Abstract

Coiled tubing drilling (CTD) has to date not yet evolved to be a worldwide, long lasting application, to be used on a daily basis, other than in places such like Alaska, Canada, and Venezuela. Locations with an extensive history and expertise of coiled tubing drilling. In these locations CTD has economical and technical advantages over conventional drilling operations.

However it seems that the drilling market in Argentina provided the right opportunities for another CTD operation. A plan was developed to drill thirty wells in the central part of Argentina, known as Golfo San Jorge.

This case history describes the set up of the project, drilling techniques used and difficulties experienced, lessons learned and the future of CTD in Argentina.

Introduction

The Cerro Dragon Contract Area, consisting of approximately twenty fields, is located onshore in the San Jorge Basin of central Argentina. In order to rapidly access shallow, low to medium pressure gas reserves, a thirty well CTD pilot was planned to start-up in late June 2001.

The subsurface work in Cerro Dragon has documented a significant volume of gas reserves available for production in the 400 to 800 meter depth range in the various fields of the operator. The recommendation to introduce CTD to Cerro Dragon seeks to develop these reserves at the same rapid pace and ultimately lower cost based on achievements of CTD technology in North America.

The 30 well pilot proposal was used to evaluate the effectiveness of the technology during the 3rd quarter of 2001 and to increase the gas supply. The CTD technology, if successful from a reduced cost and cycle time perspective, would allow the rapid development of the shallow gas reserves in the area at a cost and pace that will allow for the most effective depletion and the highest possible delivery of gas.

Project objectives

The overall objectives to be shown with this new technology for Argentina were:

  • Prove that CTD technology is a viable option in Golfo San Jorge basin.

  • Reduction in well construction costs compared with conventional drilling.

  • Drill and complete all wells with zero lost time accidents, reportable or high-potential incidents.

  • Achieve an overall non-productive time (NPT) of less than 15%.

  • Prevent any spills or damage to the environment.

  • Drill and complete the well under conventional budgeted cost and within 48 hours.

  • Reduce cycle time.

  • Ability to free up conventional rig for deeper prospects

  • Demonstrate productivity and increase reserves to meet 2002 gas sales expansion plan.

  • If successful, introduce CTD to conventional shallow oil wells and water injectors.

Drilling and Completion Program

The new wells were chosen on the basis that the neighboring wells had gas zones previously tested but not yet produced. Another criterion was that the infrastructure for taking on gas was available. Each new well was to be drilled 25 meters away, where possible, from an existing well and hooked up to the gas pipeline as soon as it was completed.

The existing wells were drilled as early as the year 1960. Not all historical drilling data was available to review potential problems for this project. A number of locations were unrecognizable and needed to be restored to accommodate the drilling equipment.

One of the challenges was the use of a ‘dry’ location. Where conventional drilling uses natural mud pits, this project received the task to be the first to use containers to collect all drilling cuttings.

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