Lost circulation fluid treatment

Abstract

A method for separating fluid from a mixture of fluid and fibrous lost circulation material, the method including introducing the mixture onto a screen assembly that is vibrating for passage of the fluid through the screen assembly and for separation of fibrous lost circulation material from the fluid, the screen assembly comprising a plurality of screens one on top of the other and including at least a first screen and a second screen, one of the screens with comprising a screen mesh woven with non-square openings as viewed from above.

Description

[0001] This is a continuation-in-part of U.S. Ser. No. 09 / 432,959 filed Nov. 8, 1999, incorporated fully herein for all purposes.

[0002] 1. Field Of The Invention

[0003] This invention is directed to methods for separating drilling fluid from a mixture of such fluid and lost circulation materials and to apparatuses useful in such methods.

[0004] 2. Description of Related Art

[0005] Often in drilling a wellbore, the circulation of drilling fluid to and then away from the drill bit ceases due to fracturing of the formation through which the wellbore is being drilled. Drilling fluid pumps into the fractured formation rather than being returned to the surface. When circulation is lost because of fracturing of the formation, it is usually supposed that the fracture occurred at some specific depth where the formation is "weak", and that the fracture extends horizontally away from the borehole. Expressions used to describe rocks that are susceptible to lost returns include terms like vugular l...

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