Appraisal of a Supergiant: The Kashagan Field, North Caspian Basin, Kazakhstan

Zempolich, William, Agip Kazakhstan North Caspian Operation Co. N.V, The Hague, Netherlands

The Kashagan field is located on the North Caspian sea, offshore Kazakhstan and is one of the largest discoveries made in the last several decades. The structure was successfully tested by the Kashagan East – 1 and Kashagan West – 1 exploration wells, which penetrat­ed a significant oil column in Late Devonian-Carboniferous platform carbonates. The Kashagan structure developed as an isolated carbonate platform and is approximately 75 km in length and 35 km in width. Due to its areal extent and complexity of the reservoir, further appraisal was required to determine the true size of the Kashagan resource. Challenges of the appraisal program include operating in shallow, ecologically-sensitive waters subjected to harsh winter and ice conditions.

The Kashagan appraisal program included acquisition of a state-of-the-art 3D seismic dataset and a sequence of wells that were designed to assess the potential of the structure as rapidly as possible. Due to water depths that range from 3 to 8 m, approximately 1600 km2 of OBC seismic data were acquired and processed to better image the reservoir. Appraisal wells have been strategically located to test the geological model and to assess reservoir quality across the structure. Well logs, core data and vertical seismic profiles were also used to tie in the 3D seismic data set in order to correlate reservoir intervals between wells.

The drilling of the Kashagan East – 3, Kashagan East – 5 and Kashagan East – 6 apprais­al wells confirmed the presence of cyclic, shallow-water platform carbonate facies across

the platform interior. The Kashagan East – 2 and Kashagan East – 4 appraisal wells support the presence of a platform rim with enhanced reservoir quality and strengthen the geologi­cal model. Further development drilling and integration with 3D seismic will allow for con­tinuing definition of the resource.