This study presents Phase 2 of a unified dynamic multiphase model describing subsurface fluid systems, focusing on fluid migration as a pressure-driven transport process. Fluid migration is defined as the movement of gases and fluids from deep geological sources toward shallower formations through porous media and fracture networks under the influence of pressure gradients. Migration is governed by the interaction between pressure gradients, rock permeability, fluid viscosity, and structural pathways, including pores, fractures, and faults. In contrast to classical models where migration is treated as a secondary or passive process, this framework defines migration as a continuous, dynamically sustained flow system driven by deep pressure sources. Fluid flow occurs through both porous media (matrix flow) and fracture systems (fast pathways), forming a coupled and heterogeneous transport network. The behavior of the system is strongly influenced by lithological variability and structural complexity, resulting in non-uniform flow patterns. The process is mathematically described using Darcy’s Law (q = -k/μ ∇P), linking flow rate to permeability, viscosity, and pressure gradient. The phase is further integrated into the global model through the parameter Λ = Pflow / Pc, where fluid flow is directly associated with pressure gradients at this stage. This phase establishes fluid migration as the mechanism that converts pressure energy into fluid motion, acting as a dynamic transport engine within the subsurface system. It provides a critical link between deep energy generation and subsequent geological processes, enabling continuous fluid movement, heterogeneous flow behavior, and dynamic reservoir evolution. Relation to Larger Work This publication is part of the research series: “A Dynamic Multiphase Model for Hydrocarbon and Hydrothermal Systems” It represents Phase 2 in a structured 13-phase framework describing the evolution of subsurface fluid systems from deep energy generation to accumulation. This phase defines the transport mechanism of the system, linking deep energy sources to higher geological levels through continuous, pressure-driven flow.
Kujtim gjoka Gjoka (Fri,) studied this question.