METHOD FOR DRY INJECTING BALLS FOR WELLBORE OPERATIONS

Abstract

Method, apparatus and a system is provided for dry launching balls. One releases a ball from the stored balls, stages the ball in a staging or launching block for exposure to fluids and then injects the dropped ball into the wellbore. Fluid in the isolated staging block is removed by pump or by drainage, minimizing risk of fluid reaching stored dry balls thereabove. This method can then be repeated for subsequent balls to be dropped into the wellbore. Further, a system for reducing the fall energy of a dropped ball comprises providing one or more impact energy dampeners along a ball drop path including providing an angled sidewall of the path bore, one more elements to periodically engage a dropped ball, or to provide a liquid sump to receive a dropped ball.

Description

FIELD

Embodiments disclosed herein generally relate generally to a method for injecting balls into a wellbore, such as drop balls, frac balls, packer balls and other balls, for interacting with downhole tools, and more particularly to an apparatus and methods for dry launching balls into the wellbore while avoiding ball deterioration.

BACKGROUND

It is known to conduct fracturing or other stimulation procedures in a wellbore by isolating zones of interest (or intervals within a zone) in the hydrocarbon-bearing locations of the wellbore, using packers and the like, and subjecting each isolated zone to treatment fluids, including liquids and gases, at treatment pressures. In a typical fracturing procedure for a cased wellbore, for example, the casing of the well is perforated or otherwise opened to admit oil and/or gas into the wellbore and fracturing fluid is then pumped into the wellbore and through the openings. Such treatment forms fractures and opens and/or enlarges drainage channels in the formation, enhancing the producing ability of the well. For open holes that are not cased, stimulation is carried out directly in the zones or zone intervals.

It is typically desired to stimulate multiple zones in a single stimulation treatment, typically using onsite stimulation fluid pumping equipment and a plurality of downhole tools, including packers and sliding sleeves. In one technique, a series of packers are inserted into the wellbore, each of the packers located at intervals for isolating one zone from an adjacent zone. Sliding sleeves can be located between packers that are selectively actuable to open to the isolated zone. It is known to introduce a ball into the wellbore to selectively engage one of the sleeves in order to block fluid flow thereby whilst opening to the isolated zone uphole from the ball for subsequent treatment or stimulation. Once the isolated zone has been stimulated, a subsequent ball is dropped to block off a subsequent sleeve, uphole of the previously blocked sleeve, for isolation and stimulation thereabove. The process is continued until all the desired zones have been stimulated. Typically the balls range in diameter from a smallest ball, suitable to block the most downhole sleeve, to the largest diameter, suitable for blocking the most uphole packer.

Similarly introduced balls can selectively engage sequential packers in a pre-perforated wellbore in order to stepwise block fluid flow through the wellbore, creating an isolated zone uphole from the selected packer for subsequent treatment or stimulation. Once the isolated zone has been stimulated, a subsequent ball is dropped to block off a subsequent packer, uphole of the previously blocked packer, for isolation and stimulation thereabove. The process is continued until all the desired zones have been stimulated.

At surface, the wellbore is fit with a wellhead including valves and a pipeline connection block, such as a stimulation flowhead or frac header, which provides fluid connections for introducing stimulation fluids, including sand, gels and acid treatments, into the wellbore. Conventionally, operators manually introduce balls to the wellbore through an auxiliary line, coupled through a valve, to the wellhead. The auxiliary line is fit with a valved tee or T-configuration connecting the wellhead to a fluid pumping source and to a ball introduction valve. The operator closes off the valve at the wellhead to the auxiliary line, introduces one ball and blocks the valved T-configuration. The pumping source is pressurized to the auxiliary line and the wellhead valve is opened to introduce the ball. This procedure is repeated manually, one at a time, for each ball. This operation requires personnel to work in close proximity to the treatment lines through which fluid and balls are pumped at high pressures and rates. The treatment fluid is typically under high pressure and gas energized, and possibly corrosive which is very hazardous.

Aside from being a generally hazardous practice, other operational problems may occur, such as valves malfunctioning and balls becoming stuck and not being pumped downhole. These problems have resulted in failed well treatment operations, requiring re-working which is very costly and inefficient. At times re-working or re-stimulating of a well formation following an unsuccessful stimulation treatment may not be successful, which results in production loss.

Other alternative methods and apparatus for the introduction of the balls have included an array of remote valves positioned onto a multi-port connection at the wellhead with a single ball positioned behind each valve. Each valve requires a separate manifold fluid pumper line and precise coordination both to ensure the ball is deployed and to ensure each ball is deployed at the right time in the sequence, throughout the stimulation operation. The multi-port arrangement, although workable, has proven to be very costly and inefficient. Further, this arrangement is dangerous to personnel due to the multiplicity of lines under high pressure connected to the top the wellhead during the stimulation operation. The multiplicity of high pressure lines also logistically limits the amount of balls that can be dropped due to wellhead design and available ports.

Additionally, the balls are later returned by reverse or produced flow up the well. However, it is even less undesirable to have to retrieve a ball mid-operation. It is not uncommon for a ball to be damaged during injection, in this case forcing many operators to flow the damaged balls back uphole, or in a worst case drill them out, prior to dropping a replacement ball. Accordingly, the use of dissolvable balls is becoming more prevalent in the industry.

Dissolvable balls, which typically break down upon contact with fluids, such as fracturing or drilling fluids, have seen increased use. Dissolvable balls are often preloaded in a ball injector and premature contact with fluids can cause deterioration thereof, compromising the integrity of the balls.

There exists apparatus such as that taught in published application US2015/0021024 to Oil States Energy Services LLC, Houston Tex., that provide a dry and atmospheric pressure storage option for dissolvable balls just prior to well injection. The system appears to adapt the principles of hot tapping access to a pressurized environment through an air lock, a hydraulic ram alternately receiving a ball into a chamber and shifting the chamber and ball through seal packs to place the ball into the pressurized environment. The balls are each mechanically manipulated from ball storage, offset from the wellbore, to the wellbore and returned to storage with a bolus of pressurized fluid therein. An equalization section reduces the pressure before return to the ball storage section. As described therein, frac balls can be stored in the dry environment until they are placed into the frac ball injection chamber to be inserted into the wellbore. Thus, a subsequent ball would appear be then stored in a wet environment of the previously operated injection chamber, in the intermediate apparatus between storage and wellbore, albeit at atmospheric pressure therein, still posing the risk of premature ball deterioration when using dissolvable balls.

Keeping dissolvable balls dry until just prior to well injection also introduces the risk of damaging balls during staging operations due to the balls falling through air at high speeds after being released with no fluids to slow them down. Applicant notes in particular that vertically stacked, multi-ball magazines or launchers permit a ball to vertically drop significant distances onto intermediate valves or other downhole equipment. Oil State also noted disadvantages with increasing heights of ball-dropping assemblies and additional structure to accommodate such configurations. Further balls dropped from increasing heights can accelerate to substantial speeds before impact, increasing the risk of damage to the balls.

SUMMARY

When storing dissolvable balls for use in the treatment of wells, it is advantageous to isolate the balls from coming into contact with fluid, and thus avoiding premature deterioration thereof. Accordingly, the dissolvable balls are kept isolated from fluids, such as fracturing, drilling or displacement fluids, and are only exposed to such fluids immediately prior to injecting the balls into the wellbore.

Dropped ball access to fluid pressurized systems, from external or atmospheric locations, typically result in residual fluid which poses a risk to the storage of stored dissolvable balls. Therefore, in one aspect, an intermediate launching block is provided to fluidly separate the dissolvable balls from fluids such as fracturing and wellbore fluids and only expose a ball currently being injected to such fluids. In another aspect, the inherent fragility of dissolvable balls is also managed by providing impact energy deflection apparatus, reducing the fall energy of a dropped ball.

One embodiment of a system and a method for dry launching balls involves providing balls for launching into a wellbore, temporarily isolating a first ball, to be dropped ball downhole, from the provided balls, staging the ball for exposure to fluids and then injecting the first ball into the wellbore. Fluid in the isolate staging block is removed by pump or by drainage, minimizing risk of fluid reaching stored dry balls thereabove. This method can then be repeated for subsequent balls to be dropped into the wellbore.

In one broad aspect, a method for dry launching one or more balls into a wellbore comprises locating a launching block between the wellbore and a source of the one or more balls. One removes at least some fluids from the launching block before dropping the ball into the open launching block. One isolates the open launching block from the source of balls and opens the isolated launching block to the wellbore for releasing the ball from the opened launching block into the wellbore.

In embodiment, and prior to opening the launching block to the source of balls, one can further equalize the pressure the ball launcher to atmosphere. In removing fluids form the launching block, one can removing said fluids to a level below an isolation interface to the source of one or more balls, such as through draining or pumping fluids therefrom.

In another aspect, apparatus and as system for implementing the method above comprises a ball launcher for storing one or more balls and having a release bore for receiving a stored ball. A launching block, having a staging bore, is fluidly connected intermediate the ball launcher and the wellbore for receiving the stored ball from the release bore and retaining the ball therein as a dropped ball. The staging bore is fluidly connected to the ball launcher for delivering the dropped ball to the wellbore. A first isolation valve fluidly isolates the release bore from the staging bore and a second isolation valve fluidly isolates the staging bore from the wellbore. A first port provided fluid communication to and from the staging bore and is operable to remove fluid from the staging bore above the first port.

In embodiments, a first pump is connected to the first port so as to pump fluids from the launching block. A second pump is provided for delivering fluid to the launch block for displacing the dropped ball into the wellbore.

In another aspect, a system for reducing the fall energy of a dropped ball comprises providing one or more impact energy dampeners along a drop path to engage a dropped ball for reducing its fall energy. The impact energy dampeners are provided along a portion of a path bore from the release bore, through the staging bore to the wellbore. In embodiments, the impact energy dampeners comprise an angled sidewall of the path bore upon which the ball rolls thereon, one more elements protruding radially inwardly into the bore to periodically engage a dropped ball, or providing a liquid sump to receive a dropped ball, that sump being sufficiently spaced from stored balls.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional representation of an embodiment of a fracturing system for deploying dissolvable balls in a dry environment, illustrating a ball launcher, a launching block, a frac header, a wellhead for accessing a wellbore, and isolation gate valves;

FIG. 2 is a cross-sectional representation of the embodiment of FIG. 1, schematically illustrating the fracturing system fluidly connected to a pumper, a reversible pump and a fluid storage tank, the launching block isolated from both the ball launcher and from the frac header, and further illustrating a valve on the launching block for permitting inflow of air or nitrogen during flushing of the launching block;

FIG. 3A is a cross-sectional representation of the embodiment of FIG. 2, illustrating a reversible pump connected for draining fluid from the launching block before establishing fluid communication between the ball launcher and the launching block for a dry ball drop, the launching block remaining isolated from the frac header;

FIG. 3B illustrates embodiment of FIG. 3A after draining the launching block and establishing fluid communication between the ball launcher and the launching block for a dry ball drop, the launching block remaining isolated from the frac header;

FIG. 4 is a cross-sectional representation of the embodiment of FIG. 2, illustrating isolation of the ball launcher from the launching block, priming the pumper and pumping a displacement fluid into the launching block to buildup pressure to at least treatment pressures;

FIG. 5A is a cross-sectional representation of the embodiment of FIG. 2, illustrating the pressurization of the launching block to at least treatment pressures by the pumper by pumping a displacement fluid into the launching block; FIG. 5B is a cross-sectional representation of the embodiment of FIG. 5A, illustrating establishing fluid communication between the launching block and frac header for injecting the dropped ball and co-injecting displacement fluid into the wellbore through the frac header and or launching block and, after dropping the ball, isolation of the launching block for terminating fluid communication between the launching block and frac header for resetting the system for a subsequent ball drop;

FIG. 6A is a close-up of the embodiment of FIG. 5B, prior to draining of fluids from the launching block;

FIG. 6B illustrates a possible scenario, according to FIG. 6A, of fluid creep that could undesirably expose the ball launcher, loaded with dissolvable balls, to fluids;

FIG. 6C illustrates a second scenario, according to FIG. 6A, implementing draw-down measures to minimize fluid creep and avoiding exposure of the ball launcher to fluids;

FIG. 7 is a time sequence and operations chart illustrating the sequence of events for dry launching a dissolvable ball for the embodiment shown in FIGS. 1 to 5B;

FIG. 8A is a cross-sectional representation of an embodiment of a fracturing system such as that according to FIG. 1, wherein the ball launcher and first isolation valve are supported at an angled, or sloped, orientation upon a non-rectangular launching block to minimize or eliminate ball-drop related damage;

FIG. 8B is a close-up of the embodiment of FIG. 8A, illustrating the trajectory of a dropped ball as it travels over a ball storage recess;

FIG. 9 illustrates the system according to FIG. 1 in which an interconnecting spool is provided as an angled obstruction to avoid ball damage, the remaining equipment remaining orthogonal to the frac header and wellhead;

FIG. 10 illustrates the system according to FIG. 1 in which isolation valves are provided which incorporate one or more angled elements to avoid ball damage, the ball launcher remaining orthogonal to the frac header and wellhead;

FIG. 11 illustrates the system according to FIG. 1 in which the launching block is modified to incorporate an angled or sloped bore;

FIG. 12 illustrates the system according to FIG. 1 in which a portion or the main bore through the ball launcher, the launching block and isolation valves are modified to incorporate obstruction elements protruding into a travel path of a dropped ball;

FIG. 13A is a plan view of an obstructive insert of the launching block of FIG. 12;

FIG. 13B is a side cross-sectional view representation the insert of FIG. 13A taken along B-B, and illustrating a dropped ball's trajectory as slowed and altered by an obstruction within a path bore.

DESCRIPTION

With reference to FIG. 1, and a first embodiment, a fracturing system 10 comprises a frac header 15, a launching block 20 and some form of a ball launcher 25, all fluidly connected to a wellbore 12 for dry launching of dissolvable balls 30 for fracturing operations. The frac header 15 is provided dependent on the well stimulation operation, in particular when providing fracturing fluids. Herein, stimulation fluids are liquids or mixtures of liquids and other additives and particulates. The ball launcher 25 stores one or more dissolvable balls 30 for selective and sequential release to the wellbore 12. The structure of the wellhead is not shown but is represented for operations by fluid wellbore 12. Multiple isolation valves 35a,35b,35c interconnect each of the frac head 15, ball block 20, ball launcher 25 and wellbore for selectively isolating each of the frac head 15, ball block 20, ball launcher 25, and wellbore from one another for operational control and safety. As shown, in an embodiment, first isolation valve 35a can interconnect and isolate the ball launcher 25 from the launching block 20, second isolation valve 35b can interconnect and isolate the launching block 20 from the frac header 15, and the third isolation valve 35c can interconnect and isolate the frac header 15 from the wellbore 12. Typically the third isolation valve 35c remains open to the wellbore 12 during operations. As shown, a common style of isolation valve used on a wellhead structure is a gate valve and herein both the terms isolation valve and gate valve are used interchangeably. The connections between components are typically bolted across facing flanges, studs through a flange to a tapped component body, and combinations thereof.

With reference to FIG. 2, and in the context of a system 10 for fracturing operations with ball-actuated packers, ball-actuated ported-sleeves or combinations thereof, often a pumper 40 is provided for introducing displacement fluids for aiding in ball launch. Pumper 40 delivers compatible fluid, such as frac fluid without add particulates (sand) and is fluidly connected to the launching block 20. In this embodiment, fluid lines are isolated or completely bypass the ball launcher 25. The first isolation valve 35a fluidly isolates the ball launcher 25 from the launching block 20.

As shown in FIG. 5B, the frac header is connected at one or more inlets to a plurality of frac pumpers that can provide a large volume of sand-laden fluids to the wellbore 12. While frac fluid is generally laden with sand, in instances where the displacement fluid pumper 40 is absent or out of service, a bypass from the frac pumpers could substitute for a temporary source of displacement fluid to the launching block 20.

The ball launcher 25 has a ball release bore 24 into which stored balls are released for ultimate delivery into the wellbore 12. The ball launcher remains separated from fluids delivered to the wellbore 12. Thus, dissolvable balls 30 store in the ball launcher 25 avoid exposure to fluids. In essence, the launching block 20 fluidly separates the ball launcher 25 from the wellbore 12 and frac header 15, staging dry-to-fluid ball release operations and avoiding premature exposure of the dissolvable balls 30 to fluids in the fracturing system 10.

The ball launcher 25 serves to effectively store the balls 30 above the launching block 20 and in a dry environment. Only when the dissolvable balls 30 are dropped into the launching block 20 during operations are they exposed to fluid. Contemporaneous exposure to fluid for the first time while dropping into the wellbore 12 ensures the balls 30 are not subject to deterioration for a period prior to operation. From within a staging bore 27 of the launching block 20, each of the dissolvable balls 30 is exposed to fluid for the first time just prior to being released or launched into the wellbore 12 or through the frac header 15 into the wellbore.

Applicant notes that FIG. 1 illustrates a particular ball launcher 25 set forth in Applicant's issued U.S. Pat. No. 8,136,585 to Isolation Equipment Services Inc. U.S. Pat. No. 8,136,585, which discloses a bail launcher having at least one radial ball array having two or more radial bores. Each radial bore houses a ball cartridge adapted to receive and release balls and an actuator for aligning or misaligning the ball cartridge with an axial bore in fluid communication with the wellbore. Applicant's radial launcher is characterized by a low profile, minimizing the height of the wellhead structure. Applicant notes that any ball launcher can be used with embodiments of this method of dry launching dissolvable balls, the ball launcher being mounted above the launching block 20.

With reference to FIGS. 2 and 6C, and in an embodiment, a method of dry launching balls into a wellbore initially involves fluidly connecting a launching block 20 and a ball launcher 25 to a wellhead accessing the wellbore 12. Typically a frac header 15 is provided and is situate intermediate the ball launcher 20 and the wellbore 12. For safety reasons and to be able to individually isolate each of the frac header 15, the launching block 20, the ball launcher 25 and the wellbore from one another, the isolation valves 35a, 35b and 35c are installed therebetween. After assembly of the wellhead components of the system 10, the frac header 15 and launching block 20 can be fluidly connected to their respective fluid delivery pumping equipment using known piping methods. The launching block 20 is connected to pumper 40 that delivers fluids to the launching block 20 for aiding in ball launching and pressure equalization before ball release. Other frac pumpers, provided by fracturing operators, are connected to the frac header 15 for delivery of frac fluids at treatment pressures.

A bleed valve 45 can be installed on the ball launcher 25 and is operable to permit pressure equalization between the interior of the ball launcher and atmosphere or to pressurize the launcher 25 with a dry gas.

In embodiments, fluid removal is applied to the structure to ensure the ball launcher is maintained in a dry condition. Thus, a first pump 50, such as a rotary gear BOWIE™ pump available from Bowie Pumps of Canada Ltd., is fluidly connected to the launching block 20 at a first port 22 for the removal of residual fluids therefrom. In an embodiment, the first port 22 is located low on the launching block 20 to enable maximal fluid removal therefrom. The first pump 50 can direct removed fluids to a fluid storage tank 55.

The first pump 50 can also be fluidly connected to a second pump of the pumper 40. In some embodiments, the first pump 50 can be utilized to deliver fluids, such as from the storage tank 55, for priming the second pump or pumps of pumper 40 and also be reversible to draw or suck fluids from the launching block 20 as described in greater detail below. The second pump is typically a positive displacement pump including triplex horizontal single-action reciprocating pumps. After pressure in the ball launcher 25 is equalized to atmosphere, the entire fracturing system 10 can be swabbed or any fluids pumped out, clearing the release bore 24 of the ball launcher 25 and at least a portion of the staging bore 27 of the ball launcher block 20 above the first port 22 and removing of excess lubricant and fluids therefrom.

After initial preparation of the fracturing system is completed, at least first and second isolation valves 35a,35b can be closed for isolating the various components of the ball launching system such as the launching block 20, and ball launcher 25, and preventing fluid communication therebetween. Further the third isolation valve 35c can isolate the frac header 15 from the launching block 20. Leakage of some fluids past such isolation valves is inherent in gate valve design, and methods incorporated herein can ensure fluid accumulation in the bore of the structure is removed periodically to avoid fluid exposure with the ball launcher 25. As the wellbore is at elevated pressures, any leakage tends to be upward towards through the staging bore 27 towards the ball launcher 25. As shown in FIG. 6A, fluid remains in the staging bore 27 from a prior ball launch cycle. If accumulated fluid is not removed from the release bore 24 and staging bore 27 prior to the next ball launch cycle, as illustrated hypothetically in FIG. 63, fluid can encroach on the ball launcher 25. The fluids typically comprise liquids and some gas G. Gas G from the fluid in the wellbore exacerbates the problem, accompanying fluids leaked or otherwise escaping past lower isolation valves. Expanding fluids or gas alone, if not removed, encroach on the ball launcher 25. Therefore, as shown in FIG. 6C, removal of liquids to a level down to about first port 22 ensures fluid is spaced below the dry ball launcher 25. With a margin of safety, the level of the liquid in the bore is lowered to a level that is below an isolation interface of the ball launcher 25 and the launching block 20.

Returning to FIGS. 2 and 3A, and with the various components of the fracturing system 10 isolated, the first pump 50, can be set to remove fluids present in the launching block 20 and actuated to create a suction thereon and thereby withdraw fluids. Fluid removal ensures that fluids do not reach the ball launcher 25 and damage the dissolvable balls 30 stored therein. Generally, when the otherwise minor fluid leaking is to be discouraged, the ball launcher 25 can be pressurized with dry gas, such as through bleed valve 45, to seat the floating gate of the first isolation valve 35a.

As shown in FIG. 3B, as the first pump 50 sucks out fluid from the ball launcher 25 and the launching block 20, a first ball 30a can be dropped from the ball launcher 25 to land on the closed second valve 35b. Vacuum created by a running first pump 50 provides additional impetus for a ball 30a to overcome any tendency to drag or hang up due to a wet or sticky bore 27 as it falls, ultimately resting upon the closed second gate valve 35b. Optionally, before ball drop, and as the Bowie pump 50 is withdrawing or sucking liquid from the launching block 20, first valve 35a can be opened to allow the first pump 50 to better withdraw or suck fluids from primarily the launching block 20 and, optionally, the lower regions of the ball launcher 25 connections. Thus, fluids remaining in the launching block 20, such as from a prior launch cycle, and fluid that has encroached on the ball launcher 25 through and in the first isolation valve 35a, can be pumped out and into the fluid storage tank 55.

In certain embodiments, where the ball launcher 25 has a relatively high vertical height, and before dropping the ball 30a, first valve 35a can be closed or remain closed. Reducing the overall height that the ball 30a drops minimizes ball damage or deterioration that could result upon impact of the ball and the launching block 20 or the second gate valve 35b. Therefore, ball drop is staged, first falling onto the first isolation valve 35a, before continuing. After the ball 30a has been dropped onto first valve 35a, first valve 35a can be opened to allow the ball 30a to drop into the launching block 20 and onto second valve 35b. By keeping first valve 35a closed for the initial drop of ball 30a, and then opening first valve 35a thereafter to allow ball 30a to drop the remaining height onto the closed second valve 35b, the height that the ball 30a drops each time is reduced, thereby minimizing negative impact-related damage to the ball 30a compared to that had the ball 30a dropped the overall height in one instance.

With reference to FIG. 4, with the ball 30a dropped onto closed second valve 35b, first valve 35a is closed or remains closed to fluidly isolate the ball launcher 25 from the rest of the system 10.

Fracturing fluids are typically delivered into the wellbore 12 independent of the launching of a ball. In such an embodiment, the frac header 15 is delivering fluids downhole at a fracturing pressure. The launching block 20 is isolated from the frac header 15 by third isolation valve 35c. First pump 50 can continue to run, removing any fluids that remain or leak into the staging bore 27 under fracturing pressures therebelow.

To release a ball 30a from the launching block. the first pump 50, is shut off or isolated so as to configure the lines for pumper 40 delivery of ball-displacement fluids. The pumper 40 is configured to pump displacement fluids into the launch block 20. The pumper 40 often requires priming and first pump 50 can be temporarily re-directed to direct fluids from storage 55 into the pumper's second pump 40 to initiate pumper operation. The gear pump configuration of the first pump 50 is generally capable of providing 100 psi to prime the pumper 40.

The pumper 40 is a high pressure triplex pump capable of about 10,000 to 15,000 psi fluid pressure. Initially, the fluid is introduced to increase the pressure in the staging bore 27 to complement the wellbore pressure. As shown in FIG. 5A, in an embodiment, the pumper 40 pumps displacement fluids into the launching block 20 at a pressure that is greater than the prevailing frac pumping pressure, for example 7-10 MPa greater than the frac pumping pressure and therefore presents a positive impetus to displace the ball 30a into the frac header 15 and wellbore 12.

As shown in FIG. 5B, once the fluid pressure is in the launching block 20 is adjusted to that in the frac header 15, the second valve 35b can be opened to fluidly connect the launching block to the frac header 15 and the wellbore 12. The ball 30a is thereby injected, dropped or otherwise delivered into the frac head 15 and the wellbore 12. Continued displacement fluid provides a co-flow for the ball 30a to ensure it is carried into the frac fluid mix in the frac header 15. The fluid flow also helps remove any potential blockages in the staging bore 27 such as hydrates and or sand gel that can accumulate therein. In embodiments, depending on the operational conditions of a particular wellbore, the amount of displacement fluid pumped through the launching block into the wellbore after opening second gate valve 35b is between about 30 to 150 L.

With reference to FIG. 6A, after a sufficient amount of displacement fluid is pumped downhole to ensure ball delivery, second valve 35b is closed. Thereafter, usual fracturing operations through the frac header 15 continue and the procedure of removing fluids and dry launching dissolvable balls can then be repeated for subsequent dissolvable balls stored in the ball launcher 25.

In summary in one method of operation, a ball dropping and fluid removal cycle is illustrated in the flow chart of FIG. 7. At step 100, with the launching block 20 and the ball launcher installed to the wellbore 12, the first, fluid removal pump 50 and the second displacement fluid pumper 40 are fluidly connected to the launching block 20. The first pump 50 is reversibly connected between the launching block 20 and the pumper 40. The first and second valves 35a,35b, straddling the launcher block, are closed before the release of the first ball and are closed again (later at step 170) by the conclusion of the launching of that ball 30a into the wellbore 12. At step 115, the appropriate ball 30a is chosen for the ongoing operation but is not yet dropped. At step 120, liquids are removed from the launching block 20 such as by draining or as shown by pumped removal using first pump 50. In one option, before opening the first valve 35a, the ball 30a can be dropped from the ball launcher 25 onto the first valve 35a, the optional step shown in dotted lines. Alternatively, as shown in solid lines at step 130, the first valve 35a is opened and the ball 30a is dropped (step 135) therethrough into the drained launching block 20. At step 140, the launching block 20 is again isolated from the ball launcher 25 by closing the first valve 35a.

At step 150, using the first pump 50, the launching block 20 is pressurized by pumper 40 to, or above, the wellbore pressure below the second valve 35b. Once the pressure is generally equalized, the second valve 35b is opened at step 160 and the ball 30a is injected into the wellbore 12, through the second valve 35b and frac header 15. In embodiments, as introduced above, in order to ensure ball movement and supplement gravity, at step 165 displacement fluids from first pump 50 are constantly pumped into the wellbore 12 from first pump 50 and into the frac header 15. Once the ball 30a has been injected, at step 170, the second valve 35b is closed to isolate the launching block 20 from the wellbore 12. In such embodiments, third valve 35c is and remains open throughout the dry launching procedure. That is, during the initial preparation of the system for dry launching balls, only first valve 35a and second valve 35b are opened and closed to access and isolate the ball launcher 25 and the launching block 20 from the frac header 15, while fracturing fluid is communicated through the frac header 15 into the wellbore.

At this point, at step 180, the cycle repeats for the next ball and removal of liquid can commence.

In other considerations, and illustrative of other aspects supportable of fluid removal from the launching block, it is common to use an isolation gate valve that has a floating gate. If the gate is in the floating or relaxed position it can allow fluids or gases to pass by. In embodiments herein, a positive pressure applied to the gate can ensure a reliable seal and thus, not allow fluid or gas to leak thereby In further embodiments where such an isolation gate valve is employed, and with reference to FIG. 7, the ball launcher 25 can be pressurized by air or nitrogen or similar to maintain the positive pressure on first gate valve 35a for keeping first gate valve 35a in a downward sealing position whenever there is a fluid pressure in the launching block 20.

Pressuring up ball launcher 25 is advantageous, as positively sealing first valve 35a prevent any fluids from unintentionally migrating upward into the ball launcher 25 and prematurely expose the balls 30 stored therein to any fluids, including displacement fluids, from the displacement pump of pumper 40, or fracturing fluids that happen to leak by second valve 35b.

Applicant notes that with sand contamination and multiple and repetitious openings and closings of second gate valve 35b results, the floating gate valve can wear which can increase the likelihood of fluid leakage in the latter stages of wellbore operations.

In another embodiment, a second port and second valve 56 can be installed onto the launching block 20. During removal of fluids from the launching block 20, valve 56 can be opened to allow additional atmospheric air, nitrogen, or other dry gas to enter into the launching block 20 and provide an inflow of gas during first pump 50 operation. The introduction of dry gas can be provided under pressure. The inflow of gas assists in the flushing or removal of any fluids in at least the launching block 20.

Ball Damage Minimization

As noted above, in dry launch applications, a dropped ball can accelerate to substantial speeds before impacting a stop potentially damaging a ball 30. This is exacerbated when the balls are falling in air, without dampening that can occur when falling in liquid.

Accordingly, and with reference to FIGS. 8 to 12, systems for launching balls can incorporate means for reducing the speed at which a ball can travel. For example, means for reducing ball speed may be implemented in the dry launch areas, during the launching of balls and before the balls enter into the frac header 15. Surprisingly, Applicant has found that even a minor interruption in a ball's free fall, such as angling the axial passageways or incorporating periodic small elements in the passageways, reduces the energy of impact. A drop path is formed along a path bore from the release bore 24 and through the staging bore 27 to the wellbore 12. Intermediate elements, such as elements in the bore, a landing zone of liquid, or formation of non-linear paths sufficiently reduce the energy. As discussed in example embodiments below, a portion or all of the passageways leading to the frac header can be angled, or fit with intermediate elements or deflection mechanisms. In other words, the system further comprises one or more impact energy dampeners along the drop path to engage a dropped ball for reducing its fall energy.

As shown in FIG. 8A, in an embodiment, an otherwise vertically oriented ball launcher and interconnections can be supported at an angle or be sloped, such that the drop path of the ball from the ball launcher to the final gate valve 35c is not vertical, thereby reducing the speed at which the dropped ball travels. Thus, in one embodiment, an impact energy dampener comprises a sidewall of the drop path is angled from vertical along at least a portion of the drop bore. The angled sidewall further comprises an angled receiving bore, an angled staging bore, or wherein at least a portion of one of, or both of, the first or second isolation valves is angled from vertical for forming the angled path bore. As shown in FIGS. 8A and 8B, a ball 30a, once launched within an angled ball launcher, will roll down an angled main bore of the ball launcher 25 rather than drop vertically onto a gate valve below. The rolling action of the launched ball 30a results in a reduced speed and thus lessens impact and energy imparted to the ball 30a when the ball lands on a gate valve below. Specifically, with reference to FIG. 8B, a ball 30a can contact a ball storage recess 28 to further reduce its speed and fall energy.

In another embodiment, and as shown in FIG. 9, one or more interconnections between the ball launcher 25, the launching block 20, and the frac header 15 can be angled or sloped to reduce the speed at which the launched ball can travel. As shown, the interconnection is a spool 26 between the launching block 20 and second gate valve 35b. The spool 26 can be angled to reduce the travel speed at which the ball 30a dropped from the launching block 20. As the ball 30a is dropped from the launching block 20, the ball 30a is deflected and engages at least a portion of the sloped interconnection, causing the ball 30a to roll down the angled bore, and thereby travelling at a speed lower than that if the ball were to have fallen vertically.

Angles as little as 5 degrees from the vertical axis are found to be adequate; the greater the angle from the vertical axis, the slower the ball speed. The extent of the selected angle is balanced against an practical aspect to keep the center of gravity of the heavy equipment reasonably centered above the wellhead. An optimal angle for each style of drop and ball launcher 25 can be determined but, in general, the velocity experienced from modification of the fall path from any vertical ball launcher 25 will be reasonably equal after the ball 30a is released from its storage or holding position. The length of fall and weight of the dropped object will determine the speed and impact.

With reference to FIG. 10, in another embodiment, many or all interconnections between the ball launcher 25, launching block 20 and frac header 15 can be angled or sloped for reducing the speed at which a dropped ball 30a can travel (as shown, where 35a can be modified to introduce a slope). Applicant notes that slopes reduce the speed at which the ball 30a can travel, thus reducing the impact experienced by the ball as it lands on closed gate valves.

In another embodiment, and shown in FIG. 11, the bore of the launching block 20 can be angled or sloped.

The location of the one or more angled components can be selected to minimize component cost and maximize integrity. Angled spools 26 (such as in FIG. 9) can be manufactured to industry specifications and be provided between otherwise standard components such as the ball launcher 25, the gate valves 35a and 35b, and launching block 20. As shown in FIG. 11, the launching block 20 is a manufactured component and could be provided with an angled internal bore while having conventional connection points and exterior appearance. Not shown, a bottom flange of the ball launcher 25 can be modified to enable an angled arrangement. Depending on the ball launcher, the inclination must not exceed the launcher's ability to reliably release a ball 30 or prevent premature release of a ball 30. Positive displacement ball launchers, such as that shown, are less sensitive to variation in angular mounting.

In another embodiment, and as shown in FIGS. 3B and 8A, a ball 30a can be dropped into liquid within the ball launching block 20, provided that enough liquid has been removed to prevent liquid from entering into the ball launcher 25. As illustrated by the test results discussed below, the liquid within the confined space of the bore of ball launching block 20 will significantly reduce the impact energy of the ball 30a as it lands on the second valve 35b.

As shown in FIG. 12, in an embodiment, obstructions, deflectors or other physical elements for transport interruption reduce the speed and impact energy of balls as the travel through the dry ball launching system. Obstructive elements can be provided in isolation or in combination with angled paths. Elements can protrude radially inwardly at least partially into a path of travel of the dropped balls to intercept and reduce the speed of travel of the dropped balls. The one or more obstructions are spaced axially along the drop path and protrude radially inward from a sidewall for periodically engaging a dropped ball 30a and therefore reducing its fall energy.

As shown, the deflective plates 60 can impede downward progress and deflect the path of the ball drop side-to-side to reduce the speed at which the balls travel and reduce the impact force of the balls as they fall onto closed gate valves. In an embodiment, the deflective plates 60 can be manufactured of metal or made of an elastomer or other resilient material.

With reference to FIG. 13, to avoid modification of standardized valves, launchers and the like, an inserted structure such as a flange plate 60, like an orifice plate, can be inserted at one or more interfaces to engage a falling ball. A protruding portion 62 of the plate 60 encroaches on the respective bore. Alternatively, an inserted structure can support a radially actuated element, such as a finger-like member (not shown) to adjustably protrude radially into the bore, the extent of encroachment dependent upon the ball size.

The elements are sized and materials chosen to ensure that the largest of the balls 30 contemplated for release from the ball launcher 25 are free to fall downward through the unobstructed bore without becoming stuck. Further, the vertical spacing is such to reduce a ball fall energy below a ball-damage threshold. Applicant has determined that a conservative spacing between the elements is between 24 to 36 inches in order to sufficiently regulate the velocity of the dropped balls.

In a series of tests, the effect of angle and drop height was investigated. The tests showed that ball drop height, angle of the ball fall path, and receiving liquid conditions affect the ball impact results. The tests were conducted using stainless steel balls dropped onto aluminum plates and the energy of impact determined from volumetric analysis of the resulting plastic deformation of the impact site, measured as impact volumes of the indent from planer. The test results indicated the basis of concern with respect to the post-drop integrity of fracturing or packer balls when dropping larger distances in known wellhead ball launching units.

The tests involved dropping 2.5 inch diameter stainless steel balls, weighing approximately 2.5 pounds each, from heights of approximately 5 feet, 8 feet and 15 feet onto a 1×18×18 inch 6061 aluminum plate. Additional tests simulated conventional wet-launch conditions by placing a reservoir of water at the impact site. The reservoir was filled with approximately 19½ inches of water above the aluminum plate.

Tests included free fall, balls dropped balls through a vertical ABS pipe and an inclined pipe. The ABS pipe had an internal diameter of 3.98 inches.

TABLE 1
DROP TEST RESULTS.
	Drop Height	Depth of Water	Impact Diameter
Test No.	(inches)	(inches)	(inches)
1	180	0	0.425
2	91	0	0.355
3	64-5/8	0	0.330
4	180	19.5	0.425
5	91	19.5	0.335
6	64-5/8	19.5	0.322
7	180	19.5	0.315
	through tube

TABLE 2
CALCULATED INDENTATION VOLUMES (IMPACT ENERGY)
		Indent Volume
Test No.	Indentation Volume (in{circumflex over ( )}3)	% of Test 1
1	0.02134	100
2	0.01026	48
3	0.00763	36
4	0.02134	100
5	0.01026	48
6	0.00691	32
7	0.00633	30

As expected, the tests revealed that the energy of impact between the steel ball and aluminum plate correlates with the drop distances, the magnitude of the impact increasing roughly proportionally with drop height. Open water being placed above the aluminum plate did not have a measurable effect on the energy of the final impact. However, with the pipe partially immersed in the water reservoir, dropping a ball from 180 inches through the water resulted in a 60 to 70% reduction in impact energy when compared with a free-fall drop through air at the same height without a pipe.

Additionally, additional tests showed that shifting the pipe 8 to 10 degrees caused the ball to roll down a side wall of the pipe rather than freefall, reducing the impact energy by 50 to 60%.

Claims

1. A method dry launching one or more balls into a wellbore comprising:

locating a launching block between the wellbore and a source of the one or more balls;

removing at least some fluids from the launching block;

dropping the ball into the open launching block;

isolating the open launching block from the source of balls;

opening the isolated launching block to the wellbore;

releasing the ball from the opened launching block into the wellbore.

2. The method of claim 1, further comprising:

fluidly connecting a ball launcher, as the source of the one or more balls, to the launching block; and

wherein the dropping the ball into the launching block comprises dropping a selected ball from the ball launcher.

3. The method of claim 1, wherein prior to opening the launching block to the source of balls further comprising equalizing the pressure the bail launcher to atmosphere.

4. The method of claim 1, wherein removing at least some fluids from the launching block comprises removing fluids to a level below an isolation interface to the source of one or more balls.

5. The method of claim 1, wherein removing at least some fluids from the launching block comprises draining fluids therefrom.

6. The method of claim 1, wherein removing at least some fluids out of the launching block comprising pumping fluids therefrom.

7. The method of claim 6 further comprising introducing dry gas to the launching block while removing the fluids.

8. The method of claim 1, wherein releasing the ball from the opened launching block into the wellbore further comprises pumping at least some fluid through the launching block at pressure at or greater than wellbore pressures.

9. The method of claim 1, wherein prior to opening the launching block to the source of balls further comprising pressurizing the ball launcher with a dry gas.

10. A system for dry launching balls into a fluid wellbore comprising:

a ball launcher for storing one or more balls and having a release bore for receiving a stored ball;

a launching block having a staging bore fluidly connected intermediate the ball launcher and wellbore for receiving the stored ball from the release bore and retaining the ball therein as a dropped ball, the staging bore fluidly connected to the ball launcher for delivering the dropped ball to the wellbore;

a first isolation valve for fluidly isolating the release bore from the staging bore;

a second isolation valve for fluidly isolating the staging bore from the wellbore; and

a first port for fluid communication to and from the staging bore and operable to remove fluid from the staging bore above the first port.

11. The system of claim 10, further comprising a first pump connected to the first port to remove fluids from the launching block.

12. The system of claim 11 further comprising a second pump for delivering fluid to the launch block for displacing the dropped ball therefrom.

13. The system of claim 12 further comprising a frac header fluidly connected between the launching block and the wellbore for delivering stimulation fluid to the wellbore.

14. The system of claim 12 wherein the first pump is a reversible pump located between the launching block and second pump and operable to pump fluid to either remove fluid from the launching block or to deliver fluid to the second pump.

15. The system of claim 10, wherein the ball launcher further comprises a bleed port for equalizing pressure of the release bore to atmosphere.

16. The system of claim 10, wherein the launching block further comprises a second port for equalizing pressure of the staging bore to atmosphere.

17. The system of claim 10, wherein the launching block further comprises a second port for inflow of dry gas to the launching block.

18. The system of claim 10 wherein a drop path is formed along a path bore from the release bore and through the staging bore to the wellbore, the system further comprising one or more impact energy dampeners along the drop path to engage a dropped ball for reducing its fall energy.

19. The system of claim 18 wherein the impact energy dampeners comprise a sidewall angled from vertical along at least a portion of the drop bore.

20. The system of claim 19 wherein the angled sidewall further comprises an angled receiving bore.

21. The system of claim 20 wherein ball launcher is angled from vertical for forming the angled receiving bore.

22. The system of claim 18 wherein the angled sidewall further comprises an angled staging bore.

23. The system of claim 18 further comprising:

a first isolation valve for fluidly isolating the release bore from the staging bore;

a second isolation valve for fluidly isolating the staging bore from the wellbore; and

wherein at least a portion of one of, or both of, the first or second isolation valves is angled from vertical for forming the angled path bore.

24. The system of claim 18 wherein the impact energy dampeners comprise one or more obstructions spaced along and protruding radially inward from a sidewall along the drop bore for engaging and therefore reducing the fall energy of the dropped ball.

25. The system of claim 24, wherein each obstruction is an element installed at one or more of the fluid connections between the first and second isolation valves.

26. A system for dry launching one or more balls into a fluid wellbore comprising:

a ball launcher having a release bore for receiving a stored ball;

a launching block having a staging bore fluidly connected intermediate the ball launcher and the wellbore for receiving the stored ball from the release bore and retaining the ball therein as a dropped ball, the staging bore fluidly connected to the ball launcher for delivering the dropped ball to the wellbore, a drop path being formed along a path bore from the release bore, through the staging bore to the wellbore; and

one or more impact energy dampeners along the drop path to engage a dropped ball for reducing its fall energy.

27. The system of claim 26 wherein the impact energy dampeners comprise a sidewall angled from vertical along at least a portion of the drop bore.

28. The system of claim 27 wherein the angled sidewall further comprises an angled receiving bore.

29. The system of claim 27 wherein the angled sidewall further comprises an angled staging bore.

30. The system of claim 26 further comprising:

a first isolation valve for fluidly isolating the release bore from the staging bore;

a second isolation valve for fluidly isolating the staging bore from the wellbore; and

wherein at least a portion of one of, or both of, the first or second isolation valves is angled from vertical for forming the angled path bore.

31. The system of claim 26 wherein the impact energy dampeners comprise one or more obstructions spaced along and protruding radially inward from a sidewall along the drop bore for engaging the dropped ball.

32. The system of claim 31 wherein each of the one or more obstructions comprises an insert installed at one or more of the fluid connections between the first and second isolation valves.