Correlations predict friction pressures of fracturing gels

Abstract

Friction pressure calculations are very important in the design of any hydraulic fracturing treatment. They are useful in determining horsepower requirements, bottomhole treating pressure, and maximum wellhead pressure. This article presents a classical approach in which flow data of various gels in multiple pipes are presented as two dimensionless quantities, Fanning friction factor and generalized Reynolds number. These dimensionless quantities are then correlated as a function of power-law flow behavior index n'. Fluids with a wide range of generalized Reynolds number (N' /SUB Re/ = 2 X 10/sup 3/ to 5 X 10/sup 5/) and flow behavior index n' = 0.272 to 1.0) have been investigated. The correlations can be used to estimate friction pressures of both uncrosslinked and crosslinked gels. A method predicting friction pressures based on these correlations has already been implemented on a field transportable rheology system and good success has been reported. The friction pressures estimated from these correlations have been compared favorably with field data from several fracturing treatments. Effect of pipe roughness pressure of gelled fluid has also been examined. This testing indicates that pipe roughness does not affect pressure at high gel concentration. This contradicts previous thinking.