Application of Compositional Kinetics to Predict Generated Fluids: An Integrated Workflow Applied to the Vaca Muerta Formation

The Vaca Muerta Formation represents the principal hydrocarbon source rock of the Neuquén Basin; therefore, understanding the relationship between organic matter characteristics and generated fluids is critical for reducing uncertainties in frontier exploration and resource development studies. The objective of this work was to evaluate the geochemical and kinetic behavior of the Vaca Muerta Formation across different sectors of the basin and to assess the application of compositional kinetics as a tool for fluid prediction. Samples from the lower section of the formation were analyzed from wells located in the Mendoza, Neuquén, and Río Negro provinces. The workflow integrated data obtained from pyrolysis, organic petrology, kerogen characterization, bulk kinetics, and compositional kinetics. In the first stage, the kinetic behavior of the samples was evaluated and related to organic matter composition, both vertically and laterally throughout the basin. Subsequently, compositional kinetics were used to characterize the distribution of products generated during primary hydrocarbon generation and to evaluate their evolution as a function of thermal maturity. The results show that the Vaca Muerta Formation exhibits a similar kinetic behavior across the different sectors studied, consistent with a relatively homogeneous kerogen composition dominated by algal-bacterial amorphous organic matter. The resulting kinetic models indicate that the dominant generated fraction is associated with activation energies of 53 and 54 kcal/mol, a distribution characteristic of marine Type II kerogen. Furthermore, compositional simulations indicate that primary hydrocarbon generation is dominated by liquid hydrocarbons, with approximately 80% oil and 20% gas. The resulting data were incorporated into petroleum systems models to simulate primary generation and secondary cracking processes, allowing links to be established between kerogen characteristics, kinetic behavior, and fluid composition. Model calibration showed a good match with laboratory-measured maturity parameters, particularly for vitrinite reflectance values above 0.85% Ro, a maturity range in which secondary cracking exerts a significant influence on fluid predictions. The results demonstrate that the integration of kerogen characterization, compositional kinetics, and petroleum systems modeling provides a robust methodology for fluid prediction and for the evaluation of unconventional petroleum systems.