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Modeling Petroleum System in Kerala - Konkan Basin, India

Jatindra K. Samal, Radha Krishan, and D. Mitra
KDMIPE, ONGC, Dehradun, India

Exploration in Kerala - Konkan Basin, India, in a passive margin set up, has become a challenge after post drill analysis suggesting charge problem, which demands for an understanding of the petroleum system through modeling. Earlier workers have identified natural oil seeps in the radar images and position of seep points over free air gravity map, indicates definite presence of hydrocarbon source in the study area. Hence an understanding of generation, maturation, charging and migration is necessary for evaluating the basin.

An attempt has been made for three 1D IES and two 2D IES PetroMod petroleum system modelling. In 1D modeling the generalized lithologies with age, thickness and eroding events were assigned from the well data and published reports. The 2D Petroleum System models were constructed in the southern Kerala Konkan area that ran NE-SW. A geologically realistic boundary assignments were given for paleo water depth, sediment water interface temperature and heat flow. Corrected bottom hole temperatures were used to determine the present day heat flow, that was input to test the fit of calculated vitrinite reflectance against observed data from drilled wells. Sweeney and Bunham was selected for kinetics of thermal calibration parameters.Main source litho facies were considered as shale and palynological studies indicate organic matter has type III to type II/III elemental composition. Average TOC is 0 .8 while average HI is 150.

The output panels of 1D models explain the subsidence rate in burial history curve, tranfomation ratio, variation of porosity and permeability, pressure variations, generation rate with depth, which in turn helps to understand the whole process of generation, maturation for charging.
On the modeled 2D line, after simulation, in the output panels by overlaying temperature, source rock properties, calibration, saturation, migration properties, the system could be understood in a detailed manner. The migration pathways for oil and vapors were analysed vectorically and migration shadow zones could be explained. This study may help to have a better understanding of the petroleum system and reduce risk and uncertainties in exploration programme of this basin.