Quantitative evaluation of produced hydrocarbon compositions and injectantreproduction in gas-miscible floods

It is not trivial to identify and to quantitatively monitor production of i njectants such as solvent and chase gas during a commercial gas-miscible fl ood. A new methodology was developed for evaluating produced amounts of tho se injectants and reservoir oil using readily available field data. This me thodology follows two major logical steps. The first step is to determine o verall compositions of the produced hydrocarbons. The new method can unique ly determine the total produced hydrocarbon composition from available fiel d data, namely a separator gas composition and a produced gas-oil ratio, us ing an equation of state adequately tuned for specific crude oil. The secon d step is to determine the most plausible proportions of injected solvent, chase gas and reservoir oil in the produced hydrocarbon composition with th e knowledge of the respective compositions. The entire process was packaged in computer software which had been tested for its reliability. The softwa re has been in use for the past two years in Imperial Oil's gas-miscible pr ojects for reporting solvent and chase-gas production. In these field appli cations, the software has proved to be capable of calculating solvent and c hase-gas contributions even in situations with gas-lift wells.