Purpose – The purpose of this paper is to present a detailed algorithm for simulating three-dimensional
hydrocarbon reservoirs using the blackoil model.
Design/methodology/approach – The numerical algorithm uses a cell-centred structured grid finite
volume method. The blackoil formulation iswritten in a way that an Implicit Pressure Explicit Saturation
approach can be used. The flow field is obtained by solving a general gas pressure equation derived by
manipulating the governing equations. All possible variations of the pressure equation coefficients are
given for different reservoir conditions. Key computational details including treatment of non-linear terms,
expansion of accumulation terms, transitions from under-saturated to saturated states and vice versa,
high gas injection rates, evolution of gas in the oil productionwells and adaptive time-stepping procedures
are elaborated.
Findings – It was shown that using a proper linearization method, less computational difficulties
occur especially when free gas is released with high rates. The computational performance of the
proposed algorithm is assessed by solving the first SPE comparative study problem with both
constant and variable bubble point conditions.
Research limitations/implications – While discretization is performed and implemented for
unstructured grids, the numerical results are presented only for structured grids, as expected,
the accuracy of numerical results are best for structured grids. Also, the reservoir is assumed to be
non-fractured.
Practical implications – The proposed algorithm can be efficiently used for simulating a wide
range of practical problems wherever blackoil model is applicable.
Originality/value – A complete and detailed description of ingredients of an efficient finite volume-based
algorithm for simulating blackoil flows in hydrocarbon reservoirs is presented.