Geotectonic Model of Cambay Basin for Hydrocarbon Exploration from Mature to Immature Stage Using Fractal Geometry

Geologic processes like structural evolution, sedimentation pattern, fluid distribution are non-linear and therefore, are expected to display chaotic characteristics evidenced by self-similar observations or fractals. A major characteristic of fractal geometry - the invariance of the observations with the scale is used to derive an empirical geotectonic model for the evolution of Cenozoic Cambay Basin and hydrocarbon exploration in it from mature stage to immature stage. The model comprises of two distinct tectonic phases of Paleocene-Early Eocene age and Mid Miocene age separated by a 'Transitional' shallow water sedimentation cycle of Middle Eocene-Early Miocene age. The boundaries of these phases are marked by frequently conspicuous angular unconformities. Most of the seismic energy is absorbedlrenected within these transitional sediments which has restricted hydrocarbon exploration to the Mid-Eocene reservoirs (Kalol-Kadi, Hazad-Ankleswar Fonnations). These are the easy-to-find accumulations and exploration in these sequences is now considered to be in mature stage with dwindling size of new prospects. Need has arisen to look for other prospective reservoirs in the deeper sequences particularly in Paleocene - Early Eocene (Olpad Fonnation) after establishing good source rock potential in it. The presence of hydrocarbons is already established in this sequence but it has remained almost unexplored due to lack of sufficient subsurface data and clear understanding of the tectonics. The model helps in forecasting economic prospects within this sequence in which the configuration of the prospects will be unlike to that of the already known 'conventional' plays of Mid-Eocene age. All the discoveries in this sequence are interestingly fitting well with this model. Moreover the model can be applicable to further deeper sequences as well in other basins like the Bombay offshore, Assam-Arakan and Rajasthan etc. because the analyzable element 'reversal of highlands and lowlands between two tectonic phases' is also observed there on various scales.