Faculty Publications
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Item Reservoir formation damage during various phases of oil and gas recovery- an overview(2012) Puthalath, P.; Murthy, C.S.N.; Surendranathan, A.O.When a reservoir of oil or gas is discovered under the ground, and reservoir engineers and drilling engineers are employed to tap that reservoir, often, they inadvertently damage it. Formation damage is an undesirable operational and economic problem that can occur during the various phases of oil and gas recovery from subsurface reservoirs including production, drilling, stimulation techniques and work over operations. The formation of a reservoir can be damaged by unforeseen rock, fluid, particle interactions etc and alterations caused by reservoir fluid, flow, and stress conditions. For example, the chemicals that the engineers have injected into the reservoir, the drilling mud used in drilling, or even by stress from the drill bit itself may cause formation damage. Control and remediation of formation damage are among the most important issues to be resolved for efficient exploitation of petroleum reservoirs and cost management. Formation damage seems to be inevitable and whether formation damage can be prevented, removed economically, or must be accepted as the price for drilling and producing a well will depend upon many factors. In this paper a general characteristics of formation damage during various stages of oil exploration are discussed. © 2012 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Structural Health Monitoring techniques in civil engineering: An overview(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Bhavana Patel, S.S.; Venkataramana, K.; Babu Narayan, K.S.; Parla, B.; Kimura, Y.Structural Health Monitoring (SHM) is an emerging and promising technology for safety and integrity of structures. Vibration Based Monitoring (VBM) has gained more importance in the field of civil engineering as damage parameters are sensitive to vibration. This paper presents brief introduction on SHM and VBM. Traditional and advanced techniques adopted for damage identification, localization and quantification by various authors have been discussed. However it is still a challenging task for the researchers to develop a technique which gives efficient and reliable solution for a particular Structure. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.Item An Investigation on the Influence of Thermal Damage on the Physical, Mechanical and Acoustic Behavior of Indian Gondwana Shale(Springer, 2020) Srinivasan, V.; Tripathy, A.; Gupta, T.; Singh, T.N.In the present study, the effect of thermal treatment on the physical, mechanical and fracturing behavior of Gondwana shale samples from India was investigated. Acoustic Emission signals were used to identify the changes brought in by temperature variations on the crack damage zones and failure attributes in shale. The results suggested that mechanical parameters such as uniaxial compressive strength, tensile strength (?t), elastic modulus, mode-I fracture toughness (KIC), cohesion, and brittleness index (B1) exhibited a strong negative correlation with thermal damage (Dt). But, the internal angle of friction and brittleness index (B2) showed a reasonable positive relation with thermal treatment. The deformation of the shale was dominated by its clay mineral enrichment, the characteristics of which changed with heating. The intensity of fracturing as observed from acoustic signals was chiefly controlled by the orientation of bedding planes and the degree of thermal treatment. The initiation and propagation of macro-crack were found to be greatly influenced by the degree of thermal damage. Under compression, thermally damaged samples showed similar deformation pattern, while under Brazilian tensile load, the deformation path became inconsistent with increasing temperatures. It was observed that thermal damage in tested shale decreased the layer compaction, which eased the fracturing intensity, thereby reducing the overall strength of the samples. The present investigation concludes that even a slight change of the thermal conditions can substantially alter shale fracturing behavior and failure attributes posing serious safety concerns of deep geo-engineering structures. © 2020, Springer-Verlag GmbH Austria, part of Springer Nature.Item An experimental study on rock damage and its influence in rock stress memory in a metamorphic rock(Springer, 2020) Srinivasan, V.; Gupta, T.; Ansari, T.A.; Singh, T.N.Rock stress memory, often referred as Kaiser effect, in rocks can be an effective tool to estimate the in situ stress conditions, if the uncertainties in rock damage and its behavior during loading conditions are properly understood. In view of this, the present study is an attempt to investigate the variations in rock stress memory, i.e., the Kaiser effect in a metamorphic rock under multi-stage uniaxial compression. The khondalite rock samples from Eastern Ghats Mobile Belt (EGMB) belonging to southeastern part of Indian subcontinent having complex geological history are examined. The effects of multi-stage compression on the damage evolution and subsequent variations in rock stress memory are investigated. The samples were categorized into different levels of rock stress memory, depending on the stress the rock was able to withhold after loading stages. The damage evolution in the tested rocks was predominantly controlled either by initial loading or failure stress. Higher damage imparted by initial loading and intense fracturing could be the possible reason for poor stress memory function in the investigated rock. Felicity ratio, an indicative of rock damage with stages of loading, supported the observation that rock damage was dominant during initial loading stage. Rock heterogeneity has played a dominant role in decay of Kaiser effect, with intense fracturing during subsequent loading stages in the investigated rocks. To summarize, Kaiser effect can be used to infer rock damage and stress conditions, provided the geological history of the region is also taken into consideration. With rocks from complex geological conditions, Kaiser effect or rock stress memory should be supported by other tools to infer in situ stress, but the method can be effectively used to understand the stress changes and damage mechanism of multiple loading. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item Influence of Fiber Content on Acoustic Emission Characteristics Related to Steel Fiber-Reinforced Concrete Subjected to Unconfined Uniaxial Compression(American Society of Civil Engineers (ASCE), 2021) Vidya Sagar, R.; Ghosh, S.; Kalloli, P.J.; Singh, M.This article reports the experimental study of the influence of the fiber volume content in steel fiber-reinforced concrete (SFRC) on the acoustic emission (AE) characteristics. Plain concrete and SFRC specimens with various steel fiber contents were tested under unconfined uniaxial compression in the laboratory. Both AE testing and ultrasonic pulse velocity (UPV) methods were used to study the fracture process in the specimens. During the fracture process, the generated AE and axial compressive strain were recorded. The differences in AE characteristics of plain concrete and SFRC specimens were discussed. An absence of a considerable amount of AE for a certain period was observed (silent period of AE) near the peak load for SFRC specimens. The AE-based b-value suddenly decreased near the peak load during the fracture process in plain concrete. However, in the case of SFRC specimens, a sudden decrease near the peak load was not observed, and the b-value decreased gradually until failure, at which point it attained its minimum value. More AE related to shear cracking was observed in the case of SFRC specimens. This was due to interlocking between steel fibers, cement matrix, and coarse aggregates. AE testing is useful for studying the material characterization of SFRC, and is beneficial for assessing damage in structures constructed with SFRC. © 2021 American Society of Civil Engineers.Item Physical model studies on damage and stability analysis of breakwaters armoured with geotextile sand containers(Elsevier Ltd, 2021) Elias, T.; Shirlal, K.G.; E.v, K.Harnessing the advantages of geotextile sand containers (GSCs), numerous submerged breakwaters and shoreline protection structures have been constructed worldwide. But an emerged breakwater structure with geotextile armour units, capable of replacing the conventional structures, is rarely discussed. A 1:30 scaled physical experimentation is chosen as a preliminary investigation to test the feasibility of using GSCs as breakwater armour units. Structural design is evolved based on a comprehensive literature survey. The paper focuses on the stability parameters and damage characteristics of the proposed structure. Four different configurations are subjected to waves, confining to Mangaluru's wave parameters. Effect of armour unit size and sand fill ratio on the stability of the structure is analysed and it is concluded that changing sand fill ratio from 80% to 100% shot up the structural stability to a maximum of 14%. Increasing bag size also resulted in the increased stability up to 8%. Experiments revealed that the best performing configuration could withstand wave heights up to 2.7 m. Stability curves for all tested configurations are discussed and can serve as an effective guideline for designing GSC breakwaters. © 2020 Elsevier LtdItem Geosynthetic reinforced rubble mound breakwater for mitigation of tsunami-induced damage(Elsevier Ltd, 2024) Sajan, M.; Chaudhary, B.; Akarsh, P.K.; Kumar, S.Several rubble mound breakwaters (RMB) were damaged and even collapsed during the past tsunamis. The main reasons for the failure of the breakwaters occurred due to the combined effects of seepage and scouring. Limited articles are available dealing with the behaviour of RMB during the tsunami. Furthermore, few available articles are related to developing countermeasures for the RMB against tsunamis. Therefore, an attempt has been made in the study to determine the exact behaviour of the RMB under the action of the tsunami. In addition, the main aim of the present study is to develop countermeasures to make the breakwater tsunami resilient. The present study proposes a novel geosynthetics-reinforced RMB to mitigate tsunami-induced breakwater damage. Based on the available information, this is the first time geosynthetics have been used in the RMB to mitigate tsunami-induced damage. Geogrid layers, geobags, sheet piles and crown walls (with shear keys) are adopted as countermeasure elements against the tsunami. Since the height of a tsunami can exceed its design tsunami height, tsunami waves were allowed to overflow the breakwater in physical model tests. Comparative analyses between the reinforced and unreinforced RMB were performed by conducting physical model tests, analytical tools, and numerical simulations. © 2023 Elsevier Ltd