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_ The boundary value problem associated with scattering of ice-coupled gravity waves by a thin vertical ice sheet in infinitely deep water is explicitly solved. The method of solution utilizes a connection that helps to decompose the problem into two relatively easy problems. The decomposed problems are explicitly solved by the aid of a weakly singular integral equation. Reflection coefficients are computed in both cases of ice sheet with and without compressive force in it. The model predicts a few resonant frequencies of ice-coupled waves at which complete reflection occurs. Further, scattering quantities are found to be sensitive to the ice sheet parameters. Introduction Flexural or ice-coupled gravity waves are created when free surface gravity waves propagate through flexible floating structures such as ice sheets and elastic sheets. They also arise in floating platforms such as very large floating structures (VLFS) whose hydrodynamic and hydroelastic behaviour is important when utilizing ocean space for activities and development. The development of these floating structures is reviewed by Kashiwagi (2000). A similar review was done by Squire et al. (1995) in the context of wave interactions with an ice-covered surface. Many mathematical techniques have been developed to study the interaction of waves with these floating ice-covered structures. Eigenfunction expansions, integral equation methods, approximate methods, Fourier transform methods, and Wiener–Hopf techniques are some of the popular methods in the literature; see Sahoo et al. (2001), Meylan (1997), and Balmforth and Craster (1999), to name a few.
Chen, Songtao (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai) | Meng, Qingjie (Wuhan Second Ship Design and Research Institute, Wuhan) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai)
ABSTRACT This paper numerically investigates breaking waves interaction with a vertical wall attached with a recurved parapet in 1:8 model scale. The in-house CFD solver naoe-FOAM-SJTU based on the open source platform OpenFOAM is used to perform the simulation. For wave generation, a novel generating-absorbing boundary condition (GABC) is adopted to replace the time-consuming moving boundary wavemaker. A geometric volume-of-fluid (VOF) method based on piecewise-linear interface calculation (PLIC) is incorporated in the present numerical model to capture the sharp interface and improve the accuracy of the predicted impact pressure. The time histories of the wave elevation and pressure at each probe are presented as well as the frequency analysis. In addition, the evolutions of free surface and pressure distribution are further provided to achieve a better understanding of this complex wave-structure interaction issue. INTRODUCTION Vertical breakwaters are typical coastal structures intended to reduce the effects of incoming waves, especially in extreme sea conditions. In practical design, wave overtopping has been a significant issue of sustained concern for decades. Among the various solutions, a parapet fixed on the top of the vertical wall has been proven effective by deflecting back the up-rushing water seawards. However, according to the previous studies, the shape and parameters of the parapet will significantly influence the impact force and pressure compared with the original vertical wall. In order to provide guidelines to predict the wave impact and wave loading, it is necessary to systematically investigate the variations under different wave conditions, including non-breaking and broken waves. As a representative shape, the recurved parapet has gradually attracted more attention recently. Kortenhaus et al. (2002, 2003) highlighted the effectiveness of the recurves and parapets in wave overtopping through abundant experimental data collected in the wave flume of the Leichtweiβ-Institute. Nevertheless, they pointed out that their existences may increase the wave loadings on the vertical wall. Ravindar et al. (2019) conducted large-scale (1:1) experiments to characterize the impact pressure under different wave breaking conditions at the Coastal Research Centre (FZK), Germany. According to their classification, it can be divided into three conditions: slightly breaking waves (SBW), breaking waves with small air trap (BWSAT), and breaking waves with large air trap (BWLAT). In addition, they reported the significant effect of the entrained air on the impact pressure. On this basis, Ravindar et al. (2021a, b) carried out small-scale (1:8) experiments in the Department of Ocean Engineering at the Indian Institute of Technology Madras, Chennai, Tamil Nadu, India. They analyzed the scale effects and proposed a combined Cuomo-Froude method for scaling up the impact pressure of small-scale results. Besides, they also discussed the impact pressure and forces of different types of parapets under the above-classified wave breaking conditions.
Singapore-based gas and LNG logistics company AG&P broke ground on its LNG import facility at Karaikal Port, Puducherry, on Thursday, which is paving the way to broader access to natural gas as a primary fuel in South India. The company said the Karaikal LNG import facility (Karaikal LNG) is expected to commence commercial operations by Q4 2021. "It will become a landmark infrastructure development for the region and is ideally suited for the Karaikal Port, a critical center of trade," said AG&P chief executive JM Sigelman. AG&P president of terminals and logistics, Karthik Sathyamoorthy, added that the company's goal is to bring down the unit cost of regasification terminals for smaller volumes to make LNG commercially viable for scattered and smaller customers. Karaikal LNG is owned and operated by AG&P, which is being built on a 12-hectare site within the Karaikal Port, having the only deepwater access on the East Coast of India south of Chennai.
Abstract This paper attempts to answer a fundamental question pertinent to fracture characterization of unconventional basement reserves using rock mechanics & petrophysics; are open fractures in basements necessary critically stressed? Evaluation of naturally occurring fractures are critical for production as well as reserves estimation. In this regard, a study well was drilled in the basement section of the Cauvery basin to explore unconventional pay zones & characterize the contributing fractures by integrated Geomechanical & Petrophysical analysis. A suite of open hole logs including the basic, acoustic and electrical borehole images were acquired and an integrated approach was taken, including geomechanical analysis to identify the contributing fractures. Standard petrophysical evaluation in basements was inconclusive and porosity quantification from fractures posed a major challenge. Image log analysis involved identification of conductive and resistive fractures in the gauged wellbore and combining Stoneley reflectivity further indicated probable open fractures. Following this, a geomechanical analysis was carried out to determine the current in-situ stress orientation/magnitudes based on observed breakouts. Finally a CSF study was done to check for fracture slip events. Based on the integrated study of Petrophysics and Geomechanics, an optimized workflow was developed and the critically stressed fractures were identified. It was found that, while some fractures strike direction was different from the present day maximum horizontal stress direction (SHmax), in general, most fractures were indeed aligned to SHmax. To check the fluid flowing capability of fracture networks, formation tester was deployed in selective zones for testing and sampling. Successful hydrocarbon sampling from selective fractures with orientation not aligned to SHmax led to the validation of the current study. The results proved that while most critically stressed/open fractures did indeed contribute to flow, a smaller fraction of the naturally occurring fractures while contributing to flow, were not necessarily aligned to the in situ orientations. The results present a discrepancy between observation and the expectation that open fractures are necessarily oriented parallel or nearly parallel to modern-day SHmax. This works highlights the fact that although paleo-stresses may influence the fracture networks, it is the contemporary in-situ stresses that truly dominate fluid flow and only through a detailed understanding of the critically stressed areas, can we come to a decisive conclusion that further improves overall recovery.
ABSTRACT The case study based on the inversion study of an area, situated in Cauvery basin, east cost of India. The objective of this area is to delineate and identification of reservoir sand through seismic inversion. We will discuss here the deterministic and the geostatistical method of seismic inversion and how their results are used for reservoir characterization. The major challenge in reservoir property modeling of Oil industries is to integrate the vertical resolution of petrophysical data with seismic data for lateral as well as vertical extension. In deterministic inversion reservoir properties are directly related with the amplitude of seismic data, but in geo-statistical inversion reservoir properties of wells are populated into the inter well space, simulated with 3D seismic data. Pre-stack deterministic and post-stack geostatistical inversion was carried out for characterization of reservoir properties. Probable litho facies and impedance volumes generated from geostatistical inversion captured distinctively the heterogeneity and small scale variations in the inter-well region that help us to delineate and identification of reservoirs. Presentation Date: Tuesday, September 17, 2019 Session Start Time: 8:30 AM Presentation Start Time: 10:35 AM Location: 217A Presentation Type: Oral
Saha, Sankhajit (Baker Hughes, a GE company) | Gariya, Bhuwan Chandra (Hindustan Oil Exploration Company Ltd) | Panda, Debabrata (Hindustan Oil Exploration Company Ltd) | Perumalla, Satya (Baker Hughes, a GE company) | Podder, Tuhin (Baker Hughes, a GE company) | Thanvi, Shrikant (Baker Hughes, a GE company) | Deshpande, Chandrashekhar (Baker Hughes, a GE company)
Abstract Drilling through the thick shale sequence (Oligocene to Paleocene age) of Cauvery offshore showed severe wellbore instability in the past due to incompatible mud program that increased overall operational cost. While new high-angle sidetrack development wells had been planned, three major challenges need to be addressed. First, proper mud weight recommendation for preventing mechanical instability; second, introduction of a cost-effective mud system preventing time-sensitive failure; and finally, mitigating the environmental impact factor of the mud system. Geomechanical modelling and Hole Stability analysis had been performed based on available dataset. An optimized mud weight (MW) program was developed based on the analysis. Considering the time-dependent failure characteristics of the shale and overall cost effectiveness, just modifying the mud weight does not address all of the challenges delineated above. Consequently, special "high-performance water-based mud system (HPWBM)" was designed instead of oil-based mud (OBM). This HPWBM was formulated based on the nature of shales encountered. While drilling, real-time geomechanics further facilitated controlled drilling conditions and optimized the mud program. The well-based geomechanical model indicated a hydrostatic pore pressure gradient in the region. The relative magnitude of three principle stresses showed a normal fault stress regime and maximum horizontal stress (SHmax) azimuth appeared to be nearly aligned to the N-S direction. Hole Stability analysis showed that a minimum of 12 ppg mud weight was required to drill the 8½" section. The sidetrack holes had a maximum inclination of 75 to 77 degrees. Different polymers and bridging agents were added to prepare the customized HPWBM in order to address shale instability and formation damage due to overbalance. Real-time monitoring during drilling operation utilized logging while drilling (LWD) log data, drilling parameters and mud logging data to promote smooth drilling operations. Through systematic planning and execution, the high-angle sidetrack holes had been drilled with zero non-productive time (NPT) in terms of well bore stability. More than 50% cost reduction was achieved on the mud system. An integrated solution that includes pre-drill geomechanics, HPWBM system design and real-time well monitoring helped to reduce the risks due to model uncertainties while drilling high angle wells through the thick shale section. This approach helped to reduce significant operational cost with an improved success rate.
Abstract This paper discusses the Hydraulic Fracturing (HF) treatment of the Andimadam Sandstone formation of Periyakudi field of India. The Andimadam sandstone is a hydrocarbon bearing formation, with estimated in-place reserves of 47.43 MMt (O+OEG) which was prognosticated after drilling and established hydrocarbon potential. Well PD#A was drilled in Andimadam Sandstone and HF in this well was attempted in order to develop and exploit the full potential of the oil and gas reserves of the field. The fracturing treatment of the tight gas reservoir in one of the deep well in Periyakudi field was performed eld. It was a challenge to carry out HF in well PD#A at such deeper depth formation. There was no previous information available to understand the formation and to predict its behaviour during HF treatment. HF treatment in tight gas Sandstone laid so many challenges. Formation breakdown, succeeding minimum rate required for fracturing and attaining high proppant concentration during job with crosslinking gel under extremely strenuous operational conditions and pressure limitations were some of the major challenges. Delayed cross-linked gel was used to minimize tubing friction pressure. Managing the pumping rate with pressure limitations during HF treatment was one of the major challenges. Execution of the treatment with low pumping rate results in stimulation of small volume of rock comparatively. All these limitations were overcomed by proper job designing, optimization of fracturing fluid and analysis of pre-frac treatments. A substantial amount of fracturing fluid and proppant placed into the formation maintaining all safety standards. Satisfactory flow back of frac fluid with gas was observed and high flow back pressure at surface was noted. This paper discusses challenges to execute hydraulic fracturing treatment in well PD#A and the lessons learned during the execution. In addition, it was the deep well (drilled upto 4945 m) in Periyakudi field with low permeability reservoir. Post analysis of pre-frac treatments done to obtain the reservoir properties and to design the main frac treatment. The results of fracturing treatment are also discussed. The promising hydrocarbon potential of the Andimadam sandstone which are based on post fracturing analysis, encourages further future development of the Periyakudi field, Cauvery Basin, India.
Augustine, M.. (Oil and Natural Gas Ltd) | Murthy, A. V. (Oil and Natural Gas Ltd) | Boindala, Amitha (Oil and Natural Gas Ltd) | Bahuguna, Somesh (Schlumberger) | Talreja, Rahul (Schlumberger) | Pattanaik, Sambit (Schlumberger) | Kalita, Deepika (Schlumberger) | Das, Sourav (Schlumberger)
Abstract Madanam field in Cauvery basin in the east coast of India, has fractured gneissic basement. As exploration focus moved to unconventional reservoirs, the gneissic basement of Madanam was seen as a potential reservoir. However, ambiguity existed about the fluid flow through the basement. For example, in Madanam field, one well (well A) flowed whereas another well (well B) located 8.5 km away had minor flow from the basement reservoir that lasted 2 days. The main purpose of this study was to find possible reasons for this anomalous behavior. This study was conducted by integrating sonic and image measurements with a geomechanics workflow to identify critically stressed open fractures. Further, this work aims to provide a fit-for-purpose solution to optimize and prioritize testing zone selection in near real time.
Malkani, Anil (Cairn India Limited) | Routray, Prabir (Cairn India Limited) | Majumdar, Pinaki (Cairn India Limited) | Kumar, Prem (Cairn India Limited) | Ghosh, Biswanath (Cairn India Limited) | Chacko, Soman (Cairn India Limited)
Abstract The study area, block SL-2007-01-001, operated by Cairn India Ltd., is located in the Mannar basin of NW offshore Sri Lankan (blue polygone in Figure-1) and contains a sedimentary section exceeding 7km, the age of which ranges from Jurassic to Recent. The large number of oil and gas discoveries in the contiguous Cauvery Basin, both in Cretaceous and Tertiary sections, makes this frontier basin an attractive candidate for exploration. In 2010 Cairn Lanka acquired 1753 sq km of 3D seismic data in order to assess the exploration potential of this deep water block. This paper focuses on the role that rock physics analysis played in the assessment, risking, and ranking of the key leads identified in the basin. Of the numerous leads identified, three were high-graded in large part due to their DHI characteristics, resulting in the Dorado and Barracuda gas discoveries (Well-A & Well-C in Figure-1, respectively), the first hydrocarbons to be discovered in the Mannar Basin. The third well, Well-B, was a dry hole. De-risking of exploration prospects was based on quantitative seismic interpretation supported by rock physics analysis. This paper emphasizes how rock physics can add value in an exploration project to influence business decisions by reducing subsurface uncertainties. The nearest well, CY-DWN-2, that provided data for depth trends and rock physics analysis is located approximately fifty kilometers south west of the study area. Although this was a dry hole, it provided significant information on the sedimentary sequence, rock properties, and their associated seismic responses. Various "what if" scenarios were created to understand associated seismic responses. The analsyis explained the dry hole at CY-DWN-2 and highgraded the prospectivity of the Dorado lead. The latter was subsequently drilled, leading to the Dorado discovery.
Sim, Shawn Y. (Earth Observatory of Singapore, Nanyang Technological University) | Yao, Yao (School of Civil and Environmental Engineering, Nanyang Technological University) | Chan, Joann Y.R. (School of Civil and Environmental Engineering, Nanyang Technological University) | Lee, Ka Sim (School of Civil and Environmental Engineering, Nanyang Technological University) | Huang, Zhenhua (Earth Observatory of Singapore, Nanyang Technological University, School of Civil and Environmental Engineering, Nanyang Technological University)
ABSTRACT: In this paper the effects of layered coastal vegetation on long wave (solitary wave) propagation were investigated experimentally in a long wave flume. This layering vegetation is represented by an open gap in a patch of vegetation that lies perpendicular to the flow direction. Solitary waves with different heights were used to simulate the leading tsunami waves. Results on the wave transmission, reflected waves, and waves within the gap in a patch of vegetation are discussed. INTRODUCTION The 2004 Indian Ocean tsunami made the world realize the devastating potential of tsunamis. With a death toll of more than 200,000; it is considered one of the most serious catastrophes in the present day. As a result, there is a neccessity to find means to mitigate the impacts of tsunamis. One viable way to attenuate tsunmai wave is through turbulence generated by trees in mangrove forests. Danielsen et al. (2005) pointed out that the presence of mangroves along Cuddalore, Tamil Nadu, India shielded several villages from the 2004 tsunami. However, the unshielded villages were not so fortunate. They were either badly damged or completely destroyed. Dahdouh-Guebas et al. (2005) also noted that besides mangroves, other coastal vegetation types such as salt marshes and vegetated sand dunes also serve a similar purpose. These natural coastal structures provide a form of additional roughness that affects both the transmitted surface elevation and velocities (Struve et al., 2003).Although there are still doubts on the effectiveness of mangroves (Overdorf and Unmacht, 2005), there is still a general consensus that mangroves do play a part in reducing tsunami impacts. However, this does not pertain to the specific mechanisms that they play. The variation in mangrove settings is one area that can be looked into (Dahdouh-Guebas and Koedam, 2006).