The BDO EOR feasibility study conducted in 2004 by PETRONAS and Sarawak Shell Berhad (SSB) identified a potential incremental recovery of over 250 MMstb from the Baram Delta Operation (BDO) fields1. This incremental oil can be realized from CO2 injection under miscible and immiscible conditions. On average, this represents an additional 12% incremental recovery above the base case of water flooding.
The regional CO2 injection covering nine (9) fields requires a very significant investment of new CO2 infrastructures and injection facilities. To mitigate the risk involved and to prove the commercial viability of the project, a regional pilot was proposed. The pilot, which will be implemented in Baronia RV2 reservoirs, will serve as a basis to formulate the way forward for CO2 injection in the whole BDO region.
Several extensive evaluations were carried out to come up with an optimized pilot design. This includes building full field compositional fluid flow simulation model for CO2 miscible flood predictions and sensitivities, streamlines analysis to identify suitable well pairing, and MMP / interfacial tension measurements in the laboratory. The proposed observation pilot were specifically designed to address several issues such as determination of current oil saturation, waterflood residual oil saturation, residual oil saturation after gas flooding and evaluation of the vertical sweep efficiency. The pilot will also serve as an opportunity to acquire additional data through extensive coring, logging, and fluid sampling programs.
This paper outlines the methodology used in the developing the most cost-effective pilot at Baronia RV2 reservoirs that could potentially lead to economic maturation of new reserves in the whole of the BDO area as well as formulating the most comprehensive monitoring and evaluation techniques of the pilot.
Introduction
The Baram Delta area which is located at offshore Miri of Sarawak consists of nine (9) fields as shown in Figure 1. The area which was discovered in 1969 is estimated to have more than 4000+ MMstb oil in place with multiple stacked sandstone reservoirs in a shallow offshore environment. They have been on production for more than 30 years and the historical production data indicated that the oil production have been relatively flat at 80 - 100 kbd of oil primarily from infill drilling and new in-field development and/or rejuvenation. Figure 2 shows historical production performance of the BDO area. Currently, many wells are shut in due to the high water production. Because of offshore environment, well spacing is relatively large and limited available space at the platform which make these characteristics present a challenging environment to carry out EOR operations.
The stratagraphic framework for Baram Delta reservoirs is mainly from Middle Miocene in age with east-west oriented coastline and a delta progradation southeast to northwest as shown in Figures 3 and 4. The principal reservoirs are cycle V/VI regressive coastal plan and fluvio-marine sandstones2. The depositional environments observed vary where shoreface deposits exhibit higher connectivity and higher areal sweep. The multiple stacked pays in multiple fields means that there are most probably many thief zones in the area reflected by a low recovery factor of around 29% only. Looking at this issue positively, it can be inferred that BDO area still has a lot of future oil potential through EOR applications.
