Ball catcher for wellbore operations

A ball catcher is adapted to be fluidly connected to a wellhead port to receive wellbore fluids and balls carried therewith. A diverter is fit to the catcher body and has a wellhead end positioned to intercept the fluid flow from the wellhead port so as to divert debris and balls carried therein into a ball recovery chamber. The diverter has a bore in fluid communication with the flow outlet and the wellhead end has flow passages formed therethrough to the bore for receiving the fluid flow free of debris and balls and discharging the fluid flow from the catcher body. The diverter and the ball recovery chamber can be connected to quick removal for replacement, repair or cleaning.

FIELD OF THE INVENTION

This invention relates generally to apparatus and method for the retrieval of balls from a wellbore, such as drop balls, frac balls, packer balls and other balls for interacting with downhole tools in the wellbore. The balls are recovered with the fluid stream which flows from the wellbore, such as after stimulation operations. More particularly, the apparatus and method uses apparatus affixed to the wellhead for intercepting, separating or diverting the balls from the fluid flow for recovery.

BACKGROUND OF THE INVENTION

It is known to conduct fracturing or other treating procedures in a wellbore by isolating zones in the wellbore using packers and the like and subjecting the isolated zone to treatment fluids at treatment pressures. In a typical fracturing procedure, for example, the casing of the well is perforated to admit oil and/or gas from the formation into the well and fracturing fluid is then pumped into the well and through these perforations into the formation. Such treatment opens and/or enlarges draining channels in the formation, enhancing the producing ability of the well. Alternatively, the completion can be an open hole type that is completed without Casing in the producing formation area.

It is desired to stimulate multiple zones, or intervals within the same zone, using onsite stimulation fluid pumping equipment (pumpers). A packer arrangement is inserted at intervals isolating one zone from an adjacent zone. It is known to introduce a drop ball through the wellbore to engage one of the packers in order to block fluid flow therethrough. Passage through a downhole packer is thereby plugged off with this drop ball that is pumped into the wellbore during the stimulation flush. The drop ball blocks off this downhole packer, isolating the wellbore uphole of the downhole packer and consequently a second zone, above this downhole packer, can be stimulated. Once stimulated, a subsequent drop ball can be dropped to block off a subsequent packer uphole of the blocked packer for stimulation thereabove. This continues until all the desired zones are stimulated.

At surface, the wellbore is generally furnished with a frachead unit including a multi-port block or a Y-type frac header, isolation tool or the like, which provides fluid connections for introducing stimulation fluids including sand, gels and acid treatments.

After the well operations, fluid from the well is flowed to surface through the wellhead or frachead. The fluid is urged from the well such as under formation pressures and/or the influence of a gaseous charge of CO2or N2. The fluid from the well exits the wellhead from a horizontally extending fitting. To separate the balls from the fluid, it is known to use a cross fitting apparatus such as a plate extending across the flow path from the wellhead. The plate is typically a plate across the flow path having large slots or screen at the face such as an upside down “U” or fork shape for impeding balls recovered with the fluid while permitting fluid to flow therethrough the “U” shape

It is known for balls, of which various sizes are employed in one well operation, to become lodged at the prior art U-shape or screen and block fluid flow. In other instances, the balls can break apart which encourages further blockages.

There is a need for a more effective apparatus for retrieving balls from a wellbore after a well operation.

SUMMARY OF THE INVENTION

Embodiments of the present invention intercept and divert balls returning with wellbore fluid into a ball recovery reservoir. A ball catcher body includes a replaceable diverter which separates balls and debris from the fluid flow.

In one aspect of the invention, apparatus is provided for retrieving oversize debris and balls carried with a fluid flow from a wellhead port. A catcher body is adapted to be fluidly connected to the wellhead port and has a flow outlet. A diverter is fit to the catcher body and has a wellhead end positioned to intercept the fluid flow from the wellhead port so as to divert debris and balls carried therein into a ball recovery chamber. The diverter has a wellhead end has flow passages formed therethrough for receiving the fluid flow free of debris and balls. The diverter has a bore in fluid communication with the flow outlet. Fluid flow through the flow passages enters the bore for discharge from the catcher body.

In another aspect of the invention, the catcher body is connected and positioned along a fluid flow path from the wellhead. The catcher body has a first flow path contiguous with fluid flow from the wellhead and an intersecting stagnant ball recovery reservoir. The catcher body has a catcher flow outlet for fluid free of debris and balls. The debris and balls have a first velocity vector along the flow path towards the catcher flow outlet. A diverter, fit to the catcher body and having a wellhead end extending into the flow path intercepts the fluid flow. The diverter has a bore being open at a tail end and in fluid communication with the catcher flow outlet. The diverter has a diverter face at the wellhead end and being positioned inline with the first velocity vector for intercepting and substantially arresting the debris and balls and for diverting the debris and balls along into the ball recovery reservoir. An annular chamber formed in the discharge outlet about the wellhead end of the diverter receives the fluid flow. A plurality of flow passages extending through the wellhead end of the diverter conduct fluid flow, free of debris and balls, from the annular chamber to the bore for discharge through the tail end.

As a result, a reliable and easy to clean ball catcher is provided for servicing wells after stimulation and cleaning operations such as after drilling removal of bridge plugs and the like.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFIG. 1, in the context of fracturing a formation traversed by a wellbore and recovering fluid therefrom, a wellhead10is connected to the wellbore (not shown) for introducing fracturing fluid and drop balls for various operations to the wellbore. The wellhead comprises a shutoff valve11and a flow port12thereabove, typically integrated with a frachead. Thereafter a fluid flow F carrying debris and drop balls B are flowed out of the well through the flow port along a fluid path13. While a variety of materials such as frac sand are carried out of the wellbore with the fluid flow, for the purposes of simplicity herein, this application discusses the apparatus and operations in the context of the recovery of balls.

With reference toFIG. 2, an embodiment of a ball catcher20is adapted to be connected to the wellhead's flow port12, such as through an isolation valve14, for catching drop balls B before they travel downstream and adversely affect other equipment.

As shown, the ball catcher20comprises a catcher body21fit to the wellhead10or isolation valve14at a wellhead connection using industry approved threaded or flanged connections. The catcher body21further comprises a stagnant reservoir or ball recovery chamber22which intersects the fluid path13. Fluid flow F flows along a first velocity vector or fluid path13and is interrupted with a diverter23fit to a catcher flow outlet24. The fluid flow F carries the balls to impact the diverter, separating fluid flow F and the balls B for discharge of the fluid flow from the catcher flow outlet24and recovery of the balls at the ball recovery chamber22.

With reference also toFIGS. 3A-3C, the diverter23has a wellhead end30for intercepting the fluid flow F and a diverter body31fluidly sealed, such as by an O-ring29, to the catcher flow outlet24. The diverter body31has bore32and a fluid discharge or tail end33. The bore32is open at the tail end33and in fluid communication with the catcher flow outlet24for the collection and discharge of fluid flow F liberated of oversize solids such as the balls B. The wellhead end30of the diverter23projects into the fluid path13and comprises a diverter face34positioned in the fluid path13. The diverter face34is positioned inline with the first velocity vector for intercepting and substantially arresting the debris and balls B and for diverting the debris and balls along into the ball recovery chamber22.

Referring also toFIG. 2, kinetic energy in balls B is dissipated at the diverter face34and the balls fall under gravity into the ball recovery chamber22. The ball recovery chamber22is intersects and fluidly contiguous with, but diverges from, the flow path13. As shown, the flow path can be substantially horizontal from the wellhead10and ball recovery chamber22is positioned below the diverter face34. The diverter face34can be angled downward, from top to bottom and away from the fluid path13, for directing, deflecting or urging the balls downward into the ball recovery chamber22. A cross-sectional dimension of the diverter face34can be substantially the diameter of that of the flow path13. Best seen inFIG. 3, the diverter face34can have a concave face having an axis oriented generally downwards towards the ball recovery chamber22.

With reference toFIG. 4, the diverter face34diverts oversize solids, such as debris or balls B.

In one embodiment, the diverter face34diverts a portion or all of the fluid flow F therearound. An annular chamber40is formed in the catcher body21or catcher flow outlet24about the wellhead end30of the diverter23. The annular chamber40receives fluid flow F continuing to flow substantially along the flow path13and about the diverter face34. The fluid flow F flows through the annular chamber40and inward through flow passages41formed or extending through the wellhead end30. The bore32receives fluid flow F free of debris and balls for discharging the fluid flow from the catcher body.

With reference toFIGS. 5A-5C, the diverter23can be removeably fit to the catcher body, similar to a cartridge, for ease of replacing the wear components. The diverter body31can be one piece31s, as shown inFIG. 5C, or two or more pieces31m, as shown inFIGS. 5A and 5B. A two-piece body31mpermits the most wear prone portion, the wellhead end30, being separable from the tail end33. The wellhead end30could be manufactured of wear resistant material. Alternatively, the flow passageways41are wear resistant, being coated with wear resistant material or be manufactured using replaceable, hardened orifices (not shown). The wellhead end30comprises the diverter face34and the flow passages41for conducting fluid flow F to the bore32. The wellhead end30of a two-piece diverter body31mhas a threaded pin portion42and fluid seal43for sealing to a box end44of the tail end33. The tail end33has a second fluid seal, such as the O-ring29, for sealing to the catcher body21.

As shown inFIG. 4, the diverter body31can be cylindrical for insertion into the catcher flow outlet24and secured or retained therein by quick connection such as a coupling50and hammer nut51. The diverter can also be retained using a flanged or similar connection (not shown). The coupling50can be threadably engaged with the diverter's tail end33. Replacement of the diverter can be effected by equalizing fluid pressure in the catcher body21, releasing the hammer nut51and replacing the entire diverter body31or replacing a worn wellhead end30of a two-piece diverter body31m.

The flow passages41can be radial flow passages41or extend substantially in-line with the flow path13. As shown inFIGS. 5A-5Cand5E, some flow passages41though the wellhead end30can be radial, extending to the bore32. Further, the flow passages41can be oriented radially and opposingly positioned to neutralize fluid energy as the fluid flow F enters the diverter bore32. The plurality of flow passages can be arranged in pairs of opposing flow passages41pfor directing fluid flow F to impinge each other within the bore32and dissipate energy to minimize erosion.

The flow passages41in the diverter are sized to pass the fluid flow F and can be oversized to accommodate accumulative loss due to plugging. Further, the fluid passages can be sized to be large (FIGS. 5B,5C and5E) for passing a range of particulates to the downstream equipment. In another embodiment, the fluid passages can be small (FIGS. 5A and 5D) for blocking the passage of large particulates for the protection of the downstream equipment, the large particulates being collected instead in the ball recovery chamber22. A plurality of small flow passages41, such as those shown inFIG. 5A, can act as screen to reject undesirable particulates. Similarly, a cylindrical screen could be fit over larger flow ports.

For example, with reference to the embodiment ofFIG. 4, eight flow passages41arranged in four pairs41p, positioned at quadrants, at ⅛″ diameter each can pass 5-7 m3(per hour) of fluid (such as water or lighter hydrocarbons). Eight flow ports at 5/32″ diameter can (each) pass 9-11 m3/hour and ¼″ ports can (each) pass 20-25 m3(per hour). The greater the number of flow passages passing the return fluid, the less the erosion, thus increasing the life and efficiency of the diverter or diverter cartridge.

With reference toFIG. 6, in another embodiment, the diverter23can further comprise in-line flow ports through the diverter face34and oriented into the fluid path13. The in-line flow passages are smaller in diameter than are the solids or balls B being rejected and collected in the ball recovery chamber22.

Operation

As shown in the embodiments shown inFIG. 2, upon establishing fluid flow F from the wellbore, balls B (and other debris) engage the diverter face34and are collected in the ball recovery chamber22. Fluid flow F continues downstream, passes through the diverter's flow passages and is discharged through the diverter's tail end33to other equipment as is the usual practice in the industry.

Periodically, the wellhead10is shut in and a bleed valve60, such as positioned atop the catcher body21, is vented to equalize pressure therein and the ball recovery chamber22can be emptied of debris and balls B. The diverter23can be quickly inspected and replaced as necessary, therefore decreasing the down time in flow back procedures. The ball recovery reservoir can further comprise a pup joint55coupled releaseably to the ball recovery chamber22using quick connect couplings56. In another embodiment the wellhead10can be isolated from a catcher body21and fluid from the downstream equipment can be backflowed through the diverter23and ball recovery chamber22for cleaning.

With reference toFIG. 7, a second ball catcher20B, or more depending upon the wellhead, can be fit to the wellhead10ofFIG. 1, also with isolation valving14,14between the wellhead10and each of the ball catchers20,20B. Accordingly, the first ball catcher20can be serviced, for replacement of the diverter23or inspection and cleaning of the chamber22, while the second ball catcher20B is in operation. In this way, wellhead flow is not interrupted. In some wellbores, even a temporary interruption can result in an unfavorable loss of suspended materials which are being elutriated from the wellbore with the fluid flow. Accordingly, redundant ball catchers20,20B are affixed to two or more flow paths13from the wellhead so that fluid flow F from the wellbore can be substantially continuous to the second ball catcher20B while the first ball catcher20is taken out of service.

Undesirable sand plugs or debris plugs can occur from the fallout and or the formation may lose its upward energy and die which requires expensive coil tubing to clean the well pipe. Also flowback disruption during coil clean out, or for example bridge plug mill out, needs to be avoided because the fallout can create a sand plug and jam around the coil tubing causing further and significant expense. The second ball catcher20B can be opened for operation, both being used temporarily, before closing in the first catcher for servicing.

In another embodiment shown inFIG. 6, an isolation valve62can be provided to optionally temporarily block the ball recovery chamber22from the catcher body21for servicing. Further, a purge port63can be provided to introduce nitrogen to purge the ball recovery reservoir of noxious gases such as hydrogen sulphide.