Reservoir Pressure Monitoring

Abstract

A method of completing a wellbore that includes providing wellbore casing having shaped charges and permanent pressure gauges on an outer surface of the casing. In an example of use, the casing is inserted into the wellbore and cement is injected into an annulus formed between the casing and wellbore. The shaped charges are strategically deployed on the casing so they aim towards a wall of the wellbore and are spaced apart along the casing. Thus detonating the shaped charges creates perforations into a formation around the wellbore and places the pressure gauges into pressure communication with the formation. Pressure readings are delivered to the surface from the pressure gauges in the form of signals.

Description

RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Application Ser. No. 61/376,327, filed Aug. 24, 2010, the full disclosure of which is hereby incorporated by reference herein.

BACKGROUND

1. Field of Invention

The invention relates generally to the field of downhole pressure measurement. More specifically, the present invention relates to measuring formation pressure with permanent pressure gauges mounted outside of wellbore casing and using shaped charges mounted outside the casing to communicate pressure from the formation to the gauges.

2. Description of Prior Art

Formation pressure adjacent to a hydrocarbon producing wellbore can be monitored to assess reservoir characteristics and forecast future hydrocarbon production. Formation pressures are also sometimes monitored for evaluating safety and environmental concerns. Over time, more complex wells have been developed that are deeper and include more elaborate lateral branches. As the deeper and branched wells generally extend through more than one formation, additional locations for pressure monitoring are identified. As well production technology advances to allow deeper and more complex well systems, similar advancements in pressure monitoring have been made.

For open hole wellbores that have not yet been lined, tools are sometimes inserted into the wellbore and a probe from the tool penetrates into the adjacent formation to directly measure pressure in the formation. Such characterization tools are impractical once the wellbore has been lined. Thus after completion of the wellbore, permanent pressure gauges are typically deployed inside the wellbore casing for measuring the internal wellbore pressure.

SUMMARY OF INVENTION

Disclosed herein is a method of completing a wellbore that includes providing wellbore casing having shaped charges and permanent pressure gauges on an outer surface of the casing. In an example of use, the casing is inserted into the wellbore and cement is injected into an annulus formed between the casing and wellbore. The shaped charges are strategically deployed on the casing so they aim towards a wall of the wellbore and are spaced apart along the casing. Thus detonating the shaped charges creates perforations into a formation around the wellbore and places the pressure gauges into pressure communication with the formation. Pressure readings are delivered to the surface from the pressure gauges in the form of signals.

Also disclosed herein is a method of characterizing a subterranean formation. In one example the method of characterizing includes providing a perforator in an annulus that is between a downhole tubular and a borehole wall. The perforator is used to form a perforation through the wall and into the subterranean formation; thus the perforation allows communication of pressure in the subterranean formation to the annulus. Pressure in the subterranean formation is then estimated by measuring pressure in the annulus. In one example embodiment, pressure measurements are taken over a period of time so that changes of pressure in the subterranean formation over the period of time can be monitored. The perforator can be a shaped charge, a perforating bullet, or a fluid jet. In one example embodiment, measuring pressure in the annulus involves providing a pressure gauge in the annulus and monitoring an output from the pressure gauge. In an example, the perforator includes a housing and the perforation extends into the housing so that an inside of the housing is in pressure communication with the subterranean formation, and wherein an input to the pressure gauge is ported to the inside of the housing. In an optional embodiment, the perforator is made up of a housing and the perforation extends into the housing so that an inside of the housing is in pressure communication with the subterranean formation, and wherein the pressure gauge is disposed inside the housing. Optionally, the subterranean formation includes multiple zones, in this example the method involves repeating the steps of providing, perforating, and measuring in at least two of the zones. Alternatively, cement is provided in the annulus after the perforator is included but before the formation is perforated.

Further described herein is a system for measuring pressure in a subterranean formation. In one example embodiment the system is made up of a perforator selectively disposed in an annulus formed between a downhole tubular and a wall of a wellbore and a pressure gauge in pressure communication with the perforator. Further included is a coupling mounted on the pressure gauge attached to a signal line, so that when the perforator is initiated to create a perforation through the wall of the wellbore, the pressure gauge is brought into pressure communication with the formation and the pressure in the formation can be measured through the signal line. In an example embodiment, the perforator is a perforating gun with a shaped charge, and cement is provided in the annulus; as such, the perforation extends through a portion of the cement. Tubing may optionally be provided that is connected between the pressure gauge and the perforator for providing pressure communication between the pressure gauge and the perforator. Yet further optionally included is a controller in communication with the pressure gauge through the signal line and in communication with the perforator through a signal line. In another alternative embodiment, the downhole tubular is casing that lines the wellbore and the perforator and the pressure gauge are each clamped to an outer surface of the casing.

Also described herein is a method of measuring pressure in a formation adjacent to a wellbore lined with casing. In one example the method involves providing a shaped charge in an annulus between the casing and a wall of the wellbore, providing a pressure gauge in the annulus and in pressure communication with the shaped charge, forming a perforation in the formation by projecting a jet from the shaped charge into the formation from the annulus, sensing pressure of the formation with the pressure gauge, and directing a signal from the pressure gauge through a signal line that represents pressure sensed in the formation. In an alternate embodiment, the shaped charge is included within a perforating gun having a housing, and the pressure gauge is in fluid communication with the shaped charge by a length of tubing connecting the housing and the pressure gauge. Optionally, the shaped charge is included within a perforating gun having a housing, and the pressure gauge is disposed in the housing. The method can optionally be repeated, and the perforation can occur in a portion of the formation that is isolated from the first portion of the formation perforated by a formation barrier.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side sectional view of a system in a wellbore for estimating pressure in a subterranean formation.

FIG. 2 is a side sectional view of the system of FIG. 1 with cement added into the wellbore.

FIG. 3 is a side sectional view of the system of FIG. 2 forming perforations in the formation.

FIG. 4 is a side view of a sample embodiment of a pressure gauge and perforator.

FIG. 5 is a side sectional view of a portion of a pressure gauge of FIG. 4.

FIG. 6 is a side view of a perforator and pressure gauge on an outer surface of a casing.

FIG. 7 is a side view of a perforator and pressure gauge on an outer surface of a well bore casing.

FIG. 8 is a side sectional view of an alternate embodiment of the system for measuring pressure in a subterranean formation.

While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

Referring now to FIG. 1, an example well bore 10 is shown in a side sectional view having a casing string 12 inserted into the well bore 10. The casing string 12 of FIG. 1 has perforating guns 14 attached on the outer surface of the casing string 12 that are disposed in an annulus 16 formed in between the casing 12 and inner wall of the well bore 10. In the embodiment of FIG. 1, each perforating gun 14 includes a perforator 18 oriented so that it is aimed away from the casing string 12 and into a formation 20 surrounding the well bore 10. Examples of perforators 18 include shaped charges, perforating bullets, and fluid jets. It should be noted that while the perforating gun 14 as shown contains a single shaped charge, a perforating gun used for this application may contain many shaped charges. In the example of FIG. 1, the perforating guns 14 may be arranged so that the perforators 18 associated with each perforating gun 14 are spaced apart axially within the well bore 10. The spacing of the perforators 18 can vary depending on the particular formation 20 in which the well bore 10 is formed. It is believed it is well within the capabilities of those skilled in the art to determine a designated spacing of the perforators 18.

Pressure gauges 22 are further illustrated that are coupled on the outer circumference of the casing string 12. In the example embodiment of FIG. 1, a pressure gauge 22 is provided for each perforating gun 14. However, other embodiments exist of the well bore assembly of FIG. 1 wherein any number of pressure gauges 22 can vary from the number of perforating guns 14. As described in more detail below, the pressure gauges 22 may be in communication with the surface and optionally coupled with other pressure gauges within the well bore 10.

FIG. 2 depicts cement 24 having been injected into the annulus 16 of FIG. 1 for anchoring the casing string 12 within the well bore 10. In the annulus 16, the cement 24 covers the outer surfaces of the perforating guns 14 and pressure gauges 22. Embodiments exist where the cement 24 is any substance flowable into the annulus 16 and/or used for securing the casing string 12. Moreover, the cement 24 may also be used to provide a barrier preventing flow along the length of the annulus 16.

Referring now to FIG. 3, perforators 18 have been detonated to form perforations 26 that extend through a portion of the cement 24 and into the formation 20 in a direction away from the casing string 12. In one example, the perforating guns 14 include a single perforator 18 with an associated detonator (not shown) for initiating detonation of the perforator 18. In the example of FIG. 3, the perforator 18 is a shaped charge and has formed and directed a jet 19 into the formation 20 to create the perforations 26. Optionally, a digital switch (not shown) may be included with the perforating guns 14 so each individual perforating gun 14 may be independently fired. The perforations 26 provide pressure communication from the formation 20 to the annulus 16. Communicating pressure from the formation 20 into the annulus 16 in turn communicates with the pressure gauges 22. Thus pressure in the formation 20 may be monitored by the pressure gauges 22 via the perforations 26. Accordingly, in one example embodiment the pressure gauges 22 are mounted onto the casing string 12 adjacent to the portion of the perforating guns 14 having the perforator 18 to maximize accuracy of pressure measurements in the formation 20. Moreover, the permanent placement of the gauges 22 in the annulus 16 allows for pressure monitoring of the formation 20 over time, where the time frame can be as discrete as minutes, up to multiples of years, and all time frames in between. The ability to monitor formation pressure over a time frame not only can help identify transient issues downhole, but also be useful in estimating production capacity of the formation and anticipated production duration.

Further illustrated in the example of FIG. 3 are multiple zones Z₁-Z_n, included within the formation. Barriers B₁-B_n separate the zones Z₁-Z_n, from one another, wherein the barriers B₁-B_n may block fluid flow between adjacent zones Z₁-Z_n, and allow a pressure gradient to form that is in excess of hydrostatic pressure. The example embodiment of FIG. 3 depicts the perforating guns 14 and pressure gauges 22 strategically located so that perforations 26 created by the perforators 18 are in separate zones Z₁-Z_n thereby enabling discrete pressure measurements from more than one, or each of, the zones Z₁-Z_n. Also, dimensions of a hydrocarbon producing reservoir in the formation 20 can affect how the pressure gauges 22 are strategically located. It is appreciated that it is within the capabilities of those skilled in the art to identify locations in a subterranean reservoir of hydrocarbons where pressure measurements would provide information useful for characterizing the reservoir. An advantage of strategically located pressure measurements is the ability to measure pressure depletion along a path where the borehole 10 intersects the formation 20; which can be used for estimating reserves in the formation 20 and also useful for maximizing recovery of hydrocarbons from the formation 20.

In FIG. 4, example tandems 27 each made up of a perforating gun 14 and a pressure gauge 22 are illustrated in a side view. The tandems 27 of FIG. 4 represent a portion of the perforating guns 14 and pressure gauges 22 included with the casing string 12 disclosed herein. As shown, tandems 27 are formed by coupling a perforating gun 14 and pressure gauge with clamps 28. Initiation lines 30 are shown connected to upper and lower ends of each perforating gun 14. The initiation lines 30 may be cables that transmit a signal instructing the firing head (not shown) within the perforating gun 14 to detonate the shape charge therein. Alternatively, the initiation lines 30 may be detonation cord that once ignited at one end transmits a detonation shock wave along the length of the initiation line 30 for detonating shape charges within each perforating gun 14. Signal lines 32 communicate pressure between the pressure gauges 22 in the tandems 27 depicted in FIG. 4 and also to the other tandems 27 with the casing string 12 thereby forming a pressure gauge circuit. A coupling 33 is shown provided with one of the pressure gauges 22 for attachment to the signal line 32. Couplings 33 can be provided at each point where signal lines 32 attach to the pressure gauges 22. A coupling 33 can be any form of attaching the signal line 32 with the pressure gauge 22, such as a male/female socket arrangement or simple contact of conducting elements (not shown) in the signal line 32 with contacts (not shown) in the pressure gauge 22. Further illustrated in FIG. 4 is tubing 34 coupled on one end to each pressure gauge 22 and on its other end to the body of an associated perforating gun 14. As such, pressure within the formation 20 communicates through the perforation 26, into the body or bodies of the perforating guns 14, and through the tubing 34 to each pressure gauge 22.

A controller 36 is further schematically illustrated in FIG. 4 shown disposed above the surface 37 and connected to ends of the initiation and signal lines 30, 32. As such, the controller 36 of FIG. 4 is in communication with the perforators 14 via the initiation lines 30 and pressure gauges 22 via the signal lines 32. Selective activation of the perforators 14 can be done using the controller 36 as well as monitoring signals from the pressure gauges 22 for collecting pressure data. The controller 36 can be an information handling system that is stand alone or incorporated within a surface truck (not shown).

Provided in a side view in FIG. 5 and taken along line 5-5 from FIG. 4, is an example embodiment of the pressure gauge 22 having a signal line 32 depending downward from a lower end of the pressure gauge 22. The signal line 32 of FIG. 5 connects to another pressure gauge (not shown) at a different elevation on the casing string. Further illustrated in FIG. 5 is a pressure port 38 formed through the outer body of the pressure gauge 22 that may optionally be threaded and adapted to receive the tubing 34 of FIG. 4.

An alternative example embodiment of the well bore assembly is shown in a side view in FIG. 6. In this example, a perforating gun 14 is anchored onto the outer surface of the casing 12 and initiation lines 30 attach to respective upper and lower ends of the perforating gun 14. The pressure gauge 22 shown adjacent the perforating gun 14 is anchored on the outer surface of the casing string 12 thereby out of the path of a perforating jet that forms upon detonation of the perforator 18. Tubing 34 connects the pressure gauge 22 with the inside of the body of the perforating gun 14. In one example, the pressure gauge is made of a device having oscillatory quartz crystal that responds to pressure variations so that pressure is experienced by pressure gauge 22 can be converted into signals that are then transmitted to surface via the signal line 32, or other communications means. Additionally, to maximize penetration of the formation 20 with the perforation 26 at 0° phase can be designated for creating the perforation 26 (FIG. 3). That is, a line generally coaxial with the perforation 26 extends substantially towards an axis A_X of the casing 12 rather than at an angle with the axis A_X.

In another embodiment provided in a side view in FIG. 7, clamps 40 are shown coupling the perforating gun 14 with the outer surface of the casing 12. Additional clamps 28 are shown attaching the pressure gauge 22 to the perforating gun 14 to define a tandem arrangement mounted on the casing string 12. Placement of the clamps 28, 40 is variable depending on position of the tubing 34 and perforator 18.

In one example of use, as illustrated in FIG. 1, a casing string 12 is provided with the perforating guns 14 and pressure gauges 22 on its outer surface and then deployed into the well bore 10. Alternatively, the pressure gauges 22 may be housed inside the perforating guns 14 and protected therein while inserting the casing string 12 into the wellbore 10. The perforating gun 14 can also shield the pressure gauges 22 during cement 24 injection, as shown in FIG. 2. Further illustrating the example, after the cement 24 is set, the perforators 18 are detonated to produce perforations 26 in the formation 20. A sequence of perforator 18 initiation may begin by first initiating the lower most perforator 18, and then sequentially initiating each successive perforator 18 towards the surface. By porting the pressure gauge to a void within the perforating gun 14, pressure from the formation 20 is communicated directly to each pressure gauge 22. Thus over time, pressure monitored with the pressure gauges 22 may be analyzed to assess characteristics within the formation 20, such as a prediction of future or expected hydrocarbon production from within the well bore 10.

FIG. 8 illustrates in a side sectional view an alternate embodiment of a system for measuring pressure in a subterranean formation. In this example the casing 12A includes collars 42 where adjacent sections of casing 12A are joined, such as by a threaded fitting (not shown). In the example of FIG. 8 a perforator 18A and pressure gauge 22A are set within the body of the collar 42. In the embodiment of FIG. 8, at least a portion of the initiation lines 30A and signal lines 32A are routed through the collar 42.

The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. For example, components of the perforating gun and pressure gauge could be integrated into a single modular unit within a single housing. In this embodiment the perforating gun components could be miniaturized to fit within a housing that would normally only accommodate the pressure gauge. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.

Claims

1. A method of characterizing a subterranean formation comprising:

a. providing a perforator in an annulus formed between a downhole tubular and a wall of a borehole that intersects the subterranean formation;

b. using the perforator to form a perforation through the wall and into the subterranean formation thereby communicating pressure in the subterranean formation to the annulus; and

c. estimating pressure in the subterranean formation by measuring pressure in the annulus.

2. The method of claim 1, wherein step (c) is performed over a period of time and changes of pressure in the subterranean formation over the period of time are monitored.

3. The method of claim 1, wherein the perforator comprises a device selected from the group consisting of a shaped charge, a perforating bullet, and a fluid jet.

4. The method of claim 1, wherein the step of measuring pressure in the annulus comprises providing a pressure gauge in the annulus and monitoring an output from the pressure gauge.

5. The method of claim 3, wherein the perforator comprises a housing and the perforation extends into the housing so that an inside of the housing is in pressure communication with the subterranean formation, and wherein an input to the pressure gauge is ported to the inside of the housing.

6. The method of claim 3, wherein the perforator comprises a housing and the perforation extends into the housing so that an inside of the housing is in pressure communication with the subterranean formation, and wherein the pressure gauge is disposed inside the housing.

7. The method of claim 1, wherein the subterranean formation includes multiple zones, the method further comprising performing steps (a)-(c) in at least two of the zones.

8. The method of claim 1, further comprising providing cement in the annulus after step (a) and before step (b).

9. A system for measuring pressure in a subterranean formation comprising:

a perforator selectively disposed in an annulus formed between a downhole tubular and a wall of a wellbore;

a pressure gauge in pressure communication with the perforator; and

a coupling mounted on the pressure gauge attached to a signal line, so that when the perforator is initiated to create a perforation through the wall of the wellbore, the pressure gauge is brought into pressure communication with the formation and the pressure in the formation can be measured through the signal line.

10. The system of claim 9, wherein the perforator comprises a perforating gun with a shaped charge and wherein cement is provided in the annulus and the perforation extends through a portion of the cement.

11. The system of claim 9, further comprising tubing connected between the pressure gauge and the perforator for providing pressure communication between the pressure gauge and the perforator.

12. The system of claim 9, further comprising a controller in communication with the pressure gauge through the signal line and in communication with the perforator through a signal line.

13. The system of claim 9, wherein the downhole tubular comprises casing lining the wellbore and the perforator and the pressure gauge are each clamped to an outer surface of the casing.

14. A method of measuring pressure in a formation adjacent a wellbore lined with casing, the method comprising:

a. providing a shaped charge in an annulus between the casing and a wall of the wellbore;

b. providing a pressure gauge in the annulus and in pressure communication with the shaped charge;

c. forming a perforation in the formation by projecting a jet from the shaped charge into the formation from the annulus;

d. sensing pressure of the formation with the pressure gauge; and

e. directing a signal from the pressure gauge through a signal line that represents pressure sensed in the formation.

15. The method of claim 14, wherein the shaped charge is included within a perforating gun having a housing, and the pressure gauge is in fluid communication with the shaped charge by a length of tubing connecting the housing and the pressure gauge.

16. The method of claim 14, wherein the shaped charge is included within a perforating gun having a housing, and the pressure gauge is disposed in the housing.

17. The method of claim 14, further comprising repeating steps (a)-(e), and wherein the perforation of step (c) is in a portion of the formation that is isolated from the portion of the formation of claim 14 by a formation barrier.