S. B. Johns and D. J. Lewis
Shell Oil Company
New Orleans, Louisiana
ABSTRACT
Shell Oil Company recently completed a four-well pressure coring program in unconsolidated Gulf Coast Miocene sands to determine residual oil saturations for a possible chemical flood program. During the period from 1972 through 1977, twenty pressure cores were attempted with a recovery efficiency of 42% and a pressure retention efficiency of 60%. By comparison, we recently attempted 26 pressure cores with a recovery efficiency of 69% and a pressure retention efficiency of 77%. Significant improvements in core recovery, pressure retention and core quality are attributed to improved equipment and more efficient operational techniques. Improvements in equipment include a basic redesign of the previous core barrels and use of a self-contained work trailer. Use of Stratapax type bits greatly enhanced core recovery while increasing drilling rates as much as ten fold. More efficient operational techniques include making a cleanout trip after each core and supervising closely all aspects of the operation using detailed check lists and data sheets. Photographs of each step of the operation are presented. Laboratory measurements of residual hydrocarbon saturations and tritium tracer derived estimates of invasion are briefly discussed.