Patent Application
20070235186
The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a pressure communication assembly external to casing with various forms of connectivity to a pressure source.
It is known to use a chamber positioned in a wellbore and connected to a tube or control line extending to the surface for monitoring pressure in the wellbore. Pressure applied to the tube at the surface provides an indication of pressure in the wellbore at the chamber. Such systems are described in U.S. Pat. Nos. 4,976,142 and 5,163,321, and in U.S. Patent Application Publication No. 2004-0031319. The entire disclosures of these documents are incorporated herein by this reference.
However, these prior systems involve installing completion or production equipment in the wellbore and (if casing or liner and cement is installed) perforating the casing or liner and cement, or otherwise forming a fluid path between the wellbore and a formation or zone of interest. These operations are relatively expensive and time-consuming. In addition, the equipment installed in the wellbore at least partially obstructs the wellbore.
Therefore, it may be seen that improvements are needed in the art of monitoring pressure in wells. It is among the objects of the present invention to provide such improvements.
In carrying out the principles of the present invention, well systems and associated methods are provided which solve at least one problem in the art. One example is described below in which a pressure communication assembly includes a chamber positioned external to a casing string. Another example is described below in which a passage is formed for fluid communication between the chamber and a pressure source after the casing string is cemented in the well.
In one aspect of the invention, a well system is provided which includes a casing string positioned in the well. A bore extends longitudinally through the casing string. A chamber is attached to the casing string and positioned external to the casing string bore. A device provides fluid communication between an interior of the chamber and a pressure source external to the casing.
In another aspect of the invention, a method of monitoring pressure in a well includes the steps of: installing a casing string in the well with a chamber positioned external to a through bore of the casing string, and the chamber being isolated from the well external to the casing string; and then actuating a device to thereby provide fluid communication between the chamber and the well external to the casing string.
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 representative embodiments of the invention hereinbelow and the accompanying drawings, in which similar elements are indicated in the various figures using the same reference numbers.
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. The embodiments are described merely as examples of useful applications of the principles of the invention, which is not limited to any specific details of these embodiments.
In the following description of the representative embodiments of the invention, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, “above”, “upper”, “upward” and similar terms refer to a direction toward the earth's surface along a wellbore, and “below”, “lower”, “downward” and similar terms refer to a direction away from the earth's surface along the wellbore.
Representatively illustrated in
Note that the well system 10 is only one example of a wide variety of possible uses of the invention, and is described herein so that a person skilled in the art will appreciate how the invention is made and used. Accordingly, the casing string 12, cement 16 and other elements of the well system 10 should be understood to represent a variety of similar elements used in well operations.
For example, “casing,” “casing string” and similar terms should be understood to include equipment known as “liner” and other forms of protective linings installed in wellbores, whether made of metal, composite materials, expandable materials or other materials, and whether segmented or continuous. As another example, “cement, “cementing” and similar terms should be understood to include any hardenable material used to secure and seal a wellbore lining in a well, such as epoxy or other polymer materials, non-cementitious materials, etc.
The well system 10 also includes multiple pressure communication assemblies 20, 22, 24, 26 spaced apart along the casing string 12. As depicted in
Each of the assemblies 20, 22, 24, 26 includes a chamber 36 and a control line or capillary tube 38 connected to the chamber and extending to a remote location, such as the earth's surface. At the remote location, the tubes 38 are connected to a pressure gauge including, for example, a transducer and instrumentation (not shown) for monitoring pressure applied to the tubes at the remote location. For establishing fluid communication with the formations 28, 30, 32, 34, each of the assemblies 20, 22, 24, 26 also includes a connectivity device 40.
At this point several beneficial features of the well system 10 can be appreciated. The assemblies 20, 22, 24, 26 do not obstruct the bore 18 of the casing string 12. Completion or production equipment does not have to be installed in the casing string 12 prior to utilizing the assemblies 20, 22, 24, 26. The casing string 12 does not have to be perforated in order to monitor pressure in the formations 28, 30, 32, 34.
Furthermore, although the assemblies 20, 22, 24, 26 are cemented in place along with the casing string 12, the devices 40 are provided to form passages between the chambers 36 and the formations 28, 30, 32, 34. Thus, the devices 40 isolate the chambers 36 from the cement 16 during the cementing operation, and subsequently provide fluid communication between the chambers and the formations 28, 30, 32, 34.
The use of the multiple assemblies 20, 22, 24, 26 allows the integrity of the cement 16 to be tested after the cementing operation (e.g., to determine whether fluid isolation is achieved by the cement in the annular space between the casing string 12 and the wellbore 14). In addition, the multiple assemblies 20, 22, 24, 26 permit vertical interference tests to be conducted between the formations 28, 30, 32, 34.
Note that it is not necessary in keeping with the principles of the invention for multiple pressure communication assemblies to be installed, since a single pressure communication assembly could still be used to monitor pressure in a pressure source downhole. Also, it should be understood that an earth formation or zone is only one type of pressure source which may be monitored using the principles of the invention. For example, another pressure source could be the interior bore 18 of the casing string 12.
Referring additionally now to
In this embodiment, the assembly 42 includes a chamber housing 44 which is eccentrically arranged about the casing string 12. The housing 44 is welded, or otherwise sealed and secured, to the exterior of the casing string 12, so that the housing becomes an integral part of the casing string. It will be readily appreciated by those skilled in the art that the housing 44 could instead be integrally formed with a section of the casing string 12.
A bow spring 46 ensures that the device 40 is biased against an inner wall of the wellbore 14, so that a large volume of cement 16 is not disposed between the device and the wellbore. This facilitates the later forming of a passage 48 for providing fluid communication between the chamber 36 and a zone or earth formation 50.
Referring additionally now to
The device 40 in this construction of the assembly 42 includes a frangible member 52. The frangible member 52 could be, for example, a rupture disk of the type known to those skilled in the art, and which breaks or otherwise opens in response to a predetermined pressure differential applied across the rupture disk.
The pressure differential could be applied by applying pressure to the tube 38 connected to the chamber 36 from the surface. However, other methods of applying the pressure differential could be used in keeping with the principles of the invention. For example, a propellant could be ignited to create increased pressure in the chamber 36, pressure in the chamber and/or external to the chamber could be increased or decreased to apply the pressure differential, etc.
Referring additionally now to
In addition, sufficient pressure has been applied to the formation 50 to cause small fractures 54 to be formed in the formation rock. These fractures 54 can increase the mobility of fluid in the formation 50 toward the wellbore 14, for example, by overcoming the skin damage caused during drilling and other previous operations. Furthermore, those skilled in the formation fracturing and testing arts will appreciate that a variety of characteristics of the formation 50 may be determined using the capabilities of the assembly 42 to directly monitor pressure in the formation, whether or not the fractures 54 are formed.
For example, the pressure communication assembly 42 may be used to repeatedly test the formation 50 over time by injecting and/or withdrawing fluid into or out of the formation. A transient pressure response of the formation 50 to this fluid transfer may be monitored by the pressure gauge at the remote location. This will enable a determination of properties of the formation 50 (such as relative permeability) over time.
Repeated micro-transient testing allows the determination of zonal relative permeabilities. This process is made possible by the pressure connectivity to the surface which is provided by the system 10 with the isolated pressure communication assemblies 20, 22, 24, 26 in observation positions relative to the zones or formations 28, 30, 32, 34. Repeated mini or micro drawdown and build-up pressure testing or injection and fall-off testing can be performed using this system 10 with the assemblies 20, 22, 24, 26 isolated behind the casing string 12 for monitoring pressure of single zones that are not producing in this well. Pressure transient analysis of this data can determine changes in reservoir permeability due to fluid saturation changes within the zones over time.
Note that it is not necessary in keeping with the principles of the invention for the fractures 54 to be formed. The passage 48 could be formed without also forming the fractures 54.
Referring additionally now to
The member 56 could be, for example, a plug of the type known as a pump-out plug or disc. Instead of breaking like the frangible member 52 described above, the member 56 displaces when the pressure differential is applied.
Referring additionally now to
Referring additionally now to
Since the devices 40 are not biased against the walls of the wellbore 14 by the bow spring 46, the devices 40 in the
Referring additionally now to
As depicted in
The devices 40 each include an extension member 62 in the form of a sleeve having a piston externally thereon. The piston is received in a seal bore in an outer sleeve 64. A frangible member 52, similar to that used in the
When a predetermined pressure differential is applied to the devices 40, the extension members 62 will displace radially outward to approach or preferably contact the inner wall of the formation 50 on each side of the housing 44. In this manner, the presence of cement 16 between the frangible members 52 and the wellbore 14 may be reduced or eliminated. The extension members may be displaced radially outward prior to and/or during the cementing operation.
Referring additionally now to
When the frangible members 52 are broken, the passages 48 are formed, thereby providing fluid communication between the chamber 36 and the formation 50. In addition, fractures 54 may be formed if desired, as described above.
Referring additionally now to
The explosive charges 60 are preferably of the type used in well perforating guns and known as shaped charges. Other types of explosive charges may be used if desired, any number of explosive charges may be used, and the explosive charges may be detonated in any manner (for example, mechanically, electrically, hydraulically, via telemetry, using a time delay, etc.) in keeping with the principles of the invention.
As depicted in
Referring additionally now to
The assembly 42 of
In addition, a pressure operated firing head 68 is included in the device 40 for controlling detonation of the explosive charges 60. The firing head 68 may be similar to conventional pressure operated firing heads used for well perforating guns. The firing head 68 may be used to detonate the charges 60 in the
A predetermined pressure differential applied to the firing head 68 causes the firing head to detonate the explosive charges 60, thereby forming the passages 48 and providing fluid communication between the chamber 36 and the formation 50. The pressure differential may be between, for example, the chamber 36 and an internal chamber of the firing head 68. The pressure differential may be applied to the firing head 68 by applying pressure to the chamber 36 via the tube 38 from a remote location, such as the surface.
It may now be fully appreciated that the well system 10 and associated methods described above provide many benefits in well operations and monitoring of downhole pressure. Furthermore, a variety of new techniques have been described for providing fluid communication between the formation 50 and the chamber 36 of the assembly 42. It should be clearly understood that the invention is not limited to only these techniques, since other techniques could be used in keeping with the principles of the invention.
In addition, although the formation 50 and the formations 28, 30, 32 and 34 of
Once the chamber 36 is placed in fluid communication with the pressure source downhole, pressure in the pressure source may be monitored by displacing a known fluid (such as helium, nitrogen or another gas or liquid) through the tube 38 and into the chamber. Pressure applied to the tube 38 at the surface or another remote location to balance the pressure applied to the chamber downhole by the pressure source provides an indication of the pressure in the pressure source. Various techniques for accurately determining this pressure (including use of optical fiber distributed temperature sensing systems, etc.) are well known to those skilled in the art, and some of these techniques are described in the U.S. patents and patent application discussed above.
Even though the pressure communication assembly 42 and its alternate embodiments have been illustrated and described as each including only one type of the device 40 (for example, including the frangible member 52, displaceable member 56 or explosive charge 60), it will be appreciated that any combination of the types of devices could be provided in a pressure communication assembly (for example, to provide redundancy). Furthermore, any number of the devices 40 may be provided in the pressure communication assembly 42 and its alternate embodiments.
Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are within the scope of the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.
