The Pattani gas field in the Gulf of Thailand is known for having marginally economic reservoirs and so the operating company, Chevron Thailand Exploration and Production LTD (CTEP formerly known as Unocal Thailand LTD), has always needed to drill wells as fast as possible and at the lowest economic cost. This quest for efficiency led to selecting a slim hole drilling program that is completed within days, and as such, puts a lot of stress on the drilling equipment and in particular the small size drill string.

Over the years, the size of the drill pipe used to drill the production interval has evolved from 3 ½ to 4 in. with the use of a streamlined second-generation double-shouldered connection. Selecting a drill pipe configuration with higher torsional strength, improved hydraulics and buckling resistance contributed to improved performance and drillers delivering wells faster. The move to a 4 in. drill pipe body increased the stiffness and fatigue resistance compared to the 3-1/2 in. pipe. As a result, the fatigue resistance of the premium drill pipe connection was considered to be an area of improvement for the special fast drilling operation.

This paper will present the various options considered to enhance the connection fatigue resistance, the results obtained in simulation, laboratory testing and ultimately in operation. This last section includes information on the inspection reject rates and impact on the frequency of inspection that directly relates to the level of confidence one has in the equipment.

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