Introduction

The Sajaa Gas field, producing from the Thamama carbonate formation, is a prolific and important gas producing field for BP-Sharjah and its partners in Sharjah, United Arab Emirates.1 

In December 2002, BP-Sharjah decided to embark on a through tubing coiled tubing UBD campaign to drill underbalanced, horizontal multilateral sidetracks to increase wellbore deliverability in this low pressure environment.2 

Due to the probability of cross-flow between multilateral legs due to variations in reservoir pressure and the existence of high intensity fractures, maintaining dynamic pressure control presented a significant technical challenge. Safely detecting and responding to rapid changes in a complex well geometry with a very small volume well annulus was of paramount importance. Adequate crew training and effective communication between rigsite decision-makers was considered to be essential success pre-requisites for conducting safe operations.

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