Borehole instability mechanism and Countermeasures Part-I

Sidewall instability is including in borehole wall collapse, necking down, formation fracturing etc three basic types during the drilling or completion process. The first two causes may enlargement or reduction of borehole diameter, the last cause which could easily lead to lost circulation. Borehole instability is one of complex situations during the down hole drilling project, Seriously affect the address data of acceptance, drilling speed, quality and cost
1. Types and phenomenon of borehole instability

During the drilling process, if drilled formation such as mud shale, sandy, sand flow, muddy sandstone or siltstone, coal seam, carbonates etc. may occur wellbore instability. Well collapse may occur in a variety of lithology, different clay mineral type and content of the formation.
Borehole instability phenomenon is divided into: 1 borehole collapse phenomenon; 2 necking down phenomenon; 3 fracturing phenomenon....

To be continued...

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