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Abstract: Application of Compositional Basin Simulation to Predict the Location and Value of Hydrocarbon Accumulations

The composition of a petroleum fluid within a basin contributes to both the location and the value of any petroleum accumulation.The composition, a function of the source type, maturation history and P-T regime, controls the mobility (density and viscosity) and hence is a factor controlling the spatial distribution of petroleum fluid movement. The composition also determines the value of the accumulation, for example a viscous oil vs. a condensate-rich gas. This paper presents an approach adopted to describe this compositional behaviour and the results of a number of basin modelling transects from a variety of hydrocarbon plays.

A fully-integrated petroleum compositional model, which includes progressive generation and secondary cracking, is implemented within a commercial 3-phase flow basin simulator. This model, based on the BP ORGAS scheme, considers a three component (light, heavy & residue) petroleum system which generates petroleum products, the distribution of which evolve with maturity of the source.The phase description of the petroleum fluid is then determined according to empirical correlations, and the density & viscosity of the liquid & vapour phases referenced as functions of gas fraction, pressure & temperature. This then enables correct fluid & petrophysical properties to be used within a conventional multi-phase flow scheme.The scheme considers oil and water to be immiscible, whilst gas is miscible (soluble) in both oil and water allowing transport in solution.

We consider three broad scenarios of dynamic petroleum systems which are controlled to varying degrees by geochemical and fluid migration processes:
i) primary cracking of a thermogenic source progressively generating a lighter product, with single phase hydrocarbon migration (undersaturated oil or critical phase fluid);
ii) primary cracking of a thermogenic source again progressively generating a lighter product, with two phase migration hydrocarbon (saturated oil & gas); and
iii) primary cracking of a thermogenic source followed by secondary (oil to gas) cracking, usually in the source but occasionally in reservoir.

Case studies covering these scenarios will illustrate the nature of accumulations (gas or oil), GOR prediction and the distribution of different petroleum accumulations within a play fairway.

AAPG Search and Discovery Article #[email protected] International Conference and Exhibition, Birmingham, England