As part of on-going initiatives to improve the Opukushi field ultimate recovery and production potential, horizontal well technology was introduced during the second phase of the field development, which started in 1995. Following the review of three previous wells, including the first Shell-Nigeria horizontal well, which was completed in 1992, some modifications of the completion design were recommended. While still on the learning curve of drilling horizontal wells, another 3-well horizontal drilling campaign was successfully executed in the Opukushi field in 1996.

Openhole liner completion design was selected because of the unconsolidated sandstone formation which characterizes the shallow horizons of the field, with the wells targeting undeveloped reserves located at a depth of ~7500 ft tv-ss. All the wells were completed in thin oil rim sands of ca. 70 ft, with 5-1/2" × 4-1/2" tapered slotted liner (SL) assemblies installed across 2300–3300 ft of 8-1/2" drainhole sections. The horizontal sections were drilled with a low-solids drill-in fluid while wellbore clean-up was effected with a coil-tubing unit utilizing a nitrified acid at underbalance condition.

This paper presents a review of the 3-well completion design and installation technique, as well as the horizontal wellbore clean-up procedure adopted. The wells’ performance evaluation, based on test data and Production Logging Tool (PLT) results, has also been presented to show a comparison with the conventional well performance. The recorded high productivity improvement factor (PIF) of above 10 has demonstrated the superiority of horizontal well applications.

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