A Giant Reservoir is Talking and We are Listening: Characterisation and Understanding of a Giant Fractured Reservoir in Oman with Extensive Years of Production

Abstract

This paper discusses the interpretation of historic data for a giant and COMPLEX fractured carbonate, leading to a different understanding of the reservoir's displacement processes, and renewed insights for future development opportunities. Specifically, the paper describes a comprehensive study to Locate The Remaining Oil (LTRO) and improve the ultimate performance of the field. The study encompassed the integration of recent seismic datasets, BHI (Borehole Imaging) data from over 100 wells, well logs for key wells at different time lapses, core data for different facies, well performance and interference data. Focus has also been placed on understanding the various recovery mechanisms that the field has undergone (water injection and Gas-Oil Gravity Drainage (GOGD) concurrently in different regions of the field). This LTRO exercise has provided insights into the distribution and intensity of inter- and intra-faults and the fracture connectivity between the field units. This warrants clustering the giant field into "development districts" i.e. to move from layer-based development to acknowledgment of vertical communication between layers It has become apparent that the reservoir architecture and fluid flow characteristics in this giant reservoir benefits from a secondary system of background fractures. The future field development concept should target- the matrix blocks with background fractures holding remaining oil for a slow GOGD development. The study is part of continued efforts to build a centre of excellence in PDO around Naturally Fractured Carbonate Reservoirs, and to help unlock reserves in PDO's extensive portfolio of NFR (Naturally Fractured Reservoir) Carbonate fields.