Interaction study of clay-bearing amphibolite–crude oil–saline water: Molecular level implications for enhanced oil recovery during low saline water flooding

Low saline water flooding (LSWF) had proved to be an efficient method for enhanced oil recovery in clay-bearing hydrocarbon reservoirs, but the interaction mechanisms among in-situ rocks – fluids and injection fluids within the reservoir – are not yet known properly. Understanding the molecular level interaction among these components is critical for designing and field scale implementation of LSWF in clay-bearing crystalline reservoir rocks, which is very limited in the existing literature. A weathered amphibolite rock and one dead crude oil from the Bakrol field (Cambay basin, India) have been used in this study. The presence of clay minerals in the weathered amphibolite rock was observed using a polarising microscope and characterised by the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. The crude oil and its fractionated SARA components have been extensively studied by spectroscopic techniques for their characterisation. The interaction study among the rock powder, hydrocarbon crude oil and saline water has been performed in the present work for gaining better insight for designing the injection fluid for LSWF. The weathered amphibolite rock powder was mixed with the dead crude oil and kept for 30 days in room temperature (T) and pressure (P) for proper interaction. The XRD, FTIR and cation exchange capacity results clearly demonstrated the incorporation of crude oil components in the interlayer surfaces of clay minerals. The oil removal efficiency, from the oil-treated rock powder of three saline water samples having NaCl concentration of 3000, 5000 and 8000 ppm, was investigated using the UV–Vis and fluorescence spectroscopies. The low saline NaCl water is capable of removing the maximum amount of polar components from the oil-treated rock powder. These molecular level insights are valuable for designing effective injection fluid for enhancing the oil recovery from the clay-rich crystalline reservoir rock.     

Hazardous area map: an approach of sustainable urban planning and industrial development—a review

Natural Hazards - A hazard map is a map which shows about all the vulnerable regions present in any country or at any specific place or location which is affected or will be affected by natural...     

Seismic Site Classification of Recording Stations in Tarai Region of Uttarakhand,from Multiple Approaches

Repeated earthquakes (EQs) are clear indication of alarming seismicity which can be witnessed across Indian subcontinent. Increase in population density with inappropriate construction practice repeatedly rise alarm that in comparison to damage scenarios experienced during previous major to great EQs in India, future catastrophes would be manifold. Performing regional seismic hazard as well as site response studies can possibly help in accurate estimation of probable future seismic scenario. Site class (SC) of EQ recording stations is an important part of both seismic hazard as well as site response analyses. In seismic hazard analysis, suitable attenuation relations are often selected based on comparison of recorded ground motion with proposed ground motion as per selected attenuation relation for the same SC. Thus, unless SC of recorded ground motions is known, suitability of selected attenuation relation cannot be validated. In addition, recent studies suggest that for same soil column, ground motion may amplify at the surface from minimal to very high depending upon input motion characteristics. Thus again, unless SC of recording station is not known, recorded ground motion cannot be considered with confidence as outcrop or base motion for region specific site response studies. In the present work, SC of eight recording stations located in Tarai region of Uttarakhand, India located adjacent to the Himalayan belt and which are part of PESMOS database, are established by three different methods namely; equivalent linear ground response analysis, generalized inversion technique and horizontal to vertical spectral ratio method. Collectively all these three methods suggest same SC for each of the eight recording stations including Roorkee, Rishikesh, Dehradun etc. Further, obtained SC based on the present study is considerably different from available SC as per PESMOS database. However, present findings are matching with recent published work. Obtained results can be very helpful in developing surface seismic hazard using regional ground motion records towards minimizing future EQ induced damages.     

Seismic behaviour of steel plate shear wall systems with staggered web configurations

Unstiffened steel plate shear walls (SPSWs) are used as lateral load‐resisting systems in building structures. The energy dissipation mechanism of SPSWs consists of the tension yielding of web plates and the formation of plastic hinges at the ends of horizontal boundary elements. However, vertical boundary elements (VBEs) of high‐rise SPSWs may experience high axial forces under lateral loading. This study explores the effectiveness of staggering of web plates on the reduction of VBE forces and drift response of SPSWs during an earthquake event. An analytical study has been conducted to determine the base shear reduction factor so as to match the overstrength of staggered systems with conventional SPSWs. A design methodology has been proposed for staggered SPSWs. Six‐, 9‐, and 20‐storey staggered and conventional SPSWs with varying aspect ratios are considered in this study to compare their seismic response. These study frames are modelled and analysed in OpenSEES platform. Nonlinear static and dynamic analyses are performed to compare the drift response, hinge mechanisms, and steel tonnage. Staggered SPSWs showed uniform drift distribution and reduction in interstorey drift and axial force demand on the VBEs.     

Reflection and transmission of inhomogeneous waves in a composite porous solid saturated by two immiscible fluids

This paper is concerned with reflection and transmission of a plane, elastic, and inhomogeneous wave striking obliquely at some discontinuity inside a porous medium composed of two distinct solids and saturated by two immiscible fluids. It is found that four P‐ and two SV‐waves are reflected, whereas four P‐ and two SV‐waves are transmitted at the interface. All reflected and transmitted waves are inhomogeneous in nature and specified with different directions of propagation and attenuation vectors. An expression for the Umov–Poynting energy flux vector is derived for the system. Continuity of energy flux along normal to the interface gives 12 required boundary conditions. Expressions of amplitude and energy ratios of various reflected and transmitted waves are derived. Variations in amplitude and energy coefficients of reflected and transmitted waves with angle of incidence are numerically studied for a porous matrix composed of shaley sandstone and clay, saturated with water and oil. The effects of change in oil saturation and volume fraction of clay are also observed on amplitude ratios. Numerical simulation reveals that the change in sign in the difference of capillary pressure across the interface causes jump in the values of amplitude ratios of all waves.     

Seismic source characterization for the Shillong Plateau in Northeast India

The present study aims at understanding the seismotectonic province of the Shillong Plateau (SP) by identifying the potential seismic source zones within a radius of 500 km from the centre of the SP. From existing literature and earthquake (EQ) data, the seismotectonic region is found to vary in terms of seismicity, tectonic features, geology, thickness of overburden, rupture characteristics and rate of movement. Thus, entire 500-km-radius seismotectonic region is divided into four seismic source zones: namely (1) the Shillong Plateau–Assam Valley Zone (SP-AVZ), (2) the Indo-Burma Ranges Zone (IBRZ), (3) the Bengal Basin Zone (BBZ) and (4) the Eastern Himalaya Zone (EHZ). EQ catalogues for each source zone is analysed for completeness of magnitude and time. Seismic parameter b estimated using a maximum likelihood method is found to be 0.91 ± 0.03, 0.94 ± 0.02, 0.80 ± 0.03 and 0.89 ± 0.03 for the SP-AVZ, IBRZ, BBZ and EHZ, respectively. In addition, the maximum likelihood method is used to estimate the mean annual activity rate, maximum possible magnitude (m _max), return period and probability of exceedance for the four zones. The b values estimated suggest that the BBZ is seismically more active; however, the rate of occurrence of EQs is highest in the IBRZ. Findings from this study are an indication of the relative contribution from each of the four seismic source zones towards a seismic hazard of the SP.     

Trend Analysis of Groundwater Levels and Assessment of Regional Groundwater Drought: Ghataprabha River Basin,India

Natural Resources Research - Groundwater drought is a relatively new concept, particularly in the Indian subcontinent, where groundwater levels are declining rapidly. The present study focuses on...     

Superpenumbral chromospheric flare

We observed a C-class flare at the outer boundary of the superpenumbra of a sunspot. The flare was triggered by an emerging magnetic bipolar region that was obliquely oriented with respect to the superpenumbral fibrils. The flare started due to the low height magnetic reconnection of emerging magnetic flux with a superpenumbral field resulting in hot multi-temperature plasma flows in the inverse Evershed flow channel and its overlying atmosphere. Inverse Evershed flows in the chromosphere start from the superpenumbra towards the sunspot that end at the outer boundary of the penumbra. The hot plasma flow towards the sunspot in the inverse Evershed channels show about 10 km s~(-1) higher velocity in Hα wavelengths compared to the plasma emissions at various temperatures as seen in different AIA filters. Even though these velocities are about seven times higher than the typical inverse Evershed flow speeds, the flow is diminished at the outer boundary of the sunspot's penumbra. This suggests that the superpenumbral field lines that carry inverse Evershed flows are discontinued at the boundary where the penumbral field lines dive into the sun and these two sets of field lines are completely distinct. The discontinuity in the typical magnetic field and plasma properties at the adjoining of these two sets of field lines further leads to discontinuity in the characteristic magnetoacoustic and Alfv′en speeds, thereby stopping the plasma flows further on. The multi-temperature plasma in the inverse Evershed channels exhibits possible longitudinal oscillations initially during the onset of the flare, and later flows towards the sunspot. In the multi-temperature view, the different layers above the flare region have a mixture of supersonic as well as subsonic flows.     

Impact of India’s new map policy on accuracy of GIS theme

With the declaration of India’s new map policy (NMP), user community is looking towards its impact on spatial accuracy of GIS theme maps arising out of transformation from existing system (Polyconic Projection on Everest 1830 spheroid datum) to Open series maps (OSM in UTM projection on WGS 84 ellipsoid) and vice versa. This results in registration error of existing maps with new maps. This study aims at finding out the impact of transformation on the spatial location and to determine the extent to which the existing theme layers can be used along with the new series maps without losing accuracy. Results show that there are some geographic regions in India whose GIS database can be used as it is available, depending on the scale and within the acceptable positional accuracy. For other region, depending on the scale of theme layers, a detail analysis of the situation will be required depending on project requirements.     

A study of secondary cosmic ray flux variation during the annular eclipse of 15 January 2010 at Rameswaram, India

The gamma ray flux was measured during the annular solar eclipse on January 15, 2010 at Rameswaram, India using NaI (Tl) scintillator detectors and the variation in charged particles and gamma rays was monitored using Geiger Mu¨ller (GM) counters. The gamma ray flux variation was studied in energy range of 0.1–3.5 MeV. Weather parameters (temperature and humidity) were continuously recorded throughout the duration of the eclipse at the site and correlation between gamma ray flux and weather parameters was examined. Analysis of the secondary cosmic ray flux using Fast Fourier Transform (FFT) was carried out to study the impact of the eclipse on the flux modulation. An overall decrease in flux was observed by both GM counters and scintillator detectors. A relative enhancement observed for short time during the eclipse which could be associated with the presence of counter electrojet observed at Rameswaram. This is suggestive of an increase in secondary cosmic ray flux at the geomagnetic equator during every counter electrojet due to decrease in geomagnetic rigidity.