Treatment of fluid having lost circulation material

Abstract

A method for separating fluid and fibrous lost circulation material from a mixture of fluid, drilled cuttings and fibrous lost circulation material, the method including introducing the mixture onto a screen assembly that has at least two layers of screening material and including at least a first layer over a second layer, the layers with rectangular openings, the first layer having first rectangular openings each having a first width and a first length, and the second layer having second rectangular openings each having a second width and a second length, the ratio of the first length to the first width ranging between 1.55 and 2.00, the ratio of the second length to the second width ranging between 1.55 and 2.00, the ratio of the first length to the second width ranging between 0.95 and 1.05, and the lengths of the first rectangular openings parallel to lengths of the second rectangular openings.

Description

[0001] This is a continuation-in-part of U.S. Ser. No. 09 / 432,959 filed Nov. 8, 1999, and a continuation-in-part of U.S. application Ser. Nos. 09 / 745,279 filed Dec. 20, 2000 and Ser. No. 09 / 749,263 filed Dec. 27, 2000 all co-owned with the present invention and application and all 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 the porosity of the formation and / or 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, it is usually supposed that the lost circulation occurred at some spec...

AI Technical Summary

Benefits of technology

0023] Such methods in which the resident time in a screen assembly of material that can swell is reduced and the passage of such material through the screen assembly is facilitated;

Problems solved by technology

Whether fractures induced by excessive mud pressure are parallel to the axis of the borehole (vertical) or perpendicular to the axis of the borehole (horizontal) is a subject of some controversy.

Certain of these screen combinations have difficulty in handling LCM material and the material often blinds these screens.

Typical known shale shaker screens or screen assemblies with square mesh openings often are clogged when attempts are made to separate lost circulation materials from a mixture of them with fluid that has been pumped down a wellbore.

In certain particular circumstances there have been problems with commercially available ULTRA-SEAL lost circulation material that has fibrous material in it.

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