Abstract
Foams provide highly attractive alternative over conventional non-Newtonian fluids for various oil and gas industry applications because of their high viscosity and low liquid content. Foams have long history of proven performance in well stimulations, drilling, acidizing, cleanout operations, and enhanced oil recovery. Foam apparent viscosity is used in hydraulic (pressure drop) calculations for various pumping operations. Thus, accurate rheological characterization is very important to predict viscosity of foam.
In this investigation, rheological experiments are carried out with guar gel and guar foam fluids rheology using a ½-in. pipe viscometer at 1000 psi and temperature ranging from 100 to 200 °F. Guar, surfactant and nitrogen are used as the gelling agent, foaming agent and gas phase respectively. Foam formulations were prepared and tested for qualities ranging from 0 to 80 % at several flow rates.
The present study has shown that both guar gel and guar foam fluids exhibit a behavior analogous to the Power law model fluid. The experimental data are used to develop new rheological correlations to predict Power law fluid flow parameters and thus, apparent viscosity of the foam fluids. These new correlations are functions of temperature, foam quality, shear rate, and fluid concentrations. The correlations were compared with various published correlations. The available correlations in the literature have assumed that the flow behavior index of the foam is similar to that of the liquid phase. This assumption does not support the basic physics that the increase in viscosity decreases flow behavior index. Our results show that the above assumption is not valid and leads to a prediction of extremely low apparent viscosity of foam fluids. In contrast to the previous studies, we report high apparent viscosities of foam fluids at high qualities.
