This study presents Phase 9 of a unified dynamic multiphase model describing subsurface fluid systems, focusing on path-dependent modification as a key mechanism controlling fluid composition. Path-dependent modification refers to the progressive evolution of fluid properties as fluids migrate through different geological environments. During migration, fluids interact continuously with varying lithologies, temperature and pressure conditions, reactive and non-reactive layers, and pre-existing fluids within the system. As a result, fluid composition does not remain constant but evolves dynamically along its migration path. The system is inherently path-dependent, meaning that identical initial fluids may develop different final compositions depending on the sequence of environments encountered, the duration of interaction, and the nature of chemical and physical processes involved. This behavior is described through cumulative transformation models, where fluid composition changes incrementally along the pathway and reflects the integrated effects of multiple interactions. Mathematically, the final composition is expressed as a cumulative function of sequential modifications, linking chemical evolution to geological pathways and time-dependent processes. This phase also establishes a coupling between fluid composition and system dynamics, where compositional changes influence flow behavior and trapping conditions. This phase introduces a history-dependent perspective into the model, transforming fluid composition into a record of the entire migration process. It provides a framework for explaining compositional variability, hybrid fluid signatures, and differences between reservoirs formed under similar initial conditions. This publication is part of the research series: “A Dynamic Multiphase Model for Hydrocarbon and Hydrothermal Systems” It represents Phase 9 in a structured 13-phase framework describing the evolution of subsurface fluid systems from deep energy generation to accumulation. This phase introduces path-dependent evolution, linking fluid composition to the full migration history and establishing a dynamic, non-linear behavior within the system.
Kujtim gjoka Gjoka (Fri,) studied this question.