The Lean Profile: a Step Change in Driling Performance

Abstract

With the conventional drilling technique, a general rule-of- thumb establishes that the surface and intermediate casing strings are to be run in holes with a diameter of up to 6-7 in. larger than the casing. This rule is based on the fact that: 1. it is difficult to drill a straight vertical well with conventional technologies; 2. the larger the casing diameter the stiffer the casingstring. The clearance between casing and open hole is then reduced to about 1î for the deeper sections, because of the higher flexibility of the casing strings. This paper presents the ìLean Profileî, an innovative drilling technique which aims at maintaining 1î clearance throughout the whole casing program, leading to a slimmer well profile but keeping the same size for the production casing string. To achieve this it is mandatory to adopt suitable drilling technologies that will be deeply discussed in the paper. The ìLean Profileî has been successfully applied to some wells drilled from on-shore clusters with parallel vertical sections long as much as 2,000 meters. The drilling environment is challenging with problems such as formationsí tendency to deviate from the vertical trajectory, wellbore instability and circulation losses. In this operating scenario the ìLean Profileî provided for dramatic time and cost reduction. In fact, the halving of the. rock volume involved in the drilling process resulted in an outstanding drilling performance (-40% on drilling time with respect to standard technology), less material consumption and less waste production. The Lean Profile is part of the drilling strategy for some 30 wells in the Val dëAgri, southern Italy, with interesting cost saving opportunities. This paper summarises experiences and results from the field along with engineering considerations.