Hasil untuk "Petroleum refining. Petroleum products"

Thomas Murphy, George Hoekstra, Marcio Wagner Silva

SONG Xuemei, ZHANG Kun, DONG Liang, MA Mengya, LIU Huihu, XU Hongjie, WANG Zhi

Injecting CO2 into deep coal seams to enhance coalbed methane (CBM) extraction has both environmental and economic benefits, indicating broad development prospects. To investigate the structural changes of different types of coal after CO2 injection, five samples with different maximum vitrinite reflectance (Ro, max) were selected to conduct supercritical CO2 injection experiments under conditions simulating a coal seam burial depth of 1 500 m. The pore and fracture structures of the coal samples before and after injection were characterized using low-temperature N2 adsorption and mercury intrusion porosimetry. The extent of changes was quantitatively compared using fractal theory. The results of N2 adsorption experiments showed that the pore volume of the coal samples before and after supercritical CO2-H2O reaction initially decreased and then increased with increasing coal rank. An inflection point was formed at coking coal, with the most significant increase in pore volume observed within the micropore range (pore diameter 0~2 nm). The changes in pore volume observed in mercury intrusion porosimetry experiments were relatively complex, with significant increases in the transition pore range (pore diameter>2~50 nm) and fracture range (pore diameter>1 000 nm). This was because the supercritical CO2-H2O reaction increased the proportion of non-effective connected pores in the coal, enhancing the local connectivity of the coal samples. Furthermore, the total pore volume of some samples even showed a decreasing trend after reaction, likely due to the blockage of pores and fractures by detached minerals. The fractal analysis results of pore parameters before and after reaction showed that the changes in pore and fracture structure depended on the characteristic coal parameters. The changes in pore volume were more pronounced in low-rank and high-rank coals after the reaction, and the extent of change was more significant in samples with higher mineral content. This study contributes to a deeper understanding of how CO2 injection changes the pore structure of deep coal seams and can provide a reference for site selection in CO2 geological storage and enhanced coalbed methane development (CO2-ECBM) projects.

Luo Xiaochun, Zhang Hushan, Zhang Wengang et al.

The drilling rigs in China have developed from mechanical， DC drive and AC variable frequency drive rigs to today's automated and smart rigs. The demand for ultra-deep well and extra-deep well drilling rigs increases year by year. To meet the needs of drilling fluid treatment capacity of ultra-deep well drilling rigs， the solids control system is equipped with more and more drilling fluid tanks， equipment and valves， and the operation becomes more and more difficult. Moreover， the existing solids control system mainly relies on manpower to conduct equipment operation， valve shut-off， process control， operating condition inspection and state monitoring. To address this issue， a full-process visual control system for solids control system was developed to achieve a full-process automated， visual and digital centralized control. The system has the functions of remote automatic switching of processes such as metering， purification， mixing and circulation， feedback of equipment operation status， and automatic monitoring and alarm of processes. The industrial application in oil fields at home and abroad shows that the automated solids control system reduces the labor intensity of operators， improves the work efficiency， and changes the current situation of low automation of solids control system. The research results provide reference for improving the automation level of drilling equipment in China.

Leng Youheng, Wang Lixin, Chen Pengyu et al.

The compatibility of percussion tools， PDC cutter types and hard rock formations is a key factor in extending the service life of percussion tools and drill bits and achieve the best rock breaking effect， but it has been rarely studied. In this paper， considering the interaction between the axial static load and the impact load， cutters and formation during rotary percussion drilling， a numerical model of single and double axe-shaped cutter three-dimensional rock breaking under conventional drilling and rotary percussion drilling modes was established. The multi-cutter rock breaking effects under different drilling modes were compared， the distribution of tensile， compressive and shear stresses in the rock which is broken by single and double cutters under impact load was analyzed， and the mechanism of multi-cutter rock breaking under impact load was revealed. The penetration depth of the cutters， the rock damage under the cutting surface and the variation of the force of the cutters under different cutter rake angles and double cutter spacing were studied. The results show that there is obvious interference of shear stress and tensile stress in the double-cutter rock breaking process. As the front rake angle of the cutters increases， the rock section damage area， penetration depth and tangential force of the cutters gradually decrease， and the best front rake angle is 20°. Given the front rake angle， increasing the cutter spacing will lead to the gradual weakening of the interference between two cutters， and the residual rock ridge will become more significant. Considering the rock cutting effect and the force of the cutters， the double axe-shaped cutters spaced at 16 mm can achieve a high rock breaking efficiency and service life. The research results provide theoretical and engineering references for the selection of PDC bit type and the layout of cutters in the process of percussion drilling.

Andrew Hardt, David Wallach

We prove that products of double Grothendieck polynomials have the same back- and forward-stability numbers as products of Schubert polynomials, characterize which simple reflections appear in such products, and also give a new proof of a finiteness conjecture of Lam-Lee-Shimozono on products of back-stable Grothendieck polynomials which was first proved by Anderson. To do this, we use the main theorems from our recent work, as well as expansion formulas of Lenart, Fomin-Kirillov, and Lam-Lee-Shimozono.

Xuxin Tang, Rehema Abulikemu, Eric Krokos et al.

Sensemaking report writing often requires multiple refinements in the iterative process. While Large Language Models (LLMs) have shown promise in generating initial reports based on human visual workspace representations, they struggle to precisely incorporate sequential semantic interactions during the refinement process. We introduce VIS-ReAct, a framework that reasons about newly-added semantic interactions in visual workspaces to steer the LLM for report refinement. VIS-ReAct is a two-agent framework: a primary LLM analysis agent interprets new semantic interactions to infer user intentions and generate refinement planning, followed by an LLM refinement agent that updates reports accordingly. Through case study, VIS-ReAct outperforms baseline and VIS-ReAct (without LLM analysis) on targeted refinement, semantic fidelity, and transparent inference. Results demonstrate that VIS-ReAct better handles various interaction types and granularities while enhancing the transparency of human-LLM collaboration.

Eugène Berta, David Holzmüller, Michael I. Jordan et al.

Machine learning classifiers often produce probabilistic predictions that are critical for accurate and interpretable decision-making in various domains. The quality of these predictions is generally evaluated with proper losses, such as cross-entropy, which decompose into two components: calibration error assesses general under/overconfidence, while refinement error measures the ability to distinguish different classes. In this paper, we present a novel variational formulation of the calibration-refinement decomposition that sheds new light on post-hoc calibration, and enables rapid estimation of the different terms. Equipped with this new perspective, we provide theoretical and empirical evidence that calibration and refinement errors are not minimized simultaneously during training. Selecting the best epoch based on validation loss thus leads to a compromise point that is suboptimal for both terms. To address this, we propose minimizing refinement error only during training (Refine,...), before minimizing calibration error post hoc, using standard techniques (...then Calibrate). Our method integrates seamlessly with any classifier and consistently improves performance across diverse classification tasks.

Nicholas Abell, Elizabeth McDermott, Christian Millichap

In this paper, we provide a complete classification of Cartesian products of graphs that embed in the projective plane. Our work requires us to determine minimal Cartesian products that are nonprojective planar, organize their essential properties to be used as constraints for projective planar embeddings, and explicitly construct projective planar embeddings for Cartesian products that satisfy these constraints. A corollary of our work shows that only six of the 35 forbidden minors for the projective plane are sufficient to classify projective planar Cartesian products.

Riccardo W. Maffucci

The Sierpiński product of graphs generalises the vast and relevant class of Sierpiński-type graphs, and is also related to the classic lexicographic product of graphs. Our first main results are necessary and sufficient conditions for the higher connectivity of Sierpiński products. Among other applications, we characterise the polyhedral ($3$-connected and planar) Sierpiński products of polyhedra. Our other main result is the complete classification of the regular polyhedral Sierpiński products, and more generally of the regular, connected, planar Sierpiński products. To prove this classification, we introduce and study the intriguing class of planar graphs where each vertex may be assigned a colour in such a way that each vertex has neighbours of the same set of colours and in the same cyclic order around the vertex. We also completely classify the planar lexicographic products.

HAN Xiao, SONG Zhaojie, LI Peiyu et al.

The core pore structure of the target shale oil block was finely characterized using scanning electron microscopy， and a microscopic numerical model of the pore-scale core was constructed to elucidate the intrinsic mechanisms and the main controlling factors of spontaneous imbibition of fracturing fluid within the complex pore space of shale. On this basis， research was conducted on spontaneous imbibition within the fracture-matrix system. The Navier-Stokes （N-S） equations were coupled with the level-set method to track changes in the oil and water interface， thus clarifying the oil and water two-phase flow characteristics and evaluating the efficiency of spontaneous imbibition under the influence of the wettability， viscosity ratio of oil and water， and interfacial tension. The research results revealed that large and small intercommunicating pores in shale form intricate microscopic displacement units under capillary action. When the rock wettability presents a water-wet state， water preferentially infiltrates from the fracture into the smaller pores， expelling oil from larger pores into the fracture， and the produced range of crude oil within the matrix pores is wider， resulting in higher spontaneous imbibition efficiency. When the rock wettability turns oil-wet， crude oil within the small pores cannot be produced during spontaneous imbibition， while the water invades from larger pores， causing crude oil to be displaced from other large pores. This results in a lower spontaneous imbibition efficiency and a small range of crude oil produced in the matrix pores. The spontaneous imbibition in the initial phase is faster but gradually slows over time. Stronger water wettability of shale indicates a lower viscosity ratio of oil and water and higher interfacial tension， resulting in a wider range of crude oil produced within the matrix pores and a cumulative efficiency of spontaneous imbibition of more than 15%.

Zhang Guohui, Li Weiqin

The noise interference caused by the electric appliances at and around well site has an impact on the received wireless electromagnetic 2FSK modulation signals,making it difficult to extract signal features when the signal-to-noise ratio(SNR)is low. Therefore,an adaptive bistable stochastic resonance system based on the coati optimization algorithm(COA)was proposed to reduce the bit error rate of 2FSK signals. This method takes full advantage of the global exploration and local optimization balance ability of COA to conduct selection and optimization of multiple parameters of the stochastic resonance system,allowing the system output to have the maximum SNR gain. Then,the convolutional neural network(CNN)was used to demodulate the output signals of the stochastic resonance system and evaluate their bit error rate. The simulation and test results show that under low SNR conditions,the characteristic frequency of output signals of the stochastic resonance system based on COA is more significant than that of the ant colony optimization(ACO)algorithm,and has a lower bit error rate. The research results provide technical support for the real-time transmission of downhole signals.

Mohamed A. Khalifa, Bassem S. Nabawy, Mohamed F. Abu-Hashish et al.

Abstract Detection of the low resistivity-low contrast (LRLC) reservoirs is among the main challenges in the oil industry. In this concern, the LRLC pay zones of the Upper Messinian Abu Madi clastic reservoirs in the onshore Nile Delta Gas fields became a main challenge for significant exploration. This type of reservoirs, including low resistivity-low contrast zones and thin-bedded intervals, are often overlooked using the conventional petrophysical evaluation techniques, especially in the wildcat exploratory wells or highly agitated shoreline depositional environments like the Nile Delta of Egypt. These hidden low contrast reservoirs are generally challenging due to the presence of many shale intercalations/laminations and/or due to increasing the shale volume represented in the form of dispersed distribution, and the dominance of conductive clay minerals. Therefore, in this study, the expected high resistivity values of the gas-bearing reservoir intervals of the Abu Madi Formation in the onshore Begonia gas Field, as a typical case study of the LRLC reservoirs, are masked due to the relatively high shale conductivity, particularly when the thickness of these intervals is less than the vertical resolution of the utilized conventional resistivity log. To verify the LRLC phenomena of the Begonia gas Field, the obtained data was compared to the South Abu El Naga gas Field as a normal case study with a relatively high resistivity gas-bearing pay zone. To overcome the impact of the conductive clay mineral content and identify these hidden low resistivity reservoir intervals, it is necessary to integrate the conventional logging data (gamma-ray, shallow and deep resistivity, density, and neutron) with the acoustic log data including shear and compressional sonic data. In this way, a useful relationship can be established enabling the detection of these hidden LRLC reservoir intervals. This integration is based on the principle that shear waves are not influenced by the fluids types, whereas the compressional sonic waves are influenced by the reservoir fluids. However, to effectively investigate these concealed LRLC reservoir intervals, which can boost production and increase the potential reserves, it is essential to have a low water cut value. The present study represents introduces an efficient workflow, which can be extended to other similar LRLC pay zones in the Nile Delta and northeast Africa. It is also extendible to the LRLC reservoirs in similar deltaic systems having conductive minerals-bearing reservoirs or thin beds.

Manav Nitin Kapadnis, Sohan Patnaik, Abhilash Nandy et al.

Radiology Report Generation (R2Gen) demonstrates how Multi-modal Large Language Models (MLLMs) can automate the creation of accurate and coherent radiological reports. Existing methods often hallucinate details in text-based reports that don't accurately reflect the image content. To mitigate this, we introduce a novel strategy, SERPENT-VLM (SElf Refining Radiology RePort GENeraTion using Vision Language Models), which improves the R2Gen task by integrating a self-refining mechanism into the MLLM framework. We employ a unique self-supervised loss that leverages similarity between pooled image representations and the contextual representations of the generated radiological text, alongside the standard Causal Language Modeling objective, to refine image-text representations. This allows the model to scrutinize and align the generated text through dynamic interaction between a given image and the generated text, therefore reducing hallucination and continuously enhancing nuanced report generation. SERPENT-VLM outperforms existing baselines such as LLaVA-Med, BiomedGPT, etc., achieving SoTA performance on the IU X-ray and Radiology Objects in COntext (ROCO) datasets, and also proves to be robust against noisy images. A qualitative case study emphasizes the significant advancements towards more sophisticated MLLM frameworks for R2Gen, opening paths for further research into self-supervised refinement in the medical imaging domain.

Georg Oberdieck

We conjecture an explicit formula for the $K$-theoretically refined Vafa-Witten invariants of the Enriques surface. By a wall-crossing argument the conjecture is equivalent to a new conjectural formula for the K-theoretically refined Pandharipande-Thomas invariants of the local Enriques surface. Evidence for the conjecture is given in several cases. We also comment on the case of K3 surfaces previously studied by Thomas.

Yuqi Shi, Chang Liu, Baosheng Zhang et al.

In order to achieve the precise control of the volatile organic compound (VOC) species with high ozone (O3) formation contribution from key sources in Panjin and Yingkou, two coastal industrial cities with severe O3 pollution along the Liaodong Bay, northeast China, the ambient concentrations of 99 VOCs species were measured online at urban-petrochemical (XLT), suburban-industrial (PP), and rural (XRD) sites in July 2019, contemporary monthly anthropogenic VOCs emission inventories were developed. The source contribution of ambient VOCs resolved by positive matrix factorization (PMF) model was comparable with emission inventories, and the location of VOCs sources were speculated by potential source contribution function (PSCF). 17.5 Gg anthropogenic VOCs was emitted in Panjin and Yingkou in July 2019 with potential to form 54.7 Gg-O3 estimated by emission inventories. The average VOC mixing ratios of 47.1, 26.7, and 16.5 ppbv was observed at XLT, PP, and XRD sites, respectively. Petroleum industry (22 %), organic chemical industry (21 %), and mobile vehicle emission (19 %) were identified to be the main sources contributing to O3 formation at XLT site by PMF, while it is organic chemical industry (33 %) and solvent utilization (28 %) contributed the most at PP site. Taking the subdivided source contributions of emission inventories and source locations speculated by PSCF into full consideration, organic raw chemicals manufacturing, structural steel coating, petroleum refining process, petroleum products storage and transport, off-shore vessels, and passenger cars were identified as the key anthropogenic sources. High O3-formation contribution sources, organic chemical industry and solvent utilization were located in the industrial parks at the junction of the two cities and the southeast of Panjin, and petroleum industry distributed in the whole Panjin and offshore areas. These results identify the key VOCs species and sources and speculate the potential geographical location of sources for precisely controlling ground-level O3 along the Liaodong Bay.

Nanjun Lai, Shufang Chen, Lei Tang et al.

Inspired by the viscoelastic displacement theory, a product called preformed particle gel (PPG) is developed as conformance control agent to enhance oil recovery and control excess water production. The migration law of PPG suspension in porous media is related to its deep profile control and displacement capability. Laboratory experiments indicate that PPG suspension has good viscosity increasing, and the apparent viscosity decreases with the increase of shear rate. PPG suspension is mainly elastic, and its network structure makes it have certain shear stability. PPG particles realize migration in porous media in the way of “accumulation and blockage→pressure increase→deformation and migration”. When the ratio of the PPG particle size to the pore throat diameter δ ranges from 35.52 to 53.38, the particles can match through the porous medium. When the permeability difference of the parallel model is 5, PPG suspension has the highest profile improvement rate, 69.10%. PPG suspension can adjust the planar heterogeneity, and increase the oil recovery rate by 20.75%. The PPG suspension can effectively start “cluster''、 “film” and “blind end residual oil”, and has a high oil washing efficiency. The core NMR T2 spectrum shows that PPG suspension mainly reduces oil saturation in mesopores and macropores. After PPG flooding, the EOR capacity of small pores is the highest, 39.11%.

Ballo Mwendapole Lonje, Gang Liu

Wax sedimentation in pipelines is a severe crude oil production and transportation challenge. Pipeline surface roughness is experienced at the early stages of the problem; with time, the effective pipe cross-sectional area is reduced due to pipeline wax plugging, causing pumping pressure increase, equipment failures, and blockages, resulting in unnecessary downtime costs and pipeline abandonments in the worst situation. This paper reviews mathematical and experimental loops models used for pipeline solid wax predictions and calculations as functions of pressure, temperature, and fluid composition; by assessing model's Assumptions, strengths and weaknesses. It is found that most mathematical models applied molecular-diffusion mechanisms in modeling and neglected shear effects; which resulted in wax over-prediction. Experimental loop was time-consuming due to mounting and dismounting of test section during wax deposition measurements; our modification has included sensor-integration to detect, measure, and analyze wax deposition; Reliable wax predictions models are essential to properly design pipelines and adopt cost-effective strategies for wax deposition prevention, control, and removal.

Xinchen Gao, Kangliang Guo, Peng Chen et al.

Abstract The closure fracture phenomenon increases the complexity of well testing and reduces the accuracy of productivity forecasts when tight oil reservoirs are exploited. However, most existing productivity models tend to ignore this. Therefore, a productivity prediction model for multi-fractured horizontal wells in tight oil reservoirs considering fracture closure has been developed by considering the stress sensitivity in the formation and combining the physical parameters of actual production. The model is solved by the Laplace transform, perturbation transform, Pedrosa transform, and Stehfest numerical inversion. Drawing productivity impact curves and discussing productivity influence factors based on the model results from this study show that the model is reasonable. In the actual production process, the hydraulic fracture parameter values are not as high as possible, and they have a reasonable range of values. The fracture closure pressure has a significant impact on the production of tight oil reservoirs. The higher the fracture closure pressure is, the greater the fracture conductivity decreases sharply, and the larger the proppant elastic modulus is, the stronger the fracture conductivity. The influence of fracture conductivity on the production in tight oil reservoirs has an obvious point, and when the value is less than the point, the production effect is good. Improved production can be achieved by balancing the relationship between fracture parameters. The findings of this study can help to better understand the influence of fracture parameters on productivity and contribute to increasing well production and improved development of tight oil reservoirs.