18. This "power up" step
144 may occur at
the same time as the previously described "power up" step
60, they may occur
on alternate pressure increases or decreases in annulus pressure, etc.
In step
146, pressure in the annulus
26 is read. As described above,
the sensor
20 may be used to input this data to the processor
50
via the analog to digital converter
54. Preferably, an appropriate time
delay is used to permit the annulus pressure to reach its maximum level.
In step
148, the maximum annulus pressure read in step
146 is compared
to predetermined high and low levels used to indicate communication bit values.
For example, a maximum annulus pressure of between 500 and 1000 psi may be a low
level which indicates a bit value of "0", while a maximum annulus pressure of over
1000 psi may be a high level which indicates a bit value of "1".
Step
150 is performed if it is determined that a bit value of "1" is
indicated by the maximum annulus pressure. A "1" bit value is shifted into the
shift register
136.
Alternatively, step
152 is performed if it is determined that
a bit value of "0" is indicated by the maximum annulus pressure. A "0" bit value
is shifted into the shift register
136.
If the maximum annulus pressure does not indicate either bit value, then no bit
value is stored in the shift register
136. In any event, the next step
154
is to compare the byte stored in the shift register
136 to a series of preprogrammed
bytes. For example, a preprogrammed command byte may be used to cause the processor
50 to perform a certain function, such as select one of the sensors
20,
22,
24 for monitoring, select one of the valves
32,
34
for actuation, etc.
If the byte stored in the shift register
136 matches the preprogrammed
byte, then the function is performed or the command is executed in step
158.
After the function is performed or the command is executed in step
158,
or if no match is found in step
154, the controller module
18 resumes
its sleep mode in step
156, which may occur when electrical power transmission
to the controller module ceases. Since the bit values in the shift register
136
are stored in the nonvolatile memory
52, they remain in the shift register
when the next "power up" step
144 is performed.
Although the above description of the flowchart
134 has been given
as though communication bits are transmitted from the remote location to the downhole
system
12 by increasing annulus pressure to certain maximum values to indicate
corresponding bit values, it will be readily appreciated that annulus pressure
decreases to certain levels or other annulus pressure changes could also, or alternatively,
be used to indicate bit values.
Referring additionally now to FIG. 14, a flowchart
160 is representatively
illustrated which is somewhat similar to the flowchart
134 described above.
However, the flowchart
160 includes changes which may be made to the communication
method if continuous electrical power is available downhole. Steps shown in the
flowchart
160 which are similar to steps of the flowchart
134 are
indicated in FIG. 14 using the same reference numbers.
One significant difference between the flowcharts
134,
160 is that
there are no "power up" or "sleep" steps in the flowchart
160. Since continuous
power is available downhole in the situation represented in flowchart
160,
these steps are not needed.
However, since the transmission of electrical power to the controller module
18 is not intermittent in the flowchart
160, the transmission of
electrical power is also not used to begin the steps in the communication method.
Instead, pressure in the annulus is continuously monitored by the processor
50
and the steps of the flowchart
160 are performed when the processor determines
that a predetermined change in the annulus pressure has occurred.
In step
162, a determination is made whether a change in annulus pressure
has occurred. This change in annulus pressure may be an increase to a certain level,
a decrease to a certain level, a change of a certain amount in either direction,
etc. If the predetermined change in annulus pressure is not detected, then step
162 is repeated.
If the predetermined change in annulus pressure is detected, then the method
proceeds
to step
146. From this point, the flowchart
160 is substantially
similar to the flowchart
134 described above. However, after step
154,
and possibly step
158, has been performed, instead of progressing to the
sleep state, the processor
50 again goes to step
162 to determine
when another change in annulus pressure occurs.
It may now be fully appreciated that the present invention provides convenient,
economical, straightforward communication between the downhole system
12
and the remote location through the use of annulus pressure changes. These annulus
pressure changes may also be used to provide electrical power to the downhole system
12, so that it is self-contained and suitable for long term monitoring of
well parameters and control of production from the well.
For example, pressure increases in the annulus
26 may be used to perform
all sensor monitoring, communicating and command executing functions while pressure
decreases are used to operate a cooling system for the downhole system
12
electronics. That is, the electrical power generated by pressure increases would
power the downhole system
12 electronics while readings from the sensors
20,
22,
24 are taken, the telemetry bit is set, the valve
device
90 or
116,
124 is operated, well tools
32,
34
are actuated, bit and count values are stored in memory
52. Each pressure
increase could, thus, result in a data bit being transmitted from the downhole
system
12 to the remote location and a command bit being transmitted from
the remote location to the downhole system. Alternatively, electrical power generated
by pressure decreases could be used to power the downhole system
12 electronics
and pressure increases could be used to operate the cooling system.
As another alternative, pressure increases could be used to power some of the
functions of the downhole system
12 electronics, such as communication between
the downhole system and the remote location (e.g., monitoring annulus pressure,
storing bit and count values, etc.) and pressure decreases could be used to power
other functions (e.g., operating the valve device
90 or
116,
124,
actuating well tools
32,
