Simulation of non‐planar three‐dimensional hydraulic fracture propagation

Hydraulic fracturing is the method of choice to enhance reservoir permeability and well efficiency for extraction of shale gas. Multi‐stranded non‐planar hydraulic fractures are often observed in stimulation sites. Non‐planar fractures propagating from wellbores inclined from the direction of maximum horizontal stress have also been reported. The pressure required to propagate non‐planar fractures is in general higher than in the case of planar fractures. Current computational methods for the simulation of hydraulic fractures generally assume single, symmetric, and planar crack geometries. In order to better understand hydraulic fracturing in complex‐layered naturally fractured reservoirs, fully 3D models need to be developed. In this paper, we present simulations of 3D non‐planar fracture propagation using an adaptive generalized FEM. This method greatly facilitates the discretization of complex 3D fractures, as finite element faces are not required to fit the crack surfaces. A solution strategy for fully automatic propagation of arbitrary 3D cracks is presented. The fracture surface on which pressure is applied is also automatically updated at each step. An efficient technique to numerically integrate boundary conditions on crack surfaces is also proposed and implemented. Strongly graded localized refinement and analytical asymptotic expansions are used as enrichment functions in the neighborhood of fracture fronts to increase the computational accuracy and efficiency of the method. Stress intensity factors with pressure on crack faces are extracted using the contour integral method. Various non‐planar crack geometries are investigated to demonstrate the robustness and flexibility of the proposed simulation methodology. Copyright © 2014 John Wiley & Sons, Ltd.     

Impact of Climate Change on Runoff of the Major River Basins of India Using Global Circulation Model (HadCM3) Projected Data

The effects of climate change on hydrological regimes have become a priority area for water and catchment management strategies. The terrestrial hydrology driven by monsoon rainfall plays a crucial role in shaping the agriculture, surface and ground water scenario in India. Thus, it is imperative to assess the impact of the changing climatic scenario projected under various climate change scenario towards the hydrological aspects for India. Runoff is one of the key parameters used as an indicator of hydrological process. A study was taken up to analyse the climate change impact on the runoff of river basins of India. The global circulation model output of Hadley centre (HADCM3) projected climate change data was used. Scenario for 2080 (A2 scenario indicating more industrial growth) was selected. The runoff was modeled using the curve number method in spatial domain using satellite derived current landuse/cover map. The derived runoff was compared with the runoff using normal climatic data (1951–1980). The results showed that there is a decline in the future climatic runoff in most of the river basins of India compared to normal climatic runoff. However, significant reduction was observed for the river basins in the eastern region viz: lower part of Ganga, Bahamani-Baitrani, Subarnrekha and upper parts of the Mahanadi. The mean projected runoff reduction during monsoon season (June–September) were 18 Billion Cubic Meter (BCM), 3.2 BCM, 3.5 BCM and 5.9 BCM for Brahmaputra-Barak Subarnrekha, Subarnarekha and Brahmini-Baitrani basin, respectively in comparison to normal climatic runoff. Overall reduction in seasonal runoff was high for Subarnrekha basin (54.1%). Rainfall to runoff conversion was high for Brahmaputra-Barak basin (72%), whereas coefficient of variation for runoff was more for Mahanadi basin (1.88) considering the monsoon season. Study indicates that eastern India agriculture may be affected due to shortage of surface water availability.     

Short term earthquake forecasts at Koyna,India

Earthquake activity is monitored in real time at the Koyna reservoir in western India, beginning from August 2005 and successful short term forecasts have been made of M ∼ 4 earthquakes. The basis of these forecasts is the observation of nucleation that precedes such earthquakes. Here we report that a total of 29 earthquakes in the magnitude range of 3.5 to 5.1 occurred in the region during the period of August 2005 through May 2010. These earthquakes could broadly be put in three zones. Zone-A has been most active accounting for 18 earthquakes, while 5 earthquakes in Zone-B and 6 in Zone-C have occurred. Earthquakes in Zone-A are preceded by well defined nucleation, while it is not the case with zones B and C. This indicates the complexity of the earthquakes processes and the fact that even in a small seismically active area of only 20 km × 30 km earthquake forecast is difficult.     

Late Acheulean hominins at the Marine Isotope Stage 6/5e transition in north-central India

Single-grain optically stimulated luminescence dating was applied to Late Quaternary sediments at two sites in the Middle Son Valley, Madhya Pradesh, India. Designated Bamburi 1 and Patpara, these sites contain Late Acheulean stone tool assemblages, which we associate with non-modern hominins. Age determinations of 140–120 ka place the formation of these sites at around the Marine Oxygen Isotope Stage 6–5 transition, placing them among the youngest Acheulean sites in the world. We present here the geochronology and sedimentological setting of these sites, and consider potential implications of Late Pleistocene archaic habitation in north-central India for the initial dispersal of modern humans across South Asia.     

Paleoseismic investigation along Nalagarh Thrust: Evidence of Late Pleistocene earthquake in Pinjaur Dun,Northwestern sub-Himalaya

The present article is the first time reporting of a paleoearthquake that occurred during Late Pleistocene time along the Nalagarh Thrust (NT) in the Pinjaur Dun in northwestern sub-Himalaya. Using CORONA satellite photographs, multi-spectral IRS satellite data, and aerial photographs, a prominent active fault has been identified at Nalagarh in Pinjaur Dun. This fault in the alluvial fan is located very close to the NT which borders the topographic front of the Tertiary rocks against Quaternary deposits. A trench excavation survey was carried out at Nalagarh for detailed paleoseismic studies across this thrust fault. Displacing all the lithologic units of the fan sequence, the fault plane has an average dip of 30° due ENE and a vertical displacement of 1.6 m and slip of ～2.5 m along the fault. The lithological units, consisting of alternating sand and gravel, show back tilting and asymmetrical tight folding. Based on Optically Stimulated Luminescence (OSL) ages, the oldest litho-unit in the trench is 85.83 ± 7.2 ka and the youngest is 67.05 ± 8.4 ka. The OSL age of the sample collected from the easterly exposure of the fault shows an age of 20 ka. The faulting and associated induced deformation features suggest occurrence of a Late Pleistocene large magnitude earthquake along NT in the Nalagarh region of the Pinjaur Dun following the deposition of the Quaternary sedimentary units. The Late Pleistocene fault substantiates the seismic potential of Pinjaur Dun and calls for more exhaustive study of paleoearthquakes in this fast developing industrial belt and highly populous mountainous region.     

Analysis of seepage from a pond

A semi-analytical solution has been derived for predicting the time of emptying a pond due to seepage. The time for the seeping water to reach the water table since the pond was initially filled has been calculated applying the Green-Ampt infiltration theory. The recharge rate after the wetting front joins the water table has been computed using a non-linear relationship between seepage head and recharge rate proposed by earlier investigators. The maximum rise in the water table beneath the center of the pond consequent to the time-varying recharge is calculated applying kernel coefficients obtained from solution of the linearized Boussinesq equation. It was observed that a pond with 50-m initial diameter at the water surface and 3-m maximum depth of water is dry after 168 days, where the subsoil is sandy clay. If the subsoil happens to be clay, the depth of water in the pond at the end of 9 months, i.e., after completion of the non-monsoon period, is 0.62 m. The maximum mound heights beneath the pond for constant recharge rate and uniform recharging area calculated from the present solution compare well with existing numerical as well as analytical solutions.     

Fertility differentials in Madhya Pradesh,India

"The present paper explains the fertility differentials among socio-cultural groups and regions in the central Indian state of Madhya Pradesh and examines the role of such factors as general and female literacy, age at marriage and infant mortality in determining the fertility levels. The study indicates that no single factor is of overwhelming importance. These factors in combination, as revealed by multivariate analysis, account for about 29 percent inter-district variation in fertility in the state."     

The detection and recognition of underground nuclear explosions

This paper reports on a joint meeting of the Royal Astronomical Society's Joint Association for Geophysics and VERTIC (the Verification Technology Information Centre) held in London in 1992. The topics presented focused on the detection and recognition of underground nuclear explosions. The objective of the meeting was to emphasize the multi-methodological approach that is important in verifying compliance with test-ban treaties. An overview of seismological monitoring was followed by a discussion of the technical and scientific aspects of a global seismic monitoring network, and in particular of the 1991 experiment to test the large-scale international exchange of seismic data between recording stations and data centres world-wide. The current capabilities of satellite remote-sensing were presented, and their use explained in terms of both the provision of information for monitoring the development of foreign nuclear testing programmes and also for providing sufficient information for the evaluation of treaty compliance. A review of radio-isotope sampling showed how the isotopic signature of both air and ground based sampling programmes can be diagnostic of the nuclear source. Finally, previously classified research on the ionospheric effects of underground nuclear explosions was presented, the generated acoustic waves disturbing the ionosphere and producing detectable changes in the reflection of radio and radar signals which have potential as a monitoring technique.