Patent ID: 7828079

Claim:
A method of obtaining core samples that minimizes contamination of the core samples by intermittently removing slough from a borehole, comprising: drilling a bore hole using a core barrel; capturing a core sample within the core barrel; retrieving the core barrel and captured core sample from the bore hole using a wireline; lowering a slough removal assembly into the borehole, the slough removal assembly including: (i) a slough barrel including a retainer adapted to allow slough to pass into, but not out of, a distal end of the slough barrel, and (ii) a shoe secured to the distal end of the slough barrel; driving the slough removal assembly into the borehole so that slough is introduced into the slough barrel of the slough removal assembly by passing through the retainer; withdrawing the slough removal assembly and the captured slough from the borehole using a wireline; drilling the bore hole to a further depth using a core barrel; capturing an additional core sample within the core barrel; and retrieving the core barrel and the captured additional core sample from the bore hole using a wireline.