Technical Field

Embodiments relate to a drive head assembly such as may be used to drive a down-hole pump in oil and coal seam gas mining.

Background

Oil and coal seam gas (CSG) prospecting and mining may involve drilling a well to access pockets of oil or gas underground. In cases where the oil or gas does not free flow to surface it is possible to use “artificial lift technologies” to allow a well to thereby produce. In CSG wells, it is necessary to remove the water from the well to allow natural gas to be produced. In oil wells, artificial lift technology can be used to pump the oil from the well. One type of artificial lift uses progressive cavity pumps (PCPs) to lift fluid to the surface. Once the well has been drilled using a drill string, the drill string and corresponding drill driving mechanism are removed, and replaced with, well casing, tubing, rods, and a down-hole pump. A drive head is used at the surface to rotate the pump.

The drive head provides the necessary torque to drive the down-hole pump, but because the drive head is removed from the pump the drive head has to support a weight of the drive rod. This can create significant stresses on the drive rod. A further requirement may be that the drive rod is vertically displaceable relative to the drive head to allow positioning of the down-hole pump.

The drive head provides a means to seal around the drive rod, often referred to as a stuffing box. The stuffing box can be below or within the drive head. The stuffing box provides the primary seal preventing produced liquids from leaking to atmosphere.

Such drive heads, an example of which is described in US 5,370,179, are often unsupervised and open to the elements. If such elemental exposure results in degradation, this may result in significant damage if remedial action is not taken in time, resulting in lost production as well as damage to in situ equipment.

Further, such drive heads can be arranged such that a primary portion of the drive rod it exposed above the primary seal provided by the stuffing box. US 2009/0272521 discloses such an example. Given that the stuffing box is below or within the drive head, if the drive rod were to break above the stuffing box the rod may fall into the well. Since the stuffing box seals against the drive rod, if the drive rod breaks or is no longer present, fluid in the well is free to impinge on the drive head assembly.

A reference herein to the background and/or prior art does not constitute an admission that such art forms part of the common general knowledge in Australia or elsewhere.

Summary of the Disclosure

A first aspect relates to a drive head assembly for driving a drive rod to drive a down-hole pump situated in a well, the drive head assembly comprising a drive head for supporting the drive rod, a motor and a transfer mechanism for transferring force from the motor to the drive rod, the transfer mechanism comprising a clamp for clamping the drive rod so that force from the motor may be transferred to the drive rod, the drive head assembly further comprising a stuffing box comprising at least one stuffing box seal to prevent down-hole liquid from interacting with the drive head and a secondary seal assembly to protect at least a portion of the drive rod, the secondary seal assembly being located above the stuffing box relative to the well.

In contradistinction to e.g. US 2009/0272521 , the drive head assembly disclosed comprises a secondary seal assembly located above the stuffing box. Thus, in the event that the drive rod breaks above the stuffing box, the secondary seal assembly can prevent fluid from escaping and damaging the drive head assembly or other equipment, or spilling to grade.

The portion of the rod protected by the secondary seal assembly may be a portion of the rod in a region at which the clamp clamps the drive rod.

The secondary seal assembly may further, or alternatively, prevent access of the atmosphere and elements such as rain to the drive rod. In an embodiment, the secondary seal assembly may be located proximate the clamp. The area of the drive rod proximate the clamp is the area of the drive rod which may be under the greatest stress. Since corrosion due to exposure of the drive rod to the elements may create weakness, it may be desirable to prevent or mitigate corrosion of the portion of the drive rod under greatest stress. In this respect, the secondary seal assembly may help to limit the potential for corrosion of the rod, and thereby avoid or delay premature failure of the rod. Failure of the drive rod can cause lost production due to the time, money and effort involved in repairing the drive rod. In addition, failure of the rod can result in oil, gas, or contaminated water escaping from the well, and the corresponding lost revenue this represents.

The secondary seal assembly may form a cover at the top of the drive head. The secondary seal assembly may create a secondary seal against the drive rod, and against a rotating structure of the drive head. In the event of a rod failure or break such that the drive head seal is compromised, the redundant secondary seal assembly can prevent liquid from leaking from the well.

The clamp may be located above the drive head.

The clamp and the motor may cause the drive rod to rotate about its longitudinal axis.

The secondary seal assembly may be adapted to engage with the drive rod (e.g. directly or indirectly). The secondary seal assembly may be engaged with the drive rod such as to rotate with the rod. In this respect, the secondary seal assembly may be engaged directly with the rod or indirectly with a portion of the drive head to rotate with the rod.

The secondary seal assembly may be engaged with the drive rod (e.g. directly or indirectly). The drive rod may comprise a polished rod which extends up and out of the drive head. The secondary seal assembly may be engaged with the polished rod.

The drive head may comprise a drivenut located on the drive rod between the clamp and the drive head. The secondary seal assembly may engage with the drivenut.

The secondary seal assembly may engage with the drive rod via the drive nut so as to rotate with the rod.

The term ‘drivenut’ is herein used to refer to the top or upper (with reference to the well) part of the drive head which rotates. It is to be realised that this may not necessarily comprise a nut. The drivenut may be part of the stuffing box.

The drive head assembly may comprise a mechanical link between the secondary seal assembly and the drivenut. The mechanical link may be a pin or bolt. A mechanical link between the seal and the drivenut may help to ensure that the seal rotates along with the drive nut and to locate the seal relative to the drivenut and the drive rod, potentially helping to avoid ingress of liquid onto the drive rod.

The secondary seal assembly may comprise a first assembly seal and a second assembly seal. The first assembly seal may engage with the drive rod and the second assembly seal may engage with the drivenut.

The first assembly seal and/or the second assembly seal may be comprised of an elastomer. It is to be realised that other water-proof or water-resistant materials may be used instead.

The first assembly seal may comprise a solid annular form.

The secondary seal assembly may comprise a housing, which when installed on the drive rod, houses the clamp. The housing may additionally, or instead, house the drivenut when installed on the drive rod.

The housing of the second seal portion may define a void in which the clamp and/or drive nut is housed. The housing may comprise a port for testing a pressure of the void.

Alternatively, the second seal portion may encase the clamp and/or drive nut in a solid form.

The secondary seal assembly may comprise a second assembly seal between the housing and the drive head. The second assembly seal may be provided between the housing and the drivenut. The second assembly seal may comprise one or more O-rings.

A further aspect extends to a secondary seal assembly for a drive head assembly, the drive head assembly being for driving a drive rod to drive a down-hole pump situated in a well, the drive head assembly comprising a drive head for supporting the drive rod, a motor and a transfer mechanism for transferring force from the motor to the drive rod, the transfer mechanism comprising a clamp for clamping the drive rod so that force from the motor may be transferred to the drive rod, the drive head assembly further comprising a stuffing box comprising at least one stuffing box seal to prevent down-hole liquid from interacting with the drive head wherein the secondary seal assembly is adapted to protect at least a portion of the drive rod, the secondary seal assembly being located above the stuffing box relative to the well.

The portion of the rod protected by the secondary seal assembly may be a portion of the rod in a region at which a clamp clamps the drive rod.

The secondary seal assembly may be adapted to engage with the drive head and/or the drive rod in an area proximate the clamp.

The secondary seal assembly may be adapted to form a cover at the top of the drive head. The secondary seal assembly may create a secondary seal against the drive rod, and against a rotating structure of the drive head.

The secondary seal assembly may be adapted to engage with the drive rod. The secondary seal assembly may be engaged with the drive rod such as to rotate with the rod. The drive rod may comprise a polished rod which extends up and out of the drive head. The secondary seal assembly may be adapted to engage with the polished rod. The secondary seal assembly may comprise at least one curved surface. The curved surface may describe a section of a cylinder.

The drive head may comprise a drivenut to engage the clamp. The secondary seal assembly may be adapted to engage with the drivenut. Alternatively, the secondary seal assembly may engage with the drive head. Further alternatively, the secondary seal assembly may engage at a top and at a bottom with the drive rod.

The term ‘drivenut’ is herein used to refer to the top or upper (with reference to the well) part of the drive head which rotates and engages the clamp. It is to be realised that this may not necessarily comprise a nut.

The secondary seal assembly may comprise a mechanical link for linking the secondary seal assembly and the drivenut. The mechanical link may be a pin or bolt.

The secondary seal assembly may comprise a first assembly seal and a second assembly seal. The first assembly seal may engage with the drive rod and the second assembly seal may engage with the drivenut.

The first assembly seal and/or the second assembly seal may be comprised of an elastomer. It is to be realised that other water-proof or water-resistant materials may be used instead. The first assembly seal may comprise a solid annular form.

The secondary seal assembly may comprise a housing, which when installed on the drive rod, houses the clamp. The housing may additionally, or instead, house at least a portion of the drivenut when installed on the drive rod.

The housing of the second seal portion may define a void in which the clamp and/or drive nut may be housed. Alternatively, the second seal portion may comprise a solid form adapted to encase the clamp and/or drive nut.

The secondary seal assembly may comprise a second assembly seal between the housing and the drive head. The second assembly seal may be provided between the housing and the drivenut. The second assembly seal may comprise one or more O-rings.

The first assembly seal may be physically distinct from the second assembly seal. The first assembly seal and the second assembly seal may be engaged with the housing. The housing may be comprised of steel; the first and second assembly seals may be comprised of steel.

Alternatively, the first and second assembly seals may be formed from one integral piece.

The second assembly seal may engage with the drive rod. Both the first and second assembly seals may engage with a drive rod at a location above the clamp.

An additional aspect extends to a secondary seal assembly for a drive head assembly, the drive head assembly being for driving a drive rod to drive a down-hole pump situated in a well, the drive head assembly comprising a drive head for supporting the drive rod, a motor and a transfer mechanism for transferring force from the motor to the drive rod, the transfer mechanism comprising a clamp for clamping the drive rod so that force from the motor may be transferred to the drive rod, the drive head assembly further comprising a stuffing box comprising at least one stuffing box seal to prevent down-hole liquid from interacting with the drive head wherein the secondary seal assembly comprises a housing to enclose at least a portion of the rod. The housing may help to protect the rod from environmental factors. A portion of the rod enclosed by the housing may be an upper portion of the rod. The portion of the rod enclosed by the housing may be a top portion of the rod.

The secondary seal assembly of the additional aspect extends may be otherwise as set forth above for the first and further aspects.

As used herein, the terms “seal” and “sealing” are used in a relative sense to indicate that the presence of the referred element helps to prevent the ingress or movement of fluid such as water.

Description of the Drawings

Non-limiting embodiments are herein described, with reference to the accompanying drawings in which:

Figure 1 is a side view of a drive head assembly according to an embodiment;

Figure 2 illustrates a section of Figure 1 in further detail;

Figure 3 is a top perspective view of a seal assembly according to an embodiment; and

Figure 4 is a bottom perspective view of a seal assembly according to an embodiment.

Detailed Description of Specific Embodiments

In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings, are not intended to be limiting. Other embodiments may be utilised and other changes may be made without departing from the spirit or scope of the subject matter disclosed herein. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.

Figure 1 illustrates a drive head assembly 10 according to an embodiment. The drive head assembly 10 comprises a motor 12 which rotates to produce torque. A drive head 14 supports a drive rod 18. The drive rod extends down a well casing (not shown) located in a well and is connected to a down-well pump (not shown). Torque is transmitted from the motor 12 to the drive head 14 by means of belts 16. The belt 16 engages with a sheave 30 which, in turn, is connected to a shaft (not shown) which is connected to drivenut 24 which is, in turn, connected to clamp 22. The clamp 22 engages with the drive rod 18.

The drive head assembly 10 further comprises a flow tee 20 through which the liquid pumped up by the down-well pump is released, in a known manner.

The drive head assembly 10 also comprises a seal assembly 26 which is illustrated in greater detail in Figure 2. The secondary seal assembly protects a portion of the rod 18 in a region where the clamp 22 clamps the rod 18. In this embodiment, the region of the rod proximate to the clamp is the portion of the drive rod 18 from directly above clamp 22 to 200mm below the clamp 22.

It is to be realised that in other embodiments, the region of the rod proximate the clamp may be a portion of the rod extending above and below the clamp. In an embodiment the portion of the rod extending 3m above and 1m below the clamp is considered the portion of the rod proximate the clamp.

The upper part of the drive head 14 is the drivenut 24 which engages with clamp 22, which engages with the drive rod 18.

As illustrated in Figures 2, 3 and 4, the secondary seal assembly 26 comprises a cylindrical case 34 made from steel which is attached to the drivenut 24 by means of a bolt 60. Therefore, the secondary seal assembly 26 rotates together with the drive head. An O-ring 38 provides a seal between the housing 34 and the drivenut 24.

The secondary seal assembly 26 further comprises a cover 40 and an O-ring 42 which seals the interface between the cover 40 and the cylindrical housing 34. The cover 40 has an annular shape and the rod 18 is located within the central void of this annulus. An annular seal 36 interfaces with the rod and is also located in the central void of the annulus of the cover 40. A cap 48 covers the annular seal 36 and is attached to the cover 40. As illustrated in Figures 2, 3 and 4, the cylindrical case 24, cover 40 and cap 48 (together with the corresponding O-rings 38 and 42 together with the seal 36) form a housing enclosing a void 44 and the clamp 22.

As further illustrated in Figure 2, the drive head assembly 10 comprises a stuffing box 50 which comprises stuffing box seals 52 and 54. These seals help to prevent fluid such as water, oil or gas from flowing up the well and into the drive head assembly 10, which could cause significant corrosion and other damage. However, if the rod 18 breaks below the clamp 22, then the rod may fall into the well. Since the stuffing box seals 52 and 54 seal against the rod 18 if the rod is no longer present, fluid in the well is free to impinge on the drive head assembly 10.

The secondary seal assembly seals against the drive head and a portion of the rod 18 above the clamp. Therefore, if the rod breaks below the clamp 22, the secondary seal assembly may prevent fluid from escaping and damaging the drive head assembly 10, other equipment, or spilling to grade. Instead, the fluid will enter the void 44 provided by the housing of the secondary seal assembly 26. As illustrated in Figure 2, the cover 40 has a probe port 46 which provides an attachment point for a pressure sensor to determine the pressure within the void 44. In this manner a user may safely and quickly determine whether the stuffing box has failed, and take the appropriate remedial action.

It is also to be realised that in certain embodiments, the secondary seal assembly 26 is located above (with reference to the direction of the well) the stuffing box 50. Therefore, the secondary seal assembly may act to prevent egress of fluid if the stuffing box fails.

As previously described, the bolt 60 attaches the cylindrical case 34 to the drivenut 24 and this may locate the case 34 relative to the drivenut, potentially ensuring that the seal is not moved by wind or other external forces, or by the rotation of the drive rod 18, and potentially helping to ensure that the housing rotates with the drivenut 22.

Furthermore, since the cover 40 extends over the clamp 22, the housing may provide a retaining force preventing clamp 22 and rod 18 from being ejected from drive head 10.

It is further to be realised that since the cap 48 and seal act to prevent ingress of matter such as water from the outside of the housing, the housing may act to protect the enclosed portion of the rod 18 from the elements and thereby potentially reducing the impact of environmental factors on the rod (which may, e.g. cause corrosion). As used herein, the term “device” shall not be limited to meaning a unitary entity, but covers both a unitary entity and an entity comprising distinct components whether manually removable, or not.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments. Similarly, the word “device” is used in a broad sense and is intended to cover the constituent parts provided as an integral whole as well as an instantiation where one or more of the constituent parts are provided separate to one another.