Fluid catching and signaling stuffing box enclosure

Abstract

A oil well stuffing box containment system is disclosed, which may be used for containing leaks from an oil well stuffing box which is used to seal around the polish rod which is connected to the rod string. The disclosed apparatus comprises a secondary container which encloses the stuffing box, a drain from the secondary container, and a storage container which is used for collecting any liquids which are drained from the secondary container. The secondary container has an upper seal for sealing around the polish rod, and a lower seal which seals around a member of the production tree. A disclosed alternative embodiment provides means for injecting the escaped liquids back into the production system.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] U.S. Prvisional Application No. 60/288,880 was filed for this invention on May 3,2001 for which the inventors claim domestic priority.

BACKGROUND OF THE INVENTION

[0002] The present invention is directed to devices that are used for preventing hydrocarbon spills from oil wells. This invention is more particularly directed to an apparatus which prevents oil spillage from oil well polish rod stuffing boxes, and which may alert the operator when a leak occurs in the stuffing box.

[0003] Many oil wells do not have sufficient pressure at the producing zone to overcome the necessary hydrostatic pressure to produce the reservoir fluids to the ground surface. Producing such wells requires the use of some type of artificial lift equipment to bring the oil and associated water to the ground surface. One of the most common types of artificial lift devices is the subsurface rod pump. The sub-surface rod pump is run into the well on a string of rods and placed below the fluid level maintained within the well. The rod pump, which is usually a positive displacement pump, is operated by reciprocating the string of rods up and down with a pumping unit set at the ground surface. The string of rods is connected to the pumping unit with a polish rod. A stuffing box, set on the production tree which in turn is attached to the top of the wellhead, encloses packing which seals around the polish rod and allows the polish rod to reciprocate up and down, hopefully maintaining a fluid-tight seal around the polish rod.

[0004] Unfortunately, stuffing boxes commonly leak. As the polish rod reciprocates through the packing elements, the packing elements begin to deteriorate from friction, heat and abrasion. The operator will commonly attempt to stop the leakage by tightening the stuffing box or replacing the packing elements. However, the operator will usually not realize there is a problem until actually observing a leak from the stuffing box. If the well is located in a remote location, considerable time may pass before the stuffing box leak is detected, resulting in substantial leakage of oil and other produced fluids. Such releases are undesirable because of the potential adverse impact on the environment and wildlife. Such releases can also be costly because of the clean up expense, the potential liability for fines, and the loss of product. Many regulatory agencies have adopted a zero tolerance for oil releases into the environment and may shut down an operator's producing operation if such leaks occur.

[0005] The need for an improved stuffing box has long been recognized. However, unlike devices which attempt to solve the problem by modifying the stuffing box itself, the present invention adds a secondary containment system which prevents leakage even where the stuffing box fails. The secondary containment system disclosed herein provides substantial volume for accumulating leaked oil, which is important for wells which are located in remote locations and checked infrequently. Also disclosed herein is a system for providing either an onsite alarm, or providing an alarm to offsite location to alert the operator when a stuffing box failure has occurred. This system may also provide for shutting down the pumping unit in the event of a stuffing box leak.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a stuffing box containment system which satisfies the above-identified need.

[0007] The disclosed apparatus comprises a secondary container which encloses the stuffing box. The secondary container has two halves, and a top and a bottom. The top of the secondary container has an upper seal which seals around the polish rod. The bottom of the secondary container has a lower seal which seals around either the bottom of the stuffing box, the stuffing box body, the tubing nipple, the production flow tee, or other fittings above the production line for the well. The secondary container utilizes a split assembly which forms the two halves which encapsulate the stuffing box. The two halves are hingedly attached together so the secondary container may be swung open or closed as required. Opposite the hinges are fastening means which are used to fasten the two halves of the secondary container around the stuffing box.

[0008] The bottom of the secondary container has a drain which allows fluids, which have escaped from a leaking stuffing box, to drain from the secondary container into a storage container. The storage container may be equipped with a pressure relief valve in the event pressure builds up from a release of gas from the well or release of associated gas from any accumulated oil. An alternative embodiment of the invention includes a pump for removing fluids from the secondary container and injecting the fluids into the wellhead flowline.

[0009] The facing edges of the two halves may be sealed with a one piece molded rubber seal. A unitary seal may be used with the device which provides a single seal element for the top seal, the bottom seal, and the seal for the facing edges of the secondary container. The secondary container may also be equipped with plexiglass windows which allow an operator to visually inspect the secondary container and determine whether any liquids have been released into the secondary container. The secondary container may also be equipped with a float switch which is triggered if the liquid level in the secondary container reaches a predetermined level. The float switch may be either connected to an onsite alarm device, such as a light or audible alarm to alert the operator to a stuffing box leak. The float switch may also be connected to an offsite device, such as a light or alarm to a centralized control system or computer. The float switch may also be connected to the motor control panel for the pumping unit to shut the pumping unit off.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a front view of the disclosed invention, showing the invention installed on a production tree of an oil well.

[0011] FIG. 2 is a front view of the secondary container, showing how the secondary container encloses the stuffing box.

[0012] FIG. 3 shows how the disclosed invention seals around the polish rod and the stuffing box.

[0013] FIG. 4 shows a top view of the two halves of the secondary container, with the two halves opened.

[0014] FIG. 5 shows section A-A.

[0015] FIG. 6 shows a top view of the two halves of the secondary container, with the two halves latched closed.

[0016] FIG. 7 shows an alternative embodiment of the secondary container, which uses a tongue and groove seal face.

[0017] FIG. 8 shows the unitary seal which may be used to form the upper and lower seal and the seal between the facing edges of the two halves of the secondary container.

[0018] FIG. 9 shows a cross-section of the unitary seal.

[0019] FIG. 10 is a front view of an embodiment of the invention which injects fluids collected in the secondary container into the wellhead flowline.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Referring now specifically to the drawings, FIG. 1 shows the disclosed device installed on an oil well W. The secondary container 10 is latched around a stuffing box 12, forming an enclosure around the stuffing box. The secondary container 10 has a top 14 and a bottom 16, the top 14 being sealed around the polish rod 18 and the bottom being sealed around either the bottom of the stuffing box 12, or some other member of the production tree 13, such as a tubing nipple or production flow tee. The secondary container 10 may be any convenient shape for manufacture, installation and storage, including the round container shown in the drawings, or a square container may also be used. The secondary container 10 may be manufactured from any suitable material, including carbon steel, fiberglass or high impact plastic. As shown in FIGS. 1 and 2, the secondary container 10 may include either plexiglass windows 20 or a sight glass, to allow the operator to see whether any liquids have accumulated inside the secondary container. The secondary container 10 is hinged to hold the two halves together on one side with hinges 22. Latching means 24 are used to hold the two halves together on the other side. A plurality of stainless steel hinges 22 and latches 24 may be used for this purpose.

[0021] The bottom 16 of the secondary container 10 has a drain 26. A suitable sized drain is 1¼″ or 1½″ equipped with a line pipe thread. A drain conduit 28 connects the drain to the storage container 30, which may be a polytank or some other suitable container. Depending on the expected maximum pressure, and the pressure rating of the storage container 30, the storage container may be equipped with a pressure relief valve or vent 32.

[0022] Various elastomeric seals, including rubber, may be used to form the various sealing means between the secondary container 10, the stuffing box 12, the polish rod 18, and the production tree 13. As shown in FIG. 8, a pair of unitary sealing elements 34 may be used to provide sealing elements for all of the surfaces which must be sealed. As shown in FIG. 9, the seal face is grooved to fit the facing edges 36 of the secondary container 10.

[0023] An alternative embodiment is shown in FIG. 7. In this embodiment, the hinge point 38 for the two halves of the secondary container is offset from the outside wall of the secondary container 10.

[0024] As known in the industry, the secondary container 10 and/or the storage container 30 may be equipped with a float switch 40, or other types of liquid detection instruments known in the industry, which may be calibrated to activate from any rising fluid level inside the containers. The switch 40 may be used to activate a local or remote alarm, signal a pager and/or provide a shutdown signal to the pumping unit 42 on the well W. In this manner, an operator may be immediately notified if a stuffing box 12 begins to leak, and/or the pumping unit 42 may be shut down.

[0025] FIG. 10 depicts an alternative embodiment of the disclosed apparatus. In this embodiment, the pumping unit 42 is equipped with an air cylinder 44, where the piston 46 of the air cylinder is connected to actuating means, which may comprise the walking beam 48 of the pumping unit. As the walking beam 48 rises, the piston 46 is pulled upwards, pulling suction on the secondary container 10. Fluids contained within the secondary container 10 are pulled through the drain 26 through a first hydraulic conduit 50 and past a first check valve 52 connected to manifold 54. As the walking beam 48 descends, the piston 46 is stroked downwards, pushing the fluids suctioned from the secondary container 10 past a second check valve 56 into a second hydraulic conduit 58 connected to the production tree 13. The air cylinder 44 may be equipped with a pressure regulator 60 so that the discharge pressure from the cylinder 44 is adjusted to a point sufficiently above the flowline pressure to allow the fluids from the secondary container 10 to be pumped into a flowline on the production tree 13. The secondary container 10 may also be equipped with an outlet 62 connected to a pressure relief valve 64 or vent to relieve any excessive buildup which may occur from either a failure of the stuffing box or a failure in the valving connecting the secondary container to the wellhead flowline.

[0026] The secondary container 10 opens 180 degrees, which allows for easy application on an existing stuffing box, so it is not necessary to remove the stuffing box to install the secondary container. This feature is important, because removal of the stuffing box usually requires a rig or hoist to pull up on the polish rod.

[0027] While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. For example, the size, shape, and/or material of the various components may be changed as desired. Thus the scope of the invention should not be limited by the specific structures disclosed.

Claims

1. A system for containing an oil well stuffing box, the stuffing box being the type which attaches to a production tree and seals around a polish rod, the polish rod connected on one end to an oil well pumping unit, and connected on the other end to a rod string which, in turn, is connected to a downhole positive displacement pump, the containment system comprising:

(a) a secondary container for enclosing the stuffing box, the secondary container having two halves, each of the halves having facing edges, the secondary container also having a top and a bottom, and fastening means for fastening the two halves around the stuffing box so the facing edges are abutted together, the container having upper sealing means for sealing around the polish rod, and lower sealing means for sealing around a production tree member, and facing edge sealing means;

(b) a drain connected to the bottom of the secondary container to allow fluids, which have escaped from a leaking stuffing box, to drain from the secondary container; and

(c) a storage container hydraulicly connected to the drain, for receiving fluids which have escaped from a leaking stuffing box.

2. The system of claim 1, wherein a pressure relief valve is attached to the storage container.

3. The system of claim 1, wherein the upper sealing means and lower sealing means comprise rubber seals.

4. The system of claim 1, wherein the upper sealing means, the lower sealing means, and the facing edge sealing means comprise a pair of unitary seal elements.

5. The system of claim 1, wherein the production tree member is the stuffing box.

6. The system of claim 1, wherein the production tree member is a tubing nipple.

7. The system of claim 1, wherein the production tree member is a production flow tee.

8. The system of claim 1 wherein plexiglass windows are placed in the secondary container, wherein the plexiglass windows are of the type which allow visual inspection of the secondary container to determine whether any liquids have been released into the secondary container.

9. The system of claim 1 wherein a float switch is disposed within the secondary container, the float switch being of the type which is activated if the liquid level in the secondary container reaches a predetermined level.

10. The system of claim 9 wherein the float switch is connected to an alarm device.

11. The system of claim 9 wherein the float switch is connected to a motor control panel for the pumping unit to shut the pumping unit off if the liquid level in the secondary container reaches a predetermined level.

12. A system for containing an oil well stuffing box, the stuffing box being the type which attaches to a production tree and seals around a polish rod, the polish rod connected on one end to an oil well pumping unit having a walking beam, and connected on the other end to a rod string which, in turn, is connected to a downhole positive displacement pump, the containment system comprising:

(a) a secondary container for enclosing the stuffing box, the secondary container having two halves, each of the halves having facing edges, the secondary container also having a top and a bottom, and fastening means for fastening the two halves around the stuffing box so the facing edges are abutted together, the container having upper sealing means for sealing around the polish rod, and lower sealing means for sealing around the bottom of the stuffing box, and facing edge sealing means, the two halves hingedly attached one to the other, so the secondary container may be swung open or closed as required;

(b) a drain connected to the secondary container;

(c) a piston and cylinder combination operationally attached to actuating means for reciprocating the piston within the cylinder, the piston and cylinder combination being of the type which creates suction when the piston is reciprocated in a first direction and creates pressure when the piston is reciprocated in a direction opposite to the first direction;

(d) a first hydraulic conduit connecting the drain to a manifold, the manifold being hydraulically connected to the piston and cylinder combination; and

(e) a first check valve inserted in the first hydraulic conduit between the drain and the manifold, the first check valve so positioned so that when the piston and cylinder combination applies suction to the manifold, the first check valve allows flow from the drain to the manifold, and when the piston and cylinder combination applies pressure to the manifold, the first check valve closes.

13. The system of claim 12, wherein the actuating means comprises connecting the piston to the the walking beam of the pumping unit, so that the piston is stroked by the reciprocation of the walking beam.

14. The system of claim 12, wherein the secondary container has a pressure relief valve.

15. The system of claim 12, further comprising a second hydraulic conduit connecting the manifold to the production tree and a second check valve, the second check valve so positioned so that when the piston and cylinder combination applies a pressure to the manifold, the second check valve allows flow from the manifold to the production tree, and when the piston and cylinder combination applies suction to the manifold, the second check valve closes.