Identifying Minor Faults and Demarcating Compartments in Areas of Large Seismic Anomalies using Time-lapse OWC Mapping - Example From the Super Giant Greater Burgan Field, Kuwait

Abstract

The Greater Burgan Field in Kuwait consists of three culminations – Burgan Dome in the south, Ahmadi in the northeast and Magwa in the northwest. The Cretaceous Burgan Formation is the main reservoir of the Greater Burgan Field. The major part of the reservoir consists of massive, stacked, fluvial channels with an active bottom water drive. The structure is dissected by a number of faults resulting in compartmentalization of the reservoir. The major faults are easily mappable with seismic data. However, mapping the minor faults is a challenge due to velocity anomalies present in the shallow formations masking the structural picture at the Burgan Formation level. Hydrocarbon saturation logs are widely used in the field to monitor the movement of the oil-water contact (OWC). At many places, uneven OWC rise is observed, that cannot be attributed to different offtakes from the wells. Time-lapse mapping of the OWC by different vintages of hydrocarbon saturation logs, in combination with open hole logs, shows that these differences can only be explained by sub-compartmentalization along structural discontinuities. Such discontinuities are mostly observed in the Magwa area where shallow velocity anomalies are also more pronounced. Mapping the trends of these discontinuities shows that they are aligned to the regional fault trends mapped seismically. Using this technique, a number of minor faults can be mapped that sub-divides the major compartments into smaller ones. This will help in better positioning of in-fill locations and also in refining the production strategy of the compartments.