Optimizing Wellbore Design using Solid Expandable Tubular and Bi-center Bit Technologies


Throughout the oil and gas industry a need exists to reduce hole size and subsequent casing strings to reach the pay zone in a safe manner with appropriate zonal isolation of the various formations. Benefits in achieving such well design can be economically advantageous to the operator. In certain fields of Saudi Arabia, a relatively thin gas cap exists at the top of the Arab-D oil-producing zone. Isolating this gas cap is necessary to prevent future production from the gap. In wells where a gas cap is expected, 300 to 400 ft of high angle 8-1/2 in. hole is drilled and cased off with a 7 in. liner. A 6-1/8 in. production hole is then drilled horizontally to total depth (TD).

This paper will discuss how the planned installation of solid expandable tubular technology in combination with bicenter bit technology was used to drill an oil-producing well and accomplish the following objectives:

  • Lower well costs and reduce environmental impact.
  • Hydraulically isolate the gas cap at the top of the Arab-D zone.
  • Reduce all hole diameters and casing string sizes above the gas cap zone by one size.
  • Drill a 6-1/8 in. horizontal production hole beyond the expanded liner.

The successful application of both technologies produced the following results:

  • All hole diameters and casing strings above the gas cap were reduced by one size from the standard well design.
  • A bi-center bit successfully drilled the build section in which the expandable casing was run.
  • An expandable liner was run and cemented across the gas cap.
  • The expandable liner was successfully pressure tested.
  • A bi-center bit was used to drill the horizontal hole beyond the expanded liner.


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Document Type
Technical Paper
Date Published
Friday, March 11, 2005
Middle East

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