Drilling Conditions Making Wells Unsuitable for Fluid Inclusion Stratigraphy (FIS) Studies

Ohm, Sverre E.¹; Haneferd, Helen ¹
(1) Exploration, ConocoPhillips, Stavanger, Norway.

A fluid inclusion study carried out on a well in the Northern North Sea showed a remarkable correlation between fluid inclusion stratigraphy (FIS) responses and depths of bit changes. Further investigation of the well data suggested that extreme temperatures occasionally had been generated at the bit-sediment interface during drilling. Cracking of mud-additives to an abundance of smaller molecules some of which are monitored during FIS studies, and trapping of these in inclusions formed by super-cooling of partly melted sediment explain the correlation. Not all wells are consequently suitable for fluid inclusion screening analyses. Thus, before initiating FIS studies, wells which have experienced intense heat during drilling should be identified and avoided.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.