Polymer Flood Application to Improve Heavy Oil Recovery at East Bodo

Abstract The East Bodo, Lloydminster SS heavy oil pool, has been exploited using primary recovery and waterflood. IOR screening showed that a polymer flood would be a preferred IOR technique. Subsequent coreflood tests indicated that the polymer flood could recover 20% OOIP incremental oil, after waterflooding to a 95% water cut. Data gathered from the coreflood was used to fine tune the reservoir model to help design the pilot and predict potential economic reserves capture for a commercial field wide polymer flood. Subsequently a pilot was initiated. During the pilot operation, achieving the target polymer viscosity, dependant on water quality, proved to be a significant challenge. Early field response is being observed through an increase in injection pressure, reduced water cut and polymer breakthrough. Further positive response of this polymer pilot allows for the expansion of the polymer flood technology to other parts of this reservoir, some with bottom water and gas cap. This paper reviews the progress of the East Bodo, polymer flood, from laboratory concept to working field application in four major steps:IOR screening using simulations and coreflooding,field pilot design/ implementation,pilot performance andnext steps. A novel sealant that uses heavy oil-in-water emulsion to block the near well bore matrix has been developed. Stable reduction in permeability to other fluids was observed as the plug withstood 42,500 kPa/m (about 1,800 psi/ft) pressure gradients. Criteria are defined for field application of this blockage phenomenon. Introduction Pengrowth has targeted East Bodo (Alberta side) and Cosine (Saskatchewan side) for waterflood optimization and subsequent enhanced oil recovery applications. Currently the most practical EOR technology for this heavy oil reservoir seems to be the polymer flood technology in combination with horizontal wells. Several investigators1,2,3,4 have demonstrated the potential of the polymer flood technology for improved oil recovery in heavy oil reservoirs. The East Bodo/Cosine reservoir produces from the Lloydminster formation, which is part of the Lower Cretaceous Mannville Group. Pengrowth provided some of the reservoir characteristics as summarized in Table 1. This particular reservoir is separated into two parallel lobes trending North/West to South/East. The North-Lobe and South-Lobe are indicated by the well densities seen in Figure 1, which delineate the overall shape of the reservoir. Table 1: Reservoir Characteristics (Available in full paper) To complicate matters, local gas caps are found primarily on the Saskatchewan side of the reservoir. Thus, the current waterflood patterns are located on the Alberta side. In the future, optimized waterflood and EOR schemes need to include those parts of the reservoir which are overlain by gas caps or influenced by bottom water. The productivity of the different waterflood patterns is largely dependent on the injectivity of the central injector. Reviewing the injection rates from existing vertical injectors showed that injection rates vary between 1 m3/day to 250 m3/day, with an average rate near 30 m3/day. As part of the waterflood optimization, an explanation needs to be found why several wells allow for high injection rates and other wells demonstrate low injection rates.