When conventional drilling technology is used, good technical practices recommend that the surface and intermediate casing strings be run in holes with a diameter of up to 6-7 inches. larger than the casing. This procedure is based on the fact that:
it is difficult to drill a straight vertical well with conventional technologies;
the larger is the casing diameter, the stiffer is the casing string.
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. The "Lean Profile" has been successfully applied to some wells drilled from on-shore clusters with parallel vertical sections. The drilling environment is challenging with problems such as formations' tendency to deviate from the vertical trajectory, well-bore instability and circulation losses. In this operating scenario the "Lean Profile" provided for drastic time and cost reduction. In fact, in the drilling process resulted in outstanding drilling performance with less material consumption and less waste to be treated. For the future, the most interesting scenario being investigated is the drilling of deep offshore wells. Applying the "lean profile" concept in this field is certainly a challenging task, yet it would provide major savings, given the high costs drilling rig hire.
borehole diameter by just one inch, even for initial well sections While drilling an oil well, the bore hole needs to be lined with casings so that Foro 17 1/2" (17"1/2 HoleConvenzionale) 13"3/8 drilling can continue with a smaller bit size. (Conventional) When conventional technologies are used, there are difficulties in drilling entirely vertical bore holes and large diameter casings (e.g. 20" or 13 3/8") are extremely rigid, so a borehole with a much larger diameter than the casing has to be drilled during the surface and intermediate stages, to ensure the casing is run to the bottom hole. The difference between the borehole diameter and external casing diameter (clearance) during these stages can in fact be more than 6-7 inches. As the depth increases and the casing diameter decreases, the clearance is reduced to values of about one inch. Obviously, due to the initially large 14"3/4 hole (Lean Profile) borehole diameters, drilling rates are fairly slow, significant amounts of material are Fig 1 Comparison between a conventional consumed, (casing, drilling mud, cement, etc), borehole diameter (17"1/2) and a "Lean and large quantities of cuttings are generated. Profile" diameter (14"3/4) drilled for running in 13"3/8 casing The "Lean Profile" technology The success of the "Lean Profile" To overcome
