This study presents Phase 5 of a unified dynamic multiphase model describing subsurface fluid systems, focusing on the role of cooling as a key regulator of fluid behavior. Cooling is defined as the process by which migrating fluids lose thermal energy as they move from deep, high-temperature environments toward shallower, lower-temperature formations. As fluids ascend through the subsurface following earlier phases of generation, migration, geological control, and chemical interaction, they encounter progressively lower temperatures governed by the geothermal gradient. This thermal decrease significantly influences fluid properties, including viscosity, density, phase behavior, and chemical reactivity. A central effect of cooling is the increase in fluid viscosity as temperature decreases, resulting in reduced flow rates according to Darcy’s Law. This relationship is expressed through temperature-dependent viscosity (μ = μ (T) ) and decreasing mobility (M = k/μ), leading to a decline in effective flow capacity. Consequently, the driving parameter Λ = Pflow / Pc decreases as fluid mobility is reduced. This phase marks a critical transition in the system, transforming fluids from a high-energy, highly mobile state into a more resistant and slower-moving system. Cooling therefore acts as a natural regulator that limits migration efficiency and promotes conditions favorable for accumulation. By integrating thermal effects into the dynamic framework, this phase provides a mechanism for understanding depth-dependent changes in fluid behavior and the transition from transport-dominated to accumulation-prone systems. This publication is part of the research series: “A Dynamic Multiphase Model for Hydrocarbon and Hydrothermal Systems” It represents Phase 5 in a structured 13-phase framework describing the evolution of subsurface fluid systems from deep energy generation to accumulation. This phase introduces thermal control as a key factor influencing fluid mobility, linking temperature evolution to the transition from migration toward accumulation.
Kujtim gjoka Gjoka (Fri,) studied this question.