U.S. patent application number 10/710513 was filed with the patent office on 2006-01-19 for seismic data acquisition system and method for downhole use.
This patent application is currently assigned to SENSORWISE, INC.. Invention is credited to Abbas Arian, Georgios L. Varsamis, Laurence T. Wisniewski.
Application Number | 20060013065 10/710513 |
Document ID | / |
Family ID | 35599246 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060013065 |
Kind Code |
A1 |
Varsamis; Georgios L. ; et
al. |
January 19, 2006 |
Seismic Data Acquisition System and Method for Downhole Use
Abstract
A method and system for conducting a seismic survey by lowering
a string of intelligent clampable sensor pods with 3-C sensors into
a borehole. The string of pods is serially interconnected by a
cable having a conductor pair which provides both power and data
connectivity. The uppermost sensor pod is connected to a downhole
telemetry and control module. The cables and pods use connectors to
allow assembly, customization, repair, and disassembly on site.
Each pod has an upper and a lower connector, a processor, and
memory which is coupled to both the upper and the lower connectors.
Each pod is capable of simultaneous and independent serial
communications at each connector with the memory. The telemetry and
control module is designed to query the pods to determine the
system configuration. The telemetry and control module then
simultaneously triggers all pods to acquire data, the pods storing
the collected data locally in the memory. After data collection,
the controller simultaneously signals the pods to immediately
transfer data serially from the local memory to the next higher
adjacent pod and receive data, if any, from the lower adjacent pod,
if any, storing the received data in memory. The first data
transferred from each pod is that data collected by its local
sensors. Subsequent data originates from lower pods and is simply
passed up the string of pods to the telemetry and control module.
In other words, the pods communicate in a bucket brigade
fashion.
Inventors: |
Varsamis; Georgios L.;
(Houston, TX) ; Wisniewski; Laurence T.; (Houston,
TX) ; Arian; Abbas; (Houston, TX) |
Correspondence
Address: |
ANDREWS & KURTH, L.L.P.
600 TRAVIS, SUITE 4200
HOUSTON
TX
77002
US
|
Assignee: |
SENSORWISE, INC.
2908 Rogerdale Road
Houston
TX
|
Family ID: |
35599246 |
Appl. No.: |
10/710513 |
Filed: |
July 16, 2004 |
Current U.S.
Class: |
367/76 ; 340/531;
340/853.1; 340/870.01 |
Current CPC
Class: |
G01V 11/002
20130101 |
Class at
Publication: |
367/076 ;
340/870.01; 340/531; 340/853.1 |
International
Class: |
G01V 1/00 20060101
G01V001/00; G08C 19/16 20060101 G08C019/16; G01V 3/00 20060101
G01V003/00; G08B 1/00 20060101 G08B001/00 |
Claims
1-19. (canceled)
20. A sensor array (18') comprising, a telemetry and control module
(21'), and a plurality of sensor pods (12') coupled to said
telemetry and control module, each of said plurality of sensor pods
(12') characterized by having a sensor (126) therein coupled to a
memory (28'), having a first interface (72) coupled to said memory,
having a second interface (74) coupled to said memory, and being
designed and arranged to transfer first data from said memory to
said first interface and second data from said second interface to
said memory, said telemetry and control module (21') coupled to
said first interface of a first of said plurality of sensor pods
(12') and said second interface of said first of said plurality of
sensor pods (12') coupled to said first interface of a second of
said plurality of sensor pods (12').
21. The sensor array of claim 20 wherein each of said plurality of
sensor pods (12') is designed and arranged to simultaneously
transfer first data from said memory to said first interface and
second data from said second interface to said memory.
22. The sensor array of claim 20 wherein, first pod data is
produced by said sensor of said first of said plurality and
transferred to said memory of said first of said plurality, second
pod data is produced by said sensor of said second of said
plurality and transferred to said memory of said second of said
plurality, said first pod data is transferred from said memory of
said first of said plurality through said first interface of said
first of said plurality to said telemetry and control module, and
said second pod data is transferred from said memory of said second
of said plurality through said first interface of said second of
said plurality and through said second interface of said first of
said plurality to said memory of said first of said plurality.
23. The sensor array of claim 22 wherein, said first pod data is
transferred from said memory of said first of said plurality
through said first interface of said first of said plurality to
said telemetry and control module, and simultaneously said second
pod data is transferred from said memory of said second of said
plurality through said first interface of said second of said
plurality and through said second interface of said first of said
plurality to said memory of said first of said plurality.
24. The sensor array of claim 22 wherein, said second pod data is
transferred from said memory of said first of said plurality
through said first interface of said first of said plurality to
said telemetry and control module.
25. The sensor array of claim 20 wherein, said plurality includes
said first of said plurality, a last of said plurality and at least
one inner of said plurality, each of said at least one inner of
said plurality has said first interface coupled to said second
interface of a first adjacent of said plurality and said second
interface coupled to a second adjacent of said plurality, said
first interface of said last of said plurality is coupled to said
second interface of one of said at least one inner of said
plurality, and said first interface of said first of said plurality
is coupled to said telemetry and control module and said second
interface of said first of said plurality is coupled to said first
interface of one of said at least one inner of said plurality.
26. The sensor array of claim 25 wherein, last pod data is produced
by said seismic sensor of said last of said plurality and
transferred to said memory of said last of said plurality, said
last pod data is transferred from said memory of said last of said
plurality to said telemetry and control module via each of said at
least one inner of said plurality, being temporarily stored in said
memory of each of said at least one inner of said plurality, and
via said first of said plurality, being temporarily stored in said
memory of said first of said plurality.
27. The sensor array of claim 20 wherein each of said plurality is
further characterized by, a communications bypass (130) coupled
between said first interface and said second interface, said
communications bypass having a switch element (132) having a first
state which enables said bypass and a second state which disables
said bypass.
28. The sensor array of claim 27 wherein each of said plurality is
further characterized by, said switch element (132) being
controlled by said sensor pod (12') in response to a signal
received at said first interface (72).
29. The sensor array of claim 28 wherein, said signal originates
from said telemetry and control module (21').
30. The sensor array of claim 28 further comprising, a surface
controller (20') coupled to said telemetry and control module
(21'), wherein said signal originates from said surface
controller.
31. The sensor array of claim 28 wherein, said signal originates
from said second interface (74) of an adjacent one of said
plurality of sensor pods.
32. The sensor array of claim 29 wherein, said switch elements
(132) of each of said plurality are in said first state, and each
of said plurality of said pods nearly simultaneously receives said
signal at said first interface from said telemetry and control
module (21').
33. The sensor array of claim 29 further comprising, a surface
controller (20') coupled to said telemetry and control module
(21'), wherein said switch elements (132) of each of said plurality
are in said first state, and each of said plurality of said pods
nearly simultaneously receives said signal at said first interface
from said surface controller (20').
34. The sensor array of claim 32 wherein, said signal causes said
sensors (126) of each of said plurality to measure data and
transfer said data to corresponding said memories (28') of each of
said plurality.
35. The sensor array of claim 20 wherein, communication between
said plurality of sensor pods uses a communications protocol, and
communication between said telemetry and control module and said
first of said plurality uses a communications protocol.
36. The sensor array of claim 35 wherein said communications
protocol is a serial communications protocol.
37. The sensor array of claim 20 further comprising, a repeater
(46) coupled between any two of said plurality of pods (12'), said
repeater designed and arranged to increase the communications range
between said two of said plurality.
38. The sensor array of claim 20 wherein each of said plurality
further comprises, a clamping mechanism (26', 122) designed and
arranged to releasably clamp said sensor pod to a borehole
wall.
39. The sensor array of claim 38 wherein each of said plurality is
further characterized by, said clamping mechanism (26', 122) being
controlled by said sensor pod in response to a signal received at
said first interface (72).
40. The sensor array of claim 39 wherein, said signal originates
from said telemetry and control module (21').
41. The sensor array of claim 39 further comprising, a surface
controller (20') coupled to said telemetry and control module
(21'), wherein said signal originates from said surface
controller.
42. The sensor array of claim 39 wherein, said signal originates
from said second interface (74) of an adjacent one of said
plurality of sensor pods (12').
43. The sensor array of claim 20 wherein each of said plurality
further comprises, a processor (120) coupled to said memory (28'),
said first interface (72) and said second interface (74), said
processor designed and arranged to interpret signals received at
said first interface and control said sensor pod.
44. The sensor array of claim 20 wherein, said sensor is a seismic
sensor.
45. The sensor array of claim 20 further comprising, a plurality of
cables (24'), wherein each of said plurality of sensor pods (12')
has upper and lower ends and characterized by being designed and
arranged to be repeatably coupled and uncoupled to a first and
second of said plurality of cables at both said upper and lower
ends, and said plurality of sensor pods are removably coupled
together upper end to lower end by said plurality of cables to form
a string, with a first end of said string of sensor pods removably
coupled to said telemetry and control module with one of said
plurality of cables.
46. The sensor array of claim 45 wherein each of said plurality of
sensor pods is characterized by, having a processor (120) designed
and arranged to communicate with said telemetry and control module
and with other sensor pods and designed to store an
identification.
47. The sensor array of claim 46 wherein, said telemetry and
control module can query each of said plurality of sensor pods, and
each of said plurality of sensor pods is designed and arranged to
answer a query.
48. The sensor array of claim 47 wherein, said telemetry and
control module harmonizes with said plurality of sensor pods to
establish a unique identification for each of said plurality of
sensor pods, and, said telemetry and control module (21') registers
the position in said string of each of said sensor pods relative to
the plurality of sensor pods.
49. The sensor array of claim 47 wherein, using a particular
identification, said telemetry and control module queries a
specific one of said plurality of sensor pods, and said specific
one of said plurality of sensor pods answers said telemetry and
control module.
50. The sensor array of claim 49 wherein, said telemetry and
control module queries about a status of a sensor (126).
51. The sensor array of claim 49 wherein, said telemetry and
control module queries about a status of a memory (28').
52. The sensor array of claim 49 wherein, said telemetry and
control module queries about a voltage level.
53. The sensor array of claim 49 wherein, said telemetry and
control module queries about a status of a clamping mechanism (26',
122).
54. The sensor array of claim 47 wherein, using a particular
identification, said telemetry and control module commands a
function of a specific one of said plurality of sensor pods, and
said specific one of said plurality of sensor pods performs said
function.
55. The sensor array of claim 54 wherein, said telemetry and
control module commands to manipulate a clamping mechanism (26',
122).
56. The sensor array of claim 54 wherein, said telemetry and
control module commands to manipulate a switch element (132).
57. The sensor array of claim 54 wherein, said telemetry and
control module commands to control a sensor (126).
58. The sensor array of claim 47 wherein, said telemetry and
control module simultaneously commands each of said plurality of
sensor pods to record data.
59. The sensor array of claim 47 wherein, said telemetry and
control module nearly simultaneously commands each of said
plurality of sensor pods to transmit data.
60. The sensor array of claim 45 further comprising, a main
controller (20') coupled to said telemetry and control module
(21').
61. The sensor array of claim 60 wherein each of said plurality of
sensor pods is characterized by, having a processor (120) designed
and arranged to communicate with said main controller and with
other sensor pods and to store an identification.
62. The sensor array of claim 61 wherein, said main controller is
designed and arranged to query each of said plurality of sensor
pods, and each of said plurality of sensor pods is designed and
arranged to answer a query.
63. The sensor array of claim 62 wherein, said main controller is
designed and arranged to harmonize with said plurality of sensor
pods to establish a unique identification for each of said
plurality of sensor pods, and said main controller (20') is
designed and arranged to register the position in said string of
each of said sensor pods relative to the plurality of sensor
pods.
64. The sensor array of claim 62 wherein, using a particular
identification, said main controller is designed and arranged to
query a specific one of said plurality of sensor pods, and said
specific one of said plurality of sensor pods is designed and
arranged to answer said main controller.
65. The sensor array of claim 64 wherein, said main controller is
designed and arranged to query about a status of a sensor
(126).
66. The sensor array of claim 64 wherein, said main controller is
designed and arranged to query about a status of a memory
(28').
67. The sensor array of claim 64 wherein, said main controller is
designed and arranged to query about a voltage level.
68. The sensor array of claim 64 wherein, said main controller is
designed and arranged to query about a status of a clamping
mechanism (26', 122).
69. The sensor array of claim 62 wherein, using a particular
identification, said main controller is designed and arranged to
command a function of a specific one of said plurality of sensor
pods, and said specific one of said plurality of sensor pods is
designed and arranged to perform said function upon said
command.
70. The sensor array of claim 69 wherein, said main controller is
designed and arranged to command a specific one of said plurality
of sensor pods to manipulate a clamping mechanism (26', 122).
71. The sensor array of claim 69 wherein, said main controller is
designed and arranged to command a specific one of said plurality
of sensor pods to manipulate a switch element (132).
72. The sensor array of claim 69 wherein, said main controller is
designed and arranged to command a specific one of said plurality
of sensor pods to control a sensor (126).
73. The sensor array of claim 62 wherein, said main controller is
designed and arranged to simultaneously command each of said
plurality of sensor pods to record data.
74. The sensor array of claim 62 wherein, said main controller
nearly simultaneously commands each of said plurality of sensor
pods to transmit data.
75. A method for conducting a survey comprising the steps of,
assembling a string (18') of intelligent sensor pods (12')
containing sensors (126) and memory (28'), connecting one end of
said string to a telemetry and control module (21'), collecting
data with said sensors, storing said data in said memory, and
transmitting said data from said memory to said telemetry and
control module in a bucket brigade transfer, wherein a bucket
brigade transfer comprises the steps of, each sensor pod
transmitting data stored in said memory upwards, and each sensor
pod receiving data, if any, from a sensor pod coupled below it, if
any, and storing said received data in said memory.
76. The method according to claim 75 further comprising the step
of, lowering said string into a borehole (14), wherein said survey
is a seismic survey, and said data are seismic data.
77. The method of claim 75 wherein, said transmitting and receiving
of data occurs simultaneously.
78. The method of claim 75 wherein, said transmitting and receiving
of data occurs sequentially.
79. The method of claim 75 further comprising the steps of, arming
each sensor pod within said string to receive a simultaneous
trigger signal by enabling a direct communications path (132, 130)
along a common conductor (24', 72) to each sensor pod within said
string.
80. The method of claim 79 further comprising the step of, powering
said string (18') of intelligent sensor pods (12') via said common
conductor (24', 72).
81. The method of claim 79 further comprising the step of, after
arming each sensor pod, simultaneously triggering each sensor pod
within said string to begin recording data.
82. The method of claim 81 wherein, said triggering is caused by a
signal transmitted by said telemetry and control module (21') along
said common conductor.
83. The method of claim 81 wherein, a surface controller (20') is
coupled to said telemetry and control module, and said triggering
is caused by a signal originating from said surface controller.
84. The method of claim 79 further comprising the steps of,
simultaneously triggering each sensor pod to begin said bucket
brigade transfer, and after said triggering, disabling said direct
communications path (130, 132), forcing communication along said
string to flow through said memory (28') of said sensor pods.
85. The method of claim 84 wherein, said triggering is caused by a
signal transmitted by said telemetry and control module (21') along
said common conductor.
86. The method of claim 84 wherein, a surface controller (20') is
coupled to said telemetry and control module, and said triggering
is caused by a signal originating from said surface controller.
87. The method of claim 75 further comprising the steps of,
choosing a desired number of sensor pods based on requirements of
said survey, choosing a combination of said sensor pods to have a
desired combination of sensor types based on requirements of said
survey, choosing cables (24') with desired lengths to couple said
string (18') of sensor pods (12') together and to couple said
string to said telemetry and control module based on requirements
of said survey, and assembling said intelligent sensor pods in the
field using said chosen sensor pods and said chosen cables.
88. The method of claim 75 further comprising the steps of, in the
field, repairing said string (18') of sensor pods (12') by
disconnecting a faulty sensor pod and connecting a replacement
sensor pod in its place.
89. The method of claim 75 further comprising the steps of, in the
field, repairing said string (18') of sensor pods (12') by
disconnecting a faulty cable (24') and connecting a replacement
cable in its place.
90. The method of claim 76 further comprising the step of, after
said step of transmitting said data, raising said string (18') from
said borehole (14), disconnecting said telemetry and control module
(21') from said string, and disassembling said string.
91. The method of claim 75 further comprising the step of,
automatically determining the composition and characteristics of
said string (18') by querying said intelligent sensor pods
(12').
92. The method of claim 76 further comprising the step of,
selectively clamping said sensor pods (12') to a wall of said
borehole (14), selectively unclamping said sensor pods from said
wall, and controlling said selective clamping and selective
unclamping with said telemetry and control module (20').
93. The method of claim 76 further comprising the step of,
selectively clamping said sensor pods (12') to a wall of said
borehole (14), selectively unclamping said sensor pods from said
wall, and controlling said selective clamping and selective
unclamping with a surface controller (21') coupled to said
telemetry and control module.
94. The method of claim 75 further comprising the step of,
extending a communications range between two adjacent of said
sensor pods (12') by coupling a repeater (46) therebetween.
95. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to seismic systems, and
more particularly to seismic systems used in the hydrocarbon
exploration and mining industries. Specifically, this invention
relates to a system and method for transmitting data from remote
measuring stations in a vertical seismic profiling or cross-well
seismic profiling toolset.
[0003] 2. Description of the Prior Art
[0004] Measuring seismic data in boreholes has origins which can be
traced back to 1917, where the technology was introduced in U.S.
Pat. No. 1,240,328 issued to Fessenden. Because of the widespread
preference for surface-recorded seismic surveys, borehole seismic
recording has often been limited to the velocity check-shot survey,
a method used to determine seismic velocities over various
intervals in the well for interpretation of surface recorded
seismic data.
[0005] A typical check shot survey involves lowering a geophone or
hydrophone into a well to a selected position and measuring the
time for an acoustic pulse at the surface to travel to the
receiver. Receivers are often simple pressure transducers and are
incapable of detecting the polarity and amplitude of a waveform in
three dimensions. Receiver locations are generally separated by
hundreds of vertical feet. The recording window is long enough to
record only the directly arriving signals; wave reflections and
total borehole response are not recorded. The check-shot provides a
direct correlation between subsurface stratigraphy and seismic
reflections measured at the surface, and it allows surface seismic
data recorded in the time domain to be converted to lineal
depth.
[0006] However, in the last twenty-five years interest has grown in
more comprehensive borehole-recorded seismic surveys, such as
vertical seismic profiling (VSP). As illustrated in FIG. 1, VSP is
the recording of seismic energy from a surface source (10) by
geophones (12) in a well or borehole (14) to obtain a high
resolution image of the subsurface geology adjacent to the
borehole. Because the downhole receivers record direct arrival
waves (16), VSP images are higher in resolution than surface
seismic images which are generated only by reflected, attenuated
waves. VSP can provide in situ rock properties, particularly
seismic velocity, impedance, anisotrophy, and attenuation, and it
aids in understanding seismic wave propagation, e.g., source
signatures, multiples, and conversions.
[0007] FIG. 1 shows the basic components of a VSP survey: a
surface-based seismic source (10), a downhole receiver array (18)
of sensors (12), and a surface-based recording/wireline truck (20)
or other recording means. The lateral distance from the surface
source to the well is referred to as "offset" (22). Zero-offset
VSP, in which the shot is located near the well, provides a seismic
time-to-depth relationship, interval velocities in depth, and a
normal-incidence reflectivity trace. Offset VSP, in which the shot
is a further distance from the well, allows for the imaging of the
subsurface away from the well. When a series of offset VSP surveys
are conducted, with sources positioned along a line radiating
outward from the well at varying offsets, it is referred to as a
walk-away VSP. Walk-away VSP creates a two-dimensional reflectivity
image away from the well. Three-dimensional vertical seismic
surveys can also be conducted using a full areal set of shots on
the surface. A related downhole seismic survey is cross-well
profiling (CWP), in which a VSP receiver array is placed in a first
borehole while the seismic source is lowered into a second borehole
and emitted therefrom.
[0008] VSP uses a number of downhole geophones (12) in the receiver
array (18), usually at a regular spacing interval of 50 to 100
feet. Single component receivers, such as vertical axis geophones
or hydrophones, may be free-hanging in the array, but
multiple-component receivers, such as triaxial geophones, must be
clamped to the borehole wall in order to couple to the wave in all
three dimensions. A common prior art VSP receiver array (18)
configuration has receiver pods (12), with three-component
geophones, deployed at five depth levels, as illustrated in FIG. 1.
The triaxial geophones are connected with standard seven-conductor
wireline logging cables (24) and are located in pods (12) designed
to clamp to the borehole wall.
[0009] In practice, the receiver array (18) is usually lowered to
the bottom of the well (14), clamped to the borehole sides, and
then set to record a surface-generated source shot or shake. The
collected data is transmitted to the recording truck (20) via the
wireline cable (24). The tool (18) is then unclamped from the
borehole sides, moved its length up the hole, and re-clamped; the
source (10) is reactivated and measured. This sequence continues up
the hole (14) to capture the entire vertical profile. VSP surveys
can be conducted in open as well as cased holes, but cased holes
are often preferred because they allow the use of magnetic clamping
tools and avoid borehole stability problems.
[0010] FIG. 2 illustrates an enlarged view of a portion of the
prior art borehole seismic recording system of FIG. 1. The system
includes a surface-based controller (20) connected to a downhole
telemetry module (21), which in turn is connected to one end of a
string (18) of remote sensor pods (12). The string (18) is lowered
into a borehole (14) and suspended by a winch or hoist (15). Each
pod has a clamping mechanism (26) to mechanically couple the pod to
the borehole wall. The pods (12) are typically hard-wired into the
array (18) and have over-molded connections to the cable (24).
Thus, the array configuration is generally fixed; it is not
possible to change the configuration at the job site, and field
repairs are limited.
[0011] It is advantageous to record measurements over the whole
vertical range of the well to provide the most complete depth and
coverage, but it is also more costly. The cost of VSP or CWP
depends on the number of depth levels recorded, the total vertical
distance of the operation, the number and type of source offsets,
time on site, tool rental costs, and mobilization/demobilization
costs. Thus, increasing the number of receivers which can collect
data in a given array or otherwise speeding up the process may
reduce cost.
[0012] One major inefficiency of the borehole seismic process is
the need for each downhole multi-component receiver to be clamped
to the borehole wall. The clamping and unclamping process takes
time. Free-hanging receiver arrays using only vertical geophones or
free-hanging hydrophone strings with simple pressure transducers
may be attractive choices for VSP or CWP; many receivers can be
deployed with minimal effort, and considerable time is saved by
avoiding repetitive clamping and unclamping. However, these
receivers provide only single component data which limits
subsurface imaging and seismic data extraction, because compression
(P) and shear (S) data cannot be resolved. Additionally, because
the receivers are free-hanging, borehole waves are a major source
of noise. Although some of this noise can be removed with various
filtering operations, free-hanging sensors do not image as deep as
their clamped-geophone counterparts.
[0013] The current trend is to record data with three-component
geophones which allow three-component data processing techniques
used to discern the different wave arrivals, such as P, SV, and SH,
for improved seismic interpretations. Cost reduction of borehole
seismic surveys using clamped geophones is gained by increasing the
number of depth layers on the toolsets. The greater number of
levels which can be measured at one time, the fewer times the array
must be moved to cover the vertical depth of the well.
[0014] As borehole seismic technology matures, the amount of data
collected increases. Higher signal resolution, a greater number of
depth layers in the arrays, the use of 3-C geophones, and increases
in the recording time to capture multiple wave reflections all
enlarge the amount of the data which must be sent to the surface
recorder. Often, a downhole telemetry module (21) is coupled
between the surface recorder (20) and the array (18). The telemetry
module may contain power supply circuitry and motor
controller/driver circuitry for the pods (12) and a large memory
buffer to temporarily store data transmitted from the pods. The
telemetry module may also contain an anchor (23) and an optional
gamma ray emitter. The telemetry module may be used to shorten the
distance and time for data transfer from the pods by receiving the
pod data and storing it within a large memory buffer for later
transfer to the surface-based main controller.
[0015] Although some systems employ cabling with enough analog wire
pairs to accommodate a large number of three-component receiver
stations, most systems continue to use standard seven-conductor
wireline cable. The cable often includes strength members which
support the weight of the sensor array. The large capital invested
in seven-conductor cable and equipment may make a transition to
another cable type cost prohibitive.
[0016] Thus, VSP and CWP often use semi-intelligent receiver pods
which digitize the measured analog seismic waveforms and store the
data in a buffer (28), as shown in FIG. 2. Although each of the
sensor pods (12) can be directly wired to the downhole telemetry
module, more commonly the pods (12) are coupled to the telemetry
module (21) using a common databus (30). Each memory buffer (28) is
tied to the bus (30) with a driver capable of driving the bus.
Generally, the system is arranged so that only one pod drives the
bus at a time. The seven-conductor wireline cable (24) contains a
coaxial cable used as a databus (30) to which each buffered
receiver pod is multiplexed. Receivers, in sequential fashion, send
their stored data to the telemetry module (21) along the common
databus (30) after the seismic event has occurred.
[0017] FIG. 3 is a schematic diagram in block level detail showing
the electronic circuit of one type of prior art receiver pod (12).
The receiver is powered by a power supply (58) which is tied to a
power bus (60) that is independent of the data bus (30). The
receiver pod (12) has a sensor (50) whose output is digitized and
stored in a memory buffer (28). In this example, the buffer (28) is
connected to a common databus (30), shared by all receiver pods in
the array (18) (See FIG. 2), by a transmitter (52) and an analog
double-throw switch (54). When the pod (12) is driving the bus
(30), switch (54) connects the upper portion (30A) of the bus to
the transmitter (52) and disconnects the lower portion (30B) of the
bus. When the pod (12) is not driving the bus (30), it is
disconnected by switch (32). The analog switch (54) is controlled
by an addressing circuit (56) and control lines (57). The
transmitter (52) must be designed to transmit the signal to the
telemetry module, which can be a significant distance.
[0018] Referring back to FIG. 2, the databus cable (30) must be
long enough to extend from the telemetry module (21) to the most
remote receiver, POD N, at the bottom of the well. The long length
reduces the available bandwidth of the databus. The most remote pod
is the most affected by the limited bandwidth. One at a time each
pod will transfer its data directly to the telemetry module. For
example, POD 1 will transfer the contents of its buffer (28) to the
telemetry module (21) in time t.sub.1, then POD 2 will transfer
directly to controller (20) in time t.sub.2, etc., until POD N
completes the cycle by transferring its collected data in time
t.sub.N. Time t.sub.N is substantially greater than time t.sub.1.
The total time for all of the data stored in the array (18) of N
sensors to be transferred to the telemetry module (21) is the
summation of the individual transfer times t.sub.1 . . . t.sub.N,
which can be significant in arrays with a large number of pods or
having a long distance to the telemetry module.
[0019] As the number of receivers continues to rise, the large data
volumes which must be transmitted to the receiver before the array
can be repositioned, bottlenecked by the insufficient bandwidth of
the databus, becomes significant. A high capacity datalink is
desirable. Some systems have explored the use of a fiber optic
cable for a databus. In addition to the obstacle of overcoming the
inertia of the capital investment in seven-conductor wireline
cable, as discussed earlier, fiber optics are problematic from a
materials standpoint because of the high downhole temperatures
encountered.
[0020] 3. Identification of Objects of the Invention
[0021] A primary object of the invention is to provide a method and
system for improved borehole seismic measurement by improving data
transfer rates between the downhole components in an array of
intelligent sensors.
[0022] Another object of the invention is to provide a method and
system to communicate with each sensor in the seismic array and
power each array sensor using a shared conductor pair. Sensor
control and power may originate from either a downhole telemetry
and control module or a surface-based controller.
[0023] Another object of the invention is to provide a method and
system to selectively allow a concurrent trigger pulse to all
sensors in the array to promote synchronous recording and sampling
by the sensors.
[0024] Another object of the invention is to provide a method and
system to send data acquisition and control parameters and commands
to each of the sensor pods by the bucket brigade method, starting
from the telemetry and control module.
[0025] Another object of the invention is to provide a method and
system for a seismic array having a varying number or type of
sensors located therein, the sensors having connectors to allow
interconnection in varying numbers and with varying lengths of
cable, thus allowing easy configuration changes and array repair in
the field.
[0026] Another object of the invention is to provide a method and
system for an intelligent sensor array which can determine its
current configuration by using either the telemetry and control
module or the surface controller to sequentially query each sensor
pod in the array to determine the capabilities and location within
the sensor array and also to assign a temporary identification
number to each sensor pod.
[0027] Another object of the invention is to provide a method and
system for a downhole sensor array of up to 200 clamping receiver
pods each equipped with 3-C sensors.
BRIEF SUMMARY OF THE INVENTION
[0028] The objects identified above, as well as other features and
advantages of the invention are incorporated in a method and system
for conducting a seismic survey by lowering a string of intelligent
sensor or receiver pods into a well or other borehole. The string
of pods is serially interconnected by a cable having a conductor
pair, e.g., a coaxial cable, which provides both power and
high-speed data connectivity to the string of pods. The uppermost
sensor pod is connected to a downhole telemetry and control module
which can control the system and provide power to the sensor pods.
The telemetry and control module in turn is connected via a
standard-speed data link to the surface-based main controller.
Preferably, the telemetry and control module has a large memory
buffer capable of storing data transmitted by the pods for a number
of seismic shots for later transmission at a convenient time to the
surface controller. While the telemetry and control module is
described as a single module, separate modules can also be
incorporated (a telemetry and a control module) without changing
the capabilities of the system. The telemetry and control module
may also include a large memory buffer either as an integrated
module or yet another separate module. The telemetry and control
module may also include a power conditioning and supply module
either as an integrated module or yet another separate module. The
"telemetry and control module" as used in the specification and
claims may encompass all four functions, i.e., power, telemetry,
control and memory (data storage) existing as a single module or a
combination of separate modules.
[0029] The cables and pods use quick-disconnect connectors to allow
assembly, customization, repair, and disassembly on site. Each pod
has an upper and a lower connector and is capable of serial
communication at its upper connector with either the telemetry and
control module or an adjacent pod and at its lower connector with
an optional adjacent pod. The string of sensor pods is connected
upper connector of one to lower connector of another.
[0030] Preferably, each pod is equipped with 3-C geophones and an
optional hydrophone and associated electronic circuits to convert
analog signals to digital signals. Alternatively, the pod may
contain analog or digital micro-electromechanical sensors. Each pod
also contains a processor and memory which is coupled to both the
upper and the lower connectors via communications converters. Each
pod is capable of simultaneous and independent communications at
each connector with the memory, but this capability is not
required. The communications converters include circuitry typically
used to link serial communications to a processor such as line
drivers, universal receiver/transmitters, etc.
[0031] Preferably, each pod has a direct current path from the
upper to the lower connector. The DC path includes an inductor to
prevent the signals, being carried on the same line, from bypassing
the pod communications converters and microprocessor during bucket
brigade communications. In the bucket brigade mode of operation,
data held in each pod's memory is transmitted upwards at the upper
connector while data may be simultaneously (or near-simultaneously)
received at the lower connector and stored in the memory in a
first-in-first-out arrangement. However, there is also a switchable
communications bypass around the inductor to allow for a
pass-through mode of communications which allows a signal at the
upper connector to pass through directly to the lower connector
without passing though the communications converters, processor and
memory The bypass is also used to allow the trigger signal to be
concurrently sent to each of the sensor pods so they start
acquiring simultaneously.
[0032] The system operates as follows: Initially, either the
surface controller or the telemetry and control module queries the
pods to determine the system configuration. Each pod sequentially
transmits upward its unique identification and capabilities, or
alternatively each pod is assigned a logical (temporary) address.
Next, the surface controller or telemetry and control module
communicates with the pods to configure the sensors, specifically
the sample rates and number of samples to record. All pods are then
placed in pass-through communications mode, where a signal present
at the upper connector is directly routed to the lower connector.
The surface controller or telemetry and control module then
simultaneously triggers all pods to acquire data. The pods store
the collected data locally in their memory. After data collection,
all pods automatically revert back to bucket brigade mode. The
telemetry and control module then commands the nearest sensor pod
to send its data. This sensor pod then begins sending its data and
simultaneously commands the next pod to send its data, and so on
all the way down the sensor array. The first data transferred from
each pod is that data collected by its local sensors. Subsequent
data originates from lower pods and is simply passed up the string
of pods to the telemetry and control module. Any sensor pod that
self determines that it is malfunctioning, will engage its
communications bypass relay so that it will be "skipped" in the
data transfer process and allow the rest of the sensor pods below
it to still transfer their data up the array. While in the
preferred embodiment transmission of data to the next upper module
and receipt of data from the next lower module occurs
simultaneously, a completely equivalent system may be configured
where the two processes are separated in time.
[0033] The bucket brigade method allows a high speed data transfer
from all of the remote pods to the telemetry and control module and
vice versa, because each pod only requires the capability to
communicate over the distance to the next adjacent device rather
than directly with the telemetry and control module. The shorter
distances allow greater data rates. Optional repeaters can be used
to increase the maximum allowable distance between any two pods if
required. Subsequent data transfer from the telemetry and control
module to the surface controller occurs using standard transmission
methods at standard transmission speeds.
[0034] The transfer of data can occur after each seismic shot or
after a number of seismic shots depending on the sample sizes and
the size of memory contained in the pods.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0035] The invention is described in detail hereinafter on the
basis of the embodiments represented in the accompanying figures,
in which:
[0036] FIG. 1 illustrates a vertical profiling system of prior art
showing a VSP array disposed in a borehole recording seismic waves
produced from a surface source;
[0037] FIG. 2 illustrates a VSP array of prior art with sensor pods
fixed to the cable and communicating with a surface controller via
a common databus;
[0038] FIG. 3 is a schematic diagram in block component detail
which illustrates the electronic circuitry of a sensor of prior
art, specifically a method of coupling to a common databus for the
transmission of data;
[0039] FIG. 4 illustrates a borehole seismic array according to the
present invention having an adjustable number of sensor pods which
may be freely interconnected with varying cable lengths and in
varying numbers and types, the pods communicating with a telemetry
and control module in a bucket brigade manner; and
[0040] FIG. 5 is a schematic diagram which illustrates in block
component level the electronic circuitry of a sensor pod according
to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] FIG. 4 illustrates a borehole seismic recording system
according to the invention. The system includes a surface-based
main controller 20' connected to a telemetry and control module
21', which is in turn connected to one end of a string 18' of
multiple remote measurement stations, or pods, 12' that are
interconnected serially by cables 24' and quick-disconnect
connectors 42, 44. The telemetry and control module 21' and the
string 18' are lowered into a borehole 14 and suspended by a winch
15. Because the pods are interconnected in the array 18' using
releasable connectors instead of e.g., overmolding, the pods 12'
and the cable segments 24' are easily removed from the array for
repair. In fact, the array can be field modified to suit particular
requirements by adding or removing pods, shifting sensor depths (by
substituting cable segments with differing lengths), or
substituting pods with different sensor types. Each pod 12' which
is equipped with sensors, e.g., 3-C sensors, also has a clamping
mechanism 26'. Additionally, the telemetry and control module 21'
has an anchoring mechanism 23'.
[0042] Each pod has an upper connector 42 and a lower connector 44
for interconnecting the pods in the array using a cable with two or
more conductors, for instance a coaxial cable. The communications
cable 24' allows serial data transfer, and can optionally be used
to supply power to the pods by carrying a DC voltage. Although this
embodiment is described using electrically conductive cable,
communications may also be implemented using fiber optic
components. Each pod 12' is capable of serial communication at its
upper connector 42 with either the telemetry and control module 21'
or an adjacent pod 12' and at its lower connector with an optional
adjacent pod 12'.
[0043] Each pod 12' has two communications modes which can be set
by either the surface controller 20' or telemetry and control
module 21'--a pass-through mode and a bucket brigade mode. In the
pass-through mode, a signal present at the upper connector 42 is
capacitively coupled to the lower connector 44, i.e., it passes
directly through the pod 12', although the signal is also received
and interpreted by the pod 12'. In the bucket brigade mode of
operation, data held in a local pod memory buffer 28' is
transmitted from the upper connector 42 while data is received at
the lower connector 44 for temporary storage in the local pod
memory buffer 28'; serial communication occurs at both ends 42, 44
of the pod 12' either in sequential fashion or concurrently and
independently.
[0044] Power to the remote measurement stations 12' is provided by
the surface controller 20' or the telemetry and control module 21'
to the string 18' of remote measurement stations 12' through cable
24''. Power is fed through each of the remote measurement stations
12' to the next lower station 12'. The voltage level to the remote
measurement stations 12' is monitored and adjusted by the surface
controller 20' or telemetry and control module 21' to compensate
for varying loads and power line resistance. The power supplies the
pod electronics and the clamping mechanisms 26'.
[0045] Referring to FIG. 4, the system operates as follows:
Initially, the main controller 20' or the telemetry and control
module 21' communicates with the remote measurement stations 12' to
determine the system configuration. Each remote station 12' within
the array 18' is intelligent, i.e., it contains a processor; when
queried, each pod 12' notifies the surface controller 20' or the
telemetry and control module 21' of its capabilities. Thus, the
method according to the invention allows a user to assemble a
linear array 18' of pods 12' on site with varying numbers of pods
12' and sensor types. The surface controller 20' or telemetry and
control module 21' queries and automatically determines the
capabilities of an array 18' attached to it.
[0046] One method by which the surface controller 20' or telemetry
and control module 21' can determine the configuration of an
attached array 18' is to first place all pods 12' in a bucket
brigade communications mode, which is accomplished by the surface
controller 20' or the telemetry and control module 21' transmitting
an appropriate signal on cable 24'. Next, when the surface
controller 20'' or telemetry and control module 21' sends a query
command, the command is received only by the uppermost pod 12'. The
first pod 12' responds to the query by transmitting up a unique
identification and whatever parameters are requested. The first pod
12' then passes the query command down to the next adjacent pod
12', which in turn sends back up its unique identification and
parameters. The second pod's information is passed up by the first
pod to the main controller or telemetry and control module. The
process continues with the second pod 12' sending the query command
to the third pod, etc., until all pod identifications and
parameters have been passed in sequence to the main controller 20'
or telemetry and control module 21'. Once the identifications and
locations of the attached pods 12' are known, communication with a
particular pod 12' on an individual basis is accomplished by
sending an appropriate signal on cable 24', either directly if the
pods 12' are in pass-through mode, or by downward bucket brigade
method if the pods 12' are in bucket brigade mode.
[0047] After the configuration of the array 18' is determined, the
surface controller 20' or telemetry and control module 21'
communicates with the remote measurement stations 12' to configure
the sensors. Preferably, the remote measurement stations 12' have
programmable sample rate and sample time parameters which are set
by the main controller 20' based on the needs of the user.
[0048] Data acquisition is triggered by the surface controller 20'
or the telemetry and control module 21'. All pods 12' are placed in
the pass-through communications mode, where a signal present at the
upper connector 42 is capacitively coupled to the lower connector
44. In the pass-through mode, no actions are required by a pod
microprocessor to propagate a signal between upper and lower
connectors, although the signal is received and interpreted by the
microprocessor. Once all pods 12' are set to the pass-through mode,
the surface controller 20' or telemetry and control module 21' can
synchronously trigger all the pods 12'. Thus, when all of the pods
12' are armed and ready, the surface controller 20' or telemetry
and control module 21' initiates data acquisition to coincide with
the seismic source, and the sensors simultaneously acquire data.
Since the distance from the telemetry module to the last pod can be
quite long, the propagation delay for the trigger signal to reach
the more remote pods should be taken into account. Thus,
simultaneous triggering as used herein is not used in its most
rigorous sense.
[0049] The pods 12' store their acquired data locally in memory,
e.g., random access memory (RAM) 28' until the data is transferred
to the telemetry and control module 21'. Unlike the seismic arrays
of prior art, the pods 12' according to the present invention do
not transfer data to the surface controller or a downhole telemetry
module on a databus. The bucket brigade mode of operation is used
in place of a databus to transfer the collected data from the pods
to the surface controller or the downhole telemetry and control
module. Recall that all pods 12' are placed in pass-through
communications mode in order to initiate data collection. During
data collection, the pods remain in pass-through mode; the
collected data is stored locally. On a command from the telemetry
and control module 21' or main controller 20', each remote station
12' simultaneously switches to the bucket brigade communications
mode and immediately begins to transfer data serially from memory
to the next higher adjacent station and receive data, if any, from
the immediately lower adjacent station, if any. The received data
is written to memory, e.g., RAM 28'. The first data set transferred
from each remote station 12' is that data collected by sensors
within that station 12' and stored locally. Each subsequent
transfer from the remote station 12' is passing data up that it
received from the pod 12' below it. In other words, the data flows
from pod to pod up the pd interconnect (e.g., coaxial) cable to the
telemetry and control module, in a bucket brigade fashion.
[0050] The bucket brigade system of the preferred embodiment is
characterized by simultaneous (or near simultaneous) transmission
and receipt of data from each pod. The transmission and receipt of
data for each pod can occur sequentially in an equivalent system.
The bucket brigade communication concept of the preferred
embodiment is illustrated by the arrows in FIG. 4. Upon initiation
of data transfer, POD 1 transmits its collected data to the
telemetry and control module 21' while simultaneously (or near
simultaneously) receiving data from POD 2. After POD 1 has
transferred its collected data to the telemetry and control module,
it transmits POD 2's collected data, now stored in POD 1's memory,
e.g., RAM 28', to the telemetry and control module, and so on. If
the longest transfer time from any pod to its superior neighbor is
designated as t', then the total time for all of the data stored in
the array 18' of N stations to be transferred to the telemetry and
control module 21' is the product of N and t'. After all the data
is transferred, the telemetry and control module 21' consolidates
the received data from the pods 12'' prior to later transfer to a
surface controller 20'.
[0051] In the prior art system using a databus (see FIG. 2), the
total transfer time is .SIGMA. (t.sub.1 . . . t.sub.N), where
t.sub.N>t.sub.1. If t' equals t.sub.1, which is likely, then the
total transfer time according to the present invention, Nt', is
less than the prior art system.
[0052] The bucket brigade communications method allows a high speed
data transfer from all the remote stations to the telemetry and
control module, and from the telemetry and control module to each
remote station, in such a manner that each remote station only has
to have the capability to communicate over the cable length from
itself to the next device, rather than all the way to the telemetry
and control module directly. This allows a simple communication
circuit and higher data transfer rates. For the preferred
embodiment, since each remote station transmits data up as it
receives data from the next station down, there is no significant
delay introduced. The telemetry and control module preferably
buffers the received data for later transfer to the surface-based
controller on a conventional data link.
[0053] Also illustrated in FIG. 4 is an optional repeater 46. A
repeater is used to boost the serial communications signal strength
for long cable runs. Preferably, the communications circuitry in
pods 12' are capable of 150 foot transmission distances at
significant baud rates, e.g., 10 Mbps or more. One or more
repeaters can be used to extend the transmission range to greater
than 150 feet when desired. The method and system according to the
invention can support many, e.g., 200, pods 12' connected within an
array 18', provided the maximum distance between any two pods does
not exceed that required to sustain a high baud rate, e.g., 150
feet.
[0054] FIG. 5 illustrates schematically in block level detail the
electronics for each pod 12' according to the invention. Each pod
12' has an upper connector 42 and a lower connector 44 for
connecting the pod to a supply conductor which carries both power
and data. A return conductor is provided, which for example can
include cable armor or the shield of a coaxial cable. Power is
supplied by standard means, for example 200V to 500V DC, which
originates from the surface-based controller 20' or telemetry and
control module 21' (See FIG. 4). Each pod contains a direct current
path 105 with a large inductor 106 which carries all direct current
to the lower pods and which prevents signals from bypassing the pod
electronics during bucket brigade communications. The direct
current from the coaxial cable is coupled to a pod power supply 108
by a smaller inductor 110, which serves to eliminate ripple on the
power supply input 109. The power supply converts the 200-500 VDC
to voltage levels suitable for the pod electronics, typically
3.3VDC, +/-5VDC, and the required voltage for the solenoid/motor
clamping mechanism.
[0055] The upper and the lower connectors 42, 44 are coupled to
nodes or interfaces 72, 74, respectively. Interface 72 is in turn
coupled to communications converter 112 by a capacitor 116, and
interface 74 is likewise coupled to a communications converter 114
by a capacitor 118. Capacitors 116, 118 block direct current but
allow signals to pass. The communications converters 112, 114
include circuitry typically used to allow a processor to
communicate serially, such as line drivers, a buffer, and a
universal receiver/transmitter which converts data from a parallel
to serial arrangement and vice versa. The communications converters
112, 114 communicate with a 120. The processor 120 includes memory,
e.g., RAM 28' for local storage of data. The processor 120 in turn
controls the clamping mechanism via a motor controller or solenoid
driver 122, communicates with the onboard sensors via a sensor
converter 124, and communicates with the telemetry and control
module 21' and/or the main controller 20'.
[0056] The pod 12' preferably accommodates a variety of sensor
combinations 126. For example, the pod 12' may contain 3 geophones,
which may be 3-C gimbaled, 3-C fixed, or 3-C fixed but including 3
axis accelerometers. When the pod contains geophones, the sensor
converter 124 may include analog circuitry in addition to
analog-to-digital converters. Alternatively, the pod 12' may
contain up to three analog or digital micro-electromechanical
systems (MEMS). A digital MEMS sensor provides direct digital
output, so that the sensor converter 124 design is simplified. The
pod may additionally contain an optional hydrophone sensor and
associated circuitry in the sensor converter 124.
[0057] The pod 12' according to the invention and illustrated in
FIG. 5 also includes a capacitor 130 which can be switched in and
out to bypass inductor 106. The switch 132 is controlled by the
processor 120. When switch 132 is closed, capacitor 130 allows a.c.
signals to pass freely from connector 42 to connector 44 and vice
versa, i.e., it places the pod 12' in pass-through communications
mode. In pass-through mode, a signal at connector 42 is still
received at the communications converters 112, 114 and is processed
by processor 120. When switch 132 is open, the pod 12' is in bucket
brigade communications mode, i.e., the inductor 106 blocks a.c.
signal transmission.
[0058] An array 18' (see FIG. 4) of pods 12' transfers the
collected data to telemetry and control module 21' (see FIG. 4), in
the following manner. Pod 12' initially has collected data by
sensors 126 and transferred the data through sensor converter 124
to memory, e.g., RAM 28'. Switch 132 is initially closed, causing
pod 12' to be in pass-through mode. The telemetry and control
module 21' or surface controller 20' (see FIG. 4) initiates data
transfer by transmitting a corresponding signal through the array
18' (see FIG. 4). The data transfer signal enters pod 12' at
connector 42 passes through capacitor 116 to communications
converter 112. The signal is then passed to the processor 120 which
interprets the signal as an instruction to commence data
transfer.
[0059] The processor 120 immediately causes switch 132 to be opened
and directs the contents of memory, e.g., RAM 28' to be transmitted
from connector 42 via communications converter 112 and capacitor
116. Simultaneously, the processor 120 stores any data received at
connector 44 via capacitor 118 and communications converter 114 in
memory, e.g., RAM 28'. The data is formatted in such a way as to
allow the telemetry and control module 21' or surface controller
20' (see FIG. 4) to identify the sensor from which it originated,
and the processor 120 transforms the contents of memory, e.g., RAM
28' in a proper format, e.g., first-in-first-out manner. This
process continues until the memory, e.g., RAM 28' is empty, i.e.,
until all of the data from pod 12' and all those below it have been
transferred upwards.
[0060] Although this system has been described in an embodiment
suitable for seismic use in the hydrocarbon exploration industry,
it is equally suitable for use wherever seismic data is recorded,
for instance in the mining industry or for earthquake monitoring.
Further, it is within the scope of the invention to use the system
and method with other than seismic sensors. Non-seismic
applications requiring a string of sensors to transmit data to a
remote collection device are within the scope of the invention.
While the preferred embodiment of the invention has been
illustrated in detail, modifications and adaptations of the
preferred embodiment may occur to those skilled in the art. Such
modifications and adaptations are in the spirit and scope of the
invention as set forth herein.
* * * * *