In this work we present the results obtained from a coreflood experiment with polymer injection in secondary mode for extra heavy oil at 5500 cP viscosity. The work was carried out on a 30 cm length reconstituted core composed from cleaned reservoir sand. The core was packed using an in-house developed method, and then saturated with live oil partially degassed in PVT cell from initial reservoir conditions down to expected pressure at start of a field test (Pres). Saturation profiles were accurately measured by means of X-Ray scans on the core, enabling the visualization of flow instability development (viscous fingering). Effluents were collected in carbon cells under reservoir conditions with X-Ray production level measurements. The effluents were then flashed to atmospheric conditions, collected in test tubes and re-measured by X-Ray and UV measurements. The polymer flood carried out in secondary mode showed excellent results with a recovery of around 60% after 1.8 PV of polymer injected at 1 cc/h, even though viscosity ratio was highly unfavourable. The estimated apparent viscosity of the polymer was 60 cP at 7 s -1 , corresponding to the frontal advancement rate achieved during the coreflood. This recovery is in the same order as that obtained in tertiary mode after water flood in outcrop cores (Wassmuth et al. 2009, Wassmuth et al. 2007).

The giant field considered in this paper, located offshore Abu Dhabi, has so far been developed with solely a pressure maintenance-oriented strategy despite having produced for nearly fifty years. Such achievement has been possible because the field, divided into three stacked isolated reservoirs, is relatively homogeneous with little-to-no flow barriers.The purpose of this paper is two-fold. First, propose a review and critical discussion of the different pressure maintenance methods employed so far, which chronologically include gravity-driven dumpflood water injection, peripheral powered water injection, and down-flank as well as crestal gas injection.Second, present a segmentation mainly based on pressure trends on which injection-production metrics can be computed to help reservoir management pinpoint areas lacking support. A key to such analysis in the presence of peripheral water injection is to account for efficient water only, i.e., discard losses to the aquifer. For this purpose, a workflow involving streamline based post-processing of reservoir simulations corroborated by material balance analysis is used.Recent increasing trends in WCT and GOR indicate that a development solely based on pressure maintenance and reservoir energy (i.e., without artificial lift) is not sustainable anymore, and must transition to sweep-oriented. Plans for such migration are discussed in the companion paper of Nakashima et al. (SPE-177801).

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