Fractures, faults, and hydrocarbon entrapment, migration and flow

This paper presents an overview of the role of structural heterogeneities in hydrocarbon entrapment, migration and flow. Three common structural heterogeneity types are considered: (1) dilatant fractures (joints, veins, and dikes); (2) contraction/ compaction structures (solution seams and compaction bands); and (3) shear fractures (faults). Each class of structures has a different geometry, pattern, and fluid flow property, which are described by using analog outcrop studies, conceptual models, and, in some cases, actual subsurface data. Permeability of these structures may, on average, be a few orders of magnitude higher or lower than those of the corresponding matrix rocks. Based on these differences and the widespread occurrence of fractures and faults in rocks, it is concluded that structural heterogeneities should he essential elements of hydrocarbon migration and flow as well as entrapment and that they should be included in large-scale basin models and reservoir-scale simulation models. This proposition is supported by a number of case studies of various reservoirs presented in this paper. (C) 2000 Elsevier Science Ltd. All rights reserved.