Apparatus and method for cleaning out sand from an underbalanced hydrocarbon producing well

An apparatus and method is used in the cleaning out of sand in underbalanced gas wells. The present invention includes a valve subassembly equipped with an emergency shutin device to remotely control the actuation of the valve via an air or hydraulic control line. Operatively coupled to the inlet of the valve subassembly is a swivel subassembly which further enables the coupling to a tubing string. A lifting assembly attaches the valve subassembly to an elevator of a well service rig. A hardened elbow coupled to an outlet of the valve subassembly directs the gas/sand mixture being removed from the well through a hose to a collection pit. The use of the apparatus of the present invention in a sand cleanout operation allows joints of pipe to be tripped into and out of the tubing string all the while keeping the emergency shutdown device actuator connected and operational.

FIELD OF THE INVENTION

The present invention relates to the field of tubing valves used in the removal of sand from underbalanced hydrocarbon producing wells.

BACKGROUND OF THE INVENTION

In hydrocarbon producing wells, in particular, natural gas wells, multiple gas producing formations in the vertical strata of the gas field may be present. A well may pass from multiple formations along its vertical height. When drilling a well that contains multiple formations, it is common practice to place a plug in the well to separate vertically adjacent formations. To protect the plug itself, it is known to place a sufficient amount of sand on top of the plug. A well having sand placed in this manner is referred to an “underbalanced well”. In a well D with multiple formations A, as shown inFIG. 1, plug B is placed in well D to separate each formation A. Sand C is then placed on top of each plug B.

When the uppermost formation has almost been depleted, the plug and the sand separating the uppermost formation and the formation beneath it needs to be removed. To remove the sand, it is known to lower a string of tubing into the well until the lower end of the tubing is near the sand. Coupled on top of the tubing is a valve subassembly, such as a ball valve subassembly commonly known to those skilled in the art. A safety valve subassembly is often used on top of the first valve subassembly. The safety valve subassembly typically incorporates a valve actuator known as an emergency shut-in device or “ESD”. Due to the explosive nature of natural gas, the ESD is operated by a compressed air or hydraulic line as opposed to an electrically-controlled actuator. The ESD is controlled by a remotely located switch situated near the floor of the well service rig so that it is easily accessible by an operator.

When a joint of tubing is lowered into a well, the first valve subassembly is closed. The tubing may be rotated about its longitudinal axis so that it may descend into the well easily. This requires that the control line to the ESD of the safety valve subassembly to be disconnected as the safety valve subassembly will also rotate as the tubing is lowered into the well. Once the tubing is positioned to remove the sand in the well, the control line is reconnected to the ESD and the first valve subassembly is opened thereby allowing the pressure of the formation to force gas up the tubing drawing along sand with it. In the event of an emergency, the ESD can be activated by an operator to close the safety valve subassembly and stop the sand cleanout operation.

If additional joints of tubing are required to be tripped into the tubing string, the first valve subassembly is closed and the control line to the ESD is disconnected. The connection between the first valve subassembly and safety valve subassembly is broken and another joint of tubing is inserted between the first valve subassembly and the safety valve subassembly. The second valve subassembly is also placed between the second joint of pipe and the safety valve subassembly. The second valve subassembly is initially placed in the closed position. The first valve subassembly is then opened and the string of tubing is then lowered further into the well. When the string is in position, the control line is reattached to the ESD and the second valve subassembly is then opened to continue with the sand cleanout operation. If multiple joints of tubing are required, this procedure is repeated for each joint of tubing placed in the tubing string.

As the safety valve subassembly with the ESD is part of the tubing string, the control line must be repeatedly disconnected and reconnected for each joint of tubing added to the tubing string. This procedure adds considerable time and inconvenience to the operation. To avoid this inconvenience, some well service operators may choose not to use a safety valve subassembly with an ESD at all. This causes a potentially hazardous situation for operators as there is no standby emergency shutdown mechanism to shut down the operation in the event of an emergency.

Therefore, it is desirable to have a safety valve subassembly with an ESD that does not have to have its control line disconnected and reconnected every time a joint of tubing is tripped into or out of the tubing string.

SUMMARY OF THE INVENTION

The present invention is an apparatus and method for use in cleaning out sand from an underbalanced well that allows the ESD of a safety valve subassembly to remain connected to its control line when joints of tubing are tripped into the tubing string.

The apparatus of the present invention is a valve subassembly, as well known to those skilled in the art, having a tubing swivel subassembly rotatably coupled to the lower or inlet end of the valve subassembly. The valve subassembly has a valve mechanism, such as a ball valve, adapted to be operated by a valve actuator or ESD. The ESD is connected to a control line operated by a remotely located switch near the platform of the well service rig.

In an illustrative embodiment of the present invention, one end of a hardened elbow, such as a Chicksan™ elbow, is coupled to the upper or outlet end of the valve subassembly. A high pressure hose is coupled to the other end of the elbow to direct sand to a pit. The use of a hardened elbow is beneficial as the material wear properties of the elbow absorb the brunt of the abrasive effects of sand being blown out of the well by the formation pressure and through the valve subassembly. This embodiment is suitable for wells having formation pressures greater than 2500 psi.

In this illustrative embodiment, the valve subassembly is supported by a valve cradle in which the valve subassembly is fastened to. The valve cradle also provides the interconnection between the valve subassembly and the swivel subassembly. A fork assembly attached to the elevator of the service rig supports the valve cradle by having the ends of the fork legs pivotally attached to said valve cradle. A singular rod projecting upwards from the upper end of the fork provides the means to attach to the apparatus to the elevator of a well service rig.

In an alternate embodiment, the valve subassembly has an exit port extending through the sidewall of the valve, the port located above the valve mechanism. The exit port has a hardened elbow, such as a Chicksan™ elbow, attached to it. A high pressure hose is connected to the other end of the elbow directs the sand to a pit. In place of a fork assembly, this alternate embodiment uses a pickup subassembly threaded into the upper or outlet end of the valve subassembly. The pickup subassembly, in turn, couples the valve subassembly to the elevator of the service rig. A sand plug is fitted within the valve subassembly between the exit port and the pickup subassembly. The sand plug is placed within the valve subassembly to absorb the brunt of the abrasive effects of the sand flowing through the valve subassembly and out the exit port. Due to the sharp bend the flow of sand makes as it passes through the valve subassembly and the exit port, the sand can wear or abrade the internals of the valve subassembly. Accordingly, this embodiment is more suitable for wells having formation pressures less than 2500 psi.

The method of the present invention comprises attaching the apparatus of the present invention to the elevator of a well service rig. The ESD control line is attached to the valve actuator on the valve subassembly and remains connected all throughout the sand cleanout operations. A hardened elbow and hose are attached to the valve subassembly to direct the sand removed from the well to a pit. A second valve subassembly is coupled to coupling means disposed on the lower end of the swivel subassembly of the apparatus followed by a joint of tubing being coupled to the second valve subassembly. Initially, the second valve subassembly is closed. As the joint of tubing is lowered into the well, the tubing may be rotated during its descent into the well. The swivel subassembly allows the tubing string to rotate while the valve subassembly remains stationary. Once the tubing has been lowered into position, the second valve subassembly is opened allowing the gas to rise up through the tubing and drawing the sand with it. The gas/sand mixture rises up the tubing, through the open second valve subassembly, through the apparatus of the present invention, and out through the hardened elbow and hose into the pit. The sand lands into the pit whereas the gas is simply released into the atmosphere.

When another joint of tubing is needed to be tripped into the tubing string, the second valve is closed and a joint of tubing along with a third valve subassembly (also in a closed position) is tripped into the tubing string between the swivel subassembly and the second valve subassembly. The second valve subassembly is opened and the tubing string is then further lowered into the well. Once the tubing string has been lowered into position, the third valve subassembly is opened allowing gas to clear out the sand in the procedure described above.

All the while, the control lines of the ESD of the valve subassembly remains connected. It does not have to be disconnected and reconnected every time a joint of tubing is tripped into the tubing string. This saves time and speeds the sand cleanout operation. In the event of an emergency, the cleanout operation can be stopped by operating the remove switch for the ESD thereby closing the valve subassembly.

Broadly stated, one aspect of the present invention is an apparatus for cleaning out sand from an underbalanced hydrocarbon producing well, comprising: a valve subassembly having a valve body comprising: an upper end having coupling means, a lower end adapted to couple to a swivel subassembly, a passageway disposed within said valve body providing communication between said upper and lower ends, and a valve mechanism disposed in said passageway for opening and closing said passageway; a swivel subassembly operatively coupled to said lower end of said valve body.

Broadly stated, another aspect of the present invention is a method for cleaning out sand from an underbalanced hydrocarbon producing well, the method comprising the steps of: attaching an apparatus consisting of: a valve subassembly having a valve body comprising: an upper end having coupling means, a lower end adapted to couple to a swivel subassembly, a passageway disposed within said valve body providing communication between said upper and lower ends, and a valve mechanism disposed in said passageway for opening and closing said passageway, a swivel subassembly operatively coupled to said lower end of said valve body, and lift support means operatively coupled to said valve subassembly for attaching with an elevator of a well service rig to an elevator of a well service rig, the valve mechanism of said apparatus in an open position; attaching a first joint of tubing to a lower end of second valve subassembly; attaching an upper end of said second valve subassembly to the swivel assembly of said apparatus, said second valve subassembly in a closed position; lowering said first joint of tubing into said well; and opening said second valve subassembly whereby the pressure of a hydrocarbon formation in said well forces said sand up said tubing and exiting through said apparatus.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring toFIGS. 2,3and4, a first embodiment of the present invention shown. Apparatus50comprises a valve subassembly62having ball valve63. Valve subassembly62can be provided as a 5000 psi, 27/8″ slimline ball valve subassembly which is readily and commercially available and as well known to those skilled in the art. Swivel subassembly70is rotatably coupled to valve subassembly62with swivel cap74. Disposed between valve subassembly62and swivel subassembly70are o-rings64, teflon ring66and thrust bearing68. Disposed between swivel subassembly70and swivel cap74are thrust bearings72. As shown inFIG. 4, swivel subassembly70can be a cylindrical or tubular member having upper end90, lower end92and retaining ring94disposed therebetween. Upper end90passes through thrust bearing68, teflon ring66and o-rings64into opening91disposed at the lower end of valve subassembly62that is adapted to receive swivel subassembly70. Upper end90is inserted into opening91until stopped by retaining ring94. Thrust bearing72is fitted over lower end92of swivel subassembly70. Swivel cap74, having opening93extending therethrough, is slipped over coupling threads88disposed on lower end92of swivel subassembly70and is operatively coupled to valve subassembly62thereby sandwiching retaining ring94between valve subassembly62and shoulder95of swivel cap74. As obvious to those skilled in the art, swivel cap74can be threaded to valve subassembly62or it can be fastened using any other suitable means. By coupling swivel subassembly70to valve subassembly62in this manner, swivel subassembly70can rotate relative to valve subassembly62while valve subassembly62remains stationary.

Sandplug54is threaded onto pickup subassembly52before pickup subassembly52is threaded into box end61of valve subassembly62. Ring80provides means for attaching a chain or a hook from a winch cable to apparatus50whereby apparatus50can be raised or lowered. O-ring56provides a seal between sand plug54and valve subassembly62. Sleeve60and breakout band58further secure pickup subassembly54to valve subassembly62. Port65extends through the sidewall of valve subassembly62and is positioned between ball valve63and box end61. A hardened elbow, such as those made by Chicksan™ is attached to port65to direct the flow of sand through a hose (not shown) to a pit for collecting the sand.

Due to the abrasive effects of sand flowing through the apparatus and the sharp bend taken by the flow of sand takes to exit valve subassembly62through port65, the use of this first embodiment is generally limited to cleaning sand from wells having formations pressures not greater than 2500 psi. ESD actuator78is mounted to valve subassembly62via ESD mounting tower76and operates the ball valve mechanism (not shown) of valve subassembly62. The control line (not shown) connects ESD actuator78to a remotely located control switch (not shown) typically mounted near the platform of a well service rig (not shown).

Referring toFIGS. 5,6and7, a second embodiment of the apparatus of the present invention is illustrated. Apparatus10comprises valve subassembly16, valve cradle20, swivel crossover22, swivel subassembly26, swivel cap24, lifting assembly12, lifting lugs18and elbow14. In this embodiment, valve subassembly16is the same type of subassembly as valve subassembly62with exception of valve subassembly16not having a port65. Valve subassembly16sits in valve cradle20and is secured in place with setscrews. Swivel crossover22is threaded into valve cradle20. Swivel subassembly26can comprise upper end40, lower end42and retaining ring41disposed therebetween. Lower end42can further comprise threads43. Upper end40of swivel subassembly fits within swivel crossover22. Swivel cap24slips over swivel subassembly26and is threaded onto swivel crossover22. This secures swivel subassembly26to swivel crossover22but still allows swivel subassembly26to rotate within swivel crossover22. Coupled to the top of valve subassembly16is elbow14. Elbow14is a hardened device, as made by Chicksan™ as an example, for bearing the brunt of the abrasive effects of sand flowing through apparatus10under pressure. As the placement of elbow14on top of valve subassembly16allows sand to flow straight through valve subassembly16, this second embodiment is generally suitable for cleaning sand from underbalanced wells having formations pressure greater than 2500 psi, but not more than the pressure rating of valve subassembly16, where the abrasive effects of sand flowing under such pressures would quickly wear out the first embodiment of the apparatus of the present invention.

ESD actuator34is mounted to valve subassembly16via ESD mounting tower36and operates the ball valve mechanism (not shown) of valve subassembly16. The control line (not shown) connects ESD actuator34to a remotely located control switch (not shown) typically mounted near the platform of a well service rig (not shown).

To support apparatus10, lifting assembly12is pivotally attached to valve cradle20. Lifting assembly12includes fork head22having two legs13secured to it by locking caps30. At the bottom of legs13are ends15having apertures for fitting over lugs18. Lugs18are threaded into valve cradle20. Ends15slide over lugs18and are secured by circlips21fitted into grooves19of lugs18. Rod32is threaded into yoke28and is capable of being connected to an elevator of a well service rig.

In operation, as shown inFIG. 8, the first embodiment of the apparatus of the invention, apparatus50is supported by pickup subassembly52which, in turn, is attached to an elevator of a well service rig (not shown). Operatively coupled to the inlet of valve subassembly62via swivel subassembly70is valve82awhich is, in turn, coupled to tubing84a. Valve82ais coupled to coupling threads88disposed on lower end92of swivel subassembly70. Additional valves82band tubing84bmay be included to form string38that is inserted to the well through wellhead86. Attached to valve subassembly62is ESD actuator34. Control line35couples ESD actuator34to a remotely located switch (not shown). Elbow14connects a port (e.g.,65shown inFIG. 4) of valve subassembly62to hose67. Hose67leads to an open pit (not shown) where sand is directed.

Valve82is closed when tubing84is inserted into the well through wellhead86. Once valve82is positioned above wellhead86, valve82is opened to allow gas from the well formation to rise through tubing84and to exit through the port of valve subassembly62, carrying sand along with it. The gas/sand mixture flows through hose67to the pit where the sand collects and the gas is released to the atmosphere. Additional joints of tubing84and valves82can be added to string38to continue to process.

During the sand cleanout operation, line35is connected to ESD actuator34. In lowering tubing84into the well, string38may be rotated to ease the descent of string38into the well. Swivel subassembly70allows string38to rotate while keeping valve subassembly62stationary. In the event of an emergency requiring the sand cleanout operation to be terminated, an operator simply activates the remote control switch to cause ESD actuator34to close the ball valve of valve subassembly62. The advantage of the present invention is that when joints of tubing84are tripped into or out of string38, line35does not have to be continuously disconnected and reconnected to ESD actuator34for each joint of tubing. This speeds up the sand cleanout operation and results in considerable time savings for the operator. It also maintains a degree of safety during these operations as ESD actuator34is kept operational even when joints of tubing84are tripped into or out of string38.

Using the second embodiment of the apparatus of the present invention in operation is similar to that of the first embodiment. The only difference is that elbow14is attached to the top of valve subassembly16. As discussed above, the first embodiment is generally used to clean out wells having formation pressures not greater than 2500 psi whereas the second embodiment is used with well with formations pressures greater than 2500 psi.