James F. Lea and Mike Brock, PLTech, LLC
Downhole sucker rod pump clearance changes from shop conditions to bottom hole conditions due to bottomhole pressure and temperature that the pump components are subjected to. Presented here are equations to estimate the change in dimensions of the plunger and barrel of top and bottom hold down pumps at bottomhole pressure and temperature conditions. The approach uses one equation for cylinder dimension changes with pressure with appropriate inputs for the internal and external pressure (or average pressure) for the upstroke when slippage is important and has an effect on the total production. Examples are given for thin and heavy wall pumps at a variety of depths, pressures, and temperatures. Corresponding production rates for the calculated downhole pump dimensions are given.