Identifying New Opportunities Through Reservoir Performance Reviews And Facies Based Dynamic Modelling Of A Mature Oil Field Under Waterflood
Authors: Nijman Madelon Petra Yvette , Paris Smir F. , Boyd-Gorst John 
Published: March 2015

The Champion Field is one of the most precious assets of Brunei Darussalam and it has been in production since 1972. There is a clear long term vision to breathe new life into the field and sustain the production for another 30 years through re-development and expansion of the existing water injection scheme. The field is geologically complex, with over 500 stacked sandstones reservoirs, heavily faulted and with depths spanning from 200–1500 mss. Primary and secondary recovery has taken place primarily from pattern waterflood in specific areas of the field since 1984.

This modeling effort is part of the ongoing Champion Waterflood project, which aims to increase the recoverable reserves and production capacity from this mature field.

The technical studies completed at Champion Main Deep comprise both the reservoir performance reviews using injection pattern analysis done for the 15 existing water injection wells, combined with the reservoir simulation modeling work based on a detailed 3D geological facies model. The additional effort of determining a workable facies scheme has allowed a better representation of the geology, capturing the different properties of the good sands, the thin heterolithics sands and shaley heterolithics more realistically in the model. This has resulted in improved understanding of the potential distribution of oil and hence targeting of new wells. The simulation study incorporated over 35 years of history matching. The combination of reservoir performance reviews and simulation modeling work has allowed identification of the potential for infill drilling and workovers to further improve recovery in the Main area.

Complementing the detailed modeling work with pattern reviews has proven a very useful technique for planning further development of mature oil fields. This approach allows improved mapping of remaining oil and evaluation of optimal well placement through better integration of the available production and surveillance data.

Introduction

The Champion field sits within Brunei Shell Petroleum's (BSP) East Asset Unit and is the largest oil field in BSP's portfolio. It contains more than 500 defined block and reservoir units which have a very complex dynamic interaction. The field is located in the first offshore license area, 40 km offshore Brunei (Fig. 1). Since the start of production in 1972, a significant amount of oil has been produced via an extensive offshore production system comprising wells, drilling and production structures and pipelines.

Treated seawater injection started in 1984 as a water injection pilot project in the central block of the Main Deep section of the field. The positive results of the pilot led to further drilling of water injectors, but several of these were less effective than the initial pilot. Instead of the simultaneous flank drive injection that was used in the central block, single water injector/producer pairs were drilled, causing quick watering out of producers due to water overrun through high permeability sands.

In 2003, an integrated study was started for the re-development of the field, and a series of models were built to understand the main development area in more detail. With the high complexity of the field, the first aim of the studies was to capture the entire field in one integrated model, so that the dynamic behaviour could be represented properly. After assessing the main bounding faults and reservoir/pressure boundaries, the field was divided into four segments, Main Shallow, Main Deep, Blocks 13–14 and South East (Fig. 2 and Fig. 3). For each of these segments, a detailed net-to-gross model was built, suitable for direct use in the simulator, i.e. with a relatively coarse layering and only average properties. These models were adequate to match field history at the field and block level, and produce reliable forecasts for the overall field re-development plan (new facilities, well counts, producer:injector ratio, etc)