Modelling fracture systems in extensional crystalline basement
Published:January 01, 2003
Using observations from the extensional basin setting in Vietnam, conceptual models were developed to simulate and analyse fracture systems typical of crystalline basement in such structural settings. Information from field observations, seismic surveys and three-dimensional (3-D) structural modelling were integrated and used to build geologically realistic 3-D fracture networks. A major advantage of the method used in this study is that it allows a better understanding of the apparently chaotic fracture networks characteristic of such rocks, and of the processes responsible for fracturing. Several fracture generating processes are discussed and modelled, with emphasis on tectonic fractures and the relation to structural modelling. An example is presented highlighting the differences in fracturing in the hanging wall and footwall during lithospheric extension superimposed on a primary (igneous) cooling fracture network. Results suggest that during flexural uplift, the hanging wall is significantly more deformed than the footwall, implying the former is more prone to fracturing than the footwall for both kinematic and flexural isostatic processes.
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Hydrocarbons in Crystalline Rocks
‘Commercial oil deposits in basement rocks are not geological “accidents” but are oil accumulations which obey all the rules of oil sourcing, migration and entrapment; therefore in areas of not too deep basement, oil deposits within basement rocks should be explored with the same professional skill and zeal as ccumulations in the overlying sediments’, Landes et al. (1960), AAPG Bulletin.
Given that most OPEC countries are currently at or within 5% Production capacity, there is a growing need to look for ‘new oil’ and other hydrocarbons in non-traditional sources.
While oil and gas fields in crystalline basement are still discovered mostly by accident, as shown in this book, such reservoirs can be very prolific, especially if the basement rock is highly faulted or fractured. The chapters in this volume cover a diverse range of topics related broadly to the theme of hydrocarbons in crystalline rocks, and challenge explorationists’ definition of basement rock, which needs to be less narrow and more responsive to new geological ideas.