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:
it is difficult to drill a straight vertical well withconventional technologies;
the larger the casing diameter the stiffer the casingstring.
The clearance between casing and open hole is then reduced to about 1" for the deeper sections, because of the higher flexibility of the casing strings.
This paper presents the "Lean Profile", an innovative drilling technique which aims at maintaining 1" 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 "Lean Profile" 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 formations' tendency to deviate from the vertical trajectory, wellbore instability and circulation losses.
In this operating scenario the "Lean Profile" 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 d'Agri, southern Italy, with interesting cost saving opportunities.
This paper summarizes experiences and results from the field along with engineering considerations.
