In January 1991, Petroleum Development Oman L.L.C. began a campaign to drill six medium radius horizontal wells in the Nimr field in South Oman. The wells were drilled with a 12-1/4" build up section followed by an 8-1/2" horizontal section. On the basis of this campaign, a decision was made to extend the number of horizontal wells to be drilled in the Nimr field during 1991. The first three wells of the second campaign were drilled to the same design as the original six wells, principally due to the non availability of certain tubulars needed for a radical design change. Once the required equipment was available, the wells were drilled and completed with a Composite Liner Design, i.e. the build up and horizontal sections were drilled and cased in the same hole size.

This paper discusses the original well design criteria, the results of the operational learning curve (the new design concept for Nimr wells), and the economic benefits. By the end of February 1992, four of the new design wells had been successfully drilled and completed.

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