Frequently Asked Questions
Will sand settle within the clearance (inactive) sections during pump operation?
No. The pump is continuously cleaned by fluid traveling through the inactive cavities up the pump. Flow through clearance sections is akin to flow through a pipe but the pipe is doing work on the fluid.
Will sand settle within the clearance (inactive) sections during a shut down?
The maximum amount of sand that might settle within the clearance sections is proportional to the sand cut of the emulsion. If the fluid is carrying 5% sand, then during a shut down 5% of the cavity will contain sand. It is doubtful that this sand will impact pump restarts because the amount of sand is similar to the amount of sand settled in sealed (active) cavities. As well, it is important to note that clearance cavities are only slightly smaller than sealed cavities and don’t represent a large gap or annular space but rather just a “size-on-size” fit as opposed to a “compression fit”.
Will the sand/emulsion wear away the elastomer in the clearance (inactive) sections during pump operation?
No. Prior experience and testing with abrasive media, such as sandy emulsions, have not shown to wear empty or non-active sections of stator elastomer. Research into abrasive erosion has indicated that the velocities required to cause
erosion to the elastomer do not occur.
Will this pump handle sand?
We are targeting sandy applications and expect this rotor to perform similarly for sand handling (torquing frequency) to a conventional rotor. Sandy applications tend to wear out the stator quickly, so this is an ideal application. Field trials
are the only way to test this capability.
Will this pump handle gas?
Yes, the PivotAL pump is a great solution for gas handling. PC pumps in general are great at handling gas; however, performance and life can be reduced when increased pressure loading and heat buildup in the discharge area of the
pump. As the gas compresses, it creates increased slip and fluid shear towards the pump discharge. These effects damage and cause premature failure of the elastomer where the rotor and stator create a seal (interference fit). The PivotAL rotor aims to restore the pump through re-engaging the rotor with undamaged, previously inactive elastomer.
When should I run this pump?
All PC pump wells are potential candidates, but the best candidates are those that have a high likelihood of stator damage as the failure mode especially due to run-dry/burnt or rapid wear, which occur quickly without a lot of damage to the rotor. Examples of good well candidates include low inflow, gassy, sandy or abrasive conditions. Recompletions or new well completions may be a good applications as a sacrificial pump to clean up the sand. Also, wells with very high rig costs should be considered given the savings from not having to pull the stator/tubing.
Is the rotor susceptible to breaking?
The rotor has 50 thousandths of an inch clearance on each side of the rotor minor cross section; LSI pump geometries are designed strong enough that this small change does not impact the overall rotor torsional strength. As well, the transition between the two sections is blended so it shouldn’t act as a stress raiser. After the rotor is lifted 12 inches to the second position, it may be at a higher risk of breaking due to bending stresses associated with the rotor protruding out of the top of the pump; only field trials will tell.
Why not use a polished rod between active sections instead of a shaved rotor section?
A polished rod would need a very small diameter to drift the stator lobes during the rotor’s orbit. The diameter is too small to realistically work under the high torques/tension experienced in a well.
What polished rod stick-up is appropriate?
Polished rod stick-up should be minimized during installation so that a 12-inch lift can be undertaken at a later date and still keep the overall stick-up within the 16 to 18 inches maximum recommended by industry. In some cases, a pony rod can be placed at the top of the rod string, below the polished rod, which can be removed in order to lift the rotor the appropriate distance.
Is my space-out procedure of the rotor off tag any different?
No. The space-out procedure is the same with Lifting Solutions conventional models.
Can we lift the rotor less than 12 inches at a time?
Yes. Incremental rod lifts may be a good strategy to maintain a proper seal during operation and as the elastomer starts to wear out. Incremental lifts also have the secondary benefit of moving wear spots on the rod and tubing strings.
Is the bottom of the pump ever inactive (clearance fit)?
No. The rotors are designed so that in both positions, initial and lifted, the bottom cavities have an interference fit.
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