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INVESTIGATION OF STRUCTURAL FEATURES OF ASPHALTENES USED FOR CARBON MATERIALS SYNTHESIS BY ARC PLASMA TREATMENT

This study presents analysis of asphaltenes isolated from two crude oils: naphthenic-aromatic biodegraded oil and paraffin-naphthenic oil, which have been used as precursors for carbon materials synthesis. The aim of this study is to investigate the interrelationship between the initial structure of asphaltene and the properties of carbon materials. Based on number of spectroscopic and other data, it can be found out that the asphaltenes from napthenic-aromatic biodegraded oil contain less paraffin and more cyclic fragments (aromatic and aliphatic), that are larger and more densely stacked. The asphaltenes of paraffin-naphthenic oil contain a larger number of labile bonds and heteroatoms. Both the asphaltenes contain sulfur enclosed in thiophene and sulfide fragments, nitrogen and oxygen, which are incorporated in different units with different thermal stability. Carbon materials are obtained from both asphaltenes via plasma of an electric arc discharge. The asphaltenes undergo graphitization as a result of plasma treatment, the general trend is an elimination of functional groups and N, S, O. The yields of the carbon materials are almost equal for two studied asphaltenes, giving graphite-like materials as the major product in both cases. The carbon material obtained from the napthenic-aromatic asphaltenes is less thermally stable, the yield of nano-structures and nanofibers are higher compared to the asphaltenes from paraffinic oil, with trace metals remaining during the synthesis process. The carbon material from paraffin-naphthenic oil is amorphous with low heteroatoms content.

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Optimization of fracturing parameters for horizontal wells in high-sulfur gas reservoirs considering the effect of sulfur deposition

During the development of high-sulfur gas reservoirs, the precipitation and deposition of elemental sulfur can lead to a reduction in reservoir porosity and permeability. Previous studies focus on the well production with optimized operational parameters, but the effect of sulfur deposition is not included, which impacts fracturing parameters, well production, and economic evaluation. Therefore, this work proposes a reasonable approach for parameter optimization considering sulfur. The variation of porosity and permeability are first evaluated during sulfur deposition. After that, fracture half-length, fracture spacing, fracture conductivity, and fracture distribution are optimized with orthogonalization factor analysis, and the influence of sulfur deposition on different fracture parameters are detailed analyzed. The results shown that the fracture half-length and fracture conductivity are greatly affected by sulfur deposition. Finally, net profit value is applied to obtain the optimal fracture spacing interval. With economic evaluation, the optimal fracture spacing interval of 125 m∼ 150 m is determined considering the net profit and the payback period. This work provides a useful economic method for fracture parameter optimization high-sulfur gas reservoirs, which benefits for the development and production of gas reservoirs.

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The role of hydrocyclone and induced gas flotation technologies in offshore produced water deoiling advancements

Produced water, a byproduct of oil and gas extraction, presents significant environmental challenges if not properly treated. This review focuses on advancements in two primary offshore deoiling technologies, namely: induced gas flotation and hydrocyclones, tracing their evolution from the 1940s to the present. The study provides a detailed comparison of these technologies in terms of efficiency, energy consumption, and waste generation, offering both qualitative and quantitative assessments. Particular attention is given to the integration of hydrocyclone-induced gas flotation (HIGF) systems, which enhance oil removal efficiency while reducing energy consumption, making them an important solution in offshore produced water management. Additionally, the review identifies specific design improvements in flotation units, such as multistage configurations, and explores the role of operational control in optimizing hydrocyclone performance. Global variations in produced water discharge standards are examined, emphasising the need for stricter environmental regulations. In addition, this study highlights the combined use of hydrocyclone and flotation technologies as a comprehensive approach for addressing both environmental and operational challenges in offshore produced water treatment.

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Combined mechanistic and machine learning method for construction of oil reservoir permeability map consistent with well test measurements

We introduce a novel method for estimating the spatial distribution of absolute permeability in oil reservoirs, consistent with well logging and well test measurements. The primary objective is to create a permeability map, incorporating the well test interpretation results and achieving hydrodynamic similarity to the actual permeability distribution around each well. This enhancement aims to improve the accuracy of reservoir modeling outcomes in reproducing real data. We utilize Nadaraya-Watson kernel regression to parameterize the two-dimensional spatial distribution of rock permeability. The kernel regression parameters are optimized by minimizing the discrepancies between actual and predicted values of permeability at well locations, the integral permeability of the reservoir domain around each well, and skin factors. This inverse optimization problem is addressed by repeatedly solving forward problems, where an artificial neural network (ANN) predicts the integral permeability of the formation surrounding a well and skin factor. The ANN is trained on a physics-based dataset generated through a synthetic well test procedure, which includes the numerical modeling of the bottomhole pressure decline curve in a reservoir simulator and its interpretation using a semi-analytical reservoir model. The proposed method is tested on the “Egg Model”, a synthetic reservoir with significant heterogeneity due to highly permeable channels. The permeability map created by our approach demonstrates hydrodynamic similarity to the original map. Numerical reservoir simulations, corresponding to the constructed and original permeability maps, yield comparable pore pressure and water saturation distributions at the end of the simulation period. Additionally, we observe a notable match in flow rates and total volumes of produced oil, water, and injected water between simulations. The developed approach outperforms kriging in terms of numerical reservoir modeling outcomes. This research advances existing geostatistical interpolation techniques by fusing well logging and well test data to build the reservoir permeability map through an optimization framework coupled with machine learning. Unlike traditional variogram-based geostatistical simulation algorithms, our method provides a permeability distribution that is hydrodynamically similar to the actual one, enhancing initial guess in the history matching process. The novel incorporation of well test interpretation results into the permeability map represents a significant improvement over existing methods, offering an innovative approach that can benefit the petroleum industry. We also provide recommendations for further development of the proposed algorithm to account for geological realism.

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Mitigating Gas Migration with Eutectic Bismuth Alloy Plugs

Gas migration is an important concern to address in oil wells, especially in those that are to be abandoned. Stopping a gas leakage is not a simple task, and this can be particularly detrimental when setting a cement plug, as the migrated gas can undermine the integrity of said plug. In this context, and considering the recent attention given to metal plugs, we investigate the capability of bismuth plugs in shutting off gas leakages. The bismuth alloy employed to form the plug is to be melted downhole, and thus its proper solidification may be compromised if a leakage is underway. We test the sealing capability of two bismuth alloys – the eutectic bismuth-tin and the eutectic bismuth-tin-indium – along with two pipes – acrylic and steel. Results indicate that the bismuth plug can seal off the inner space of the pipe as long as the alloy used is eutectic; otherwise, a channel is created if the alloy is only near eutectic, effectively permitting that the leakage still continues. This sealing capability has been verified for both eutectic alloys tested, although it was also observed that voids are still present within the plugs themselves, potentially undermining their mechanical properties. Furthermore, we also observed that a slow and controlled cooling approach reduces the volume of inner voids, thus mitigating the plug degradation caused by the migrating gas. Further works should verify how these voids impact the hydraulic shear bond strength of the plug. From a microstructural perspective, it seemed that the solidification cooling rate plays a key role in the grain size of the material, which significantly impacts the microstructure of the alloy and, consequently, its mechanical properties. Considering the findings discussed in this work, we recommend that a two-plug approach is employed in leaking wells: a first, eutectic plug would shut down the leakage at the cost of its strength, and then a second – eutectic or non-eutectic – plug would be placed under no leakage ensuring the desired strength and sealability requirements. This study further highlights the potential of bismuth alloys to enhance safety and efficiency in plug and abandonment (P&A) operations by mitigating gas migration issues.

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Comparative organic geochemistry of shale deposits of northern Appalachian Basin

The organic-rich black shales in the Appalachian basin are a vital producer of natural gas. In this study, we present new multiproxy geochemical data from the Ordovician and Devonian black shales in New York (NY) and Pennsylvania (PA). The samples include outcrop samples collected in NY (Utica Group and Marcellus Formation) and core samples from PA (Marcellus Formation, Skaneateles Formation, and Genesee Group). We combined organic geochemical data (% total organic carbon or %TOC, δ13Corg, C/N ratio, and lipid n-alkane distribution) with trace element (TE) data to identify the organic matter (OM) sources and depositional conditions. The TE analysis data shows that water conditions were variable during the deposition of these black shales, fluctuating between oxic and dysoxic conditions with occasional anoxia. There was probably a change from an open water condition (Co∗Mn = 0.2) during the deposition of the Flat Creek Formation to a more restricted exchange later during the deposition of the Indian Castle Formation (Co∗Mn = 2.9) in the Ordovician. Basin circulation likely remained restricted during the deposition of the Devonian black shales (Co∗Mn ranges from 0.4 to 1.3). Based on δ13Corg values (−32.9‰ and −29.6‰) that are more depleted than marine OM δ13Corg, C/N ratios (11.2 and 9.2) higher than marine OM, and the presence of longer chain n-alkanes in the range of C25 to C33, we suggest that bryophytes were possibly a significant organic source to the Ordovician Utica Group in NY. The kerogen type in Utica Group samples is type III, mostly terrestrial OM. The Devonian NY and PA samples show mostly bimodal distributions. In some samples, a secondary, though sometimes dominant, shorter chain peak in the range of C14 to C20 is present, in addition to the long chain peak. We suggest the bimodal n-alkane distribution signifies a mixed OM source consisting of terrestrial and marine contributions with differing degrees of thermal maturation compared to the samples with a unimodal distribution. Our results suggest that samples from the NY Marcellus Group are composed of type III kerogen, while samples from the PA Marcellus Formation, Skaneateles Formation, and Genesee Group contain both type II and type III kerogens.

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Modelling of physical and chemical properties of activated carbons which affect methane adsorption mechanisms

Effect of important physical and chemical properties of activated carbons which affect the way methane adsorbs were studied. The Grand Canonical Monte Carlo (GCMC) simulations were used to study how the curvature and size of the platelets affect the mechanisms of methane adsorption process; and which role is played by the amount of oxygen present in activated carbons. Furthermore, Molecular dynamic (MD) simulations were carried out to study the effect of those properties on motion behavior of methane molecules during adsorption. The two simulations are very vital because they were able to exploit mechanisms which are difficult to obtain by using experiments alone. It was found that oxygen content, degree of curvature of platelets and size of basic structural units affected the availability of suitable methane binding sites in activated carbons and hence total methane adsorbed amount. Furthermore, the studied parameters were found to have impacts to the energy of interaction between activated carbons and methane, methane diffusion characteristics and amount of heat generated during adsorption process. It is concluded that the studied activated carbon properties hugely affect the way methane adsorbs and should be given attention during designing of the optimal adsorbent for methane adsorption.

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Production Optimization of Heavy Oil Recovery Utilizing Mo-Ni Based Liquid Catalysts: A Simulation Approach

In recent years, the demand for heavy oil has increased due to its abundant availability and low cost. However, the extraction of heavy oil poses a significant challenge due to its high viscosity and low mobility. Therefore, various methods have been developed to enhance the recovery of heavy oil, including the use of catalysts. This study has created a unique simulation approach that uses liquid catalysts (LCs) to improve heavy oil recovery. In this work, laboratory testing dataset and numerical simulation studies were used to examine the potential of applying LCs as an alternative chemical agent for enhancing heavy oil recovery. CMG-STARS and CMOST modules were used to historical match the laboratory scale results of two sand-pack flooding experiments (water flooding and liquid catalyst flooding in tertiary recovery mode). Moreover, a sensitivity study was conducted to apply a wide range of assumptions to determine the most effective process controlling parameters. Finally, oil production optimization is performed using a genetic algorithm (particle swarm optimization) by selecting the optimum-operating parameters. In comparison to typical water flooding, the results revealed a discernible rise in the heavy oil recovery factor (RF) when injecting LCs. The simulation results showed that the optimized production strategy could increase the ultimate oil recovery by up to 45.06%. The injection rate, slug size, and injection temperature were found to be significant factors in optimizing the production of heavy oil. This simulation approach can be used to optimize the production of heavy oil using acidic Mo-Ni based liquid catalyst in different reservoirs.

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