Foaming agents drilling fluids

Surfactants. Surfactants (qv) perform a variety of functions in a drilling fluid. Depending on the type of fluid, a surfactant may be added to emulsify oil in water (o/w) or water in a nonaqueous Hquid (w/o), to water-wet mud soHds or to maintain the soHds in a nonwater-wet state, to defoam muds, or to act as a foaming agent. 

A drilling fluid comprising air, water, and a foaming agent (surfactant). These substances travel into a well as a mist, then change into a foam before returning up the annulus. See also Air Drilling Fluid, Stable Foam, Stiff Foam. 

To eliminate imwanted influxes, many wells have been intentionally drilled overbalanced with foam. Proper fluid chemistry is essential in these situations. If the foam breaks-down, or specifically, if the viscosity of the foam is altered by the influxes, the friction factor decreases and, in turn, the bottom hole pressure is reduced. A general understanding of fluid chemistry, and the selection of the proper foaming agent, is essential in assuring a successful project. Many projects have failed in the past due to inadequately applied chemistry. 

The foam is essentially killed by the addition of an acidic solution. Of commercial importance is the fact that this fluid can then be reeyeled, as this interference is reversible. Once the pH is elevated the foaming action returns and the fluid can be reused. This foam, defoam, refoam cycle can continue on for many cycles. However, makeup foaming agent must be added to replace the foaming agent lost due to surface adsorption of the drilled solids. 

Uses Wetting and foaming agent for sat. brines incl. CaClj, HCI, NaCI, high-temp, acidizing drilling fluid additive removes oil-based muds prior to cementing or stimulation stable to 400 F stable to acids Properties Water-wh. liq. 50% act. 

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