New PDC Design Process Solves Challenging Directional Application in Abu Dhabi Onshore Fields

Abstract

fax 01-972-952-9435. AbstractRoller cone bits have dominated the 8-1/2" steerable application in Abu Dhabi due to their proficient steerability, consistently achieving the required build rates in the soft Nahr Umr shale. In the vertical section, PDC bits often achieve up to four times the penetration rates of TCI bits. However, directional performance when using PDC bits to build angle was compromised by fluctuations in reactive torque resulting in poor tool face control and inconsistent build up rates. The overall result was poor penetration rate and performance compared to roller cone bits. The operator and a service company utilized a new design process and cross functional team approach to aggressively seek new steerable PDC technology to drill the curved section with controllable torque response and consistent directional behavior while achieving the full penetration rate advantage of PDC bits. This process was complemented by the Well Delivery Limit process (WDL) that was already established by the operator that focused on delivering high value wells with significantly reduced costs. The team analyzed the drilling operations from virtually every perspective using numerical models, laboratory drilling tests, and field testing. The key to the PDC solution was the team process that identified the relevant drilling problems and performance requirements in order to develop the needed technology. After 30 bit runs from November 2001 to June 2002, the team reduced drilling costs by $44.26 per foot for a total savings of $3,792,367 over 85,682 ft and 2,386 drilling hours. The average ROP for the section doubled from 18 ft/hr with TCI bits to 36 ft/hr. The current ROP record stands at 60 ft/hr over a 3,169 ft interval.

A Model for Borehole Oscillations

“…Specifically, the recent papers on reducing torque fluctuations with PDC bits have had a significant impact on utilization of these bits on steerable motor systems. [1][2][3] Over the last 30 years several models have been published to predict DLS based on the bit and BHA. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] The experimental and analytical work in this area has significantly improved the state of the art and this continues today.…”

“…The bit cutting into the side wall is shown as the dashpot. At each time step the force on the dashpot (bit side cutting force) has to be equal and opposite the BHA spring force as defined by equation(2).…”

Kuwait Oil Company Sets Drilling Record Completing the Zubair Section in One Run

“…6 Cutters were underexposed in the cone area and a bearing was placed on the blade surfaces in the cone area that became active when target penetration rates were reached.…”