Accuracy of Nitrogen Temperature Correction Factors
Rob Sutton
Marathon Oil Corporation
Abstract
Nitrogen gas is used to charge domes in gas-lift valves and some downhole safety valves, to provide the closing
force for the valve. The design pressure and temperature conditions in the well must be equated to the shop
conditions where the valve is set up and tested. Shop conditions are typically established at 60°F so the nitrogen
pressure at operating conditions in the well must be adjusted to the shop conditions; hence, the name “temperature
correction factor.”
Early downhole design conditions were typically in the 500 - 1,000 psig range which formed the basis for the
development of early tables used within the industry. As more challenging conditions were encountered, the
accuracy of these tables diminished and new methods were developed that form the basis of the procedures used
today. These methods were developed using published nitrogen Z factor data that ranged to 3,000 psig and 300
°F. The new methods used 2nd and 3rd order polynomial equations as the model. These types of polynomial
equations typically do not offer an accurate extrapolation as boundary conditions are reached or exceeded.
This talk examines the calculation methodology and accuracy of nitrogen temperature factor methods at operating
conditions ranging to 5,000 psig and 400 °F.