Articles written in Journal of Earth System Science

    • Application of neural network modelling for classifying hydrocarbon bearing zone, water bearing zone and shale with estimation of petrophysical parameters in Cauvery basin, India


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      This work has been developed to classify sand and shale from seven wells in the Cauvery basin using a multilayered feedforward neural network (MLFN) model. Seven wells distributed over $5100 \rm{km}^{2}$ of this basin have been utilized for analysis of conventional well logs and reservoir characterization. Hydrocarbon bearing sediments of Andimadam, Bhuvanagiri, Nannilam and Niravi formations of the Cauvery basin are evaluated in terms of shaliness, cementation factor, porosity, water saturation, and permeability. Pickett plot has been applied to investigate the cementation factor, formation water resistivity, permeability. The cementation factor ($m$) varies from 1.31 to 1.86 in these formations, whereas permeability varies from 0.01 to 400 md. Very good quality reservoir exists in the Bhuvanagiri formation with high permeability 300–400 md, whereas a good quality reservoir is occurring in Niravi, Nannilam and Andimadam formations with hydrocarbon saturation 60–70%.

    • Geomechanical characterization of subsurface formations with stress rotation in Assam Gap, Northeast India


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      Modification of local stress orientation is an interesting issue for fluid migration and seal integrity at the faulted region of Assam Gap holding major oil/gas fields of India. Main objective is to scrutinize the stress pattern at the faulted blocks in this seismic gap. Geomechanical characterization of the study area has been carried out by integrating seismic and well log data through velocity model. A fresh approach adopting inverted post-stack seismic section tied with wells is considered to map the geomechanical parameters and stress magnitudes of the study area. The 3D structural model considers the geomechanical layers delineated by the mapped rock mechanical properties and local faults revealed in post-stack seismic sections. The 3D finite element model proposed in this study allows the computation of stress orientation, constraining deformation at the north facing edge and imposing the regional stress field towards NE–SW direction. The pattern of stress orientation shows the limited variation in stress direction across the geomechanical layers paralleling the regional stress direction of NE–SW. However strong stress rotation amounting about 20$^{\circ}$ is observed near the fault blocks and scattered rotation ranging from 20 to 90$^{\circ}$ in the fault plane. The model predicted stress direction is validated with the stress direction at well location from Fullbore Micro resistivity Imager data.

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