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Journal of Petroleum Science & Engineering
Elsevier Science B.V.
Journal of Petroleum Science & Engineering

Elsevier Science B.V.

0920-4105

Journal of Petroleum Science & Engineering/Journal Journal of Petroleum Science & Engineering
正式出版
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    Experimental investigation on the tribological behavior and surface damage due to embedment of ceramic proppant - analog mudrock composite systems

    Jing RenKostas Senetakis
    20页
    查看更多>>摘要：The analysis of interface problems involving proppants and rocks is of major interest in unconventional reservoir exploitation and modeling as well as in geophysics, mining engineering and rock mechanics. Despite the significant progresses that have been reported in hydraulic fracturing, there has been given less attention in the fundamental understanding of the interactions between proppants and rocks, which can provide enhanced input parameters in computational-based analyses involving complex multi-phase processes. In this study, the tribological behavior of three types of contacts including ceramic-ceramic (analog) proppants, kaolinite-kaolinite blocks (analog mudrock) and ceramic-kaolinite composite interfaces was investigated performing laboratory tests using a custom-developed loading apparatus and the experiments involved force and displacement measurements by the application of high-precision transducers. Based on a series of normal loading tests, it was observed that the ceramic beads exhibited a completely elastic behavior, whereas the kaolinite blocks showed a softer response with, predominantly, plastic deformations. The results of the shearing tests indicated that for the ceramic-kaolinite composite contacts, the arrangement of the clay microfabric significantly affected the shearing load-displacement response in terms of the post-peak softening behavior, the development of the microslip regime as well as the dynamic friction. It was also shown that even though the interface friction was controlled, predominantly, by the softer kaolinite block, the interface tangential stiffness had different involved mechanisms, in which case the kaolinite blocks showed the highest stiffness specifically at greater magnitudes of normal load, whereas the ceramic-kaolinite composite interfaces had the lowest values of stiffness.
      原文链接:
    • NSTL

    A flexible and scalable model to improve decision quality in shale plays

    Andrew BeckJ. Eric Bickel
    14页
    查看更多>>摘要：Shale asset investment decisions are difficult to model because they are portfolios of options under complex and time-evolving uncertainties. Sequential development decisions must balance short-term cash flow with long-term value creation. Typical assets consist of thousands of locations, making exact analysis impossible. Consequently, decision support tools are very simple, usually consisting of decision trees, fixed price decks, and no midstream constraints. We develop a heuristic that maps the current information of an asset, such as inventory, prices, and estimated production, to a well schedule. We combine the heuristic with Monte Carlo simulation and decision trees to form a shale field development model that includes all relevant features while being scalable to realistic problem sizes. To demonstrate our method's performance, we create a sample shale asset with 370 wells, price and production uncertainty, midstream constraints, and 30 decision periods. On the sample problem, our method exhibits first-order stochastic dominance over the decision tree approach and improves expected value by 407%. Using our modeling approach will improve overall decision quality in shale asset management.
      原文链接:
    • NSTL

    Modified graft copolymers based on ethylene vinyl acetate as depressants for waxy crude oil and their effect on the rheological properties of oil

    Grigoriy A. MunTimur BekbassovZhomart Beksultanov
    10页
    查看更多>>摘要：In this work, modified ethylene-vinyl acetate (EVA)-based copolymers were synthesized by graft copolymerization of hydrophobic monomers onto commercial EVA using a low energy electron beam (EB). The mechanism of graft copolymerization was studied by the spin trap method using a model reaction of the interaction of a tert-butoxy radical with an EVA copolymer. The results show that the main contribution to the initiation of graft copolymerization is made by the reactions of hydrogen abstraction from the methine CH groups of the vinyl acetate units. Oil from the Kumkol region treated with PPD showed better rheological properties, lower pour point temperatures, as well as lower wax content when tested on a cold finger, and better performance on the transportation route of the Kumkol - Karakoin - Shymkent. Moreover, EVA-based graft copolymers (gEVAp) performed better PPD than those obtained for commercial pour-point depressant (PPD). The rheological parameters of oil have been dramatically improved, which can be characterized as better oil pumpability in the cold season, which reduces the load on mainline pumps and saves energy for the transporting company. The pour point of the tested oil dropped from 12 to -3 °C, which led to the formation of wax crystals of the regular, compact platelet shape. Field tests using pigs showed significantly less wax deposited along the pipeline.
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    • NSTL

    Simulation for discharging of phase change material within a porous duct utilizing multi layers

    Fuzhang WangRebwar Nasir DaraAhmed Msmali
    13页
    查看更多>>摘要：Effect of nanoparticles on solidification within a duct with multi air layer was scrutinized in current research. Impose of wavy canal and nanoparticles can augment the solidification rate and these factor were checked in current unsteady modeling. Exergy drop and solid fraction distributions were analyzed. As mass of liquid reduces, exergy drop declines and impose of sinusoidal wall can augment the exergy drop. Cold air make the liquid PCM convert to solid and its temperature augments. With use of sinusoidal wall, better exchange of heat occurs and solidification occurs in lower time. Air temperature reduces as mass of liquid decreases and same behavior was reported for temperature of NEPCM. At t = 1.4hr, Tair of two cases were the same and after this time, temperature of flat plate is greater than another case. After full solidification, temperatures of air for two cases become equal. Solidification time reduces about 26.6% with utilizing wavy surface.
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    • NSTL

    Estimating elastic parameters from digital rock images based on multi-task learning with multi-gate mixture-of-experts

    Zhiyu HouPanping Cao
    11页
    查看更多>>摘要：Digital rock physics analysis has become an effective approach complementary to traditional experimental physics in estimating elastic parameters from digital rock images to study the relationship between the grain structure and rock mechanical properties. However, conventional numerical simulation requires lots of computational time and GB voxels memory. Recently, the convolutional neural network (CNN) has proven to be a successful method for estimating physical parameters from digital rock images, and multi-parameter simultaneous prediction using multi-task learning has been the focus of attention. But these methods don't achieve satisfactory results due to tasks' mutual interferences that affect network performances such as accuracy, robustness, and efficiency. To address these issues, a multi-task learning network with multi-gate mixture-of-experts was proposed to estimate elastic parameters from two-dimension digital rock images (MMOEROCK) in this paper. Parallel operational expert networks were used to replace traditional serial operational networks in order to reduce the mutual interferences of tasks. Gate networks were used to control the output weights of different expert networks in order to allow selective sharing among independent expert networks. The homoscedastic uncertainty loss function was used to automatically adjust the weight of each task loss function to improve network performance in searching for the optimal solution. The experimental results showed that the R~2-scores of the bulk modulus, shear modulus, P wave velocity, and S wave velocity could reach 0.89, 0.92, 0.92, and 0.91 on the validation set and 0.97, 0.96, 0.96, and 0.94 on the test set, respectively, and MMOEROCK afler fully training achieved an 800 speedup factor compared with the finite element method.
      原文链接:
    • NSTL

    Qualitative assessment of improved oil recovery and wettability alteration by low salinity water injection for heterogeneous carbonates

    Juliana M.F. FacanhaS. Amir FarzanehMehran Sohrabi
    14页
    查看更多>>摘要：This study aims to evaluate the qualitative potential for low salinity water injection (LSWI) to alter the wettability and increase oil production in heterogeneous oil-wet coquina cores (one of the facies of Pre-Salt reservoirs) in relevant conditions of brine salinity, temperature, and initial wettability. We also aimed to verify the impact of micro-porosity fraction on oil recovery. Finally, we verified whether the presence of micro-dispersion in the oil phase upon contact with low salinity would have a positive correlation with improved oil recovery due to low salinity water injection. To achieve these objectives, we performed zeta-potential experiments to evaluate the charges at the oil-brine and brine-rock interfaces that affect rock wetting state and contact tests to test for the presence of micro-dispersions in the oil phase and potential for LSWI. A series of spontaneous imbibition and coreflood experiments were performed to calculate the Amott index and evaluate wettability of coquinas in core-scale as a function of brine salinity. Tertiary and secondary low salinity waterfloods were carried out to investigate whether a diluted desulfated seawater would increase oil production in coquina cores. The effect of predominance of macro-, meso-, and micro-porosity on secondary low salinity waterflood was also evaluated. Our results have shown that heterogeneity had a greater impact on recovery factor compared to brine salinity. Oil recovery for low salinity brine for a core with predominance of macro-pores was smaller than for cores with higher fraction of micro-pores flooded with FW and DSW. Low-salinity oil recovery was also smaller than high-salinity was for core with microporosity but with presence of dead-end pores. Secondary injection of low-salinity using the same core with large fraction of micro-porosity showed that it accelerated oil production compared to high-salinity brine. We have also observed that LSWI resulted in increased oil recovery in coquinas both in tertiary mode (average 10%) compared to FW/DSW and secondary mode using the same core (18% compared to FW) due to wettability alteration. This result was supported by spontaneous imbibition as well as zeta-potential results. The contact test between crude oil and low salinity brine resulted in a micro-dispersion ratio of 11.7, showing that a positive oil is likely to result in improved oil recovery due to low salinity injection. Despite the increased oil recovery seen during the tests, the results showed that oil production in tertiary mode was significantly delayed (after 4 PV), likely due to adverse oil/water viscosity ratio and water dispersion due to mixing between low- and high-salinity brines. We observed that for the shorter more oil-wet core significant oil production was measured during bump flow with both high-salinity and low-salinity brines, due to capillary end effects. This could mean that residual oil saturation was not achieved during high-salinity water injection and an overestimation of recovery factor due to low-salinity was seen.
      原文链接:
    • NSTL

    A state of the art review on the performance of high-pressure and high-temperature drilling fluids: Towards understanding the structure-property relationship of drilling fluid additives

    Sidharth GautamChandan GuriaVinay K. Rajak
    71页
    查看更多>>摘要：Deepwater drilling using high-pressure and high-temperature (HPHT) drilling fluids draws significant attention for the quest of increasing energy demand. In this regard, selecting appropriate drilling fluid plays a pivotal role in trouble-free and safe drilling operations. This study presents a comprehensive literature review on the performance of HPHT drilling fluids concerning the structure-property relationships of the drilling fluid additives. The advantages and disadvantages of the different categories of drilling fluids are presented. The significant features of the drilling fluids, such as their synthesis of additives, formulations, structure-property relationships, performances, process engineering, economics, and environmental aspects, are thoroughly discussed. Data for 84, 42, and 9 traditional HPHT, ultra-HPHT, and HPHT-hc drilling fluids are collected, analyzed for performance evaluation. In addition to the above drilling fluids, the performance of several high-performance drilling fluids involving ionic liquids, cationic surfactants, functionalized nanoparticles. and functionalized biopolymers are also deliberated. The present review highlights the current state in the industry, future position, and strategies for the researchers to follow. In conclusion, the top 10 high-performance HPHT drilling fluids are presented based on thermal stability, rheology, filtration loss control, lubricity, salt tolerance, and environmental aspects. It was found that the presence of (i) sulfonate, methyl, phenyl, furan, lactam, and pyrrolidine functional groups enhance thermal stability, (ii) amide, hydroxyl, cellulose derivatives, quaternary ammonium, and acrylate functional groups improve rheological performances, (iii) quaternary ammonium, pyridine, and cellulose derivatives maximize filtration control, (iv) sulfonate, acrylamide, diallyl dimethyl ammonium chloride, itaconic acid, and fatty acid esters enhance the lubrication behavior, (v) carboxylate. sulfonate, quaternary ammonium functionality, polyoxyethylene chains prevent flocculation under HPHT environment, and (vi) carboxylic acid, and sulfonic acid salts improve salt tolerance power.
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    • NSTL

    An experimental study of displacement flows in stationary and moving annuli for reverse circulation cementing applications

    A. EslamiS. AkbariS.M. Taghavi
    15页
    查看更多>>摘要：We present an experimental study of buoyant displacement flows in vertical narrow centric/eccentric annular configurations, representing the oilfield primary cementing process, from a fluid mechanics perspective. In this study, we consider the reverse circulation cementing case, i.e. the case in which the cementing fluids are pumped down from the surface into the annulus and the in-situ fluids are taken through the casing or tubing. The fluid proxies used to represent the industrial fluids are miscible, with different rheological behaviours, i.e. salt-water (Newtonian), Xanthan (shear-thinning) and Carbopol (viscoplastic) solutions, and they have various density contrasts. Our dimensional analysis and systematic simplifications allow us to describe the flow using five dimensionless numbers: m (viscosity ratio), Fr (densimetric Froude number, quantifying effects of the density difference or buoyancy), Re (Reynolds number, quantifying the effects of the imposed flow rate), e (eccentricity) and / (reciprocation frequency). We examine the effects of the aforementioned parameters in stationary and moving annuli, wherein we change the frequency of the inner pipe reciprocation motion, over a fixed amplitude. Using mainly high-speed camera imaging techniques, we analyse displacement flow patterns and mixing between the fluids. We show that the density-stable or density-unstable configurations, the non-Newtonian effects, and the annulus eccentricity exert a significant impact on the displacement flow features, which we explain through a detailed comparison between Newtonian and non-Newtonian displacements. In addition, we demonstrate that an interplay between the yield stress and the annulus motion can remarkably change the displacement flow behaviour, particularly the wall residual layer thicknesses of the displaced fluid. Finally, we quantify the effects of different flow parameters on the leading front velocity, representing the displacement efficiency in the reverse circulation cementing.
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    • NSTL

    Effect of hydration on Pore Structure and Physical Properties of Permian Basalt and tuff in Sichuan Basin during pressurized imbibition

    Xiangyu FanLiang HeQiangui Zhang
    16页
    查看更多>>摘要：The volcanic rock with developed pores is important reservoir for oil and gas, but its complex pore-fracture structural characteristics lead to the hydration reaction when the volcanic strata is invaded by drilling fluid or fracturing fluid, which brings great challenges to the drilling operation and oil and gas production in volcanic rock reservoir. In order to understand the influence of clay hydration on the pore characteristics and permeability of different types of volcanic reservoirs. In this paper, we selected distilled water as the imbibition solution, and obtained the variation law of pore structure and physical properties of Permian tuff and basalt in Sichuan Basin during pressurized imbibition through a series of indoor test methods. The results show that the clay content of tuff is high, and the clay hydration produces new cracks during soaking, which leads to the increase of nuclear magnetic porosity of tuff after soaking. At the same time, it also makes some unconnected pores connected with each other, resulting in the increase of rock permeability in the later stage of soaking. During soaking, mineral particles peel off, and some clay minerals are transported to pores and fractures under hydrodynamic action, resulting in the reduction of effective porosity of tuff. The basalt is dense with poor physical properties. There are almost no cracks in the rock soaked for 0-24 h. After soaking for 48 h, new cracks are generated in the rock, which may be caused by the increase of pore pressure in the rock. The mineral particles around the crack obviously fall off and block the pore throat, resulting in the reduction of rock permeability after soaking. This study provides not only helps for avoiding the occurrence of lost circulation, well collapse and other accidents, efficient and safe drilling, but also a theoretical basis for the development of hydraulic fracturing in volcanic reservoirs.
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    • NSTL

    Graph regression for pressure peak prediction in fracturing processes

    Wei ZhangYupeng HePing Li
    8页
    查看更多>>摘要：In the oil and gas industrial field, fracturing construction technology is commonly used for increasing oil-gas production. A major concern in fracturing construction is whether the pressure at the wellhead will exceed safety threshold, when a large amount of sand-containing fluid is periodically injected into a well. To avoid accidents like blowout caused by extreme wellhead pressure, it is critically important to monitor pressure change in real time. In this work we propose to predict the pressure peaks during each fracturing period, for better designing future fracturing strategy. Towards this end, we present a novel non-parametric graph regression method, which is able to model the correlation of historical pressure peaks and learn the features of fracturing cycles via Laplacian-smoothness based graph learning, whereby the periodic fracturing signals, namely, fracking fluid concentration sequence, together with peaks, are able to be encoded in a latent Euclidean space by Laplacian-smoothness inspired graph learning. Then we introduce non-parametric linear regression for peak prediction based on the most similar nodes (e.g. peaks) w.r.t the node in the predicting period. Meanwhile, the current graph is updated using the predicted peak value. In the graph update, we particularly introduce a node forgetting mechanism to control the graph scale and to reduce the computational complexity, so as to achieve rapid prediction of construction operations. We conduct extensive experiments on real-world datasets from a well. The experimental results demonstrate that the proposed method can effectively predict the oil pressure peak and significantly outperform the state-of-the-art models.
      原文链接:
    • NSTL