The Use of Stable Foam
The successful application of foam as a circulating fluid is relatively new. The industry has long recognized the need for a low damage circulating fluid and has used various fluid systems to minimize formation damage. Foams low density and high viscosity at low shear rates make it exceptionally useful as a circulating medium in low pressure reservoirs. These properties minimize fluid loss to the formation and diminish required annular velocities yet provide high lifting capability at the lowest possible circulating pressures.
Exceptional Safety Record
Stable foam circulation has an exceptional safety record with no incidence of downhole or surface fire reported. This record can be accredited to:
- Very little foam (air) enters the hydrocarbon bearing zones because of the low pressure gradients and viscosity displayed by foam.
- Accelerated clean-out and drilling rates diminish the time that foam (air) is in contact with the hydrocarbon bearing formations.
- The gaseous phase in a foam is encapsulated in a film of liquid and any realistic amount of formation gas is immersed into the bubble.
At high pressures, nitrogen or other non-oxidizing gas can be implemented for superior safety if crude oil or flammable solvents are present in the well.