Carbonate rock is a predominant Middle Eastern Region geologic feature. Penetration of 16" hole sections through carbonates in the Kuwait Northern Field has in the past required the use of more than one bit. This paper describes an engineering methodology that has produced bit designs that are consistently able to complete the entire 16" Kuwait Northern Field Section with a single bit as demonstrated by production drilling over the course of many bits. Case information is included.

The new design results from a symptom / cause / remedy approach that identifies root causes of unsatisfactory bit life and suggests productive, remedial solutions. Critical drilling information for prior bits was collected and analyzed to identify roller cone bit problems (symptoms). Remedies responsive to each symptom were developed. Remedy engineering was not constrained by traditional design guidelines and certain preferred solutions are considered to be unconventional. Specific, implemented remedies described by the paper include new cutting insert carbide materials and new cutting insert shapes both optimized for Middle Eastern carbonate drilling, and use of seal / bearing systems suitable for extended operation under high WOB.

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