Ajay Malkoti

• Doctor of Philosophy
• Scientist at CSIR National Geophysical Research Institute

Modern geophysical imaging techniques exploit the full wavefield information which can be simulated numerically. These numerical simulations are computationally expensive due to several factors, such as a large number of time steps and nodes, big size of the derivative stencil and huge model size. Besides these constraints, it is also important to...

The accuracy of a numerical derivative has a significant effect on any numerical simulation. Long stencils can provide high accuracy as well as reduce the numerical anisotropy error. However, such a long stencil demands extensive computational resources and with their growing size, such derivatives may become physically non-realistic since contribu...

Seismic modeling plays an important role in geophysics and seismology for estimating the response of seismic sources in a given medium. In this work, we present a MATLAB-based package, FDwave3D, for synthetic wavefield and seismogram modeling in 3D anisotropic media. The seismic simulation is carried out using the finite-difference method over the...

The promise of passive seismology has increasingly been realized in recent years. Given the expense in installing and maintaining seismic station networks, it is important to extract as much information from the measurements as possible. In this context, the ellipticity or H/V amplitude ratio of Rayleigh waves can prove to be a valuable observable...

Seismic waves interact with a broad range of heterogeneities as they propagate through the earth. Simulating this full range of scales for wave propagation requires capturing heterogeneities of all scales, which can be computationally unaffordable. In such cases, we have relied on macroscopic representations of media obtained through an upscaling p...

Raniganj Basin is the eastern most coal producing basin of the Damodar Valley located in West Bengal, India. The basin has a large reserve of high-volatile coal deposits in the Raniganj and Barakar formations. The aim of this study is to map the Raniganj Formation in the eastern Raniganj basin as very limited information is available in the area. W...

Estimating the seismic impedance from the band-limited seismic data has proven to be a difficult task, especially due to the absence of low frequencies. This situation can be mitigated using the information obtained from well logs which can be used as a constraint. This prior information can be incorporated in various forms and for the stochastic t...

India is the one of the largest coal producer countries in the world and is the primary source of Energy in India. The main coalfields in India are: Jharia, Raniganj, Karanpura, Singareni, IB valley, Talcher, Neyveli, Singrauli, Nagpur and Chandrapur. Raniganj coalfield is situated in the easternmost part of the Damodar Valley Gondwana coalfield of...

The permeability of sandstone varies significantly from site to site at the field scale. Well-established methods for permeability estimation depend on lab-measured parameters, which are available only at sparse locations. To overcome such dependency, we developed a method to estimate sandstone's site-specific and field scale permeability using wel...

In seismic modelling experiments, the propagating seismic wave experiences attenuation when real media is simulated. However, for computational ease, we often ignore this effect and model the Earth as either an acoustic or an elastic medium. In this paper, we briefly discuss the importance of considering attenuation in seismic modelling, by using a...

Petrophysical properties and ultrasonic P- and S-wave attenuation measurements on 35 Deccan basalt core specimens, recovered from Killari borehole site in western India, provide unique reference data-sets for a lesser studied Deccan Volcanic Province. These samples represent 338-m-thick basaltic column, consisting four lava flows each of Ambenali a...

Estimation of petrophysical parameters from well logs is an important procedure in reservoir characterization. Here we present a method, based upon improved estimates of average mineralogical composition of shale, to estimate the petrophysical parameters from the well log data of a sandstone reservoir. The shale response is dependent of its distrib...

Petrophysical properties and ultrasonic P-and S- Wave attenuation measurements on 37 Deccan basalt cores recovered from Killari borehole (18°03′07″N, 76°33′20″E), western India, provide a unique and new reference data set for less studied Deccan volcanic province of India. The area is being explored for possible discovery of Mesozoic oil bearing se...