Refracturing method using spaced shaped charges straddled with isolators on a liner string

Abstract

A re-fracturing method involves placement and centralization of a liner string that has shaped charges at predetermined locations that are externally isolated with packers. The shaped charges can be set off in a desired order and re-fracturing can then take place in new locations. In a bottom up order for perforating sequentially larger balls can be landed on seats and developed pressure or component movement generated by applying pressure can be used to set a shaped charge and isolate portions of the borehole below. The balls and even the seats can be later milled out or just allowed to disintegrate or dissolve with well fluids that are present or later added to clear the liner for subsequent production. Alternatively, the liner could be removed by release of the packers before production or injection begins.

Claims

1. A re-fracturing method for a predetermined formation in a borehole, with existing fractures, at locations offset from the existing fractures, comprising: positioning shaped charges in offset locations along a longitudinal axis from the existing fractures in the predetermined formation borehole, said existing fractures present in the borehole before said positioning is initiated, and radially with respect to said axis; isolating at least one said charge at each said offset location from the existing fractures in the predetermined formation in the borehole; setting off said charges in said offset locations in a predetermined order and in a single trip to create perforations before pressure that causes fractures is applied: fracturing said offset locations with applied pressure through said perforations after said setting off of said charges in the single trip; defeating said isolating after said fracturing.

2. The method of claim 1, comprising: setting off said charges in a bottom up sequence.

3. The method of claim 1, comprising: setting off said charges in a top down sequence.

4. The method of claim 1, comprising: setting off said charges in a random order.

5. The method of claim 1, comprising: locating said shaped charges on a tubular string; centering said string in the borehole with spaced external isolators.

6. The method of claim 5, comprising: positioning said charges at said spaced axial locations, an equal radial distance to an internal wall of said string.

7. The method of claim 5, comprising: straddling at least some of said shaped charges on opposed axial sides with said external isolators.

8. The method of claim 7, comprising: making said isolators selectively releasable; removing said string after all the charges are fired and before producing or injecting in the borehole.

9. The method of claim 7, comprising: leaving said string in position for said producing or injecting.

10. The method of claim 7, comprising: positioning a bottom hole assembly with a resettable packer sequentially in the string adjacent said shaped charges; sequentially setting the resettable packer adjacent said shaped charges; setting off said charges directly or indirectly by using said sequential positioning and setting.

11. The method of claim 10, comprising: using said bottom hole assembly to move a sleeve associated with a respective shaped charge of said shaped charges which movement of said sleeve in turn sets off said associated shaped charge for an indirect setting of said associated shaped charge.

12. The method of claim 11, comprising: engaging said sleeve with an inflatable member for subsequent moving of said sleeve; using an inflatable for said resettable packer.

13. The method of claim 10, comprising: providing a field on said bottom hole assembly that communicates directly to an adjacent said shaped charge for setting off said adjacent shaped charge.

14. The method of claim 10, comprising: delivering said bottom hole assembly with said resettable packer on coiled tubing with an internal wireline.

15. The method of claim 14, comprising: providing a device on said bottom hole assembly to selective engage and sequentially move a plurality of axially spaced sleeves whose movement sets off an associated shaped charge.

16. The method of claim 15, comprising: firing said shaped charge through said sleeves or through openings in said tubular opened with movement of said sleeves or through the wall of said tubular string.

17. The method of claim 16, comprising: leaving said tubular in position for production or injection after setting off said shaped charges or releasing said external isolators and removing said tubular string before production or injection.

18. The method of claim 15, comprising: making said sleeves identical so that said sleeves can all be engaged by a single device for movement.

19. The method of claim 18, comprising: actuating said device through a wireline running through coiled tubing that supports said bottom hole assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic section view of the liner with shaped charges being run in; and

(2) FIG. 2 is the view of FIG. 1 with the shaped charge fired to create new perforations;

(3) FIG. 3 is a section view of an embodiment using wireline in coiled tubing with a packer and a shifting device to set off the shaped charge and re-fracture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(4) FIG. 1 shows a borehole 10 in a formation 12 that has casing 14 sealed with cement 16. A liner 18 is placed in position such that packers or seals 20 and 22 are below and packers 24 and 26 are above a seat 28 that is capable of receiving a ball or other object 30 for obstruction of the passage 32. While FIG. 1 shows a single shaped charge 34 flanked by two packers on each side, those skilled in the art will appreciate that this pattern can be repeating such that multiple shaped charges can be similarly disposed with straddling packers to define multiple locations for re-fracturing that are isolated from the existing fractures such as 37. Similarly there can be multiple existing fractures that are isolated from the locations of the re-fractures by spaced packers such as 20 and 22. In FIGS. 1 and 2 the actuation of each shaped charge 34 is discrete in time. One way this is done is that object 30 lands on seat 28 to shift a sleeve 36. The movement of the sleeve 36 can trigger the igniter schematically illustrated as 38. Alternatively the pressure buildup on seat 28 can also trigger the igniter 38. Another alternative is to have the shifting of sleeve 36 align ports that are not shown so that the shaped charge 34 can fire through aligned ports into and through the casing 14 and the surrounding cement 16. The shaped charge 34 can fire through the sleeve and in that event the sleeve need not have any openings. While a single shaped charge is shown in the drawings associated with a respective barrier in passage 32, the representation is schematic and an array of shaped charges can be located at a single transverse section through the liner 18 or alternatively at more than one transverse section. The object 30 can be blown through a given seat 28 or one or both can disintegrate over time. The objects 30 can also be brought to the surface with production that can also undermine or disintegrate the seats 28. In another variation the seats 28 can all be milled out before production or injection begins. Another way to prepare for production or injection is to release the external packers 20, 22, 24 and 26 along the liner 18 and to remove the liner 18 before production or injection begins. Alternatively the object 30 when in close proximity to the charge 34 can trigger firing of the charge by transmitting a signal to a receiver associated with the charge 34 to cause the firing. The object can transmit a magnetic, acoustic, vibratory or some other signal that can be processed at a given charge 34 to fire it.

(5) FIG. 3 is an alternative way to accomplish the setting off of shaped charges and re-fracturing. Coiled tubing 50 has a wireline 52 that is connected to a bottom hole assembly (BHA) 54. The BHA 54 features a resettable packer 56 akin to Optipacker offered by Baker Hughes Incorporated of Houston, Tex., USA that can be triggered to set and release and reset multiple times as is known in the art. The packer 56 can be set before or after the shaped charge 62 is fired. The BHA 54 has a device 58 that grabs and moves a sleeve 60 which has the result of setting off the shaped charge 62. Device 58 can be an inflatable. The setting off of the shapedcharge 62 penetrates the casing 64 and the cement 66 that is behind it to create a fracture 68 in the formation 70. Packers 72 and 74 isolate a portion of the annulus 76 on opposed sides of a shaped charge such as 62 such that when fluid under high pressure represented by arrow 78 is pumped down annular space 80 from the surface, the fractures 68 are further opened up. The assembly can be spotted as needed with casing collar locators or other devices and can also carry an assortment of sensors to transmit real time data to the surface. The sleeves 60 can thus be identical and engaged in any desired order to fire an associated shaped charge triggered by sleeve movement. The sleeves 60 are each associated with a shaped charge and the configuration of components in FIG. 3 can be in a repeating pattern in a borehole. While the order of firing the shaped charges is preferably bottom up, the opposite direction or a random order is also contemplated. After all the charges are fired or at another time, if desired, the coiled tubing 50 can be spooled back to the well surface with the BHA 54. The sleeves 60 can be mechanically grabbed by device 54 or the power available from the wireline 52 can be communicated to a motor or other device not shown to electrically power the sleeves 60. A signal powered from the wireline can create a field 61 that triggers a sleeve driver to shift the sleeve using a self-contained power source or alternatively simply triggers the shaped charge to fire with or without any sleeve movement. The charge 62 can be supported on the inner string 82 or on the sleeves 60. Movement of the sleeve 60 can open ports 84 through which the shaped charges 62 can fire or alternatively the charges 62 can just fire through the string 82 or even the sleeves 60. One advantage of not using the balls and seats of FIGS. 1 and 2 is that a milling step can be avoided for removal and the wellbore is made ready for production or injection that much faster with the FIG. 3 embodiment. More sleeves can be used with the FIG. 3 embodiment because the limitation of having only a finite number of different ball sizes is not an issue with the FIG. 3 embodiment.

(6) Those skilled in the art will appreciate the benefits of the present invention. The shaped charges can be precisely placed on the liner and fired in a desired order. The placement of the charges can be consistent with respect to the liner wall so as to make the perforations more uniform. The shaped charges virtually disintegrate after firing enabling the re-fracturing flow after the charges are fired so that the perforations are more optimally fractured. The liner can be removed for production or injection to facilitate higher flow rates. The sleeves that shift from pressure on objects landed on seats can set off the charges mechanically by reason of sleeve movement or electrically or otherwise indirectly by movement that triggers an assembly that results in ignition of the shaped charges. The movement of the sleeves can be locked in the position where the respective shaped charges are set off. Movement of the sleeve can also open lateral ports with the shaped charges firing through such ports. The temporary zonal isolation in the liner can be accomplished with objects landing on seats or valves that are remotely operated preferably without well intervention. The perforations can be created one by one in a single trip. The charges can be located at predetermined locations with respect to the liner length and oriented with respect to the liner wall in a similar fashion to gain uniformity in the perforations regardless of the orientation of the borehole.

(7) The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: