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Showing papers by "Suresh Govindarajan published in 2021"


Journal ArticleDOI
TL;DR: In this article, the degradation of total petroleum hydrocarbons (TPH), nC12 to nC23 alkanes and priority pollutants such as polycyclic aromatic hydroCarbons (PAHs) in petroleum-contaminated water using an inexpensive Ti/Sb-SnO2/PbO2 anode.

33 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of the material composition (content of calcite and dolomite) of carbonate rocks on the efficiency of acid treatments and developed recommendations for the application of acid treatment of oil fields in the Perm Krai (Russia).

18 citations


Journal ArticleDOI
TL;DR: In this paper, a fully coupled two-phase fluid flow and geomechanical model has been used to investigate the impact of injection fluid flow on reservoir pressure, effective stresses and strain, vertical displacements, viscous fingering instability, and viscous dissipation during the displacement of a viscous oil by water in a heterogeneous fractured porous medium.

12 citations


Journal ArticleDOI
TL;DR: In this article, a new Visco-Elastic Gel (VEG) with adjustable degradation times (can vary from 3 to 120h) is proposed to preserve and reinstate the filtration characteristics of bottom-hole formation zone efficiently.
Abstract: Well killing remains to be the critical technological stage before proceeding with workover operations. Well killing using Visco-Elastic Gel (VEG) has been found to preserve and reinstate the filtration characteristics of bottom-hole formation zone efficiently. Since, these methods exclude the possibility of penetration of well-killing fluids into the reservoirs, the natural permeability of the reservoir retained. In this article, the authors have reported for the first time about a new VEG with controlled fracture times that remains appropriate for killing oil wells associated with both terrigenous carbonate reservoir operations. A distinctive feature of the proposed technology using a VEG with adjustable degradation times (can vary from 3 to 120 h) is that it requires a relatively smaller volumes of the composition in comparison with that of the conventional technologies. As a result, a significant reduction in the negative impact on the reservoir is achieved resulting from a relatively low penetrating ability of the proposed VEG. High structural properties of the VEG make it possible to reliably block the overlapped reservoir interval and it excludes the penetration of process fluid into the reservoir. In addition, it also eliminates the flow of formation fluid from the reservoir, which is absolutely necessary for trouble-free repairing work. It was found from the present study that the use of a breaker of a particular, single type does not provide the desired results and in the present study, the authors have deduced a relatively complex breaker based on peroxyhydrate and citric acid with a 1:1 ratio. The introduction of the encapsulated peroxyhydrate at the stage of preparation of the VEG ensures monodispersity of its dispersion characteristics. The developed VEG was successfully tested in 32 wells of oil fields in the Perm Krai fields in Russia. The well killing technology developed and described in this article using a VEG with adjustable destruction times has successfully been applied in the fields of the Perm Krai. The economic effect from the application of this technology was found to be $6.000 per well.

11 citations


Journal ArticleDOI
TL;DR: In this paper, the concentration profiles of nitrogen species in a fracture-matrix system under non-isothermal conditions were modeled by adopting a finite differential numerical scheme, and the numerical results clearly depicted the spatial-temporal profiles of the concentration of all the species in response to the observed peak values.
Abstract: Subsurface contamination is a frequent occurrence in fractured porous systems, posing a potential threat for the groundwater contamination. Tracking the movement of these contaminants is an inherent aspect of effective remediation strategy. The non-isothermal conditions prevailing in the subsurface environment further add to the complexity of the existing scenario. The current study focuses on simulating the concentration profiles of nitrogen species in a fracture-matrix system under non-isothermal conditions. The kinetics and biochemical thermodynamics of nitrogen transformation reactions were explicitly modelled in this study by adopting a finite differential numerical scheme. The numerical results clearly depicted the spatial-temporal profiles of the concentration of all the species in response to the observed peak values. Considering the sensitivity of the model parameters, an increase in flow velocity triggered the migration of all nitrogen species in the fracture, while an increase in matrix porosity reduced the concentration by enhancing the chemical reactions. An increase in fracture aperture also could trigger the denitrification process in the fracture to reduce the nitrate-nitrogen contamination in the fracture. The temperature variation between 25 °C and 45 °C in the fracture and the matrix essentially reduced the availability of nitrate-nitrogen and nitrogen gas in the fracture under non-isothermal conditions. Hence, an increase in the temperature coefficient can reduce the spike of nitrate-nitrogen and nitrogen gas in fracture by minimizing such transformation rates.

4 citations


Journal ArticleDOI
TL;DR: In this paper, Sen et al. extended their study to N = 4 CHL orbifold models and identified hair modes in the untwisted as well as twisted sectors, and they showed that after removing the contributions of the hair modes from the microscopic partition functions, the 4d and 5d horizon partition functions agree.
Abstract: Although BMPV black holes in flat space and in Taub-NUT space have identical near-horizon geometries, they have different indices from the microscopic analysis. For K3 compactification of type IIB theory, Sen et al. in a series of papers identified that the key to resolving this puzzle is the black hole hair modes: smooth, normalisable, bosonic and fermionic degrees of freedom living outside the horizon. In this paper, we extend their study to N = 4 CHL orbifold models. For these models, the puzzle is more challenging due to the presence of the twisted sectors. We identify hair modes in the untwisted as well as twisted sectors. We show that after removing the contributions of the hair modes from the microscopic partition functions, the 4d and 5d horizon partition functions agree. Special care is taken to present details on the smoothness analysis of hair modes for rotating black holes, thereby filling an essential gap in the literature.

3 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied a family of Siegel modular forms that are constructed using Jacobi forms that arise in Umbral moonshine and obtained closed formulae for these vector-valued modular forms.

2 citations


Journal ArticleDOI
TL;DR: The influence of hydraulic conductivity on the movement of flow and nonreactive solute transport through aquifers was evaluated in this paper, where several different log-normal probability distribution functions bounded within a fixed range were adopted for simulating the heterogeneous spatial distribution of hydraulicconductivity.
Abstract: The influence of hydraulic conductivity on the movement of flow and nonreactive solute transport through aquifers was evaluated. Several different log-normal probability distribution functions bounded within a fixed range were adopted for simulating the heterogeneous spatial distribution of hydraulic conductivity. Programming codes for two-dimensional confined aquifers were developed to solve the groundwater flow and solute transport equations for a hypothetical setup. Well capture zones were delineated using capture fractions and calculated the concentration moments. Results indicated that an increased shape parameter leads to more heterogeneity in the hydraulic conductivity field and significantly enhances the non-uniformity in the flow and solute plume movements. The findings were generalized for the continuous, discrete, and mixed zonal models, simulated with different parameter values, to yield a lower and upper range for the model derivatives. The results also described the influence of the connectedness of hydraulic conductivity fields on groundwater flow and transport, using capture fractions and plume moments as connectivity indicators. Hence, capture fractions and plume moment statistics aided the careful characterization of aquifer conductivity as a reasonable method of ranking flow and transport connectivity in aquifer flow and transport processes.

2 citations


Journal ArticleDOI
TL;DR: In this paper, a one-dimensional cleat for an under saturated low permeable coal bed methane reservoir is semi-analytically solved, and an empirical equation to calculate cleat properties, approximate to the field, is developed from the research.
Abstract: Coal reservoir productions depend entirely on cleat permeability and porosity values. The models used to date to calculate cleat parameters are either stress-dependent or strain-dependent. A study is carried to analyze the individual effects of stress and strain on the reservoir and fluid properties. A one-dimensional cleat for an under saturated low permeable coal bed methane reservoir is semi-analytically solved. Standard stress models, Shi-Durucan and Cui-Bustin, predict a range within which field values lie. A comparative study between strain and stress model behavior is carried out. The strain model considers matrix swell and shrink but ignores stress effects due to them, while a stress model considers them all. The stress-model is dependent on effective horizontal stresses in the reservoir. Stress models are preferred to strain model. Stress-dependent permeability being closer to actual values captures the field in a better manner. Though standard stress models are more accurate than the strain model, yet they cannot determine a specific permeability value at any given point in time. Emphasis is, therefore, laid on developing a new stress-dependent model. An iterative combination study of the standard models provides the new model. An empirical equation to calculate cleat properties, approximate to the field, is developed from the research. The new permeability model is substituted in the fluid production equation to obtain cumulative gas/water produced at any time interval. The results lie in the range predicted by the standard stress models and match the field observations, thus more reliable. The stress model is simple to use and is mathematically easy to formulate. It is flexible and can accommodate reservoir temperature and sorption strain changes.

2 citations


Journal ArticleDOI
20 Sep 2021
TL;DR: A detailed list of fundamental queries that will be required to be addressed at the instance of an oil spill has been deduced, which will be extremely useful for the oil spill respondents.
Abstract: The global lifestyle of this modern world has become more dependent on petroleum-based products, whose applications are involved almost everywhere. Since a large quantity of oil is being used on a daily basis, the spilling of oil by various means during its storage and transportation has become inevitable. This work focuses on the spilling of oil in a marine environment, generally referred to as an offshore oil spill, in contrast to an onshore oil spill associated with a terrestrial environment. These oil spills not only devastate the natural resources and unsettle the economy, they also jeopardize marine life, as well as human health. The remediation of an oil spill remains very challenging, when the disaster is associated with a large aerial extent. In this context, a sound understanding is required on the origin, seeping, composition and properties of the spilled oil in order to better monitor the spreading of the oil spill. In this manuscript, a detailed list of fundamental queries, which will be required to be addressed at the instance of an oil spill has been deduced, which will be extremely useful for the oil spill respondents as there are no previous studies that exclusively provide the type and nature of data required to be collected, immediately following an oil spill. Furthermore, this manuscript has deduced a list of sensitive and essential plots that will be required in order to analyse and forecast the spreading of an oil spill. An essence of weathering and its associated movement of oil spill has been included.

1 citations


Journal ArticleDOI
TL;DR: In this article, a hybrid artificial intelligence (AI) technique was developed and used to optimize flow-influencing parameters to minimize the pressure drop and shear viscosity and improve flow behavior index.
Abstract: The present work focuses on the improvement of flow properties during the transportation of heavy oil via 0.0254-, 0.0381-, and 0.0508-m-diameter pipelines. The effect of temperature, water cut, natural extract Madhuca Longifolia (ML), and potato starch (PS) on pressure drop, shear viscosity, and flow behavior index (n) was experimentally investigated. Minimum pressure drop occurred in the 0.0508-m-inner-diameter (ID) pipeline because of the combined consequence of temperature and 2,000 ppm ML during the transportation of 85% heavy oil + 15% water. A new correlation was developed to predict the friction factor for the heavy oil/emulsions during its transportation in a 0.0254-m-ID pipeline using the linear regression method for friction factor. Flow behavior index inclined toward Newtonian from shear-thinning behavior (i.e., n = 0.2181 to 0.9834) after the addition of 2,000 ppm ML at 50°C. From the comparative studies of the bioadditives ML and PS, it was found that ML was more effective in decreasing pressure drop. A new hybrid artificial intelligence (AI) technique was developed and used to optimize flow-influencing parameters to minimize the pressure drop and shear viscosity and improve flow behavior index. Minimum pressure drop (58,659.72 Pa), shear viscosity (1.56 Pa·s), and maximum flow behavior index (0.71) were achieved during the heavy oil flow in the 0.0508-m-ID pipeline after addition of 15% water, 1,320 ppm ML for 12.33-m3/h flow rate at 27°C. ML and PS are substantially efficient enough to decrease the pressure drop and shear viscosity and increase the flow behavior index in pipelines. However, from the studies, it was concluded that ML shows better performance compared with PS. Because both ML and PS are biodegradable and nontoxic, the petroleum industry may use both as a cost-effective alternative to decrease pour point and improve flowability for heavy crude oil.


Journal ArticleDOI
TL;DR: In this article, the Brylinski filtration induced by a principal Heisenberg subalgebra of an affine Kac-Moody algebra was studied, and it was shown that the corresponding Verma module of the affine kac-moody algebras is an irreducible Verma.
Abstract: We study the Brylinski filtration induced by a principal Heisenberg subalgebra of an affine Kac-Moody algebra $\mathfrak {g}$ , a notion first introduced by Slofstra. The associated graded space of this filtration on dominant weight spaces of integrable highest weight modules of $\mathfrak {g}$ has Hilbert series coinciding with Lusztig’s t-analog of weight multiplicities. For the level 1 vacuum module L(Λ0) of affine Kac-Moody algebras of type A, we show that the Brylinski filtration may be most naturally understood in terms of representations of the corresponding ${\mathscr{W}}$ -algebra. We show that the sum of dominant weight spaces of L(Λ0) in the principal vertex operator realization forms an irreducible Verma module of ${\mathscr{W}}$ and that the Brylinski filtration is induced by the Poincare-Birkhoff-Witt basis of this module. This explicitly determines the subspaces of the Brylinski filtration. Our basis may be viewed as the analog of Feigin-Frenkel’s basis of ${\mathscr{W}}$ for the ${\mathscr{W}}$ -action on the principal rather than on the homogeneous realization of L(Λ0).

Posted Content
TL;DR: In this paper, the authors studied a family of Siegel modular forms that are constructed using Jacobi forms that arise in Umbral moonshine and obtained closed formulae for these vector-valued modular forms.
Abstract: We study a family of Siegel modular forms that are constructed using Jacobi forms that arise in Umbral moonshine. All but one of them arise as the Weyl-Kac-Borcherds denominator formula of some Borcherds-Kac-Moody (BKM) Lie superalgebras. These Lie superalgebras have a $\widehat{sl(2)}$ subalgebra which we use to study the Siegel modular forms. We show that the expansion of the Umbral Jacobi forms in terms of $\widehat{sl(2)}$ characters leads to vector-valued modular forms. We obtain closed formulae for these vector-valued modular forms. In the Lie algebraic context, the Fourier coefficients of these vector-valued modular forms are related to multiplicities of roots appearing on the sum side of the Weyl-Kac-Borcherds denominator formulae.

Journal ArticleDOI
TL;DR: In this paper, the product formulae for all conjugacy classes of M24 were expressed in terms of standard modular forms, and a new proof of their modularity was provided.
Abstract: A second-quantized version of Mathieu moonshine leads to product formulae for functions that are potentially genus-two Siegel Modular Forms analogous to the Igusa Cusp Form. The modularity of these functions do not follow in an obvious manner. For some conjugacy classes, but not all, they match known modular forms. In this paper, we express the product formulae for all conjugacy classes of M24 in terms of products of standard modular forms. This provides a new proof of their modularity.

Journal ArticleDOI
TL;DR: In this article, a fully coupled dynamic thermo-hydro-geo-mechanical model was employed to investigate the advantage and disadvantages of supercritical CO2 over water as geofluids.
Abstract: In the present work, fully coupled dynamic thermo-hydro-geo-mechanical model was employed to investigate the advantage and disadvantages of supercritical CO2(SCCO2) over water as geofluids. Low-temperature zone was found in both SCCO2-EGS and water-EGS systems, but spatial expansion is higher in water-EGS. Although, the spatial expansion of SCCO2 into the rock matrix will help in the geo-sequestration. The expansion of stress and strain invaded zones were identified significantly in the vicinity of fracture and injection well. SCCO2-EGS system is giving better thermal breakthrough and geothermal life conditions compared to the water-EGS system. Reservoir flow impedance (RFI) and heat power are examined, and heat power are high in the water-EGS system. Minimum RFI is found in the SCCO2-EGS system at and 0.05 m/s. Maximum heat power for SCCO2-EGS was observed at , 20 MPa, and 0.15 m/s. Therefore, the developed dynamic THM model is having greater abilities to examine behavior of SCCO2-EGS and water-EGS systems effectively. The variations occur in the rock matrix and the performance indicators are dependent on the type of fluid, injection/production velocities, initial reservoir pressure, injection temperature. The advantages of SCCO2-EGS system over the water-EGS system, providing a promising result to the geothermal industry as geofluid.

Journal ArticleDOI
TL;DR: In this article, the influence of four inflow boundary conditions on solute plume migration and compared their concentrations was explored and a numerical model was used to simulate the solute transport for different boundary conditions at the injection well with three different recharge and six hydraulic conductivity scenarios.
Abstract: In this study, an attempt has been made to explore the influence of four inflow boundary conditions on solute plume migration and compared their concentrations. A numerical model was used to simulate the solute transport for different boundary conditions at the injection well with three different recharge and six hydraulic conductivity scenarios. Dirichlet concentration boundary, constant point source, and two Robin boundary conditions were applied to exemplify their effects on the outcomes. Significant variations were visible in the solute concentration profiles and their respective spreading patterns. Results show discrepancies between solutions obtained from the first-type and the third-type inflow boundary conditions for smaller Peclet numbers. The applicability of the M5′ model tree, a tree-based machine learning approach, was investigated and thereby exploited its capability to interpret the plausible functional dependency among the input parameters. The model tree also produced a dominancy structure within the parameter space with its combined classification and regression features. It was concluded that adopting a general boundary condition or generalization of solutions remained highly challenging, given the different input space parameters dictating a hydrogeological model.

Journal ArticleDOI
TL;DR: In this article, the injection of supercritical CO2 (sCO2) is numerically modeled, in a naturally fractured coal bed methane (CBM) reservoir, and it is shown that non-dewatered is a better alternative for the dewatered formation.