CASED WELLS

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates generally to systems and methods for creating tunnels within subterranean formations surrounding cased wellbores. 2. Description of the Related Art

[0002] Metallic casing is used to line wellbores. To date, it has been necessary to use explosive perforating guns to form openings in the casing and the surrounding formation. Abrasive jetting has also been used, although it is not as common. Both explosive perforating and abrasive jetting used for perforating existing casing have the purpose to make tunnels as long as possible through the casing, cement and near wellbore region. The shape and length of these tunnels cannot be controlled.

SUMMARY OF THE INVENTION

[0003] The invention provides systems and methods for creating controlled tunnel openings in formations surrounding cased bores. Fluid, or fluid-solid jetting is used to form a controlled opening in the casing, if casing is present. Thereafter, acid tunneling is used to create tunnels in the formation.

[0004] In preferred embodiments, the perforating tool (if used) and the acid tunneling tool include sensors which can measure one or more downhole parameters, including deviation, azimuth, pressure, temperature and gamma ray. These sensors are installed within or upon the bottom hole assembly. In some embodiments, the bottom hole assembly incorporates a casing collar locator for measuring depth and/or a lateral camera.

[0005] Preferably, Telecoil ^® is used to transmit information obtained by the sensors of the bottom hole assembly to surface. Other telemetry means, such as optical fiber, could also be used. Information obtained by the sensors is used to control the abrasive jetting and acid tunneling tools as well as the perforating and tunneling processes. The abrasive perforating tool may have one or multiple nozzles. If the perforating tool has more than one nozzle, these nozzles could be distributed radially (i.e., at the same depth) or axially (i.e., at different depths) along the tool body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:

[0007] Figure 1 is a side, cross-sectional view of an exemplary wellbore containing a perforating tool arrangement in accordance with the present invention.

[0008] Figure 2 is an isometric view of an exemplary perforating tool constructed in accordance with the present invention.

[0009] Figure 3 is an enlarged isometric view of a centralizer portion of the perforating tool of Figure 2.

[0010] Figure 4 is an enlarged isometric view of a nozzle portion of the perforating tool of Figure 2.

[0011] Figure 5 is a side, cross-sectional view of an exemplary wellbore containing an acid tunneling tool arrangement in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Figure 1 illustrates an exemplary wellbore 10 that has been drilled through the earth 12 from the surface 14 down to a hydrocarbon-bearing formation 16. It is noted that, while wellbore 10 is illustrated as a substantially vertical wellbore, it might, in practice, have portions that are inclined or horizontally-oriented. The wellbore 10 is lined with a metallic casing 18. In alternative embodiments, the wellbore 10 would lack such a casing.

[0013] A perforating tool arrangement 20 is disposed within the wellbore 10. The perforating tool arrangement 20 includes a running string 22 which is preferably made up of coiled tubing. A flowbore 24 is defined along the length of the running string 22. A bottom hole assembly 26 is located at the distal end of the running string 22. A perforating tool 28 is affixed to the bottom hole assembly 26.

[0014] The perforating tool 28 is useful to create openings 30 in the casing 18 using fluid jetting or fluid-solid jetting. Fluid, or a fluid containing a solid such as sand, is injected through the flowbore 24 of the running string 22, the bottom hole assembly 26 and outwardly from lateral nozzles 32 of the perforating tool 28. Although there are multiple nozzles 32 shown, it should be understood that there may be only a single nozzle 32. In certain embodiments, the nozzle(s) 32 can be controlled from the surface 14 to open and/or close depending upon the requirements for forming an opening 30 of a particular size. An exemplary perforating tool 28 is shown in greater detail in Figs. 2-4 and includes a tubular body 34 with centralizer fins 36. In particular embodiments, perforating tool sensors 38 are incorporated into the body 34 of the perforating tool 28. The perforating tool sensors 38 can measure one or more downhole wellbore parameters, including depth, deviation, azimuth, pressure, temperature and gamma ray, which are useful for identifying a location or attributes of one or more of the openings 30 being formed. Perforating tool sensors 38 may also include a camera which is capable of obtaining visual images of the wellbore 10 environment. A camera would be useful for determining the size of an opening 30 that has been made by the perforating tool 28. In accordance with certain embodiments, the camera could have registry marks on its lens which would be useful to visualize and measure the size of the opening 30.

[0015] Bottom hole assembly 26 preferably includes an electronics board with storage or memory 40 to receive and store information received from the perforating tool sensors 38. The bottom hole assembly 26 also preferably includes a deviation/azimuth sub and casing collar locator which will help identify the exact position of the openings 30 formed by the perforating tool 28 so that a tunneling tool that is subsequently run can be positioned at or near the openings 30. A data communications conduit 44, such as tube-wire, is preferably used to transmit the received information to a surface controller and storage medium 42 from memory 40 of the bottom hole assembly 26. Telecoil ^® is coiled tubing which incorporates tube- wire that can transmit power and data. Tube-wire is available commercially from manufacturers such as Canada Tech Corporation of Calgary, Canada. Tube-wire 44 is shown within the flowbore 24 of the coiled tubing running string 22 and is operably interconnected with the controller/storage medium 42 at surface 14. The controller/storage medium 42 preferably includes suitable programming to use mathematical modeling to determine the location where the acid tunneling tool needs to begin bending in order to have the nozzle 60 be moved through the opening 30. Suitable programming for this application includes CIRCA™ RT modeling software for coiled tubing applications which is available commercially from Baker Hughes Incorporated. The entry location might be determine using information relating to the casing size, coiled tubing size and bottom hole size and length.

[0016] Figure 5 illustrates the wellbore 10 now with the perforating tool arrangement 20 removed and openings 30 having been created in the casing 18. An acid tunneling arrangement 50 is now disposed within the wellbore 10 after the openings 30 have been created in the casing 18. The acid tunneling tool arrangement 50 includes a running string 22 which is preferably made up of coiled tubing. A bottom hole assembly 26 is secured to the distal end of the running string 22 and may be the same bottom hole assembly as described previously. An indexing tool 52 is preferably incorporated into the acid tunneling arrangement 50 which permits components below the indexing tool 52 to be rotated angularly within the wellbore 10 with respect to the running string 22. An acid tunneling tool 54 is secured to the indexing tool 52. The acid tunneling tool 54 is preferably jointed and useful to form tunnels 56 within the formation 16 radially surrounding the wellbore 10 by injection of acid into the formation 16. The acid tunneling tool 54 may be constructed and operate in the same manner as the tool which is described in U.S. Patent No. 8,205,672 issued to Misselbrook et al. U.S. Patent No. 8,205,672 is owned by the assignee of the present application and is herein incorporated by reference in its entirety.

[0017] Tunneling tool sensors 58 are preferably incorporated into the acid tunneling tool 54 to detect downhole parameters such as those detected by perforating tool sensors 38 described previously. These downhole parameters can include depth, deviation, azimuth, pressure, temperature and gamma ray. The bottom hole assembly 26 receives data sensed by the tunneling tool sensors 58 and transmits the data to processor/storage medium 42 at surface 14. [0018] In accordance with preferred methods of operation, openings 30 are formed by the perforating tool 28 which are large enough for a distal nozzle 60 of the acid tunneling tool 54 to be inserted through the openings 30 in order to effectively create tunnels using acid injection. At least some portion of the process of forming tunnels 56 within the formation 16 is controlled based upon wellbore parameter sensed by the perforating tool sensors 38 of the perforating tool 28. The acid tunneling tool 54 run in is assisted in locating the opening(s) 30 as well as appropriately-sized openings 30 in the casing 18 which were created previously by the wellbore parameters detected by the perforating tool sensors 38 of the perforating tool arrangement 20. Insertion of the acid tunneling tool 54 into an opening 30 is more accurate. In a non-limiting example, the openings 30 are large enough to allow the nozzle of a 2 1/8" StimTunnel tool to pass through the casing 18. Injection of acid into the formation by the acid tunneling tool 54 will create small tunnels 56 within the formation 16. If desired, hydraulic fracturing can thereafter be used to increase reservoir connectivity further.

[0019] It can be seen that the invention provides a system for forming tunnels within a formation surrounding a subterranean wellbore 10 which includes a perforating tool arrangement 20 and an acid tunneling arrangement 50. The perforating tool arrangement 20 includes a perforating tool 28 for forming an opening 30 within casing 18 of the wellbore 10 using fluid jetting or fluid-solid jetting. Perforating tool sensors 38 are located upon the perforating tool 28 and are configured to detect at least one wellbore parameter which is useful for identifying a location or attributes of one or more of the openings 30 being formed in the casing 18. The perforating tool arrangement 20 preferably also includes a bottom hole assembly 26 having on-board memory storage 40 for retaining data provided by the sensors 38. In described embodiments, the perforation tool arrangement 20 further includes a controller 42 which is configured to determine location or attributes of one or more of the openings 30 being formed in the casing 18 based upon the wellbore parameter(s) sensed by the perforating tool sensors 38. A data communications conduit 44 transmits data from the bottom hole assembly 26 to the controller 42.

[0020] The acid tunneling arrangement 50 of the system for forming tunnels includes an acid tunneling tool 54 for forming a tunnel 56 within the formation 16 radially surrounding the wellbore 10. Tunneling tool sensors 58 are disposed upon or within the acid tunneling tool 54 and are configured to detect wellbore parameters that are useful for controlling operation of the acid tunneling tool 54 to create one or more tunnels 56. The acid tunneling arrangement 50 also includes a bottom hole assembly 26 which transmits data representative of the wellbore parameters sensed by the tunneling tool sensors 58 to the controller 42.