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Reducing Exploration Well Construction Costs with Top-hole Casing Drilling

Holt, Calvin S.
Tesco Corporation, Houston, TX.

Today, more than ever, drilling economics are under scrutiny, as cost increases and commodity price fluctuations are jeopardizing well construction exploration to development projects. In offshore environments, whether floaters or jack-up, the spread rates can easily exceed $500,000 per day and more.

The combination of the Top Drive, a Casing Drive System (CDS), and Casing while Drilling (CwD) make it possible to run and directionally drill casing at the same time, which provides significant time savings. This unique combination of mature and new technologies has proven success in exploration drilling programs.

With Casing Drilling, these sections can be drilled easier since the well is cased before the onset of instability and lost circulation usually can be cured with the well-documented Plastering Effect. Other factors contributing to Casing Drilling benefits are elimination of tripping, casing running, and the fact that every foot drilled is cased and secured.

Currently Casing Drilling is practiced as an enabling technology to drill both shallow and deepwater subsea exploration wells. The technology has proved to be very flexible, effective and feasible under different circumstances. Case Histories from Asia Pacific and Norway with riser-less drilling systems to drill top-hole sections will be presented; some of them are industry firsts and address the significant cost problem for exploration wells.

Casing Drilling allows for improved drilling performance in top-hole formations in exploration offshore applications. The paper discusses the challenges, planning, implementation, economics, operational results, and lessons learned from several Casing Drilling operations performed to successfully drill through top-hole sections. This paper will discuss proven technology and its results, as well as new systems in development that promise to reduce total exploration well costs by 50% or more.

 

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012