Debashish Sengupta | IIT Kharagpur (original) (raw)

Papers by Debashish Sengupta

Journal of Geochemistry, 2014

Ilmenite from the Chhatrapur coast, Odisha, India, was studied using optical microscope, X-ray di... more Ilmenite from the Chhatrapur coast, Odisha, India, was studied using optical microscope, X-ray diffraction, particle size analysis, and electron microprobe to decipher their micromorphology, texture(s), and elemental composition. The micromorphological features by electron microscope indicate that weathering processes such as mechanical and chemical, affected the placer heavy mineral ilmenite. These detrital ilmenites contain TiO2 in the range of 50.25% to 55.41% and FeO 42.72% to 49.99% in addition to Al2O3, MgO, MnO, CaO, Na2O, Cr2O3, NiO, ZnO, ZrO2, V2O5, and HfO2 (0 to 0.034%). Ti/(Ti + Fe) ratio in the ilmenite varied from 0.413 to 0.5, which indicates the effect of weathering/oxidation confirming microscopic observations. All the results revealed that these ilmenite grains were derived from the gneissic/granitic, basic and high grade metamorphic rocks, belonging to the Eastern Ghats Group of the Precambrian complex of coastal Orissa.

&amp;lt;p&amp;gt;The study of geomechanics is receiving substantial importance re... more &amp;lt;p&amp;gt;The study of geomechanics is receiving substantial importance recently in the petroleum industry as various problems, encountered during drilling a well to the completion stage of the extraction of hydrocarbon from the reservoir, can be addressed and mitigated with the knowledge of geomechanics. Particularly, for unconventional shale reservoirs, where challenges are more to have well stability and to extract a significant amount of production from the reservoir with ultra-low permeability, geomechanics plays a key role.&amp;amp;#160; Well logs can be used to analyze and estimate various parameters related to geo-mechanical properties of the rock formations in a time-efficient and cost-effective manner. The present work is aimed to study geomechanical properties of Cambay Shale, Jambusar-Broach block, Cambay Basin, India, with the application of basic and advanced well logs like Sonic Scanner, Elemental Capture Spectroscopy (ECS) and Formation Micro Imager (FMI).&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Sonic Scanner log, with state-of-art sonic measurements, has been utilised to obtain a quantitative estimation of parameters related to elastic and geomechanical properties of the formation like Poisson&amp;amp;#8217;s ratio, VPVS ratio, Young&amp;amp;#8217;s modulus, Bulk modulus, Shear modulus and strength of the rock. These parameters are useful for manipulating drilling programmes with lesser complications, analysing wellbore stability and designing an effective hydro-fracture operation for optimum production. Analysis of FMI log has been used to get information on drilling-induced features like breakouts and drilling-induced fractures (DIFs) which are indicators of the orientation of horizontal stresses and provide useful information in controlling wellbore stability.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Brittleness index (BI) is commonly used as a key geomechanical parameter in evaluating fracturability of the formation. Two log-based methodologies have been used in the present study to evaluate continuous BI. In one method, Sonic Scanner measurements have been used to estimate elastic moduli-based BI.&amp;amp;#160; The other method of BI estimation is based on the mineral composition of the formation. ECS log has been used to obtain the continuous mineralogical composition of the formation. As both of the methods for BI estimation are having intrinsic limitations, a combination of the two methods will provide more realistic information for brittle regions in the shale formation. The advantage of evaluation of the geomechanical properties of the studied shale formation using advanced well logs will be beneficial to the petroleum industry to reduce the cost and to have continuous information for targeting potential regions for hydrocarbon extraction with fewer complications.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;strong&amp;gt;Acknowledgement&amp;lt;/strong&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The authors would like to thank Oil and Natural Gas Corporation Limited, India for providing the requisite dataset and core samples to carry out the present study.&amp;lt;/p&amp;gt;

GSA Annual Meeting in Phoenix, Arizona, USA - 2019, 2019

$Research paper thumbnail of Trends in (n,$\gamma$) reaction with atomic number(6 to 109) for most abundant isotope of each element using TALYS and.. EXFOR$

DAE Symp.Nucl.Phys., 2017

Advances in intelligent systems and computing, Sep 2, 2018

The unsupervised data mining methods help to extract the hidden patterns within a large multidime... more The unsupervised data mining methods help to extract the hidden patterns within a large multidimensional dataset of subsurface well log measurements. The well logs are continuous measurements of some parameters related to the physical properties of the rocks in subsurface with respect to depth. Log data are used by oil and gas industries to understand the lithology of the formation, and to detect potential hydrocarbon-bearing zones if any. The present study has utilized principal component analysis (PCA) to consider the contribution of each of the well logs, and to reduce the dimensionality of the multivariate logs. The first four principal components from PCA, which define around 90% variance of the dataset, were utilized for clustering using k-means clustering technique. The elbow method was employed and the optimum number of clusters was obtained to be four for the present dataset. The obtained clusters were interpreted to determine the electrofacies associated with each of the clusters. The electrofacies reflect the lithology and the potential hydrocarbon-bearing zones, in the study area.

Petroleum Science and Technology, May 8, 2021

Abstract Brittleness index (BI) is an important parameter in evaluation of rock frackability. Two... more Abstract Brittleness index (BI) is an important parameter in evaluation of rock frackability. Two different methods are used to estimate continuous BI of Cambay Shale of Jambusar-Broach block, Cambay Basin, India, using advanced logs like ECS, Sonic Scanner (SS) and mineralogical analysis of core samples by XRD. First method is based on mineral composition using ECS log and second method is based on elastic moduli using SS log. ECS-based BI is in good agreement with BI from XRD-based mineralogy. BI estimated by two log-based methods will provide a cost effective and continuous information to identify potential regions for effective hydro-fracture.

Journal of Medical Physics, 2010

The concentrations of natural radionuclides in surface soil samples around selected villages of J... more The concentrations of natural radionuclides in surface soil samples around selected villages of Jaduguda were investigated and compared with the radioactivity level in the region. Concentrations of (238)U, (232)Th, and (40)K were determined by a gamma ray spectrometer using the HPGe detector with 50% relative efficiency, and the radiation dose to the local population was estimated. The average estimated activity concentrations of (238)U, (232)Th, and (40)K in the surface soil were 53.8, 44.2 and 464.2 Bq kg(-1) respectively. The average absorbed dose rate in the study area was estimated to be 72.5 nGy h-1, where as the annual effective dose to the population was 0.09 mSv y-1. A correlation analysis was made between measured dose rate and individual radionuclides, in order to delineate the contribution of the respective nuclides towards dose rate. The radio-elemental concentrations of uranium, thorium and potassium estimated for the soils, in the study area, indicated the enrichment of uranium series nuclide. The results of the present study were subsequently compared with international and national recommended values.

$Research paper thumbnail of Brittleness estimation and mineralogical analysis for evaluation of fracturability: Application to the Cambay Shale, Gujarat, India$

Brittleness index (BI) has been considered as a key geomechanical parameter in evaluating fractur... more Brittleness index (BI) has been considered as a key geomechanical parameter in evaluating fracturability of the shale formation for optimal extraction of hydrocarbon. BI is commonly used to quantit...

Petroleum Science and Technology, Mar 4, 2019

Abstract The objective of the present study is to estimate total organic carbon (TOC) content ove... more Abstract The objective of the present study is to estimate total organic carbon (TOC) content over the entire thickness of Cambay Shale, in the boreholes of Jambusar–Broach block of Cambay Basin, India. To achieve this objective, support vector regression (SVR), a supervised data mining technique, has been utilized using five basic wireline logs as input variables. Suitable SVR model has been developed by selecting epsilon-SVR algorithm and varying three different kernel functions and parameters like gamma and cost on a sample dataset. The best result is obtained when the radial-basis kernel function with gamma = 1 and cost = 1, are used. Finally, the performance of developed SVR model is compared with the ΔlogR method. The TOC computed by SVR method is found to be more precise than the ΔlogR method, as it has better agreement with the core-TOC. Thus, in the present study area, the SVR method is found to be a powerful tool for estimating TOC of Cambay Shale in a continuous and rapid manner.

Journal of Radioanalytical and Nuclear Chemistry, May 22, 2010

... T = counting duration (min), h = Radon build up period in the bubbler (min), k = Decay consta... more ... T = counting duration (min), h = Radon build up period in the bubbler (min), k = Decay constant ... Michel R (2004) Appl Radiat Isot 61:14691475 2. Eappen KP, Nair RN, Mayya ... Sangeetha SJ (2002) Natural radioactivity levels and exposure due to population in high background ...

Indian Journal of Pure & Applied Physics, Oct 1, 1991

Material Science Research India, Dec 10, 2011

Here a method has been described to study the attenuation of flux and energy of the neutrons pass... more Here a method has been described to study the attenuation of flux and energy of the neutrons passing through different materials. Variation of activity of the irradiated and activated sample by 14 MeV neutrons was observed by changing the matrix around it. The sample was a combination of Aluminium foil and copper powder placed at 0 o position (position of maximum flux) and the matrices were Air, Water, Iron, sand and carbon powder.

Annals of Geophysics, Jun 5, 2012

The bathymetry of the southwest Indian Ocean is dominated by three mid-oceanic ridge systems: the... more The bathymetry of the southwest Indian Ocean is dominated by three mid-oceanic ridge systems: the Chagos-Laccadives Ridge, the Central Indian Ridge, and the Mascarene Plateau. Although there have been a number of geophysical and geological investigations over the region, the genesis of these morphological features is still contradictory. Most of the estimations of effective elastic thickness in this region have been carried out in the spectral domain, either by transfer function analysis or by freeair admittance analysis. As these investigations were along some one-dimensional profiles or discrete blocks, spatial variation of the effective elastic thickness was not achieved. Here, we reappraise the estimation of effective elastic thickness in the southwest Indian Ocean by performing the computation in the spatial domain using flexure inversion. During this process, we also estimate the Moho depth throughout the region by two independent processes: gravity inversion, and flexural inversion. The Te values (effective elastic thickness) are estimated in the spatial domain, which match well with the results in the spectral domain obtained with the free-air admittance method. In addition, there is spatial variation of the Te values over the area analyzed. Our estimated Te values are low (1-6 km) along the Chagos-Laccadives ridge, implying its proximity to a spreading ridge at the time of creation. The Te values along the Mascarene Plateau show spatial variation with a seafloor age from north (Te, ca. 4 km) to south (Te, ca. 20 km). These findings substantiate earlier data and suggest that Réunion was created due to intraplate volcanism.

Journal of Radioanalytical and Nuclear Chemistry, Aug 2, 2020

Samples like p-type silicon and metallic glasses containing boron, were taken and used as target ... more Samples like p-type silicon and metallic glasses containing boron, were taken and used as target to induce the reaction 10B (n,α)7Li. In addition, samples containing lithium were also irradiated with thermal neutrons to induce 6Li (n,α)3H reaction. The alpha particles emitted through the reactions lose energy while traversing through the sample from point of emission to the surface and can be detected using a surface barrier detector. The out coming alpha particle spectrum can give the depth profile of boron or lithium atoms in the sample, if the energy loss of alpha particle within the matrix is known.

Journal of the Physical Society of Japan, Oct 15, 2012

Arabian Journal of Geosciences, 2022

In the present study, 130 shale samples of Cambay Shale were selected from two wells of the south... more In the present study, 130 shale samples of Cambay Shale were selected from two wells of the south Cambay Basin in the Jambusar-Broach block, India, to evaluate their source rock potential. Analysis with an integrated approach has been carried out using organic petrography, mean random vitrinite reflectance (R̄r), total organic carbon (TOC) estimation and Rock–Eval (RE) pyrolysis techniques. The variation of the TOC (wt%) values of the selected samples is in the range of 0.9–5.3% with an average value of 2.5%. Organic petrography of the shale samples reveals vitrinite as the major maceral type followed by liptinite and inertinite. The analysis of RE data of the shale samples also indicates the prevalence of type III as the dominant kerogen type. Based on the results of TOC estimation, hydrogen index and generation potential, the analysed samples are indicative of good to excellent source rocks with poor to good potential to generate hydrocarbon. R̄r (0.53–0.88%), Tmax (413–467 °C) and production index (0.02 to 0.5) indicate that thermal maturation of the shale samples lies from immature to peak oil window. Analysis of oil saturation index and oil crossover effect indicates a substantially higher risk of production of oil from the Cambay Shale based on geochemical consideration. The variability of source rock quality of the Cambay Shale in different blocks has been analysed. A comparative study of the Cambay Shale in the studied region with some of the producing shale plays in the world has been done based on organic geochemical characteristics.

Lunar and Planetary Science Conference, Mar 1, 2007

The discovery of maskelynite [1] in the moderately shocked basalt in the ejecta clasts of the ~50... more The discovery of maskelynite [1] in the moderately shocked basalt in the ejecta clasts of the ~50,000 year old Lonar crater [2-4] on Deccan Trap was an important criteria for establishing the meteoritic impact origin of this crater. However, little is known about the detailed petrology and geochemistry of this mineral, particularly the loss of volatiles during its formation. It was only found experimentally that the Lonar maskelynite was formed under a shock pressure between > 200 and < 400 kbar [5], and it reverted to a crystalline state only at a temperature of 800 o C [6]. In the present paper we focus mostly on the loss of volatile elements from the maskelynite due to impact, and its compositional variation compared to plagioclase of unshocked basalts.

Coal combustion in thermal power plants releases ash. Ash is reported to cause different adverse ... more Coal combustion in thermal power plants releases ash. Ash is reported to cause different adverse health hazards in humans and other organisms. Owing to the presence of radionuclides, it is also considered as a potential radiation hazard. In this study, based on the surface radiation measurements and relevant ancillary data, expected radiation risk zones were identified with regard to the human population residing near the Thermal Power Plant. With population density as the risk determining criteria, about 20% of the study area was at ‘High’ risk and another 20% of the study area was at ‘Low’ risk zone. The remaining 60% was under medium risk zone. Based on the findings remedial measures which may be adopted have been suggested.