AAPG Middle East Region GTW, Regional Variations in Charge Systems and the Impact on Hydrocarbon Fluid Properties in Exploration

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From Regional Maturity to Local Prospect Charge: How Basin and Play-Level Processes Affect Charge Volume and Value at the Prospect Scale


Prospect charge evaluations require the convolution of regional petroleum systems concepts with local variations. Crustal genetic domains are mapped and interpreted in order to understand the basin-forming mechanisms which are translated by basin models into thermal fields through geologic time. We use long-offset seismic data and potential field data to constrain crustal domains that are subsequently restored in order to determine regional heat flow variations. Heat flow is not given as input but calculated from these models, as sedimentation and crustal processes may be coupled with each other (e.g. rifting, uplift, rapid sedimentation). Maturity is then determined as a function of heat flow history. This can be done independently of source rock presence as various types of maturity data may be available. Source rock presence and quality is presented in form of play maps that are constrained by RockEval data and paleogeographical interpretations. Uncertainty of thermal field and source rock presence and depth is used to determine ranges of maturities and expelled bulk volumes. Source rock kinetic data which depend on kerogen type and organofacies are usually based on in-house defaults and rarely customized. These regional considerations are then used as input to local models of prospect charge and associated HC kitchens as variations of charge access/loss or multiple charge events are oftentimes related to local variations rather than regional trends. Fluid data such as PVT reports and geochemical composition of fluids can help to constrain such local charge modeling. We will show with various examples how such a workflow can be applied and how regional maturity and fluid data can be used to constrain the local prediction of charge volume, type and properties. It turns out that regional variations are more easily constrained and that main uncertainties are oftentimes related to the lack of data or alternative interpretations at the local level which makes predictions particularly challenging.