New downhole tools improve core recovery : D. P. Huey & M. A. Storms, Oil & Gas Journal, 93(4), 1995, pp 42–47

Abstract

The need to analyze cores at downhole conditions prompted the development of a series of pressure core barrels, which can capture cores without disturbing the sample through depressurization. In upper marine sediments, tungsten carbide insert roller cone bits tend to have life expectancies of several hundred rotating hours and thousands of meters of penetration. A bit can drill through hundreds of 10-m core intervals before a pipe trip is required for a bit change. For time efficiency in coring operations in water depths averaging 3,000--5,000 m, both the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) made a full commitment to wire line coring techniques wherever possible, thereby minimizing the number of pipe trips. The initial rotary core barrel became inadequate for the high quality of cores desired for scientific analysis. The first new core barrel developed by DSDP to satisfy the increased scientific specifications was a wire line-retrievable pressure core barrel. The paper describes this pressure core barrel, as well as a pressure core sampler, hydraulic piston corer, advanced piston corer, extended core barrel, motor-driven core barrel, core catchers, coring mud motor, and a diamond coring system.