Optimizing Wellbore Design Using Solid Expandable Tubular and Bi-center Bit Technologies
Throughout the oil and gas industry there exists a need to reduce hole size and subsequent casing strings to reach the payzone in a safe manner with appropriate zonal isolation of the various formations. Benefits in achieving such well design are both economically and environmentally advantageous to the operator. In certain fields of Saudi Arabia, a relatively thin gas cap exists at the top of the oil-producing Arab-D Zone-2A formation. It is necessary to isolate this gas cap to prevent future production from that zone. In wells where a gas-cap is expected, 300 to 400 ft of highangle 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 in the drilling of the Ain Dar-497 well was used to accomplish the following objectives: 1. Lower well costs and reduce environmental impact 2. Hydraulically isolate the gas cap at the top of the Arab-D Zone 2A. 3. Reduce all hole diameters and casing string sizes above the gas cap zone by one size. 4. Drill a 6-1/8in. horizontal production hole beyond the expanded liner. Applying the above technologies produced the following results in the Ain Dar-497: 1. All hole diameters and casing strings above the gas cap zone were reduced by one size from the standard well design. 2. A bi-center bit successfully drilled the build section in which the expandable casing was run. 3. An expandable liner was run and cemented across the gas cap at the top of the Arab-D Zone 2A. 4. The expandable liner was successfully pressure tested. 5. A bi-center bit was used to drill the horizontal hole beyond the expanded liner.