Question

A conventional Sucker Rod Pumping (SRP) unit is used to lift 25 API oil from a depth of 5000 ft. During operation, the maximum and minimum values of the polished rod load are recorded as 14300 lbf and 5200 lbf respectively.
The ideal counterbalance load (in lbf) is _________ (answer in integer).

Hint:

The ideal counterbalance load is the arithmetic mean of the peak and minimum polished rod loads.

Answer 1

Correct Answer: 9750

Step 1: List the given polished rod load readings:
$PPRL = 14300$ lbf and $MPRL = 5200$ lbf
Step 2: Instead of averaging directly, work with the load range:
The total swing in the polished rod load over one stroke is the range, given by \[ \text{Range} = PPRL - MPRL \]
Step 3: Compute the range:
Range = 14300 - 5200
Range = 9100 lbf
Step 4: Take half of this range:
Half range = 9100 / 2 = 4550 lbf
Step 5: Subtract this half range from the peak load to get the ideal counterbalance load:
\[ ICL = PPRL - \frac{\text{Range}}{2} \]
ICL = 14300 - 4550
ICL = 9750 lbf
Step 6: Cross check by adding the half range to the minimum load instead:
ICL = MPRL + 4550 = 5200 + 4550 = 9750 lbf, which matches the previous step and confirms the result.
Final Answer:
\[ \boxed{ICL = 9750 \text{ lbf}} \]