MICA FLAKES have been preferably used in water-based and oil based oil-well drillings operations as an additive mud chemical to prevent loss of circulation and seepage. Mica is specially added to seal-off the lost circulation zones. The platy structure of mica facilitates the overlapping of particles to form a layer or wall and acts as a sealent that bridges the openings. The use of mica helps to seal porous formations and contributes to regain circulation keeping the solids in suspension.
The technique adopted is to mix quantities of mica flakes and granular bentonite into special batches of mud which is pumped down the hole. The drill pipe is then withdrawn and the hole left undisturbed for a time being. Mica flakes tends to plate out on the walls at the lost zones and reduce the size of the holes through which the mud can pass. After a short interval, the plug is strong enough to permit circulation to resume without loss. Drilling then proceeds normally until a depth well below the lost circulation zone.
Suitably used for sealing openings. Apparent density = 0.17kg/ltr. Particle Size : Max 10% retained on 9.50mm B.S.Sieve. Material retained on Sieve 4.75mm + material passed through 1.70 mm = 30-40% Max.
Generally used to combate mild circulation in porous formations. Apparent density=0.18 kg/ltr. Particle size: Max 10 % retained on 3.35 mm B.S.Sieve. Material retained on 1.70 mm + material passed through Sieve 0.425 mm = 30-40% Max.
Suitable for use when a sealing agent is needed to be small enough to pass through a shaker screen without interfering with the operations. Apparent density=0.20 kg/ltr. Particle size : Nil retained on 0.850 mm B.S.Sieve. Matertial retained on Sieve 0.425 mm + material passed through sieve 0.15 mm = 30-40% Max.