Rod/Tubing Wear

Figure 1 illustrates a conventional rod coupling in the deviated section of a directional or horizontal wellbore. The side-load in the well curvature is concentrated at the couplings which can cause holes through the tubing requiring service, replaced tubing, replaced couplings.

Figure 2 illustrates Pro-rod (coiled rod) in the same deviated section of a directional or horizontal wellbore. The side-load in the well curvature is spread over the length of the tubing, significantly reducing the likelihood of holes through the tubing.

The comparative difference in the measured side-loading (lbs/foot) can vary from moderate to extreme depending on rates, pumping speed, and fluid characteristics. Pro-Rod used the latest available software to calculate the side-loading on each specific well.

Frictional Flow Losses

Figure 3 illustrates fluid flow around a conventional rod coupling. The couplings are a restriction (typically every 25 ft), and can have a dramatic effect on the entire pumping system, especially in a PC Pump application.

Figure 4 illustrates the absence of couplings when using Pro-rod (coiled rod), which by design has only (2) couplings in its entire length (top and bottom). The elimination of these couplings removes the flow restriction (typically every 25 ft), thus lowering the pressure the pump must overcome, which in turn reduces Hp and torque requirements.

The comparative difference in the measured flow losses can vary from moderate to extreme depending on rates, pumping speed, and fluid characteristics such as viscosity.

Rod Fall

In a reciprocating application, rod fall can cause the rod string to go into compression on the down-stroke. The couplings create a "piston" or "floating" effect, causing the upper portion of the rod string to "fall" faster than the bottom section. A rod string going in and out of compression will shorten its run life and can create problems such as bridle separation at the pumping unit. The absence of couplings when using a Pro-rod (coiled rod) string remove this effect entirely.

Viscosity and tubing size are the biggest factors in determining how likely a "rod-fall" issue will occur.