The technology of stabilizing foamed fracturing fluids has been extended to include the use of cross-linked gels as foam stabilizers. Gasified treating fluids prepared from these gels have unique properties which differentiate them from both traditional foams and gels. Traditional foams require that the gas/volume ratio be greater than 0.52 in order to obtain a stable foam structure. Such high gas ratios produce foams with low fluid densities and low proppant concentrations. Using crosslinked gelled fluid as the stabilizer for foams, very stable dispersions of gas in liquid can be prepared with almost any gas content. Stable foams having a gas/volume ratio (GVR) greater than 0.52 as well as stable energized fluids having a GVR of less than 0.52 can be prepared. Stable energized fluids containing less gas can have appreciably higher fluid densities and proppant concentrations. This paper describes the properties of foams stabilized with crosslinked gels, their broadened uses in stimulating wells and the results of treatments.

Recent studies under downhole conditions show the relationship between foam texture, i.e., bubble size and foam rheology. They also show that under the low shear conditions that exist in a fracture during treatment, foams behave as power law fluids. Dynamic fluid-loss testing indicates ·stabilized foams are some of the more efficient fracturing fluids available.Formation damage results help explain why foam-fractured wells clean up so well.As a result of our better understandi ng of the properties of foam under downhole conditions, we have developed new, highly stable foam systems. These systems a re 100 to 1000 times more stable than conventional foams and, therefore, greatly broaden the downhole conditions under which foams can be used.Fi el d results demonstrate the successful pl acement of large amounts of proppants with stable foams in both oil and gas wells at temperatures up to 300°F. In addition, foam-fractured wells clean up better and, therefore, payout faster than we 11 s fraced with conventional fluids.