Ugly Pump Cards Caused by Mechanical Friction - Analysis and Troubleshooting of Dynamometer Surface-Pump Cards

Mechanical Friction applied to the rod string along the wellbore impacts the measured surface rod loading.  This friction acting on the rod string changes the shape of the pump card. The friction acting on the rods are not correctly modeled by the wave equation, resulting in the excess frictional loads and horsepower being displayed in the plot of the pump card (even though the friction is not applied at the pump).  When the pump card loads are higher than expected on the upstroke or plot below the zero-load line on the downstroke; then the displayed pump card loads are outside the expected load range and these excessive pump loads often indicate the effects of mechanical friction acting up hole on the rod string not being accounted for by the wave equation.  The pump card in effect, becomes the trash can for any mechanical loads applied to the rod string, including the weight of the rods that rest on the side of the tubing in a deviated wellbore. Many sets of field data will be used to show various downhole conditions that impact operations.  Dynamometer cards, particularly calculated downhole pump cards are difficult to use for diagnostics of problems that exist in these wells having unaccounted friction.  The process of using dynamometer and fluid level analysis to recommend possible solutions to correct operational problems will be highlighted.  Following list are some of the topics planned for this short course.

1.    Rod stretch shown in the surface dynamometer data used to identify the depth to a severe dogleg in the well that is causing the downhole sticking.

2.    Data collected using downhole load cells will be discussed

3.    Discussion on how the deviation and mechanical friction makes the calculation of down hole sucker rod loadings complex and difficult

4.    Examples dynamometer data showing different types of  Mechanical Friction:
a.    Paraffin
b.    Scale
c.    Over Tight Stuffing Box
d.    Misalignment
e.    Dog-Leg Severity
f.    Deviated Well
g.    Pump Friction
h.    Crimped Tubing
i.    Other