Recently, CNOOC launched the EOR with chemical flooding on more and more offshore oilfields in Bohai Bay in china. With the useful life of platform and the present production state, polymer flooding is considered as an important technology for the strategic development of offshore heavy oil fields in Bohai bay. Up to 2010, there are 3 polymer EOR projects on heavy oil field which the water cut is between 10 – 80%. And about 20 thousand tons polymer powder was used in 27 wells in the past 5 years. It has been seen that the water cut declined while the oil production increased. The application result shown it is feasible. The history of polymer EOR in Bohai Bay was present in the paper.
Summary
We derive and implement an interwell-numerical-simulation model (INSIM), which can be used as a calculation tool to approximate the performance of a reservoir under waterflooding. In INSIM, the reservoir is characterized as a coarse model consisting of a number of interwell control units, where each unit has two specific parameters: transmissibility and control pore volume (PV). By solving the mass-material-balance and front-tracking equations for the control units, the interwell fluid rates and saturations are obtained so that phase-producing rates can be predicted. The ability of INSIM to predict water cut and phase rates is the most important innovation included in INSIM. INSIM is applied to perform history matching and to infer the interwell connectivity and geological characteristics. INSIM has a number of advantages. First, the model parameters estimated from history matching provide a relative characterization of interwell-formation properties. The model can handle changes in the flow directions caused by changing well rates, including shutting in wells or converting producers to injectors, whereas with the common correlation-based interwell-connectivity method, the well interactions are assumed to be fixed. Second, the previous methods, which have similar computational complexity to INSIM, can only provide the total liquid-production rate, whereas with our procedure, we can calculate the oil- and water-flow rates and hence history match water-cut data. Third, because we can calculate the oil- and water-flow rates, our method can be used for waterflooding optimization but with far-less computational effort than with the traditional method by use of a reservoir simulator.
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