Characterization of Barriers to Flow in Burgan Reservoirs Using Geological and Dynamic Pressure Data, Burgan Field, Kuwait.

Abstract

The Burgan sands Formation is one of the main reservoirs of Greater Burgan field in Kuwait, producing under primary depletion since the late 1940s. Massive sands reservoirs (Lower Burgan BGSL2 and Middle Burgan BGSM) interpreted as deposited in fluvio-tidal depositional environments, alternate with lower quality and muddy interbedded sandstones (Lower Burgan BGSL1 and Upper Burgan BGSU), deposited in tidal-influenced delta settings. The complex reservoir architecture of these sand reservoirs is dependent of the sinuosity and complexity of the channel system but also on the lateral extend and distribution of the muddy deposits that will create heterogeneities and barrier to flow. In the context of future development plans of the Burgan reservoirs, the Burgan Subsurface Team implemented a workflow to identify the main barriers to flow at the interface between the massive and the lower net-to-gross reservoirs. This workflow combines geological (cores), petrophysical (Rock-Types, conventional logs) and dynamic data (pressures), to characterize the main barriers to flow between the different reservoirs. Shale barrier types and thicknesses of shales are picked and defined from logs using wireline conventional log data, and the huge database of pressures available was used to visualize and check the impact of the shale barriers on the connectivity of the reservoir and the pressure drop or continuity between the sandy units. This multiple approach allows to capture the main geological heterogeneities (shale barriers) by their type and thicknesses and combining the information with dynamic data (pressures within the reservoir zones) gave a direct link to the connectivity (pressure communication or not) between the main reservoirs. The data generated by these two approaches were used to produce maps of connectivity as well as maps of pressure differences between the main reservoirs. Modeling complex reservoir heterogeneities in clastic environments is a challenge in the oil industry. An accurate sand body distribution is crucial for a good understanding and representation of the reservoir behavior but a good representation and image of the barrier to flow is fundamental to complete the picture. In the context of the future development of Burgan reservoirs, such workflow and products will be very useful to take some decisions about the strategy to develop efficiently such type of reservoirs.