Addressing Reservoir Heterogeneities in the Development of Upper Jurassic Carbonate Reservoirs, Offshore Abu Dhabi

Abstract

AbstractDetailed seismic interpretations and an integrated reservoir characterization study were performed on a field offshore Abu Dhabi which reveals new insights into reservoir heterogeneities, both laterally, as well as vertically. The new interpretations provide the team with new insights into the subsurface heterogeneities and address them during the development plan.The Upper Jurassic carbonate reservoirs, offshore Abu Dhabi, exhibiting heterogeneities on different scales. The lower reservoir section is a large shoaling-upward sequence with an upward increase in reservoir properties. Smaller-scale sequences are superimposed and define the major flow units. Stromatoporoids build-ups or layers are intercalated in the upper part of the lower reservoir section. These layers are characterized by vuggy porosity and the intervals exhibit significant higher permeablities. The upper reservoir section is characterized by meter-scale sabkha cycles composed of mixed carbonates and evaporites. The major reservoir units are separated by thick continuous evaporite units which are regionally continuous. The smaller scale sequences which are the major flow units might be separated by evaporite layers or dense carbonate intervals. Reservoir quality in the major flow units is controlled by dolomitization and anhydrite cementation and further compartmentalizes the reservoir. Understanding the spatial distribution of these reservoir heterogeneities (depositional and diagenetic) is crucial for the development plan.Reservoir heterogeneities, lateral and vertical, have a major impact on the placement of producers and water and gas injectors. Changes in reservoir quality create sweet spots but also lower productive interval in the individual flow units. The use of intelligent wells and new completion strategies will be also applied to monitor and control early gas and water break through within the field. Our current understanding of the reservoir heterogeneities, therefore, helps us to mitigate some of the subsurface uncertainties. These heterogeneities will be further appraised and mitigated during early field development.