Now showing 1 - 10 of 181
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    Synthesis of porous, hydrophobic aerogel through the reinforcement of bamboo-shaped oxidized multi-walled carbon nanotubes in the silica matrix for oil spill cleaning
    (01-08-2023)
    AlZubi, Ahmad Ali
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    Devarapu, Srinivasa Reddy
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    Al Moghrabi, Hannoud
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    Dora, D. T.K.
    In the present work, bamboo-shaped Oxidized Multi-walled Carbon Nanotubes (O-MWCNT) synthesized through catalytic decomposition of natural gas were reinforced in a silica matrix to achieve a robust O-MWCNT-silica aerogel. The synthesized aerogel was hydrophobisized through surface modification with trimethylsilyl chloride for its application as an oil spill cleaning agent. The developed aerogel possesses high specific surface area of 795 m2/g evaluated from Brunauer–Emmett–Teller (BET) model, with a pore size of 11.2 nm. The density of the O-MWCNT-silica aerogel was 0.02 g/cc with a porosity of 87%, confirming its ultra-light and high porosity nature. Moreover, the synthesized aerogel exhibited hydrophicity, with a water contact angle of 136.2°. The sorption capacity of the aerogel investigated using motor oil projected an oil sorption capacity of about 13.72, 16.70, and 19.48 g/g at 25, 30, and 40 °C, respectively. The oil sorption kinetics revealed that the oil sorption on to the O-MWCNT-silica aerogel followed the pseudo-second-order kinetics with the particular correlation coefficients (R2) of 0.9898. Furthermore, the aerogel can be regenerated by the treatment with acetone and sustain its oil sorption capacity up to 5 regeneration cycles. Thus, the outstanding characteristics and hydrophobicity of the synthesized aerogel in this work establish itself as a capable adsorbent for oil spill cleaning. Graphical abstract: [Figure not available: see fulltext.].
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    Experimental study of the influence of the content of calcite and dolomite in the rock on the efficiency of acid treatment
    (01-01-2022)
    Martyushev, Dmitriy A.
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    Li, Yingwen
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    Yang, Yongfei
    Injection of acidic formulations into a carbonate reservoir is commonly used in the oil industry to enhance or restore well productivity. The purpose of this method is to create empty channels, the so-called wormholes, which pass deeper into the formation further than the perforated area in the near-wellbore zone of the formation. During the oil production, wormholes become pathways for crude oil to flow into wells. Most of the experimental and numerical studies carried out on this issue are limited in their observations, because they think the issue of wormhole formation only depending on the technological parameters of acidizing (speed and volume of injection). Our study aimed at investigating the effect of the material composition (content of calcite and dolomite) of carbonate rocks on the efficiency of acid treatments. We focus on investigating the effect of the percentage of calcite and dolomite fractions in a carbonate rock on acidizing efficiency, and try to elaborate the influence caused by the percentage of calcite and dolomite associated with the carbonate samples. Note that not all carbonate rocks need to use the same technological parameters for acidizing. However, it is necessary to individually select a few critical technological parameters based on the holding time of the composition in the reservoir as well as on the volume of the composition. In conclusion, the authors have developed recommendations for the application of acid treatment of oil fields in the Perm Krai (Russia), which differ in the material composition of the rock. At one of the oil fields, the authors have conducted pilot tests considering the developed recommendations and received a significant increase in oil recovery (on average, an increase of 1.5–2.0 times) compared to the previous acidizing measures. The results obtained have scientific and practical significance and prospects for further improvement of acid action in carbonate reservoirs.
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    Improvement of anti-SAg and rheological properties of water based muds using nano-barite
    (01-01-2019)
    Ponmani, Swaminathan
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    Kumar, Gopal
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    Khan, Sarfraz
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    Naga Babu, A.
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    Reddy, Mohan
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    Srinivasa Reddy, D.
    Barite Sag is an adverse phenomenon observed in horizontal drilling or Extended Reach Drilling (ERD) operations. It has been reported to occur majorly due to settling of weighing material such as barite on the lower side of directional wells. The barite sagging has been reported to cause drilling operational problems such as induced well-bore instability, mud losses and pipe stuck up leading to well control problems. In this context, an attempt has been made to address the barite sagging problem through application of laboratory synthesized nano-particles of barite as they are known to posses' high area to volume ratio, hence required in low quantities in formulating optimum gravity drilling fluid. However, low quantities of barite nano-particles aids in lowering Plastic-Viscosity (PV) and increasing Rate Of Penetration (ROP) due to low solids concentration associated with it. Further, the larger surface area of barite nano-particles also aids in improved heat dissipation from bottom hole, thereby increasing the life of bits. The sagging test results have projected a reduction in sagging phenomenon with the application of nano-barite particles. However, the rheology analysis results have projected a decrease in PV with unchanging filtration-loss properties meeting the API standards. Further, the rheological behaviour at various temperatures better fits with Herschel-Bulkley model establishing its shear thinning characteristics. The present work aids in formulating efficient drilling fluids for economical directional drilling operations.
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    Effect of random fracture aperture on the transport of colloids in a coupled fracture-matrix system
    (01-02-2017)
    Bagalkot, Nikhil
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    A variable aperture model, including the random variation of fracture aperture as against the conventional parallel plate model, has been developed to adequately examine the transport of colloids/suspended particles in a single coupled fracturematrix system. Rather than relying on a complex geostatistical method for an accurate representation of fracture aperture, which requires an enormous field data and resource for its validation, a simple statistical method (linear congruential generator) is implemented in the present article. The random variation of fracture aperture is an honest representation of the unpredictable geometry/ morphology of fracture aperture in comparison with widely applied the conventional parallel plate model or the simple mathematical functions based on fractal theory (self-affine structures). A considerable number of parameters are involved in investigating the extent of penetration of colloids into the rock matrix, which creates complexity and ambiguity in the analysis. To overcome this problem, a single parameter “Maximum Penetration Factor” has been introduced for simple and reliable assessment of diffusion of colloids within the rock matrix. Additionally, a non-dimensional parameter ‘Matrix Mitigation Factor’ has been introduced in the present study, which can provide a means of evaluating the diffusion of suspended particles within the rock matrix when it comes to real time applications like microbial enhanced recovery (MEOR) and chemical enhanced recovery (CEOR) in the petroleum industry (nanoparticles and nanofluids). A semi-implicit finite difference model has been adopted for solving the coupled partial differential equations in the present numerical study. Finally, Neumann and Robinson boundary conditions as a function of time have been applied at the fracture inlet to better represent the field scenario as against the conventional constant source condition (Dirichlet). The model results indicate that there is a difference in concentration between the parallel plate model and random fracture model when it comes to colloidal concentration in the fracture and rock matrix. The variance in concentration is due to the inclusion of variation of the aperture in the variable aperture model, which is absent in the parallel plate model. Additionally, the results suggest that the variable source boundary condition has a significant influence on the transport of colloids in fracture-matrix system. Finally, from the evaluation of the extent of diffusion of colloids into rock matrix, it was concluded that that variable aperture model is associated with more mitigation of colloids compared to the parallel plate model, especially in the case of random fracture.
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    Numerical modeling the injection of Super-Critical CO2 in non-dewatered coal bed methane formation
    (01-03-2021)
    Nainar, Subhashini
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    Dewatering the formation is the conventional methodology used when extracting methane (CH4) from the coal bed formation. A novel approach of not initially dewatering is to be studied. The approach has many advantages regarding the quantity of water produced, ground subsidence, and many more. Proving the latter best over the former requires several steps to be followed. The injection of Super-Critical CO2 (sCO2) is numerically modeled, in a naturally fractured coal bed methane (CBM) reservoir. Part-by- the part influence of each factor on the gas produced and the cleat properties are understood. Eventually, the sorption strain, effective stresses, reservoir compaction, varying overburden, and reservoir temperature, for the purpose, were coupled. The impact of non-isothermal conditions of the reservoir in the non-dewatered formation behavior is significant enough to reframe the conclusions. sCO2 enhances the recovery to 100% from 54% (with no injection) and is an essential application in CH4 production. The injection pressure is selected to sequester it to nearly 100%, assuming no breakthrough. The drainage distance dynamically varies with time as the production of gas proceeds. Flow phases are analysed, from the start, including the transitional effects till either the reserves are 100% recovered or pay zone length reaches. Earlier works relied on the conventional means, and the injected fluid was not the sCO2 to analyse the gas produced. The CO2 injected into the formation exists in supercritical form, which was, so far, ignored in the earlier models. The present study establishes that non-dewatered is a better alternative for the dewatered formation. The production time differs by 30 days. The additional production cost incurred is compensated by reduced water treatment costs. An economic analysis of the operations is required to support the work.
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    Modelling of mineral precipitation in fractures with variable aperture
    (04-05-2017)
    Patwardhan, Samarth D.
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    Singh, Deepak
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    Abhishek, Rockey
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    Fractures act as a highly permeable conduit for flow in naturally fractured reservoir. Geo-chemical reactions inside fractures may lead to partial or complete filling of pore spaces inside fractures over time. This reduction in fracture aperture directly affects its capability to transport fluid. The current study presents a 1-D mathematical model to simulate the geochemical filling of natural fractures. The fracture walls have been represented by simple mathematical functions to reflect variable aperture of natural fractures. Mass transfer through convection/diffusion and mineral precipitation due to precipitation/dissolution reaction were solved as a simplified mathematical representation of the actual processes. Precipitation reaction is coupled with mass transport by the fluid to ensure mass conservation of reacting components. For simplification, calcite precipitation in fracture has been modelled. The effect of pressure drop, diffusion constant, type of fracture aperture profile on evolution of fracture aperture was simulated in this study. Comparison is made between increasing, decreasing and constant fracture profiles to understand their effect on fracture evolution. This study aims to present a methodology to model variable fractures and study its effect on deposition inside the fracture. The model shows that the simple parallel model over predicts the precipitation that occurs in a fracture.
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    Complexities of Natural Gas Hydrates as an Energy Resource and its relation with Climate Change
    The ever-growing energy demands, declining oil prices, dwindling new findings of oil/gas reservoirs, complexity, and uncertainty associated with unconventional oil/gas supplies; and the seriousness towards mitigating the greenhouse gas emissions essentially implies the risky and uncertain nature of future energy at the global scale. Such a risky and complex pathway has made the exploration of unconventional hydrocarbons resources such as natural gas hydrates one of the potential alternatives that can significantly contribute to the growing energy demand. There is a huge gap between the experimental investigations and its associated up-scaling to a larger field-scale as these gas hydrates are generally located in highly remote places such as polar- and marine-environments. Thus, more studies are still required towards the field-scale exploration and production of gas-hydrates with their associated environmental, economic, and social consequences. In this context, an attempt has been made in order to list out the practical difficulties that are experienced during the exploration and production of natural gas hydrates as a possible and new energy resource given the constraints associated with the conventional fossil fuels. These complexities associated with the real field-scale production of gas hydrates are expected to provide improved insights for experimental scientists working on gas hydrates. In addition, the way the natural gas hydrates gets associated with climate change has been discussed in detail, and critical conclusions have been drawn.
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    Numerical modeling of real-time gas influx migration in vertical wellbores during drilling operation
    (01-01-2019)
    Chandrasekaran, Sridharan
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    In this work, a mathematical one-dimensional two-phase model (liquid + gas) has been developed to simulate the dynamic flow system in the event of a gas kick during vertical drilling. The flow system is a drift-flux model where the fluid properties are represented by averaged mixture properties rather than by two independent formulations. With this model, different flow scenarios and influx fluid propagation are investigated in vertical wells. The numerical solution is based on finite volume staggered discretization solved implicitly by a first-order upwind scheme. A sensitivity analysis of the influx model parameters, namely, the gas slip velocity, was performed and its impact on the bottom hole pressure and kick propagation is demonstrated. This model is further extended to predict the kick velocity and pressure in the annulus at the bit based on surface flow measurements in real-time drilling. This paper details on the model development of transient two-phase flow along with validation with experimental results. It is foUnd from the study that the developed light-weight simulation model could be employed in real-time drilling to model influx events, and the drift -flux simulation approach is comparable with the experimental and analytical results.
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    Numerical investigations on feasibility of surfactant enhanced remediation of polycyclic aromatic hydrocarbons in an unsaturated subsurface system beneath an onshore surface spill site
    (01-01-2017)
    Berlin, M.
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    Vasudevan, M.
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    Mohanasundaram, S.
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    The adaptability of in situ remediation techniques for low soluble fractions in petroleum products such as polycyclic aromatic hydrocarbon (PAH) is generally constrained due to their limited bio-availability owing to hydrophobicity. In the present study, a numerical model is developed to evaluate the effect of unsaturated hydraulic properties, equilibrium chemical partitioning as well as coupled reactions on the fate and transport of a typical PAH (phenanthrene) originating from a surface spill. Simulation of surfactant enhanced remediation using a non-ionic surfactant (Triton N-101) resulted in significant modifications in unsaturated hydraulic properties. The presence of natural organic matter (adsorption partitioning coefficient of 8.97 × 10-4 L/mg) as well as viable bacterial consortium (specific growth rate > 3.06 × 10-7 /sec) in the soil is found to be favouring the biodegradation in order to limit the reach of phenanthrene up to a depth of 200 cm. The results suggest that selection of surfactant type and dosage affected the extent of solubility enhancement of phenanthrene (from 1.27 to 11.5 mg/L); however, ultimately the typical bio-geochemical features of the subsurface seemed to control the success of remediation.
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    Experimental and numerical investigations on nitrogen species transport in unsaturated soil during various irrigation patterns
    The transport of nitrogen coming from wastewater applied agricultural field is a major problem in assessing the vulnerability of groundwater contamination. In this study, laboratory column experiments are conducted in order to simulate the paddy, groundnut and wheat irrigation with wastewater. The experiments are carried out with high clay content (≈35%) soil from Kancheepuram, Tamilnadu and low clay (≈9%) soil from Ludhiana, Punjab, India. Furthermore, a numerical model and HYDRUS-1D model are developed to simulate the experimental results. The experimental results show that there is no effluent collected at the bottom of the column during groundnut irrigation in Kancheepuram soil and effluent collected except during first irrigation in the case of wheat irrigation in Ludhiana soil. The experimental and numerical results illustrate that when 50 mg/l of ammonium and 20 mg/l of nitrate nitrogen applied during paddy irrigation, the peak nitrate nitrogen concentration of 50 mg/l is arrived after 10 days in Kancheepuram soil due to low permeability and relatively less background soil nitrogen. But in the case of Ludhiana soil with 94 mg/l of total nitrogen applied during paddy irrigation, the peak nitrate nitrogen concentration of 1,620 mg/l is observed at first day due to high permeability and high soil background nitrogen concentration. Additionally, the model results show that the application of high nitrogen content wastewater for irrigation in Ludhiana soil will affect the groundwater quality even when the groundwater table is deep as compared with Kancheepuram soil.