A fluid inclusion study conducted on a well in the northern North Sea showed a remarkable correlation between fluid inclusion stratigraphy responses and depths of drilling 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 larger organic molecules to an abundance of smaller ones and trapping of these in inclusions formed by supercooling of partly melted sediment explain the correlation. Not all wells are consequently suitable for fluid inclusion screening analyses. Thus, before initiating fluid inclusion studies, wells that have experienced intense heat during drilling should be identified and avoided.

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