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.

A joint gas injection feasibility study by Shell International E&P Inc., PETRONAS and PETRONAS Carigali Sdn. Bhd. has been conducted for the Baram Delta Operation (BDO) fields, offshore Sarawak, Malaysia.The goal of the study was to design a robust pilot project to evaluate and prove the commercial viability of basin wide gas injection.The study consists of several phases, the first of which, and the focus of this paper, is to conduct a screening study to estimate EOR potential and select a gas injection pilot location.The total EOR potential from initial screening was estimated at 200+ MMSTB from six of the nine BDO fields.Building prototype static and dynamic models of the top five ranking EOR targets further refined these opportunities. To enable screening and ranking of these targets, a spreadsheet based tool was constructed, which allows for rapid re-screening of reservoirs based on starting assumptions.The tool developed, BDO EOR Screening Tool (BEST), is based on several subsurface and surface criteria.The design of the tool allowed for screening of the total EOR potential and to determine the optimal pilot location.The screening required both immiscible and miscible gas injection potential to be estimated. The top five candidates, based primarily on EOR potential, were modeled and the potential verified using reservoir simulation.The fully miscible injection cases, Baram field as an example, showed similar results to screening estimates; however, the near miscible and immiscible cases at West Lutong and Tukau fields respectively showed a lower potential.Ultimately, the West Lutong M/N reservoir was chosen as the gas flood pilot location for the following reasons:large EOR potential in the M/N and K/L reservoirs,minimum miscibility pressure (MMP) is at or near current reservoir pressure,depositional environment analogous to several other reservoirs in BDO, andconsidered one of three large targets required to implement large scale gas flooding in BDO. This paper presents the methodology used in the screening of 1,000+ reservoirs and the unique features employed to develop representative prototype models using analogue field data. Background The nine offshore Baram Delta fields were discovered in 1969, as shown in Figure 1, and contain an estimated 4,000+ MM stock tank barrels in place ranging in gravity between 20 and 40 API.The productive reservoirs range in depth from 2,000 to 9,000 ftss.Historical production rates have been relatively flat at 80–100,000 barrels of oil per day maintained primarily through infill drilling and new infield development and/or expansion.Most reservoirs are supported by strong aquifer drives with two notable exceptions at Baronia (RV2 reservoir) - currently under waterflood, and several Baram reservoirs currently under depletion. The stratagraphic framework for the BDO reservoirs is Middle Miocene in age with east-west oriented coastline and a delta progradation southeast to northwest as shown in Figures 2 and 3.The principal reservoirs are cycle V/VI regressive coastal plan and fluvio-marine sandstones.1The depositional environments observed vary where shoreface deposits exhibit higher connectivity and higher areal sweep, such as in the deep Baram and moderately shallow West Lutong reservoirs. After 30 years of production, several of the large producing reservoirs have achieved high recovery efficiencies (>45%) and have begun producing at high watercuts.Therefore, different enhanced oil recovery techniques are now being considered.Reviewing published data, by the Journal of Petroleum Technology on EOR, suggests that gas flooding is appropriate for commercial EOR projects in the depth and API range of most BDO fields.Shell and PETRONAS agreed in 2003 to conduct a screening study and implement a gas injection pilot to materialize this opportunity, limited to six of the nine existing fields.

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