Integration of Subsurface Technology to Mitigate and Manage Structural Geology Uncertainty in the Development of a Mature Field in Brunei

Abstract

The area of interest is located at the NE flank of an anticline, under shallow waters with depth ranging from 1 to 8 m. It is up to 10 km along strike (NE to SW) and 4 km along dip (NW to SE). The reservoirs are shore face interbedded sands range from 485 m to 2080m TVDss. Hydrocarbons are trapped in south-heading faults, so the spatial location and uncertainty of these faults are critical for successful well placement. Although it has been producing since 1955, it is relatively a less developed area compared to the rest of blocks in the field. To stop production decline, the asset is currently focusing on future infill and NFE opportunities in this area of which more than 10 drilling wells opportunities have been identified. From the learnings of last campaign (17 producers and 17 injectors drilled between 2010 and 2014), the biggest risk and uncertainty in this area is structural geology related. Structural uncertainties cover sub-block compartmentalization, fault positioning and structural dip uncertainties. Sub-block compartmentalization has known to ultimately impact reserve and hence the economics of the well by reducing production drainage area and oil producer and water injector connectivity. Structural uncertainties such as fault positioning and dip uncertainty has resulted into suboptimal well penetration and in some cases well must be sidetracked for recovery (increased unplanned costs and impact returns). To mitigate these uncertainties for the next development phase planned for kick off in the middle of 2018, the asset has used: (1) 3D DAS VSP (vertical seismic profile) technology: VSP seismic imaging has been proven to reduce fault positioning and structural dip uncertainties, hence de-risking new wells placement. The existing wells have been equipped with DAS cables (permanently installed behind casing). VSP has also de-risk the presence of intra-fault compartmentalization, thus optimizing the placement of oil producers and injectors (2) High resolution 3D streamer seismic PsDM: provides a crisp subsurface image for shallower depth targets, allowing de-risking presence of compartmentalization and suboptimal well penetration due to presence of gas caps (3) Horizontal well concept: ensures full block drainage coverage and de-risks compartmentalization, replacing the fishhook well concept used in the past. It would able to drill through all the possible sub-blocks compartments that potentially limit the production drainage. The structural and fault dip uncertainty estimated from the joint interpretation of High-Resolution 3D PsDM and 3D DAS VSP surveys provides the critical information to ensure a safe and successful horizontal well placement The drilling campaign demonstrates the importance of an integrated subsurface technology effort to de-risk structural uncertainty of new opportunities in a mature field: sub-block compartmentalization, fault positioning and dip uncertainty.

AAPG Datapages/Search and Discovery Article #90328 © 2018 AAPG Middle East Region GTW, Maximizing Asset Value: Integrating Geoscience with Reservoir Management & Facilities Optimization, Muscat, Oman, April 30 – May 1, 2018