Exxon Company, U.S.A. extended application of existing hole opening and underreaming technology and improved tool performance in two recent deep offshore directional wells. These Gulf of Mexico wells experienced an almost 100% increase in tool life even with the added complexity of hole enlargement to directional depths deeper than previously encountered in this offshore region. Earlier straight wells in the area were characterized by short tool life and loss of cutters. Improved hole opening and underreaming practices were major factors in this success.

This paper discusses the general evolution of hole enlarging techniques, examines hole opener and underreamer performance in four recent offshore wells, develops a correlation between specific operating practices and increased drilling performance and recommends guidelines to improve operation of these tools in both straight and directional offshore wells. The analysis includes an investigation of penetration rate, bit hydraulic horsepower, bit weight, rotary speed, cutter type, stabilization, bull nose design and shock sub employment.

Keywords:
tool life, depth category, bull nose, hole opener, society of petroleum engineers, cutter, feet tvd, bit weight, casing design, underreamer
Subjects:
Drillstring Design, Drilling Operations, Casing and Cementing, Hole openers & under-reamers, Casing design
Copyright 1985, Society of Petroleum Engineers
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