Schlumberger

Technical Paper: High Angle Directional Drilling with With 9 5/8-in. Casing in Offshore Qatar

Society: SPE
Paper Number: 119446
Presentation Date: 2009
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Abstract

Programs which require drilling through unstable formations at high angle before entering the productive zone for a horizontal well are becoming more common. Casing while drilling is becoming a powerful method in mitigating both lost circulation as well as wellbore stability issues in offshore directional wells.

Occidental Petroleum of Qatar Ltd. (OPQL) is faced with this task in drilling horizontal Shuaiba wells offshore Qatar. The unstable Nahr Umr shale formation lies directly above the Shuaiba payzone and is typically drilled with 12 ¼-in. bits. The Nahr Umr shale tends to break up shortly after drilling, leading to stuck bottom hole assemblies (BHA) and difficulty running 9 5/8-in. casing. Exposure time with the Nahr Umr is often lengthened due to the requirement of continuous angle building and turning to land near horizontal.

This paper details the directional casing while drilling (DCwD) developments that have been accomplished offshore Qatar and the various advantages of the process. Due to recent advancements in tool design, it is now possible to circulate, rotate, and reciprocate the casing during BHA retrieval and setting operations, all without modifications to the rig. These advantages coupled with the versatility of rotary steerable systems allow for a much more flexible process and enables defensive measures to be taken in the event of unforeseen complications.