Total Depth Solution Technologies Provide Effective, Efficient and Safe Well Construction Method to Mitigate Borehole Problems
Authors: Reading Richard , Whitby David , Utama I. Made Budi 
Published: May 2011

Abstract
Permit TL/2 in the Carnarvon Basin, Western Australia, presents several challenges for top hole drilling and casing running operations. Previous experience showed that drilling the 16?? hole section and running 13-3/8?? casing was typically a time consuming phase of the well due to fluid losses and tight hole conditions consequently requiring the use of Seawater to drill, back reaming, wiper trips and occasional spotting of pills.
The initial solution delivered to the operator as an alternative method to get 13-3/8?? casing to TD was to employ a casing drill bit to ream the casing to bottom whilst also delivering an improved drill-out time. This would be coupled with a sophisticated, unique, reliable and simply-operated top drive casing running system that was already installed on the rig. Pending a review of the service company capabilities, Total Depth Solution systems with cost & time savings analysis, the operator was certain that the application of a complete drilling with casing system (DwCTM) would mitigate the known hole problems and yield a safe and more cost effective surface hole operation, reducing non-productive time (NPT) significantly.
This paper fully reviews the problems that were traditionally encountered during conventional surface hole drilling and casing running operations; the decision making process that the operator followed prior to employing DwCTM technology along with the hazard mitigation & economic benefits realized through a one way trip to Total Depth of +/- 1,000 m TVD RT; breaking to date the longest Weatherford 13-3/8?? DwCTM interval globally by the service company & operator.

Introduction
Barberry-1 is located in permit area TL/2. Previous experience showed that drilling the 16?? hole section & running 13-3/8?? casing in the area was typically time consuming due to losses (requiring use of Seawater to drill) & tight hole (requiring back-reaming & wiper trips & occasional spotting of pills).
Initially Weatherford suggested the use of a 13-3/8??×15-1/2?? PDC Drillable Casing Drilling Bit with TSP cutters to aid in reaming casing to bottom & affording fast drill-out times. Coupled with the Weatherford Top Drive Casing Running & Drilling System already installed on the Jack-Up drilling rig, Weatherford were confident that some of the issues noted in offsets would be overcome in regards to tripping in casing.
From this Apache Energy challenged Weatherford to provide a complete casing while drilling solution incorporating the Top Drive Casing Running & Drilling System to mitigate the known hole problems, associated time combating the issues & to deliver time savings through one way trip to TD at +/-1,000 m (3,281 ft) TVD RT.

Offset Well Study for Casing Drilling Bit Selection
Offset wells provided for drillability analysis were Chervil-1 & Basil-1. Casing drilling bits have certain design limitations & considerations that must be accounted for when comparing against conventional drill bits & their performance. D-Exponent is a common method Weatherford apply where formation evaluation data is not available, which is quite common in top hole applications. Based on regional experience, offset findings & previous product performance, the premium 13-3/8??×17-1/2?? DPC519 DefyerTM casing drilling bit was recommended to ensure TD would be achieved at high ROP, (Figure 1).