U.S. patent application number 10/085030 was filed with the patent office on 2003-09-04 for pressure sensor assembly for wellbore.
This patent application is currently assigned to Promore Engineering, Inc.. Invention is credited to Jabusch, Kirby D., Moffatt, Terrence G..
Application Number | 20030164037 10/085030 |
Document ID | / |
Family ID | 29713003 |
Filed Date | 2003-09-04 |
United States Patent
Application |
20030164037 |
Kind Code |
A1 |
Moffatt, Terrence G. ; et
al. |
September 4, 2003 |
Pressure sensor assembly for wellbore
Abstract
In the context of a casing-conveyed downhole pressure sensor
assembly, there is provided a perforating charge which can be
detonated from ground surface to open a perforation providing a
pathway between the exterior formation and the pressure sensor.
Inventors: |
Moffatt, Terrence G.;
(Cochrane, CA) ; Jabusch, Kirby D.; (Edmonton,
CA) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
Promore Engineering, Inc.
1550, 520 - 5th Avenue
Calgary
AB
T2P 3R7
|
Family ID: |
29713003 |
Appl. No.: |
10/085030 |
Filed: |
March 1, 2002 |
Current U.S.
Class: |
73/152.46 |
Current CPC
Class: |
E21B 43/11 20130101;
E21B 47/01 20130101; E21B 47/06 20130101 |
Class at
Publication: |
73/152.46 |
International
Class: |
E21B 044/00 |
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A downhole pressure sensor assembly for conveyance on the
exterior surface of a string of casing to a subterranean formation
to measure pressure in the formation, comprising: housing means,
for attachment to the exterior surface of the casing string,
forming a sensor chamber; a sensor, mounted within the sensor
chamber, for measuring formation pressure; and a shaped explosive
perforating charge, associated with the housing means and oriented
to form an outwardly extending perforation, when detonated, for
penetrating the formation and enabling transmission of pressure
from the formation to the sensor.
2. The downhole pressure sensor assembly as set forth in claim 1
wherein: the perforating charge is contained within the housing
means; the housing means has an external surface and forms a
passageway, connecting the external surface with the sensor, for
transmitting formation pressure to the sensor; and the charge is
oriented so that the perforation will intersect the passageway when
the charge is detonated.
3. The downhole sensor assembly as set forth in claim 2 wherein:
the housing means forms a second chamber, separate from the sensor
chamber, wherein the perforating charge is positioned.
4. A method for connecting a subterranean formation with a sensor
for measuring a formation condition, comprising: providing a
downhole sensor assembly, externally conveyed on a string of casing
cemented in a wellbore so that the sensor assembly is located
opposite the formation, the sensor assembly comprising housing
means containing a sensor for measuring the formation condition and
means for forming, when activated, an outwardly directed
perforation penetrating into the formation for enabling the
formation condition to reach the sensor for measurement thereof;
and activating the perforation-forming means from ground surface,
when required, to form the perforation.
5. A method for connecting a subterranean formation with a pressure
sensor, comprising: providing a downhole pressure sensor assembly,
externally conveyed on a string of casing cemented in a wellbore so
that the sensor assembly is located opposite the formation, the
sensor assembly comprising housing means containing a pressure
sensor and means for forming, when activated, an outwardly directed
perforation, the housing means having an external surface and
forming a passageway connecting the sensor with the housing means
external surface, the perforation-forming means being oriented so
that the perforation, when formed, will intersect the passageway
and penetrate into the formation so that formation pressure may be
transmitted through the perforation and passageway to the sensor;
and activating the perforation-forming means from ground surface,
when required, to form the perforation.
6. A method for connecting a subterranean formation with pressure
sensor means comprising: providing perforation-forming means in
association with a casing-conveyed downhole pressure sensor
assembly, said sensor assembly having housing means containing
pressure-measuring sensor means and being mounted to the exterior
surface of a cemented casing string in a wellbore penetrating the
formation; and activating the perforation-forming means from ground
surface to form a perforation extending into the formation, the
perforation being in communication with the sensor means to enable
pressure transmission between the formation and the sensor
means.
7. A downhole formation condition measuring sensor assembly for
conveyance on the exterior surface of a string of casing to a
subterranean formation to measure a condition in the formation,
comprising: housing means, for attachment to the exterior surface
of the casing string, forming a sensor chamber; a sensor, mounted
within the sensor chamber, for measuring the formation condition;
and an explosive perforating charge, associated with the housing
means and oriented to form an outwardly extending perforation, when
detonated, for penetrating the formation and enabling transmission
of the condition from the formation to the sensor.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a casing--conveyed sensor
assembly for use in a wellbore to measure a subterranean formation
condition, such as pressure.
BACKGROUND OF THE INVENTION
[0002] Casing--conveyed downhole pressure sensors are presently
used in the oil/gas industry, to monitor pressure in a subterranean
formation. A conventional downhole pressure monitoring system
comprises:
[0003] a pad or housing which is secured at ground surface to the
exterior surface of a joint of tubular casing--the joint is run
into a wellbore as part of a casing string with the result that the
housing is located opposite the subterranean formation whose
pressure is to be monitored;
[0004] the side wall of the housing forms an interior chamber in
which is mounted the pressure sensor;
[0005] a cable extends down the wellbore and is secured to the
outside surface of the casing string--wiring in the cable is
connected to the sensor, for providing power to it and conveying
signals indicative of pressure measurement to recording means at
ground surface;
[0006] the sensor is sealed within the sensor chamber by suitable
seal means, to keep it dry; and
[0007] a pressure port or passageway extends from the sensor
chamber through the housing side wall to the exterior surface of
the housing--the port and sensor chamber are packed with a filling
of oil and grease, which function to isolate the sensor means from
wellbore or formation fluid and which act as a pressure
transmission medium.
[0008] The casing string is cemented in place within the wellbore.
As a result, a layer of cement fills the annular space defined
between the casing string and the wellbore. The layer of cement is
usually sufficiently porous and thin enough so that formation fluid
pressure can penetrate therethrough to reach and pressurize the
pressure transmission medium. As a result, measurements of
formation pressure can be taken by the sensor.
[0009] However, in some cases it has been found that formation
pressure does not reach the sensor. This may be due to invasion by
the cement out into the formation or plugging of the pressure port
with cement or an impermeable drilling fluid filter cake. It
therefore is desirable to provide a sensor assembly adapted to
overcome this problem, should it arise.
SUMMARY OF THE INVENTION
[0010] The present invention is preferably concerned with a
pressure sensor assembly for use downhole in a wellbore as part of
a pressure monitoring system. A preferred embodiment of the sensor
assembly comprises:
[0011] housing means for conveyance on well casing, the housing
means forming a sensor chamber and a separate charge chamber;
[0012] a pressure sensor positioned in the sensor chamber,
operative to measure formation pressure for transmittal to ground
surface, for example through a monitoring system cable;
[0013] a shaped explosive perforating charge positioned in the
charge chamber. The perforating charge can be detonated from ground
surface using means such as suitable wiring incorporated in the
monitoring system cable;
[0014] the housing means forms a passageway, containing pressure
transmission medium, connecting the sensor with the exterior
surface of the housing means; and
[0015] the passageway is positioned in the path of the jet produced
by detonating the perforating charge.
[0016] As a result of this combination, if desired one can detonate
the perforating charge to produce a jet which creates a perforation
extending through the housing side wall and the cement layer to
penetrate the formation. This perforation will cross or intersect
the pressure transmission passageway. As a result, formation fluid
may enter through the jet perforation and reach the passageway to
apply its pressure to the sensor through the pressure transmission
medium.
[0017] A single housing may be used to form both the sensor and
perforating chambers. Alternatively, the perforating chamber and
part of the pressure transmission passageway can be provided in a
second housing, forming part of the housing means.
[0018] While the invention is described in connection with a
pressure sensor, it will be understood that it can be applied with
other instrumentation for measuring another formation condition,
such as temperature. Therefore the words "formation condition
measuring", used to modify "sensor" or "sensor assembly", are to be
widely interpreted.
[0019] In accordance with the invention, therefore, a
casing-conveyed condition measuring sensor, contained in a
protective housing means, is combined with selectively activatable
means for forming a perforation (for example, a shaped explosive
perforating charge). The perforation-forming means is oriented and
capable of forming an outwardly directed perforation extending
through the cement layer and into the formation. In addition it is
selected so as to form a perforation adapted to enable formation
pressure or the like to reach the sensor. The perforation-forming
means may be contained within the housing means or may be external
of it.
[0020] Broadly stated, in one embodiment the invention is concerned
with a downhole formation condition measuring sensor assembly for
conveyance on the exterior surface of a string of casing to a
subterranean formation to measure a condition in the formation,
comprising: housing means, for attachment to the exterior surface
of the casing string, forming a sensor chamber; a sensor, mounted
within the sensor chamber, for measuring the formation condition;
and an explosive perforating charge, associated with the housing
means and oriented to form an outwardly extending perforation, when
detonated, for penetrating the formation and enabling transmission
of the condition from the formation to the sensor.
[0021] In another embodiment, the invention is concerned with a
method for connecting a subterranean formation with a formation
condition measuring sensor, comprising: providing a downhole sensor
assembly, externally conveyed on a string of casing cemented in a
wellbore so that the sensor assembly is located opposite the
formation, the sensor assembly comprising housing means containing
a sensor for measuring the formation condition and means for
forming, when activated, an outwardly directed perforation
penetrating into the formation and operative to enable the
formation condition to reach the sensor; and activating the
perforation-forming means from ground surface, when required, to
form the perforation.
DESCRIPTION OF THE DRAWING
[0022] FIG. 1 is a schematic side view showing a wellbore, cemented
casing string, and casing-conveyed downhole pressure sensor
assembly positioned opposite a subterranean formation;
[0023] FIG. 2 is a partly sectional side elevation showing a
perforating charge in a separate lower housing; and
[0024] FIG. 3 is a partly sectional side elevation showing a
pressure sensor in a separate upper housing, for use with the
assembly of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] The invention involves the concept of:
[0026] providing perforation-forming means, such as a shaped
explosive perforating charge, in association with a downhole
pressure sensor assembly having housing means containing a sensor
in a sensor chamber, the sensor assembly being mounted to the
exterior surface of a casing string, often cemented, in a wellbore
penetrating a subterranean formation; and
[0027] activating the perforation-forming means from ground
surface, when required, to form a perforation extending into the
formation, the perforation being in communication with the sensor
to enable pressure transmission between the formation and the
sensor.
[0028] FIGS. 1-3 show a preferred embodiment for implementing the
invention. However, it will be apparent to those skilled in the art
that various alternatives can be used to implement the steps just
described.
[0029] In this embodiment, a downhole pressure sensor assembly 1 is
provided. The sensor assembly 1 will have been secured to the
exterior surface 2 of a casing joint 4 forming part of a casing
string 5, prior to running the string into a wellbore 6. The casing
string 5 is cemented in place in the wellbore 6. The sensor
assembly 1 is positioned opposite a subterranean formation 7, whose
pressure is to be monitored. A layer 8 of cement surrounds the
casing joint 4 and sensor assembly 1. A cable 9 extends from ground
surface 10 along the outer surface of the casing string 5. The
cable 9 is operatively connected with the sensor assembly 1 to
power the electronics (not shown) of a conventional pressure sensor
11 and convey pressure measurement signals back to a data recorder
12 at ground surface 10.
[0030] The sensor assembly 1 comprises a charge housing 13 formed
by a bottom protector nose sub 14, a standoff pressure port sub 15
and a top protector nose sub 16. The subs 14, 15, 16 are connected
together by socket bolts 17.
[0031] The side wall 18 of the port sub 15 forms an internal
perforating charge chamber 19. A charge carrier 20 is positioned in
the chamber 19. This charge carrier 20 has a locator sub 21 at its
base which includes a pin 22, which seats in a pin hole 23 formed
in the bottom wall 24 of the port sub 15 to orient the carrier 20.
One or more shaped explosive perforating charges 25 are carried by
the carrier 20. A conductor 26 from the cable 9 connects to a
firing boot 27, for activating or detonating the detonator 3 of the
charge 25. The carrier 20 is suspended at its upper end from a
connector insulator block 28 which closes the top end of the charge
chamber 19. The connector insulator block 28 is sealed by O-rings
29 with the interior surface 30 of the port sub 15. The connector
insulator block 28 forms an axial bore 32. A top connector block
33, having an axial bore 34, is threaded into the upper end of the
bore 32. The conductor 26 extends through the axial bores 32, 34
and continues through the cable 9 to ground surface 10.
[0032] The side wall 18 of the port sub 15 also forms a pressure
port or passageway 35 having horizontal and vertical sections 36,
37. The pressure passageway radial section 36 terminates in an
opening at the outer surface 39 of the port sub 15. A connector 40
is screwed into the upper end 41 of the port vertical section 37.
The connector 40 connects with a conduit 42 extending up through a
top aperture 43 formed through the top nose sub 16.
[0033] The sensor assembly 1 further comprises a sensor housing 50
formed by a bottom sub 51, sensor sub 52 and top sub 53, connected
together by socket bolts 54.
[0034] The sensor sub 52 forms a chamber 55 in which is positioned
a pressure sensor 11.
[0035] The sensor 11 is connected at its upper end by wiring 57
through a bulkhead 60 to the cable clamp 58 of the cable 9.
Suitable wiring (not shown) forming part of the cable 9 provides
connection between the sensor wiring 57 and recording means 12 at
ground surface.
[0036] At its lower end, the sensor 56 is connected through a
bulkhead 58 with the conduit 42 extending from the pressure
passageway 35.
[0037] Thus, formation pressure, transmitted through the pressure
passageway 35 and conduit 42 and their contained grease and silicon
oil medium 59, reaches the sensor 56 under normal operation.
However, in the event the formation pressure is not being
transmitted through the pressure passageway 35, a perforating
charge 25 can be detonated to form a perforation intersecting
passageway 35 and penetrating through the cement layer 8 into the
formation 7.
[0038] It will be appreciated by those skilled in the art that
downhole perforating charge assemblies and pressure-measuring
sensor assemblies are conventional and require no detailed
description. It is their combination and the orientation of the
charge and pressure passageway that come together to yield the
desired objective.
* * * * *