Core capture and recovery from unconsolidated or friable formations and methods of use

Abstract

Methods and systems for enhanced capture and recovery of core samples from unconsolidated or friable formations are provided using drilling fluids that permit increased overpressures to preserve the ability to cut core samples and to strengthen the core samples obtained. Drilling fluids used during capture and recovery of core samples may comprise a solid particulate loss prevention material having a size range from about 150 microns to about 1,000 microns. The solid particulate loss prevention material prevents fracture initiation and propagation in the subterranean formation to allow the use of higher overpressures than would otherwise be possible. Thus, by circulating drilling fluid in the borehole while drilling a core sample, higher overpressures may be achieved, which have been found to be beneficial during core capture and recovery by maintaining core integrity and avoiding core loss. In this way, core sample integrity is improved, yielding more accurate representations of the subsurface.