Foam drilling formation water

In air drilling areas, the use of air drilling technique can be prolonged when formation water enters the hole by adding a small stream of liquid surfactant to the air stream. The addition of surfactant forms foam at the contact with formation water. The foam carries out cuttings and produced water. Considerable volumes of formation water can be held using this technique. 

Chemical additives for gas-based drilling fluids are limited to surfactants (qv), certain polymers, and occasionally salts such as sodium or potassium chloride. An aqueous solution of the additives is iajected iato the air or gas flow to generate a mist or foam. No additives are used ia dry air or gas drilling operations. Gas-based fluids are not recirculated and materials are added continuously. As the fluid exits the well, air or water vapor escapes to the atmosphere, gas and oil are burned, and water and formation soflds are collected into a pit for later disposal. Stable foams must be destabili2ed to separate the air from the Hquid phase for disposal. 

In oil-producing formations with high fluid loss, drilling in with foam and foam completion proves beneficial. Usually, these formations cannot stand a column of water—so it is impossible to establish returns with conventional mud. The use of foam for drilling in and completion results in substantial increases in production. 

The superheated water melts the sulfur in the vicinity of the well, forming a molten sulfur pool at the bottom of the well. As production continues, the formation fills with water. To continue production, bleed wells are drilled at the periphery of the formation to allow for discharge of the cooled mine water. In some mine fields, sufficient mine water is lost to the geological formation to provide for continued production. To limit mine water loss, mud or synthetic foam sometimes is pumped into the formation to seal major crevices. 

Down-hole pressure fluctuations, due to the termination of flow in the annulus, are unquestionably of great concern. When circulation is stopped, during a connection or survey, for example, the foam can break-back to soapy water and its gas phase. The gas can then expand toward the surface. In order to re-establish circulation of foam, the "broken-back water in the bottom of the well must be displaced by newly introduced foam through the drill pipe. The BHP increases until the fluid begins to move up the wellbore. As the fluid is lifted out of the well, the BHP decreases, subjecting the formation to a dramatic pressure drop. In pressure sensitive formations this may have an unfavorable effect on borehole stability. In these cases, special additives can be used to create exceptionally stable foams. These foams are many times referred to as "stiff, or "stable, foams. 

Large Diameter Well with Recyclable Foam. The objective on this well was to drill a 26-inch surface hole to 1500 feet and a 17.5-inch intermediate hole to 6000 feet with foam. Previous drilling in this particular region had proven to be excessively expensive due to low penetration rates. There existed a known potential for lost circulation, large fresh water influxes, and unconsolidated formations in the upper section of the well. Foam was chosen as the drilling fluid of choice, due to its ability to function effectively in the presence of high water influxes and... 

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