Kudu Industries Inc.

Other

Kudu Indutries, Inc.

Kuda Industries, Inc.

Robert A Mills

The present invention provides a method and apparatus for controlling the production rate of a rotary downhole pump to prevent well pump-off. The method includes the steps of operating the pump at a first speed less than a maximum rate of the pump until well fluid is produced at the wellhead. The operation is continued at the first speed until a first dynamic fluid level in the annulus between the production tubing and the wellbore or the well casing is stabilized. A first static load on the drivehead at the first dynamic fluid level is determined. The pump is then operated at a second speed higher than the first speed until the fluid level in the annulus is stabilized at a second dynamic fluid level. A second static load on the drivehead at the second dynamic fluid level is determined. A linear function of the load on the drivehead is determined as a function of the fluid level in the annulus. The linear function is used to calculate a critical load on the wellhead at a pump off point of the well where the fluid level in the annulus is equal to the insertion depth of the pump. The speed of the pump is reduced when the critical load is reached to prevent pump-off. The method and apparatus of the invention provides for the monitoring and control of the well pumping operation to prevent pump-off without the need for downhole monitoring or measuring equipment.

Method and apparatus for controlling the liquid level in a well

A safety coupling for preventing backspin at excessive speeds of a torque transmitting drive string which stores reactive torque due to torsional stress. The safety coupling includes a rotatable driving member to be coupled with a rotatable driven member to be coupled with the driving string for axial rotation therewith. The driven member is movable relative to the driving member between an engaged position wherein the driving and driven members are coupled by a torque transfer structure to provide a positive driving connection between the torque transmitting drive and the shaft, and a disengaged position wherein the driving and the driven members are freely rotatable relative to each other so that back-spin of the torque transmitting drive is prevented. The driven member is biased into the disengaged position and forced into the engaged position only during forward rotation of the shaft. To start rotation of the shaft, the coupling further includes an auxiliary coupling component which transfers a selected torque between the driving and driven members for start-up of the shaft from standstill and to force the driven member into the engaged position. The auxiliary coupling component is disengaged before potentially dangerous levels of reactive torsion are stored in the shaft, which prevents potentially hazardous back-spin, should the main coupling components of the driving and driven members and torque transfer structure fail.

Safety coupling for rotary pump

A method and an apparatus for producing fluid hydrocarbons through a single production tubing string from first and second zones which communicate with a hydrocarbon wellbore is disclosed. The apparatus includes a packer positioned in the wellbore for selectively preventing a flow of fluids through the wellbore from the first zone to the second zone, a production tubing string that extends through the wellbore and is in fluid communication through the packer with the second zone, and first and second pumps for displacing fluid through the production tubing string. The second pump displaces fluid from the lower zone into the production tubing string. A perforated joint is placed in the production tubing string between the second and the first pump. The second pump has a given displacement capacity at a given speed and is of a type that inhibits a flow of fluid in either direction through the pump when it is not pumping fluids from the second zone. The first pump is positioned in the production tubing above the second pump and has a predetermined displacement capacity at the pumping speed which is greater than the capacity of the second pump by the capacity desired to be produced from the first zone. The lower pump meters fluid from the lower zone and the upper pump produces fluids from the well so that both zones are produced simultaneously without fluid loss from either zone regardless of which zone has lower pressure. The means for controlling fluid communication through the packer depends on which zone has higher pressure. The advantage is a simple inexpensive apparatus for efficiently producing hydrocarbons from two production zones with pressure differentials without loss of fluid to either zone. Hydrocarbon production from the well is thereby maximized, stabilized and potentially prolonged.

Apparatus and method for dual-zone well production

A method and apparatus is disclosed which reduces or removes axial loads on the drive string of a rotary downhole pump, i.e. tensile loads due to the hydrostatic load of the pumped liquid on the pump rotor, and/or at least part of the weight of the drive string, or thrust loads caused during pressurized fluid injection operations by backpressure of injected fluid on the pump rotor. This substantially prevents drive string/production tubing friction, wear and/or buckle in downhole rotary pumping arrangements operated in straight or curved well bores. When used in connection with fluid production pumping arrangements, the apparatus reduces the friction between the drive string and the production tubing of a downhole rotary pump for the pumping of well fluids which pump has a pump rotor connected to the drive string and is operated in a well bore. When used in connection with fluid injection pumping arrangements, the apparatus prevents drive string buckle, especially in curved well bore situations. The apparatus includes a support for rotatably supporting the drive string in the production tubing at a location above the pump, and a fluid passage for permitting the pumped fluid to flow from the pump to a wellhead of the well. The support includes an axial load bearing structure for supporting, from the production tubing, at least part of an axial load on the drive string either generated by the hydrostatic load of a pumped liquid on the pump rotor or backpressure of injected fluid on the pump rotor. The fluid passage is shaped and constructed such that the pumped fluid can flow from the pump past the axial load bearing means to the wellhead. In fluid pumping applications, the apparatus can also be used to support at least part of the weight of the drive string to reduce the axial load on the drivehead.

Downhole swivel

A hardfacing for downhole progressing cavity pumps is disclosed as well as a method for producing same. The hardfacing consists of a metal carbide layer applied to the ferrous pump rotor body by way of plasma spraying and a top layer of metallic material having a lower hardness than the metal carbide. The metal carbide layer has a grainy surface with a plurality of peaks and intermediate depressions, the peaks being formed by metal carbide grains at the surface of the metal carbide layer. The thickness of the top layer is adjusted such that the depressions between the peaks of the metal carbide layer are completely filled thereby providing the rotor with a metal carbide hardfacing of significantly reduced surface roughness. In the process of the invention, the pump rotor, which may be provided with a molybdenum bonding layer, is plasma coated with the metal carbide and the resulting carbide layer is covered with the metallic material top layer. The top layer is polished either until the dimensions thereof are within the tolerances acceptable for the finished rotor or until a majority of the peaks of the carbide layer are exposed. The hardfacing significantly increases the service life of the rotor and stator of downhole progressing cavity pumps.

Method of applying a filled in metal carbide hard facing to the rotor of

A leakproof seal arrangement is disclosed for use in the drivehead of a downhole rotary pump, which pump is operated by a drive string suspended from the drivehead for rotation in a production tubing about a longitudinal axis, the drivehead having a bore in fluid communication and coaxial with the production tubing and sized to permit the passage of a polished rod attached to a top end of the drive string. The seal arrangement includes a centralizer sleeve for receiving a portion of the polished rod; a bearing for rotatably supporting the centralizer sleeve in the drivehead coaxial with the bore, whereby an annular gap is created between the centralizer sleeve and an opposite, cylindrical wall of the drivehead which gap is in fluid communication with the production tubing. The seal arrangement further includes a centering packing for sealingly and concentrically connecting the centralizer sleeve with the polished rod for simultaneous rotation about the longitudinal axis. The centering packing is sufficiently elastic to accommodate wobble of the polished rod in the centralizer sleeve while preventing leakage of a pumped liquid present in the production tubing and the centralizer sleeve during operation of the pump. The seal arrangement also includes an annular drivehead seal for sealing the annular gap which is also filled with the pumped liquid during operation of the pump, to substantially prevent leakage of the pumped liquid from the drivehead. With this seal arrangement, polished rod wobble compensation and sliding sealing of the drivehead are carried out at separate locations in the drivehead which results in a more reliable seal and reduced stress on the seal materials used and provides the seal with an extended service period.

Seal arrangement for the drivehead of a downhole rotary pump

A safety coupling for preventing backspin at excessive speeds of a torque transmitting drive powering a drive shaft which stores reactive torque due to torsional stress is disclosed. The safety coupling includes a rotatable driving member to be coupled with a torque producing power source, a rotatable driven member to be coupled with the drive shaft for axial rotation therewith, a support structure for coaxially and rotatably supporting the driving and driven members in relation to each other, a radial abutment provided on the driving member, and a centrifugal force responsive pawl pivotally mounted to the driven member for releasable engagement with the abutment. The pawl is pivoted from a locking position wherein it engages the radial abutment upon mutual rotation of the driving and driven members to provide a positive driving connection therebetween, to a disengaged position wherein the driving and driven members are freely rotatable relative to each other by the centrifugal force acting thereon when the driven member is coupled to a drive shaft backspinning at a speed in excess of a selected speed. The coupling substantially prevents damage to the torque transmitting drive upon excessive back-spin of the drive shaft and reduces the risk of injury to personnel working in the vicinity of a drive shaft subject to elastic torsion.

Safety coupling for rotary down hole pump

Hardfacing for progressing cavity pump rotors

A drive head for a down hole rotary pump driven from a well head assembly by a drive string that extends through the well to the pump is disclosed. The drive head includes a hollow rotatable drive shaft having an axial passage for accommodating a slip shaft, a housing attachable to the well head assembly, radial bearings centering the drive shaft in the housing and a thrust bearing for supporting the weight of the drive shaft and the drive string suspended therefrom. A pulley is mounted on the shaft for driving the drive shaft. The slip shaft is mounted to the top end of a polished rod which is attached to a top end of the drive string. The slip shaft and the passage in the drive shaft are preferably hexagonal so that drive torque is transmitted to the drive string without slippage of the shaft. The drive string is suspended in the well by a clamp that grips a top end of the slip shaft and rests on a top of the housing. The advantages include the elimination of damage to the polished rod and/or the down hole pump due to polished rod clamp slippage, improved transmission of drive power, and a drive train that cannot be lost down the well when a clamp slips or breaks.

Drive head for rotary down hole pump

A relatively simple hydraulically operated disc brake mechanism for drive systems which store reactive torque by reason of being under torsion is disclosed. Certain drive systems such as the drive strings for deep well submersible pumps store considerable reactive torque due to torsional stresses. Such torque must be controllably released if drive power is interrupted. The disc brake mechanism includes a housing that defines a reservoir for lubricating oil for the bearings of a shaft that drives a bi-directional hydraulic pump. When the shaft turns in an operating direction, the pump pumps the lubricating oil in a closed circuit through a filter and back to the reservoir. If normal operation is interrupted and the reactive torque in the system is released, the bi-directional pump forces oil through a control manifold to a disc brake caliper which brakes a disc rotor attached to the shaft. The faster the shaft turns as it releases reactive torque, the more braking force applied. As reactive torque is released, pump speed drops and brake force is correspondingly reduced until all reactive torque is released from the drive string permitting safe handling and soft restart of the drive string. The advantage is much improved safety and a self-regulating brake mechanism that handles power interruptions without manual intervention.

Safety disc brake assembly

A drive head for a downhole rotary pump operated by a drive string rotatable in a production string includes a hollow rotatable drive shaft having an axial bore for a polished rod, a housing attachable to a wellhead assembly, radial bearings centering the drive shaft in the housing and one axial thrust bearing to support the weight of the drive shaft and the drive string suspended therefrom. A pulley mounted on the shaft for the driving of the drive shaft, which includes a chuck arrangement for the concentrical clamping of the polished rod in the drive shaft. The drive head is used in combination with a polished rod clamp which is affixed to the polished rod for the suspending of the weight of the drive string and rests on top of the chuck arrangement. This construction substantially prevents polished rod wobble and the associated stuffing box leakage as well as accidental downward slippage of the drive string which could lead to serious damage of the downhole pump.

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Bragg Creek, Canada

Robert A Mills