An Advanced Well Log and an Effective Methodology to Evaluate Water Saturation of the Organic-Rich Cambay Shale     

De  Sanjukta  Sengupta  Debashish 《Natural Resources Research》2021,30(2):1719-1733

Water saturation (S_w) is a vital parameter in the evaluation of hydrocarbon reservoir. Realistic estimation of S_w in shale reservoir is a challenging problem because of the presence of significant clay minerals and organic matter. The present study aims to estimate S_w of organic-rich Cambay Shale, Jambusar–Broach block, Cambay Basin, India, using an effective methodology and improved equation (TOC–clay equation), considering the appropriate corrections to counter the effect of clay minerals and organic matter in modifying resistivity. Advanced log like Litho-scanner has been utilized for the continuous estimation of clay content and total organic carbon (TOC), required for the estimation of S_w. Elemental capture spectroscopy and support vector regression were also applied for evaluation of clay content and TOC in one well where Litho-scanner log is not available. To investigate the effectiveness and applicability of the TOC–clay equation, results of S_w estimated from this equation and various other models have been compared with core S_w for a well. The analysis indicates that S_w derived from TOC–clay equation is having the closest agreement to core S_w data with an average absolute percentage error of 7.9% and coefficient of correlation 0.95. For other models, average absolute errors are significantly higher (16.8–32.7%). The application of TOC–clay equation will be useful for evaluation of the Cambay Shale reservoir. In addition, the resistivity-based TOC–clay equation used in this study is simple with a practical approach; it can be applied easily and efficiently for any organic-rich shale reservoir elsewhere.

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Agent-Based Simulation of Urban Residential Dynamics and Land Rent Change in a Gentrifying Area of Boston     

Jeremy Jackson  Benjamin Forest  Raja Sengupta 《Transactions in GIS》2008,12(4):475-491

Certain complex processes are most effectively modeled not on the macro-scale, but from the bottom-up, by simulating the decisions of individual entities, or agents. This study uses an agent-based modeling (ABM) approach to simulate residential dynamics in an area of Boston that has increasingly experienced gentrification in the past decades. The model is instantiated using basic empirical data and uses simple decision-making rules, differentiated into four classes, to simulate the process of residential dynamics. The model employs the consumption explanation of the cause of gentrification, which emphasizes the choices of individuals drawn to urban amenities, while testing the production explanation, which suggests that major investments from the public and private sphere attract and explain gentrification. Verification shows that the processes in the model work according to its construction, simulates complexity and emergent phenomena, and may be a valuable explanatory tool for understanding and learning about some processes underlying gentrification.  相似文献   

Evidence of biodegradation of chlorpyrifos by a newly isolated heavy metal-tolerant bacterium <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. strain MemCl4     

Santanu Pailan  Kriti Sengupta  Urmimala Ganguly  Pradipta Saha 《Environmental Earth Sciences》2016,75(12):1019

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Numerical Study of a Failure of a Reinforced Earth Retaining Wall     

A. Sengupta 《Geotechnical and Geological Engineering》2012,30(4):1025-1034

The case history of a failure of a RE wall has been presented. The wall failed immediately upon completion due to the overestimation of the strengths of the foundation clay layers and due to the underestimation of the self weight of the fill materials. A typical cross-section of the wall along with the stabilizing embankment and the foundation are modeled numerically by the limit equilibrium method and by a finite element method. The strengths of the foundation soils are determined by field tests done after the failure of the wall. Both the analyses predicted failure of the wall. The deformations predicted by the finite element method are found to be comparable to the observed field data. The numerical analyses further indicate that by consolidating a foundation clay layer to a minimum undrained strength of 45 kPa, the required factor of safety for the wall along with the road embankment can be achieved theoretically. Accordingly, prefabricated vertical drains are used to expedite the drainage and consolidation of the foundation clay layers. After the field tests confirm that the required minimum undrained strength is achieved, the RE wall and the embankment have been rebuilt successfully and now in full operation.  相似文献   

A Cross Section from the Pre-Sinian to Triassic Along the Three Gorges of Yangtze River, Central China: a Pre-Symposium Field Trip of IGCP-368/411/440 in 1999     

S. Sengupta  M. Yoshida  X. Wang 《Gondwana Research》2000,3(4):564-566

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Rain-triggered slope failure of the railway embankment at Malda,India   总被引：2，自引：2，他引：0  

Monal Raj  Aniruddha Sengupta 《Acta Geotechnica》2014,9(5):789-798

The common slope stability analysis is incapable of accurately forecasting shallow slides where suction pressures play a critical role. This realization is used for elaborate stability analyses which include soil suction to better predict rainfall-induced slides at railway embankment at Malda where three known cases of slope failures and train derailments occurred after heavy rainfall. The relationship between the soil–water content and the matric suction is established for the embankment soil. It is then used in the coupled analyses of seepage and slope stability to estimate performances of the embankment at different intensity and duration of rainfall. The numerical simulations are performed with the FE code Geo-Studio. The numerical results show significant reduction in the factor of safety of the railway embankment with the increase in the intensity and duration of rainfall. The effectiveness of the proposed mitigation measures including placement of 2 m-wide free draining rockfill across the slopes and drilling 5-m-long sheet pile wall at the toe of the embankment is studied numerically. The study confirms that the proposed mitigation measures effectively increase the factor of safety of the embankment and stabilizing it even in case of a heavy rainfall of 25 mm/h over 12 h.  相似文献   

Mechanism of activation of the Lanta Khola landslide in Sikkim Himalayas   总被引：4，自引：2，他引：2  

K. Anbarasu  A. Sengupta  S. Gupta  S. P. Sharma 《Landslides》2010,7(2):135-147

The Lanta Khola is a major landslide on the North Sikkim Highway in the Indian state of Sikkim. The abnormally low width-to-length ratio and slope instability in spite of the gentle surface slope (24°) make this slide unique. Geological, geophysical, and geotechnical studies reveal that a major Himalayan discontinuity daylights within the slide. At the contact, the schist is weathered to fine sand and silt with lower shear strength and permeability. The overlying gneiss is less weathered and exposed at the contact. Surface runoff enters the contact zone through crevices in the overlying gneiss, and debris material is extruded laterally from within this zone rendering instability, with blocks collapsing and eventually rolling down the slope after cloud bursts. Numerical modeling of the slide confirms this mechanism of instability. Diversion of runoff, plugging of crevices, and construction of pipe piles and horizontal drains are suggested as remedial measures.  相似文献   

Non-circular beam correction to the CMB power spectrum     

Tarun Souradeep  Sanjit Mitra  Anand Sengupta  Subharthi Ray  Rajib Saha   《New Astronomy Reviews》2006,50(11-12):1030

In the era of high precision CMB measurements, systematic effects are beginning to limit the ability to extract subtler cosmological information. The non-circularity of the experimental beam has become progressively important as CMB experiments strive to attain higher angular resolution and sensitivity. The effect of non-circular beam on the power spectrum is important at multipoles larger than the beam-width. For recent experiments with high angular resolution, optimal methods of power spectrum estimation are computationally prohibitive and sub-optimal approaches, such as the Pseudo-C_l method are used. We provide an analytic framework for correcting the power spectrum for the effect of beam non-circularity and non-uniform sky coverage (including incomplete/masked sky maps). The approach is perturbative in the distortion of the beam from non-circularity allowing for rapid computations when the beam is mildly non-circular. We advocate that when the non-circular beams are important, it is computationally advantageous to employ ‘soft’ azimuthally apodized masks whose spherical harmonic transforms die down fast with m.  相似文献   

Site-Specific Modeling of SH and P-SV Waves for Microzonation Study of Kolkata Metropolitan City, India     

Franco Vaccari  M. Yanger Walling  William K. Mohanty  Sankar K. Nath  Akhilesh K. Verma  A. Sengupta  Giuliano F. Panza 《Pure and Applied Geophysics》2011,168(3-4):479-493

Kolkata, one of the oldest cities of India, is situated over the thick alluvium of the Bengal Basin, where it lies at the boundary of the zone III and zone IV of the seismic zonation map of India. An example of the study of site effects of the metropolitan Kolkata is presented based on theoretical modeling. Full synthetic strong motion waveforms have been computed using a hybrid method that combines the modal summation and finite difference techniques. The 1964 Calcutta earthquake, which was located at the southern part of Kolkata, is taken as the source region, with the focal mechanism parameters of dip?=?32°, strike?=?232° and rake?=?56°. Four profiles are considered for the computation of the synthetic seismograms from which the maximum ground acceleration (A _MAX) is obtained. Response spectra ratios (RSR) are then computed using a bedrock reference model to estimate local amplifications effects. The A _MAX varies from 0.05 to 0.17?g and the comparison of the A _MAX with the different intensity scales (MM, MSK, RF and MCS) shows that the expected intensity is in the range from VII to X (MCS) for an earthquake of magnitude 6.5 at an epicentral distance of about 100?km. This theoretical result matches with the empirical (historical and recent) intensity observations in Kolkata. The RSR, as a function of frequency, reaches the largest values (largest amplification) in the frequency range from 1.0 to 2.0?Hz. The largest site amplification is observed at the top of loose soil.  相似文献   

A simplified method for determination of contents of arsenic in ground water from major oxide element of iron by regresssion analysis     

B. J. Sengupta  S. Lahiri  U. K. Biswas 《Journal of the Geological Society of India》2017,89(5):613-613

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