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

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Getting the Right Fluid Out of the Source Rock: Use of Extensive Data Sets from Shale Plays and Improved Compositional Modeling


Improving reservoir fluid prediction relies to a large part on the accuracy of the composition of the fluids that are generated and expelled from the source rock formation. The factors that affect the properties and composition of the expelled fluids are multiple, complex and often interrelated. Therefore this step in the modeling workflow brings many significant uncertainties. This paper intends to show how we can use both datasets from unconventional systems and newly developed software to reduce those uncertainties. Here we propose to learn from the extensive and multidisciplinary dataset of the Vaca Muerta source rock formation of the Neuquén basin in onshore Argentina which serves as a meaningful platform for inputs and constraints of our modeling. The Vaca Muerta source rock consists of type I/II kerogen with thermal maturity that varies from 0.5 to 2.5%Ro in the study area. Although seemingly homogeneous in terms of organic matter content, the richer Late Jurassic, Lower Vaca Muerta formation exhibits various heterogeneities at every scale that may affect fluid composition and distribution. Geological, geomechanical, petrophysiscal and geochemical data will be presented and discussed with regards to their representativeness and usefulness for the estimation of fluid composition. For operational reasons, in TOTAL we oftentimes use simple dimensionless modelling based on empirical source rock and fluid data bases and robust fluid thermodynamic calculations to expel and migrate petroleum fluids from the kitchen to prospects at various maturation timesteps. In addition, we recently have developed a source rock simulator calculating the expelled fluid composition based on source rock properties derived from laboratory experiments. It is based on a zero-dimensional model that includes multi-channel compositional kinetics, an equation-of-state based multiphase fluid formulation, a thermo-poro-elasto-plastic rock mechanics formalism, as well as sorption of oil and gas on and in kerogen. The resulting set of equations is solved in a fully coupled numerical implementation to simulate the complex physics at hand in a fast and accurate manner.