This study presents Phase 4 of a unified dynamic multiphase model describing subsurface fluid systems, focusing on the role of biogenic layers as zones of chemical interaction and compositional transformation. Biogenic layers are sedimentary strata containing organic material and biologically derived compounds that interact with migrating deep fluids. As fluids migrate upward through the subsurface (following pressure-driven transport and stratified geological control), they encounter biogenic layers containing organic matter and early-stage hydrocarbons. In this framework, these layers are not treated solely as primary sources, but as reactive zones where continuous chemical exchange modifies fluid composition. Key processes include dissolution of organic compounds, catalytic reactions, and mixing between deep-origin gases and biogenic material. These interactions generate hybrid chemical signatures, reflecting both deep and biological contributions. The transformation is described through composition-based equations (Cₒut = Cᵢn + ΔC), where changes depend on organic content, temperature, pressure, and time. A coupled transport–reaction model further describes the evolution of fluid composition along migration pathways, introducing path-dependent geochemical behavior. This phase establishes biogenic layers as active chemical filters and transformation zones, capable of imprinting signatures that reflect the full migration history of the fluid system. It provides a mechanism for explaining mixed geochemical signals and variability between reservoirs, bridging the gap between abiotic and biotic models of hydrocarbon formation. This publication is part of the research series: “A Dynamic Multiphase Model for Hydrocarbon and Hydrothermal Systems” It represents Phase 4 in a structured 13-phase framework describing the evolution of subsurface fluid systems from deep energy generation to accumulation. This phase introduces chemical transformation processes within the system, linking fluid migration to geochemical evolution and hybrid signature formation.
Kujtim gjoka Gjoka (Fri,) studied this question.