US20130180721A1

US20130180721A1 - Downhole Fluid Treatment Tool

Info

Publication number: US20130180721A1
Application number: US13/727,950
Authority: US
Inventors: Donald Getzlaf; Marty Stromquist; Robert Nipper
Original assignee: NCS Oilfield Services Canada Inc
Current assignee: NCS Multistage LLC
Priority date: 2011-12-27
Filing date: 2012-12-27
Publication date: 2013-07-18
Also published as: CA2799967A1

Abstract

A treatment device and method for use in delivering fluid treatment to a wellbore is described. The device includes a first treatment housing and a second treatment housing, mounted along a tubing string, each of the first and second housing defining a fluid pathway which is continuous with the tubing string and each of the first and second treatment housing defining a port for fluid communication between the tubing string and the wellbore. Fluid flow through the first housing may be selectively blocked by delivery of a deformable ball to the tubing string to seal against a ball seat disposed between the first and second housing. While the first pathway is blocked, fluid may be selectively delivered to the wellbore through the port on the second treatment housing. The ball may be removed from the ball seat by application of hydraulic pressure in excess of the deformation threshold of the ball, forcing the ball to deform and pass through the seat, re-opening the fluid flow through the first treatment housing and allowing for treatment through port defined in the first housing.

Description

RELATED APPLICATIONS

This U.S. patent application claims priority to U.S. Provisional Application 61/580,500 filed on Dec. 27, 2011, the disclosure of which is considered part of the disclosure of this application and is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to the delivery of treatment fluid to a geological formation intersected by a wellbore. More particularly, the present invention relates to tubing-enabled completions, in which treatment fluid is delivered through tubing to a target interval of the wellbore.

BACKGROUND OF THE INVENTION

In completing a cased well, the casing may be perforated in specific locations to provide access to the surrounding formation. Various fluid treatments may be delivered through the perforations, and formations fluids may ultimately be produced through the perforations.
In some wells, the casing may incorporate pre-perforated sleeves, in which the perforations may be opened as needed to provide access to the formation. However, sleeve failure does occur, requiring re-perforation of that wellbore interval. Accordingly, multistage fluid treatment assemblies may incorporate a perforation device, such as fluid jet perforating device, to avoid the need for tripping in and out of the well each time perforation, or re-perforation, is necessary.
When delivering treatment fluid to a perforated interval, the interval of interest may be fully or partially isolated from the remainder of the wellbore, using a bridge plug or other sealing device. The sealing device may be conveyed downhole on wireline or tubing string and is typically set below the interval to be treated. Once set, treatment fluid may be delivered to the interval by pumping fluid down the wellbore. As fluid treatment is delivered to the wellbore, the hydraulic pressure within the wellbore increases, ultimately forcing fluid through the perforations and into the formation. At intervals of great depth, large volumes of fluid are required to achieve the hydraulic pressures required to penetrate the formation at each interval. Such excessive fluid usage limits the economic viability of the operation. Accordingly, at deep intervals, delivery of treatment fluid through the tubing string would be desirable. However, when the tubing string is used to deliver treatment fluid, the tubing string may not then be used for other purposes such as perforation.
While some fluid treatment assemblies have been developed in which perforation may be accomplished by wireline, these assemblies have a limited capacity for multiple perforation as the explosive charges must be replaced once depleted, necessitating a return to surface.
The use of tool assemblies for performing multiple functions in a single trip downhole can reduce the cost of completion operations. In tool assemblies incorporating a jet perforation device, it is useful to incorporate means that allow for other treatment operations, such as fracturing, in a different portion of the tool assembly. This allows for more efficient treatment of the wellbore, since perforation and fracturing can occur in two different regions of the same isolated wellbore interval.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, there is provided a downhole treatment assembly, the assembly comprising: a first housing disposed on a tubing string, the first housing defining a first fluid pathway continuous with the tubing string and including a wall defining a first port for passage of fluid between the first fluid pathway and the wellbore; a second housing disposed on the tubing string above the first housing, the second housing defining a second fluid pathway continuous with the tubing string and with the first fluid pathway, the wall of the second housing including a second port through which fluid can flow from the tubing string to the wellbore; and a ball valve disposed on the tubing string between the first and second port, the ball valve comprising a ball seat at the upper end of the valve, the ball seat configured to receive a deformable ball, and a ball trap for preventing unseated, deformed balls from re-entering the ball valve.
In accordance with one embodiment of the invention, the ball valve is mounted within the first housing above the first port.
In accordance with another embodiment of the invention, the second housing comprises a jet perforation device and the second port comprises a jet nozzle.
In accordance with another embodiment of the invention, the ball valve is provided as a removable insert in the first housing.
In accordance with a second aspect of the invention, there is provided a system for wellbore treatment, the system comprising: a first housing disposed on a tubing string, the first housing defining a first fluid pathway continuous with the tubing string; a first port defined in the first housing for lateral fluid flow from the first fluid pathway to the wellbore; a second housing disposed on the tubing string above the first housing, the second housing defining a second fluid pathway continuous with the tubing string and with the first fluid pathway; a second port defined in the second housing for fluid communication between the second fluid pathway into the wellbore; a ball valve disposed the tubing string between the first port and the second port, the ball valve adapted to receive a deformable ball, wherein when seated the ball prevents fluid flow through the fluid pathway of the first housing; and a sealing device deployed on the tubing string below the first housing, the sealing device for sealingly engaging the wellbore and thereby defining a wellbore interval to be treated above the sealing device.
In one embodiment, the ball valve is disposed within the first housing above the first port.
In one embodiment, the second housing comprises a jet perforation device and the lateral port is a jet perforation nozzle.
In accordance with a third aspect of this invention, there is provided a method of selectively treating a wellbore, the method comprising: deploying a tool assembly on a tubing string into a wellbore, the tool assembly comprising a first housing and a second housing, the first and second housing being fluidically continuous with the tubing string and the first and second housing each having a fluid port for fluid communication from the tubing string to the wellbore, and a ball valve between the ports of the first and second housing, the ball valve comprising a ball seat for receiving a deformable ball having a pressure deformation threshold; delivering fluid to through the tubing string to the first housing to effect a wellbore treatment through the port of the first housing; dropping the deformable ball through the tubing string to land on the ball seat, thereby blocking fluid flow from the tubing string to the first housing; continuing to deliver fluid to the tubing string while the ball remains seated in the valve seat; increasing the pressure differential across the ball seat to exceed the pressure deformation threshold of the ball, thereby unseating the ball from the ball seat so that fluid can flow through the first housing.
In accordance with one embodiment, the method further includes delivering fluid to the tubing string to effect fluid treatment through the port of the first housing once the ball is unseated.
In accordance with another embodiment of the invention, the method further includes passes the ball through a lower end of the ball valve to a region within the first housing after the ball has been deformed.
In accordance with another embodiment, the method further comprising delivering fluid suitable for fracturing before the ball has been seated and delivering fluid suitable for sand jet perforation once the ball has been seated.
In accordance with another embodiment, the method further includes sealing the tubing string in the wellbore below the first port prior to fluid delivery down the tubing string.
In accordance with a fourth aspect of the invention, there is provided a method for selective delivery of treatment fluid from tubing string to a wellbore, the method comprising the steps of: deploying a tool assembly within a wellbore on tubing string, the tool assembly comprising a first housing and a second housing, the first and second housing being fluidically continuous with the tubing string and the first and second housing each having a fluid port for fluid communication from the tubing string to the wellbore, and a ball valve between the ports of the first and second housing, the ball valve comprising a ball seat for receiving a deformable ball having a pressure deformation threshold; delivering treatment fluid through a tubing string to effect treatment of the wellbore through the port of the first housing; delivering a ball to the tubing string, the ball of suitable size to seal against the ball seat; seating the ball against the ball seat; continuing to deliver fluid to the tubing string to effect fluid treatment of the wellbore through the port of the second housing; delivering fluid treatment to the wellbore annulus at a rate suitable to reverse circulate the ball to surface through the tubing string; and delivering fluid to the tubing string to effect fluid treatment through the port of the first housing.
Other aspects and features of the present invention will become apparent to those skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

FIG. 1 is a schematic drawing of a dual treatment device in accordance with an embodiment of the invention.

FIG. 2 a is a schematic cross sectional view of the first treatment housing, in accordance with an embodiment of the invention.

FIG. 2 b is a sectional view taken from A-A of FIG. 2 a, in accordance with an embodiment of the invention.

FIG. 3 is a schematic perspective view of the ball valve insert, in accordance with an embodiment of the invention.

FIG. 4 shows a schematic view of a tool assembly incorporating the dual treatment device, according to one embodiment of the invention.

FIG. 5 illustrates schematically the different stages of wellbore treatment mediated by the dual treatment device, according to an embodiment of the invention.

FIG. 6 illustrates schematically an embodiment of the dual treatment device disposed in a casing string with a sliding sleeve, according to an embodiment of the invention.

DETAILED DESCRIPTION

Generally, the present invention provides a device and method for providing multiple tubing-conveyed fluid pathways through a single tool assembly. Delivery of fluid though a first fluid pathway effects a first fluid treatment within a wellbore interval, while delivery of fluid through a second fluid pathway effects a second fluid treatment within the wellbore. A ball valve allows for diversion of fluid from the first fluid pathway to the second fluid pathway upon delivery of a deformable ball to the ball valve. Hydraulic pressure is applied to force the ball against the seat and thereby build up pressure within the tool assembly and/or tubing string above the sealed ball seat. Once treatment through the second fluid pathway is complete, the deformed ball may be removed, either by reverse circulation from the tool assembly to surface, or may be forced through the seat by application of increased hydraulic pressure so as to deform the ball. Such deformable balls may be engineered to deform at a particular threshold pressure, based on the range of operating pressures of the downhole operation of interest.
Referring to the drawings, FIG. 1 shows a dual treatment device for completion operations according to one embodiment of the present invention. The device is generally designated by reference 10 and is intended to be incorporated into a tubing string, with upper end 13 of dual treatment device 10 being adapted for connection to the upper tubing string and lower end 14 of dual treatment device being adapted for connection to the lower tubing string. Fluid flow would occur lengthwise through the tubing string, and thus, through the dual treatment device 10, during wellbore operations. The fluid flow can be diverted to various fluid ports positioned at different regions of the device by dropping a deformable ball through the tubing string, as described below.
Dual treatment device 10 includes a first treatment housing 15 defining a first fluid pathway 20 in the interior of the first treatment housing, the first fluid pathway 20 being continuous with the tubing string. Ports 25 are formed through the wall 30 of the first treatment housing 15. The ports 25 of the first treatment housing are also herein referred to as “first ports” to refer to the first ports of dual treatment device 10. The first ports 25 allow for lateral fluid communication from the tubing string to the wellbore, and more particularly, to the annulus defined between the tubing string and the wellbore casing. Device 10 includes a second treatment housing 35 disposed on the tubing string above first ports 25. The second treatment housing 35 includes a fluid pathway 21, herein referred to as the second fluid pathway. Second fluid pathway 21 is fluidically continuous with the tubing string and with first fluid pathway 21. The second treatment housing 35 includes ports 45. The ports 45 of the second treatment housing 35 are herein referred to as “second ports”. Ports 45 are fluidically continuous with second fluid pathway 21.
In the embodiment shown, the second treatment housing 35 includes a jet perforation device, and the second ports 45 are jet perforation nozzles. The diameter of the jet perforation nozzles 45 is generally smaller than the diameter of the first ports 25, so that during fluid delivery through the tubing string, the pressure differential across the jet perforation nozzles 35 and the annulus is greater than the pressure differential across the first ports 25 and the annulus. Thus, when fluid flow through the first treatment housing 15 is unobstructed, fluid would preferentially exit the tubing string to the wellbore through first ports 25. A ball valve 50 for receiving a deformable ball is disposed between the first treatment housing 15 and second treatment housing 35.
Although the illustrated embodiment shows first ports 25 as longitudinal slots extending lengthwise through the wall of the first treatment housing 15, other port configurations are possible. For example, the ports may be circular and may be disposed around the circumference of the first treatment housing. While the embodiment shown includes multiple first ports 25 disposed around the first treatment housing 15, there may be a single port. Similarly, variations in the nozzles 45 in the jet perforation device 35 are possible. For example, the nozzles may be angled, and may be disposed around the device in any manner suitable to achieve perforation of the wellbore region of interest.
It will also be appreciated that the invention generally relates to a device and method for performing multiple operations within a length of tubing, the length of tubing having multiple treatment ports, slots, apertures or other pathways through which fluid can be delivered laterally from the tubing string to the wellbore. Accordingly, the term “housing” is generally used to refer to a length of tubing through which fluid flow can occur lengthwise through the tubing string and having a fluid pathway for lateral fluid communication from the tubing string to the wellbore. For example, in the embodiment shown, the first treatment housing 15 is mounted as a single tubular element with associated ball valve 50. In an alternative arrangement, the ball valve and second treatment housing may also form a single tubular element, with the ball valve located below the ports of the second housing. It will be appreciated that the housings can be connected to each other various ways, such as through adaptors or connectors or by other means known in the art.
Referring to FIG. 2 a, first treatment housing 15 is shown. First treatment housing 15 includes a wall 30 which defines a first fluid pathway 20, the first fluid pathway 20 being continuous with the tubing string. Ports 25 extend longitudinally through wall 30 of first treatment housing 15. A ball valve 50 is disposed within the upper end of first treatment housing 15 above first ports 25. Ball valve 50 includes a body 55 defining a hollow bore 60. The bore 60 of ball valve 50 is continuous with the tubing string, so that when bore 60 is unobstructed, fluid can flow from the surface of the wellbore, through the tubing string to the first fluid pathway 20. The lower end of the bore 60 is of smaller diameter than the diameter of the ball in the undeformed state, but is of larger diameter than the ball in its deformed state, so that deformed balls can pass through bore 60. The upper body 55 has a tapered inner surface that forms the ball seat 65. The ball seat 65 has a width that is suitable for grasping a deformable ball 125 when ball 125 is launched from the surface and down the tubing string, in such a way so as to substantially prevent fluid flow to the first treatment housing 15. Deformable ball 125 has a threshold pressure differential. When the threshold deformation pressure has been exceeded, ball 125 becomes deformed and can longer engage with ball seat 65. The ball seat 65 is arranged in body 55 in such a way fluid flow forces deformed balls through the length of bore 60 of ball valve 50.
In the embodiment shown, ball valve 50 is provided as an insert, threadedly connected to the first treatment housing 15 through set screws 80, the set screws spaced 120 degrees apart, and sealed to the first treatment housing 15 by O-rings 56. It is possible, however, that the first treatment housing 15 could be engineered with the ball valve 50 drilled directly into the housing wall 30.
As shown in FIGS. 2 b and 3, the bottom end of body 55 has a plurality of fingers 66 extending downwardly, radially spaced around the diameter of the bore 60. The tips of fingers 66 have tapered inner surfaces 67, to assist in preventing deformed balls from re-entering through the lower end of ball valve 50 once they have been unseated from the ball seat 65, and more particularly, to prevent upward movement of deformed balls that have passed through to first treatment housing 15. Thus, the plurality of fingers act as a ball trap or ball catcher for preventing upward movement of deformed balls, for example, during reverse circulation through the wellbore annulus.
With reference to FIG. 4, an embodiment of the invention is shown in which dual treatment device 10 is incorporated as part of a downhole tool assembly 75. Suitable downward tools are known in the art. The downhole tool shown in FIG. 4 is similar to that described in Canadian Patent No. 2,693,676 issued to Stromquist and assigned to the assignee of the present invention and which is herein incorporated by reference. The dual treatment device 10 shown in FIG. 1 is incorporated into the tool assembly: a first treatment housing 15, with associated ports 25 for carrying out a first wellbore treatment, a second treatment housing 35 (e.g. a jet perforation device) with nozzles 45, and a ball valve disposed between jet perforation device 35 and first ports 25 are all present. The tool assembly 75 also includes a compressible sealing element 95. Mechanical slips 96 may also be present to assist in actuation of sealing element 95. An equalization valve 100 is also present, with an equalization port 105 is defined in the wall of equalization valve 100. A mechanical casing collar locator 111 is present for locating tool assembly 75 in the appropriate region of the wellbore. In downhole tool assembly 75, fluid may be delivered down the tubing string to effect both fluid jet perforation, through the nozzles 45 of jet perforation device 35, and fracturing, through the first ports 25 in first treatment housing 15.
While the embodiment shown in FIG. 4 illustrates a particular downhole tool, other arrangements are possible. For example, the tool may incorporate any type of anchor device, suitable for locating the tool assembly in the wellbore region of interest. Those skilled in the art would also appreciate that other types of sealing devices may be used. The tool may further include additional devices, such as pump down cups, to assist in manipulating the tool assembly, or adding functionality thereto.
When dual treatment device 10 is in the unactuated state (i.e. before the ball is seated on the ball seat 65), fluid delivered from the surface through the tubing string will primarily exit through the first ports 25. This is because first ports 25 are generally larger in size than the nozzles 45 of the jet perforation device 35, and thus, a larger pressure differential is required in order to effect fluid jetting through nozzles 45. However, there may be some fluid exiting through nozzles 45, even when fluid is predominantly flowing through the first treatment housing 15 and out first ports 25. When a deformable ball is delivered from the surface with treatment fluid, the ball will travel through the tubing string. The ball, acting under pressure of the supply of the fluid, is engaged in the ball seat 65 and thereby blocks fluid communication to first ports 25 of the first treatment housing 15. Thus, when the ball 125 is dropped, and lateral fluid flow through first ports 25 is prevented, fluid will be diverted to jet nozzles 45, regardless of the relative size of jet nozzles 45 and first ports 25.

Operation

FIG. 5 shows, in a highly schematic manner, successive stages 1, 2 and 3 of the use of the dual treatment device 10 and the associated launching of a deformable ball through tubing string 110 in a cased wellbore. When the tool string is configured as shown in the drawings the wellbore intervals will typically be treated from the lowermost interval and proceed to further intervals, moving sequentially uphole.
In use, downhole tool assembly 75, including dual treatment device 10, is lowered as part of a tubing string 110 into a wellbore to an interval to be treated. An annulus 106 is defined between tubing string 110 and casing 120. The downhole tool assembly 75 is generally located at the appropriate position through mechanical collar locator 111. Sealing element 95 is then engaged against the casing 120 (for example, through mechanical actuation as is known in the art), thus defining a wellbore interval to be treated above sealing element 95. Treatment fluid may be delivered down the tubing string 110 to effect perforation, fracturing, debris cleaning, or various actuation functions, such as movement of a sliding sleeve.
In the first position (Stage 1), prior to the launching of the ball, treatment fluid is directed through the tubing string 110, primarily to first ports 25. Sealing element 95 is engaged against the casing 120 and therefore, fluid flow across the sealing element 95 to the wellbore region below the sealing element is largely prevented. Fluid from the tubing string 110 exits first ports 25 of first treatment housing 15 through perforations 137 in casing 120. The fluid may be fracturing fluid, and the wellbore region around first ports 25 is then fractured, as is indicated by arrows 135.
In Stage 2, the deformable ball 125 is launched while continuing to deliver treatment fluid from surface. The pressure of the treatment fluid causes the ball 125 to engage within ball valve 50, preventing fluid flow to the first treatment housing 15. Treatment fluid, such as fluid suitable for sand jet perforation, may then be delivered through the tubing string 110 to jet perforation device 35 and such fluid exits nozzles 45. The flow of perforating fluid (such as that suitable for sand jet perforation) through nozzles 45 is indicated by 136. This flow of fluid results in the creation of perforations 137 in the region of the casing adjacent the perforation device 35.
To ensure ball 125 remains seated in ball seat 65 during jet perforation, the pressure differential across the ball seat 65 should be less than the threshold ball deformation pressure. Accordingly, the ball is selected to deform under a hydraulic pressure differential that is greater than the pressure differential required to carry out jet perforation at the interval depth. Generally, the pressure for fracturing (e.g. when treatment fluid is exiting first treatment ports 25) is greater than the pressure for perforating (e.g. when treatment fluid is exiting jet nozzles 45). For example, the pressure required for perforation may be about 2000 psi. The pressure for fracturing may be about 4000-6000 psi, and the ball may be designed to deform at about 3000 psi.
In Stage 3, once perforation is complete, the pressure differential across the ball seat 65 is increased, for example, through increased volume of fluid delivery down the tubing string, and because the seating of ball results in a pressure increase across the ball seat. Once the pressure differential across the ball seat 65 exceeds the deformation threshold of ball 125, the ball 125 will deform sufficiently to pass through the bore 60 of ball valve 50 to a region within the first treatment housing 15. The deformed balls are shown schematically as dotted lines. The region of the first treatment housing 15 for receiving deformed balls is also referred to herein as a ball containment region. Fingers on the ball valve 50 prevent re-entry of deformed balls into the ball valve 50. The disengagement of ball 125 from ball valve 50 will result in the re-opening of fluid flow through first treatment housing 15 and through first ports 25. Once fluid flow through the first treatment housing 15 is re-established, additional fracturing fluid may be pumped downhole and would primarily exit through first ports 25. As stated above, some fluid flow may still occur through the jet nozzles 45, even when treatment fluid predominantly exits first ports 25.
As will be readily understood, the pressure differential across the ball seat 65 or across the jet perforation nozzles 45 may be adjusted by adjusting the rate of fluid delivery to the tubing string 110 or to the wellbore annulus. The hydraulic pressure in each may be monitored as is known in the field, to determine appropriate adjustment as necessary.
It will also be appreciated that although the illustrated embodiment includes Stage 3, whereby delivery of treatment fluid through the first treatment housing 15 is resumed following deformation of the ball. However, it is also possible that no additional treatment through first ports 25 is needed, and that fracturing fluid is delivered to perforations 137 formed in the casing next to jet perforation device 35 immediately following sand jet perforation in that region.
It will also be appreciated that while the illustrated embodiment primarily relates to the dual treatments of perforating and fracturing, delivery of other fluids through the first ports and through the second ports is also possible using the dual treatment device 10 of the present invention.

Ball Composition

When deformable balls are used to seal the primary fluid pathway, custom deformable balls may be required, for example, to correspond to the pressure seen during the downhole operation of interest. Deformable ball sealers, of the type typically used to temporarily seal perforations within a wellbore, are typically formed from materials such as elastomeric substances and/or wax, or other predictably deformable material. Balls composed of high stiffness polymers and thermoplastics such as polytetrafluoroethylene and polyoxymethylene have provided suitable composition for the presently described application.
The ball should be resistant to deformation at pressures encountered during fluid treatment through the second fluid treatment pathway (e.g. jet perforation). However, the ball may be deformable at pressures lower or higher than those required during fluid treatment through the first fluid treatment pathway (e.g. fracturing). For example, following treatment through the second fluid pathway, the pressure differential across the valve seat is increased until deformation and release of the ball from the ball seat is achieved. Fluid treatment through the first treatment pathway may be resumed. If fluid treatment through both the first and second fluid pathways is effected at similar pressures, a ball that deforms at significantly greater pressure differential may be used as long as the tool assembly and tubing string can accommodate the higher pressures required to achieve passage of the deformable ball. Otherwise, reverse circulation of the ball to surface through the tubing string may be considered.
In the embodiment shown in the figures, fracturing of a wellbore segment occurs via the first treatment housing. Fracturing of a formation through a cased and perforated wellbore may take place at a first tubing pressure. However, fluid jet perforation may take place at a second tubing pressure. Accordingly, a ball would be selected that will not deform at pressures less than the second tubing pressure. When the first tubing pressure is significantly greater than the second tubing pressure, it may be convenient to have the ball deformable at pressures between the first and second tubing pressures, so the ball can deform and pass through the seat as the pressure is increased. For example, a ball can be dropped down the tubing string to seal against the ball seat 65 and enable perforation at a first pressure differential, after which the pressure differential across the ball seat can be increased by delivery of fracturing fluid to the tubing string. Once suitable pressure differential is achieved, the ball will deform and fracturing will be initiated as fluid passes through the open ball seat 65 to the ports 25 of the first treatment housing 15.

Alternative Embodiments

Casing string: The invention was described in reference to a cased wellbore. It will be appreciated that variations in the casing are possible. For example, the wellbore may be cased and unperforated, cased and perforated, or cased with perforated collars or sleeves incorporated into the casing at predetermined intervals. When the wellbore is cased and pre-perforated (or otherwise already contains apertures to provide access to the formation), the secondary fluid pathway may not be used frequently. However, should one of the perforations fail to take up fluid, or should it be determined that additional perforations are necessary, the primary fluid flow pathway can be temporarily blocked by delivering a deformable ball to the ball seat. The ball can be subsequently removed by deformation through the ball seat, or by reverse circulation of fluid through the annulus.
Reverse circulation: The illustrated embodiment shows the use of a deformable ball which is released from its position in the ball seat 65 when the ball threshold deformation pressure is exceeded. It is possible to release the ball from its seated position by reverse circulation through the annulus. To unseat the ball from the ball seat, fluid can be reverse circulated through the annulus 106 (once sealing element 95 has been released from its engagement against the casing), and upwardly into ports 25 in first treatment housing 15. This upward force releases the ball from its seated position. When the ball is to be reverse circulated to surface, a lightweight, non-deformable composition may be suitable, such as aluminum alloys, composites, and the like. Use of a heavy material, for example, steel, may make reverse circulation to surface difficult.
Treatment housings: The invention generally relates to a method and system for diverting fluid flow in a downhole tool to carry out two different treatments. Accordingly, the invention has applicability in any downhole tool comprising a section of tubing having suitable, longitudinally spaced-apart fluid treatment ports, apertures, slots or other fluid pathways for performing treatment operations between the tubing string and the wellbore. For example, the first treatment housing may not be incorporated as an additional tubular region, but rather may be part of the existing tool assembly. For example, in a downhole assembly such as that illustrated in the figures, fluid treatment may be delivered down the tubing string and exits port 105 of equalization valve 100, the equalization valve housing forming the first treatment fluid housing of the tool assembly. A ball valve would then be provided on the tubing string between the equalization port 105 and the second fluid treatment housing 35 (which may be a jet perforation device). In yet another embodiment, the lower mandrel of the tool assembly may serve as the first treatment housing, with ports or apertures located in the mandrel allowing for fluid treatment to the wellbore. For example, there may be apertures present in the mechanical collar locator 111 or on the tubular on which the mechanical collar locator is disposed. Fluid can be delivered to the wellbore through these apertures. In this embodiment, the mechanical collar locator (or tubular on which the locator is disposed) would form the first treatment housing, and the apertures in the mechanical collar locator would form the first ports.
Sliding Sleeve: The dual treatment device of the present invention may be used in conjunction with a casing string having a sliding sleeve. A suitable sliding sleeve system is described in Canadian Patent No. 2,738,907, issued to Getzlaf and assigned to the present assignee and which is herein incorporated by reference. This embodiment is schematically illustrated in FIG. 6. Casing string 145 includes an inner sliding sleeve 150 disposed within a ported sub, the ported subs being connected to each other along the casing string. A downhole tool assembly 180 including dual treatment device 10 is deployed as part of a tubing string 155. First treatment housing 15 with first ports 25 are present, as is jet perforation device 35 and nozzles 45. A ball valve (not shown) is disposed between the first treatment housing 15 and jet perforation device 35. The tool assembly 180 includes a sealing element 95, as well as a sleeve locator 175. Optionally, a decompression sub 180 may be present when the lowermost interval of a wellbore is to be treated.
In use, hydraulic pressure may cause sliding sleeve 150 to shift downward, engaging with locator 175. This downward movement of sleeve exposes ports 160 in ported sub. Fracturing fluid can be applied through tubing string, exiting first ports 25 present in first treatment housing 15 and resulting in the fracturing 135 of the region around ports 160 of ported sub. If perforation is desired in the region of the casing string 145 above ports 160, a ball can be dropped to prevent fluid flow down the tubing string to the first treatment housing 15. This results in fluid diversion to jet perforation nozzles 45.
The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the invention.

Claims

What is claimed is:

1. A downhole treatment assembly, the assembly comprising:

a first housing disposed on a tubing string, the first housing defining a first fluid pathway continuous with the tubing string and including a wall defining a first port for passage of fluid between the first fluid pathway and the wellbore;

a second housing disposed on the tubing string above the first housing, the second housing defining a second fluid pathway continuous with the tubing string and with the first fluid pathway, the wall of the second housing including a second port through which fluid can flow from the tubing string to the wellbore; and

a ball valve disposed on the tubing string between the first port and the second port, the ball valve comprising a ball seat at the upper end of the valve, the ball seat configured to receive a deformable ball, and a ball trap for preventing unseated, deformed balls from re-entering the ball valve.

2. The assembly of claim 1, wherein the ball valve is mounted within the first housing above the first port.

3. The assembly of claim 1, wherein the second housing comprises a jet perforation device and the second port comprises a jet nozzle.

4. The assembly of claim 1, wherein the ball valve is provided as a removable insert in the first housing.

5. A system for wellbore treatment, the system comprising:

a first housing disposed on a tubing string, the first housing defining a first fluid pathway continuous with the tubing string;

a first port defined in the first housing for lateral fluid flow from the first fluid pathway to the wellbore;

a second housing disposed on the tubing string above the first housing, the second housing defining a second fluid pathway continuous with the tubing string and with the first fluid pathway;

a second port defined in the second housing for fluid communication between the second fluid pathway into the wellbore;

a ball valve disposed the tubing string between the first port and the second flow port, the ball valve adapted to receive a deformable ball, wherein when seated the ball prevents fluid flow through the fluid pathway of the first housing; and

a sealing device deployed on the tubing string below the first housing, the sealing device for sealingly engaging the wellbore and thereby defining a wellbore interval to be treated above the sealing device.

6. The system of claim 5, wherein the ball valve is disposed within the first housing above the first port.

7. The system of claim 5, wherein the second housing comprises a jet perforation device and the lateral port is a jet perforation nozzle.

8. A method of selectively treating a wellbore, the method comprising:

deploying a tool assembly on a tubing string into a wellbore, the tool assembly comprising a first housing and a second housing, the first and second housing being fluidically continuous with the tubing string and the first and second housing each having a fluid port for fluid communication from the tubing string to the wellbore, and a ball valve between the ports of the first and second housing, the ball valve comprising a ball seat for receiving a deformable ball having a pressure deformation threshold;

delivering fluid to through the tubing string to the first housing to effect a wellbore treatment through the port of the first housing;

dropping the deformable ball through the tubing string to land on the ball seat, thereby blocking fluid flow from the tubing string to the first housing;

continuing to deliver fluid to the tubing string while the ball remains seated in the valve seat; and

increasing the pressure differential across the ball seat to exceed the pressure deformation threshold of the ball, thereby unseating the ball from the ball seat so that fluid can flow through the first housing.

9. The method of claim 8, further comprising delivering fluid to the tubing string to effect fluid treatment through the port of the first housing once the ball is unseated.

10. The method of claim 8, further comprising passing the ball through a lower end of the ball valve to a region within the first housing after the ball has been deformed.

11. The method of claim 8, further comprising delivering fluid suitable for fracturing prior to seating the ball and delivering fluid suitable for sand jet perforation after seating the ball.

12. The method of claim 8, further comprising sealing the tubing string in the wellbore below the first housing prior to fluid delivery down the tubing string.

13. A method for selective delivery of treatment fluid from tubing string to a wellbore, the method comprising the steps of:

deploying a tool assembly within a wellbore on tubing string, the tool assembly comprising a first housing and a second housing, the first and second housing being fluidically continuous with the tubing string and the first and second housing each having a fluid port for fluid communication from the tubing string to the wellbore, and a ball valve between the ports of the first and second housing, the ball valve comprising a ball seat for receiving a deformable ball having a pressure deformation threshold;

delivering treatment fluid through a tubing string to effect treatment of the wellbore through the port of the first housing;

delivering a ball to the tubing string, the ball of suitable size to seal against the ball seat;

seating the ball against the ball seat;

continuing to deliver fluid to the tubing string to effect fluid treatment of the wellbore through the port of the second housing;

delivering fluid treatment to the wellbore annulus at a rate suitable to reverse circulate the ball to surface through the tubing string; and

delivering fluid to the tubing string to effect fluid treatment through the port of the first housing.

14. The method of claim 13, wherein the second fluid treatment housing is a jet perforation device.

15. The method of claim 13, wherein treatment through the first treatment pathway comprises fracturing.

16. The method of claim 13, further comprising the steps of setting a sealing device against the annulus defined between the tubing string and the wellbore prior to delivering the ball and unsetting the sealing device prior to reverse circulation.