The Sarir and Messla fields are two major oil fields operated by Arabian Gulf Oil Company (AGOCO). Due to the heavy oil production activities with time, these two fields became depleted. Therefore, drilling infill vertical and horizontal development wells was one of the optimum solutions to sustain the oil production. However, in the meantime, due to reaching the well spacing limitations (500 meters) in most of the two fields, and the associated high cost of the horizontal wells aggravated by limited assigned budget, conventional vertical and horizontal drilling could not assist AGOCO to achieve its production target. The primary task for the reservoir engineer is to look for means and ways to develop currently operating assets economically by the improved oil recovery (IOR) methodology. However, there are challenges that reservoir engineers face to achieve a proper field development plan. Research and technology development became dynamic that many historic challenges have been overcome by the fast advancement especially in the fields of directional drilling and geosteering. Recently, the AGOCO Reservoir Engineering Department has adapted an innovative operational strategy i.e., sidetracking or horizontal re-entry as a strategic plan to touch undrained reserves and to increase subsurface withdrawal in a very economic approach. The project was targeting the observation wells, abandonment wells, low oil production wells with high water cut, and the suspended oil wells due to the previous drilling operational issues. Sixteen re-entry oil wells have been drilled thus so far, using the high technology provided by directional drilling service company (Geo-Sphere reservoir mapping), gaining an actual daily oil production rate of 22,654 BOPD.

Today, service companies use various approaches to address the growing demand for reentry drilling. AGOCO promotes its reentry drilling services with support from directional drilling tools and has gained a reputation as a reentry specialist in both giant oil fields in Sirte Basin.

This paper presents innovations, motivations, actions, challenges and results, as well as lessons learned from the re-entry exercise was done by the AGOCO reservoir characterization team.