Abstract

The Abu Dhabi Company for Onshore Oil Operations (ADCO) has a program of exploration and appraisal drilling from artificial islands in an environmentally sensitive shallow marine location. In early 2000, ADCO management set up a team to look at the feasibility of drilling extended-reach wells to reduce both the impact on the environment and the cost of drilling these wells.

This paper summarizes the work that has been done and the progress that has been made in delivering ADCO's first extended-reach well. It describes how the key risks to delivering the well were addressed and how a systematic approach to well planning contributed to the exceptional results. The modeling and simulation work performed in planning the well and preparing a comprehensive well program, and the use of real-time data to validate the models are detailed. The process adopted to ensure that every member of the team understood the program and was committed to the successful delivery of the well is also described.

The company is in the process of drilling the extended-reach well with a measured depth of 18,748 ft and a horizontal displacement of 13,780 ft. At the time of writing the horizontal section is being drilled. Well construction up to the completion of the pilot hole is covered in this paper.

When ADCO started to prepare for this well the company and the newly formed drilling team had limited experience of extended-reach drilling (ERD). However, progress on the well has been extraordinary. When the pilot hole reached target depth the well was 39 days ahead of the program. This drilling performance is in the upper quartile of global land-based ERDwells (defined by industry analysts as better than 24.6 days per 10,000 feet drilled).

Introduction

The Abu Dhabi Company for Onshore Oil Operations (ADCO) operates onshore and in the shallow waters of the Emirate of Abu Dhabi, one of the seven members of the United Arab Emirates, which was established on 2 December 1971.

The company produces mainly from five onshore oil fields. Its continuing program for the evaluation of new reserves includes exploration and appraisal drilling activity in an area that is classified as environmentally sensitive. The area, which holds numerous important archaeological sites and substantial populations of various endangered and threatened wildlife, has been proposed as a UNESCO World Heritage Site. Operating in such an area requires special procedures and precautions, and ADCO has taken on this duty of care with considerable success.

Mangrove swamps and very shallow marine waters make gaining access to the area difficult. The appraisal-drilling program has included the construction of man-made islands to give access to offshore parts of the field. In this context, the need for ERD was identified for this field. By minimizing the footprint of drilling operations in such a pristine environment, ERD offers a way of controlling the impact of drilling activity. It also has considerable cost impact by reducing the number of islands to be built.

However, global experience indicates that nonconventional wells, including extended-reach wells, typically require a higher allowance for nonproductive time. Incomplete knowledge, unscheduled events and equipment limitations can add 30% or more1 to the overall time taken to deliver the well.

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