Hydrodynamic secondary hydrocarbon migration

The system of hydrodynamic secondary hydrocarbon migration, whether the hydrocarbons move in separate phase, in very fine suspension or in aqueous solution, is influenced by the porosity and permeability distribution in a sedimentary basin, and the magnitude and direction of the net driving force for groundwater flow. As a consequence, the different processes and associated forces that are responsible for the hydrodynamic conditions in a sedimentary basin also determine to a greater or less extent the characteristics of the hydrocarbon migration system in a hydrodynamic basin (Sections 4.3.4.1, 4.S.4.2 and4.3.4.3). 

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A quantitative analysis of present-day secondary hydrocarbon migration for basin evaluation can be restricted to the prospective parts of a sedimentaiy basin as selected on the basis of the previously described qualitative study (Chapter 7). The quantitative assessment of present-day hydrocarbon migration systems is described separately for hydrostatic and hydrodynamic conditions of the prospective parts of the basin (Sections 8.1, 8.2 and 8.3). Section 8.4 briefly describes the available approaches for a quantitative analysis of the evolution of secondary hydrocarbon migration systems. 

The process of migration may lead to focussed movement of hydrocarbons into economic accumulations. The secondary migration of hydrocarbons may occur under hydrostatic or hydrodynamic conditions. Under hydrostatic conditions, the hydrocarbons migrate through the water-saturated carrier-reservoir rocks as separate phase hydrocarbons. Under hydrodynamic conditions, the hydrocarbons may be transported in continuous separate phase, in suspension or in aqueous solution. Under both hydrostatic and hydrodynamic conditions, the hydrocarbons ultimately appear as separate phase hydrocarbons before they can accumulate in a trap (Tissot and Welte, 1984). 

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