Abstract

While the oil and gas market continues to fluctuate, operators are forced to reduce drilling costs and increase efficiency to remain profitable; therefore, the focus on well reentry, sidetracks, and multilaterals from existing wellbores is growing in popularity, particularly within Australasia. Coiled tubing drilling (CTD) technology has been explored in New Zealand; however, successfully executed operations have so far been limited. After evaluating economic benefits and finding a suitable candidate trial well, a Canadian-based operator attempted a CTD operation in New Zealand that was technically successful.

This case history outlines the two-phase project and discusses well intervention to isolate existing perforations and the sidetrack from the primary motherbore to drill to the base of the new reservoir. The objectives were to convert the suspended well from an oil producer to a water injector, enhance oil recovery within the field, and prolong oil production by reviving an underused asset. This paper discusses the engineering and technology used as well as regulatory obstacles and challenges encountered that were overcome to reach the operator’s objective.

A 2 7/8-in. coiled tubing (CT) string was used for both phases of the operation, spanning intervention and drilling to perform all scheduled operations as efficiently as possible. The resulting completion, post-sidetrack, was to incorporate the CT workstring with approximately 100 m of a perforated 2 7/8-in. jointed pipe to maintain openhole stability across the injection zone.

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