A Regional Approach to Understanding Basin Evolution and Play Systematic in Brunei - Unearthing New Opportunities in a Mature Basin
Authors: Gartrell Anthony , Torres Jose A. , Hoggmascall Nick 
Published: May 2016

Abstract
Improvements in the understanding of basin evolution, stratigraphic architecture and play systematics on the NW Borneo margin has resulted in the identification of new exploration opportunities in Brunei Darussalam. A Play Based Exploration (PBE) approach was adopted with particular attention being focused on developing an understanding of the interplay between structural and sedimentary processes. Reinterpretation of the tectonostratigraphic architecture was achieved by integrating multiple data sets and by comparisons to regional and global analogues. Reconstruction of basin deformation and fill history for key intervals is captured in a series of paleaogeographic maps that show active structural and sedimentary features for a given play interval. The palaeogeographic maps are linked to 2D structural restorations and mapped key seismic horizons. These products provide a basis for the development of a robust, internally consistent geological model from which new plays and prospects have been defined and assessed.

Introduction
Brunei is currently the 3rd largest oil producer and 4th largest producer of LNG in South East Asia. Oil and gas production has been active for over 80 years in Brunei and now accounts for more than 90% of the country's exports. However, the majority of the large fields are in decline. A ground up regional re-assessment of the basin's prospectivity was initiated by Brunei Shell Petroleum (BSP) in late 2007 as part of a strategy to rejuvenate the exploration portfolio.
Although a large amount of high quality regional geology work has been done in Brunei in the past, significant revision of the basin's deformation and fill history and chrono-stratigraphic framework was required in order to more accurately characterize the basin and assess the remaining prospectivity. The study takes advantage of the integration of a comprehensive data base including near wall-to-wall 3D seismic coverage, access to almost all well data available in Brunei, regional satellite gravity imagery, Digital Elevation Models and outcrop data.
Particular areas of focus discussed here are:
o What is happening at depth? New insights into the deep mechanical basement architecture have helped develop a better understanding of high order deformation and deposition controls. These observations also highlight the potential for deep untested plays.
o What was the structural evolution of the basin and what controlled deformation? Understanding the interaction between gravity-driven delta deformation and regional compressional tectonics is key.
o What are the mechanisms that have controlled the stratal architecture of the Miocene to present delta system? The interplay between deformation and eustacy is critical for understanding the sequence stratigraphic architecture.
o How do processes on the shelf affect the deepwater? Determining the linkage between shelf and deepwater environments and processes is important for assessing reservoir presence in deepwater plays.