Foam drilling

Keep mud weight as low as possible. Maintain minimum flow resistance of mud. Consider air drilling or foam drilling. 

Foam Systems. The preparation, composition, and maintenance of foam completion and workover fluids is similar to that of foam drilling fluids. The advantage of foam is the combination of low density and high lifting capacity at moderate flow rates. The use of foam as a completion fluid can be justified by. 

The volumetric rate of flow requirements for air drilling operations and unstable foam drilling operations are quite large, on the order of 1,000 actual cfm to possibly as high as 4,000 actual cfm. 

For stable foam drilling operations, much less volumetric rate of air flow is needed (i.e., usually less than 500 actual cfm). Also, the compressor should be capable of variable volumetric rate of flow and variable output pressure. The back pressure must be continuously adjusted to maintain a continuous column of stable foam in the annulus. This continuous adjustment of back pressure requires, therefore, continuous adjustment of input volumetric rate of airflow and output pressure (also, water and surfactant must be adjusted). 

Pertinent engineering calculations can be made for air and gas drilling operations and for unstable foam drilling operations. 

The downhole turbine motor designed to be activated by the flow of incompressible drilling mud cannot operate on air, gas, unstable foam or stable foam drilling fluids. These downhole turbine motors can only be operated on drilling mud or aerated mud. 

Aquafoam. [Aquaness] Ethoxy ether sulfates foaming agent for foam drilling. 

Yelvetex . [Henkel/Emety/Cospha] Betaines, propionic acid, acetates amphoteric surfactants for personal care prods., cleansers, foam drilling and blanketing. 

Desirable foams Foam drilling fluid Foam fracturing fluid Foam acidizing fluid Blocking and diverting foams Gas-mobility control foams... 

The features of foam application in petroleum industry were summarised by Schramm [224], Thereafter only very few publications appeared on this subject, so that we mainly describe Schramm s concepts. First of all, these are foams which contribute to an enhanced efficiency of oil recovery foam drilling fluids, foam fracturing fluids, gas mobility control foams, and foam acidising fluids. 

Foams produced at a wellhead are usually undesirable. When a foam-drilling fluid is brought to the surface, defoaming is needed to prevent overfoaming of the pit or tank. This can be accomplished by adding a defoamer, such as a poly-dimethylsiloxane [24, 162]. In primary oil production, oil flows under its own pressure, through permeable porous rock formations, to a production well. When oil nears and enters the annulus of a production well, it experiences a decreased system pressure, dissolved gas may come out of solution, and the oil may foam. 

Anderson, G.W. (1976) Foam drilling technoques and uses. Proceedings, Rotary Drilling Conference of lADC, International Association of Drilling Contractors, Houston, TX, March 9-12, 1976. 

Gas/Liquid Systems Producing oilwell and well-head foams Oil flotation process froth Distillation and fractionation tower foams Fuel oil and jet fuel tank (truck) foams Foam drilling fluid Foam fracturing fluid Foam acidizing fluid Blocking and diverting foams Gas-mobility control foams... 

Figure 5. Schematic illustration of a foam drilling fluid system.

Flexibility of Foam Drilling. Foam is the most versatile of all the low density drilling fluids. The water (LVF) and percentage of gas (GVF) can be easily controlled at the surface to achieve bottom hole pressures sufficient to drill the well. Various surfactant chemicals can be added to the water phase to address such problems as influxes, shale... 

Widely used because of their relatively low cost, glycol ethers, such as ethylene glycol mono butyl ether, can have beneficial effects as demonstrated below, in Table 6. In this table, the effect of various glycol ethers on the performance of a typical commercial foam drilling product is... 

Well Site Safety. Containment of a foam drilling fluid into a closed loop system provides a measure of safety that open systems do not allow. Hydrocarbons, acid gases and oxygen depleted air are kept safely away from personnel. Additionally, open foam pits can create a hazard, as they are typically plastic lined pits, that could allow the unknowing person to slip in and possibly suffocate under a blanket of foam. 

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