Paper: Drilling String Designs For Deep Drilling Operations

Before 1950, drilling strings contained few drill collars, and the hole depth was shallow enough so that grade-E drill pipe easily satisfied most requirements for drilling and drill-stem testing. In 1957, when Great Western Drilling Company drilled the Phillips Petroleum Company Montgomery A-l to 23,400 feet, engineered drilling strings became necessary. Between 1957 and the time the API published RP7G, drilling-string design was a daily necessity for drilling engineers to avoid operational problems and to satisfy contractural requirements. Each engineer designed his drilling strings based on his knowledge and training, and the procedures were based on techniques previously used in the design of casing. In the vacuum created by operational necessity and the lack of API recommended practice we developed a philosophy and two report forms for our use which have worked well. Examples of the use of these report forms and a comparison between our philosophy and the API RP7G recommended approach are presented in this paper.