Stability and Rheological Behavior of Aqueous Foams for Underbalanced Drilling

This paper presents evaluations of stability and theological behavior of aqueous foam formulations. The stability of these systems was evaluated by the Ross-Miles method, using half-life measurements, and was studied as a function of the type and concentration of surfactants, polymers and salts. The effect of contaminants such as crude oil is also examined. A capillary tube viscometer was used to perform the rheological studies. The effect of variables such as quality of the foam, pressure system, tube diameter and polymer type is shown. Results were corrected for wall slip effect and normalized by using equalized volume corrections. Results indicated that the sensitivity of the foam to contamination with oil and salts depends on the chemistry of the foaming agent system and crude oil used. The rheological evaluations showed that the flow behavior is highly dependent on the foam quality for a given pressure, the chemistry of polymer and the tube diameter.