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Saha S.,Indian Institute of Technology Bombay | Saha S.,BG Exploration and Production India Ltd | Ghosh A.,Jadavpur University | Banerjee S.,Indian Institute of Technology Bombay | And 3 more authors.
Journal of the Geological Society of India | Year: 2011

This study highlights lithofacies and biofacies characteristics of the open coast tidal flat near Daman on the eastern flank of Gulf of Khambhat. Sedimentological and biological observation record six facies within the tidal flat area including older beach, beach face, sand flat, mud flat/mixed flat, sand bar and beach rock. Distinct sedimentary structures, foraminiferal assemblage and bioturbation intensity characterize each facies. A wide variety of wave and current generated sedimentary features characterize the sand flat facies. Semiconsolidated sands of older beach running parallel the coastline at a level higher than the present beach face possibly records the latest sea level highstand. The beach rock reflects early cementation of sands in tropical environments. Foraminifera are widely distributed in sand flats, mixed flats and mud flats and grouped into two biofacies - Ammonia-Elphidium-Quinqueloculina biofacies (sand flat and mixed flat) and Trochammina-Miliammina biofacies (mud flats). The beach face and sand bar facies contain forminifera reworked from sand flat and mud/mixed flat. Seasonal variation in depositional style is marked by deposition of fresh mud deposited over large areas of the intertidal flat during monsoon time, most of which is washed away by waves and current actions well before the onset of the next monsoon. © 2011 Geological Society of India. Source


Goswami A.,Indian Institute of Science | Kumar S.,BG Exploration and Production India Ltd
Engineering Failure Analysis | Year: 2014

This paper presents a specific kind of failure in ethylene cracking coils coated with anti-coking film. It investigates a case in which the coils made of 35Cr 45Ni high temperature alloy failed within two years of operation. The damage occurred due to heavy oxidation in localized regions of the coil resulting in the formation of blisters, which eventually failed by cracking. The mechanism involved was determined by studying the oxidized samples under a scanning electron microscope with an energy dispersive system and is attributed to the presence of rare earth metals in the anti-coking film and inherent casting defects in the base alloy. The cerium present in the anti-coking film diffused preferentially to a defect site in the parent alloy thereby resulting in its segregation which further led to embrittlement. © 2014 Elsevier Ltd. Source


Saha S.,Indian Institute of Technology Bombay | Saha S.,BG Exploration and Production India Ltd | Banerjee S.,Indian Institute of Technology Bombay | Burley S.D.,Cairn India Ltd. | And 4 more authors.
Sedimentary Geology | Year: 2010

Petrographical and geochemical data of modern coastal and estuarine sediments from the Gulf of Khambhat, western India, illustrate the problem of inferring tectonic setting from petrographic and geochemical discrimination diagrams. The passive margin basin at the western coast of India receives sediments from diverse sources from the stable craton of peninsular India, in which a considerable input is from the Cretaceous Deccan basalt that occupies a major part of the hinterland. Tectonic setting discrimination diagrams do not correctly identify the passive margin signature of sediments from the Gulf of Khambhat in most cases. Tectonic setting is correctly interpreted only in the absence of basaltic derivatives in modern sediments. The sediments predominantly derived from the Deccan basalt are wrongly placed in the oceanic island arc setting in the tectonic discrimination diagrams. Mixing of basaltic sediments derived primarily from the southern rivers with felsic sediments supplied from the northern rivers in the gulf tends to reflect active continental margin and oceanic island to continental island arc settings. Discrimination of the tectonic setting is complicated in estuaries because of the mixing of mafic and felsic derivatives in different proportions. Correct identification of the tectonic setting is possible in the inner estuaries, lying beyond the range of tidal influence, because of negligible mixing of sediments supplied by rivers and by tidal currents. Tectonic setting discrimination diagrams are therefore misleading for modern shallow marine basins situated close to continental flood basalt and, by implication, should be used carefully for ancient successions, given the common occurrence of basalts in the geological record. © 2010 Elsevier B.V. Source


Saha S.,Indian Institute of Technology Bombay | Saha S.,BG Exploration and Production India Ltd | Burley S.D.,BG Exploration and Production India Ltd | Burley S.D.,University of KeeleStaffordshire | And 3 more authors.
Marine and Petroleum Geology | Year: 2016

Tidal sand bars and tidal sand ridges are extensively developed in the macrotidal Gulf of Khambhat, offshore western India. The inner and outer regions of the gulf are characterised by the development distinct tidal sand bodies with discrete geometries and dimensions. The outer gulf ridges are long, narrow, curvilinear and several metres high (∼20 m). They are asymmetric in cross-section and migratory in nature, forming ‘ribbon’ like sand bodies separated by tidal channels. Active dunes on these ridges indicate the presence of sand and their orientation parallel to palaeo-shorelines supports a tidal origin. In contrast to the outer gulf tidal sand ridges, sand bars associated with macrotidal estuaries flanking the Gulf of Khambhat typically have an elongate to diamond shape and are only hundreds of metres in width and a few kilometres length. These tidal sand bars occur in the estuary mouths and within the tidally influenced fluvial reaches of the rivers flowing into the gulf. The height of these sand bars is in the range ∼1–3 m. Due to high tidal ranges and bi-directional flow the sand bars do not develop significant height and are formed between the mutually evasive ebb and flow channels. Their bi-directional foresets and the presence of abundant mud drapes associated with the dunes within in-channel sand bars indicate a tidal origin. The Gulf of Khambhat acquired the present configuration in the last few thousand years since the Pleistocene sea-level lowstand (last glacial maximum, ∼18 ka) when the entire continental shelf was subaerially exposed and rivers down-cut into the coastal plain. With increasing sea-level rise, the exposed shelf was drowned, flooding parts of the Modern western Indian peninsula, and large tidal sand ridges formed in the outer gulf. After the fall of sea-level at 2 ka the gulf acquired the Modern configuration with multiple estuaries on both coastlines, rivers supplied the embayment with sandy sediment, and tidal sand bars formed in the Modern estuaries. Quantitative data gathered from the Modern Gulf of Khambhat indicates that for the P50 case, a vertical drill hole will encounter tidal sand bodies (ridges and bars combined) of approximate dimensions 1700 m long, 470 m wide and 1.5 m high, with a spacing of 400 m. In subsurface hydrocarbon reservoirs, where data is sparse and only limited amount of core is available, this quantitative dataset can be useful to constrain subsurface geocellular models. Also, the overall geometry, distribution and aspect ratio of the tidal sand ridges and tidal sand bars can be used to identify ancient counterparts through seismic geomorphology or in core. © 2016 Elsevier Ltd Source


Effiong G.,Baker Hughes Inc. | Dean G.,Baker Hughes Inc. | Nayak S.,BG Exploration and Production India Ltd | Satyarthi R.S.,BG Exploration and Production India Ltd
SPE Production and Operations | Year: 2010

Available footprint on offshore platforms (Fig. 1) can be a significant challenge for coiled-tubing (CT) operations. Many times, platform limitations require that a smaller CT unit be deployed for work that would be faster and easier operationally with CT of a larger diameter. Often the platform's crane capacity dictates the size of CT used, which in turn reduces the working envelope of the CT. Some wells offshore India are completed horizontally and require intervention using larger sizes of CT in order to gain horizontal reach and manipulate sliding sleeves. When CT is used for these operations, the weight of the CT reel itself is critical to the effectiveness of the overall operation and requires proper management. Traditional methods of managing/reducing CT-reel weight involve spooling the CT string from a boat to the platform or joining CT sections by butt welding on the platform. Bringing the required length of CT onboard in two or more sections and joining them with a spoolable connector provides significant benefits over the traditional methods. The use of just one spoolable connector can reduce the maximum CT-reel lifting weight by typically 30 to 40% while increasing the CT size by one or two gauge sizes. This paper describes the results of a feasibility study performed to address typical challenges and presents actual case histories in which a spoolable connector was used to connect two CT strings. Required equipment was built and mobilized so that two separate strings could be joined on the platform with the aid of a connecting jig. Several trips were performed safely without the need to change the spoolable connector. Specific benefits of the spoolable connector over the traditional methods are explained. Methods to monitor the usable life of the spoolable connector while tripping in and out of the well (Fig. 2) will also be discussed, as well as new developments currently under way. Copyright © 2010 Society of Petroleum Engineers. Source

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