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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
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    Hybrid modeling for submergence depth of the pumping well using stochastic configuration networks with random sampling

    Ying HanXinping SongKun Li
    18页
    查看更多>>摘要：In oilfield production, the submergence depth of a pumping well is an important indicator for measuring the fullness of the pumping pump, determining reasonable oil well production parameters, and formulating efficient production measures. In order to solve the problems of high security risks, high production costs and large errors, a method of submergence depth prediction based on a hybrid model is proposed in this paper. Firstly, according to the production process of oil recovery, the analytical model is built to ensure that the submergence depth prediction meets the actual production requirements;; then, the data-driven model is used to compensate the prediction results of the analytical model, which in order to reduce the influence of various production parameters on the prediction accuracy. When using stochastic configuration networks (SCNs) to build the data model, it may encounter the problem that the generalization ability is easily affected by the noise of training set, outliers and multi-states. So, a SCNs modeling method based on random sampling strategy is proposed to solve this problem. Random sampling was conducted on the training set, and different training subsets are evaluated by defining V indexes, which not only considers the prediction accuracy, but also considers the stability of the model. Through comparisons of SCNs and SCNs with random sampling, the latter approach can reduce the prediction error at least by 11.65% in the training phase, and at least 62.19% in the testing phase. The simulation experiment results of predicted submergence depth show that, compared with other methods, the proposed SCNs with random sampling method can reduce the average prediction error at least by 1.95%, 30.52%, 0.28% and 34.36% at RMSE, MAE, MSE and MAPE for the testing set. These prove that the proposed model has advantages in comprehensive prediction performance and can meet actual production needs.
      原文链接:
    • NSTL

    Effects of vertical anisotropy on optimization of multilateral well geometry

    Marcell LuxJanos Szanyi
    10页
    查看更多>>摘要：Multilateral wells have been increasingly used in recent years by different industries such as the oil-and gas industry (incl. coal-bed methane (CBM)) and geothermal energy production. The common purpose of these wells in the oil industry and partially in the geothermal industry is to achieve a higher production rate per well without increasing the hydraulic gradient signifcantly. In geothermal systems the ultimate objective is to improve heat extraction performance by enhancing productivity but also by increasing the heat transfer area. Optimal design of multilateral wells has been the focus of numerous publications in CBM and unconventional oil-and gas production, but as a result of cross-fertilization and technology-transfer among different sectors in the energy industry in the last few years, the focus of research on multilateral wells has turned to enhanced geothermal systems (EGS). Recently, several papers have been published on the use of multilateral wells in deep geothermal reservoirs. Coaxial closed-loop geothermal systems with multilateral wells utilize only the increased heat transfer area due to the laterals while EGS’s with multilateral injection and production wells also beneft from the hydrodynamic advantages of such well confgurations. However, substantial emphasis is-understandably-placed on the effect of artifcial and natural fracture networks of EGS reservoirs and less focus is devoted to the impact of vertical permeability anisotropy which can seriously infuence the fow pattern of a given confguration. Similarly, in CBM-related studies, the effect of horizontal permeability anisotropy along the face cleats to the butt cleats on multilateral well-design was investigated and vertical permeability anisotropy was not considered. In the current work we present a generalized approach for evaluating the effects of vertical permeability anisotropy on multilateral well geometry by numerical hydrodynamic modelling in an idealized, homogeneous hydrogeological setting. Current paper proposes an alternative modelling approach for representing the non-horizontal branches of multilateral wells by introducing a thin layer for the laterals with the same inclination as the well branches. This approach is then is used to investigate the effect of anisotropy on the fow pattern and near-wellbore drawdown and hydraulic gradient in the case of different branch deviations. Results suggest that the benefts of highly deviated or horizontal laterals emerge when vertical anisotropy is high. Evaluation of branch deviation vs. anisotropy indicates that above approx. 60? there is no signifcant beneft in increasing deviation which implies that very highly deviated or horizontal laterals might not necessarily pay off the associated technical challenges and extra costs.
      原文链接:
    • NSTL

    Investigation of sorptive interaction between phosphonate inhibitor and barium sulfate for oilfield scale control

    Zhaoyi DaiAmy T. KanYuan Liu
    9页
    查看更多>>摘要：In both offshore deepwater and shale fields, a large amount of produced water will be generated during field operations. One consequence of significant produced water production from the field is mineral scale formation. Barium sulfate (barite) is one of the toughest scales to manage in oilfield. To combat scale issues, scale inhibitor has been widely adopted to inhibit scale deposition. Previous studies have confirmed that sorptive interactions between chemical inhibitor and scale particles play a vital role in scale prevention and control. Although extensive studies have been carried out on inhibitor-scale interaction, a comprehensive understanding of inhibition is yet available and the detailed sorptive interaction between inhibitor and mineral scale is not fully understood. In this study, experimental efforts have been made to explore the governing mechanism of sorptive behavior of a common phosphonate inhibitor onto the surface of barite particles. Adsorption and desorption experiments involving phosphonate and barite were carried out over a wide range of physiochemical conditions in a systematic manner. It shows that both adsorption and desorption of inhibitor to and from barite surfaces proceed rapidly. At a low phosphonate concentration, surface adsorption mechanism accounts for the interaction between phosphonate and barite. The release of phosphonate inhibitor from the barite surface is controlled by the dissolution dynamics of the formed Ca-phosphonate precipitate. This study is the first report of investigation of barite with phosphonate inhibitor with low and ultra-low concentrations as well as the inhibitory mechanism. The obtained results will improve our understanding of the interaction between phosphonate inhibitors and mineral scale. The findings can provide fundamental information that can benefit the inhibition performance and efficiency for barite scale control in oilfield operations.
      原文链接:
    • NSTL

    Application of electrical rock typing for quantification of pore network geometry and cementation factor assessment

    Parvin Kolah-kajShahin KordAboozar Soleymanzadeh
    12页
    查看更多>>摘要：Rock typing with its various applications reduces the required time and cost for petrophysical analysis by categorizing similar rocks into distinct groups. Rock typing is divided into different categories, one of which, is electrical rock typing. An application of static electrical rock typing is cementation factor prediction which significantly affects fluid saturation estimation. Many factors, such as pore geometry, affect cementation factor in various means. Hence, achieving an explicit correlation to compute it as a function of these affecting factors is difficult. However, examining petrophysical properties which influence cementation factor is feasible. In this study, two definitions of formation resistivity factor are merged to achieve the cementation factor correlation as a function of effective cross-sectional area, porosity, and electrical tortuosity. To determine effective cross-sectional area and electrical tortuosity in wellbore through a time-efficient and inexpensive method, electrical rock typing is used. The results of this study reveal that Kozeny's factor is perfectly correlated with effective cross-sectional area and electrical tortuosity. Therefore, effective cross-sectional area and electrical tortuosity are computed throughout the wellbore. Moreover, investigating the relation between flowing porosity and rock capacity for transmitting electricity shows that they are directly related. Cementation factor and stagnant porosity also have a direct relationship. The findings of this study aid the assessment of porous media for attaining a clear understanding of petrophysical properties relationships, and their impact on porous media capability for storing and transferring fluid and transmitting electricity. Determining petrophysical properties continuously in wellbore leads to a better comparison between different segments of the reservoir. Regarding the fact that all presented methods are mainly based on log responses, they are easy to apply-However, the availability of enough samples is essential to initiate the analysis.
      原文链接:
    • NSTL

    Advanced control applied to a gas compression system of an offshore platform: From modeling to related system infrastructure

    Rodrigo S. GesserRafael SartoriThaise P. Damo
    19页
    查看更多>>摘要：This work presents the development of an advanced control strategy using Model Predictive Control (MPC) for controlling the gas compression system of an offshore platform. It includes details about the complete phenomenological model of the system and of the software infrastructure developed to support the system implementation in real conditions. The proposed control structure has two main goals;; (i) avoid unwanted regions of operation;; and (ii) increase stability margins and availability. These goals are achieved by using a zone-control MPC and by adequately interacting with the regulatory control level. Although the proposed structure is general, this work exemplifies its application in a particular compression unit of a real offshore platform. Simulation results are presented in two different scenarios, one to test how the controller rejects a gas-load varying disturbance and another to analyze how the controller copes with an abnormal situation, losing real-time data of process variables or manipulated variables during operation. The good performance obtained in these two cases confirm the benefits provided by the proposed MPC strategy to the operation of the gas compression unit.
      原文链接:
    • NSTL

    Microscopic response mechanism of electrical properties and saturation model establishment in fractured carbonate rocks

    Siyu WangMaojin TanXiaochang Wang
    12页
    查看更多>>摘要：Fractures are common in carbonate formations, and it is challenging to characterize electrical properties and establish saturation models for the fractured rocks by conventional petrophysical experiments. Therefore, it is necessary to study the fractures' electrical conduction and establish water saturation models by pore-scale numerical simulation and microscopic analyses. First, a multi-composition digital rock is constructed by the X-ray CT scan, Maps, and quantitative evaluation of minerals by scanning electron microscopy multi-scale supporting experiments. Next, the fractal Brown motion is used to construct the fractured digital rocks, and the lattice Boltzmann method is used to simulate the oil-water distribution. Then, the resistivities of these digital rocks are calculated by the finite element method. Finally, the microscopic response mechanism of the electrical properties is studied in detail, and new water saturation models are established. The study shows that resistivity decreases as the fracture aperture, length, or quantities increase. Still, it has different changes in three directions with the rise of the fracture dip, indicating the fractures lead to electrical anisotropy of the rock. Additionally, the resistivity index (RI) is strongly correlated to the water saturation (S_w. In the highly water-saturated region, the RI-Sn, curve conforms to Archie's law. However, the RI-Sw curve bends in the lowly water-saturated region, revealing the so-called 'non-Archie' behavior. Hence, we established new saturation models for fractured carbonate rocks and use one of the saturation models to calculate water saturation for formation evaluation in Talie Oilfield. The calculated results are more consistent with the oil test results, demonstrating the proposed saturation model is more applicable in the fractured formation. In summary, the pore-scale numerical simulation in fractured carbonate rocks provides a microscopic theoretical basis for electrical mechanism analysis and a water saturation model for log interpretation.
      原文链接:
    • NSTL

    On the reduction of the residual oil saturation through the injection of polymer and nanoparticle solutions

    Wenxiu SongDimitrios Georgios Hatzignatiou
    22页
    查看更多>>摘要：Polymer flooding has been traditionally applied to achieve favorable mobility ratios compared to water flooding, and thus increase formation sweep efficiency in oil displacement processes. Based on laboratory studies, several authors have reported lower residual oil saturations, Soro to the waterflood residual oil saturation, Sonv, when viscoelastic polymers were used during polymer flooding. The reported mechanisms contributing to the observed reduced residual oil saturation include mobility control, improved sweep efficiency, and improved microscopic displacement efficiency. The limitations of polymer flooding are obvious;; high oil viscosity requires high concentration of polymer which increases the process cost, presence of clays which increases polymer adsorption, formation brine and water make-up salinity and type of ions which will affect the injected polymer viscosity, and extensively fractured formations which will cause sweep challenges. This review paper summarizes the most recent research findings, observations, conclusions, and reported physical mechanisms contributing to more efficient oil displacement processes and lower than Sorw residual oil saturation. The discussion focuses on viscoelastic polymer oil displacement processes and includes formation water and polymer solution salinity, resistance factor (RF), and polymer molecular weight effects. The use ofnanoparticles (NPs) during polymer flooding is examined and results obtained are also reported in this review. More specifically, the polymer-NP system rheological behavior for several different types of NPs and surface modified silica NP are examined to find the most efficient system for oil displacement. Mechanisms contributing to more effective oil displacement processes when carefully screened NPs are added into the viscoelastic polymer solutions include interfacial tension reduction, formation wettability alteration, increased injected polymer solution viscosity, and prevention of asphaltene precipitation.
      原文链接:
    • NSTL

    A new method to predict brittleness index for shale gas reservoirs;; Insights from well logging data

    Yapei YeShuheng TangZhaodong Xi
    14页
    查看更多>>摘要：Brittleness is a significant mechanical property which determines the degree of fracturing difficulty in shale gas exploitation and hence, the brittleness index (BI) is a key parameter for the selection of suitable hydraulic fracturing intervals in shale gas reservoirs. However, at present there are no universal and convenient methods for the prediction of BI. Therefore, this study proposes a well logging data-driven BI prediction method based on principal component analysis (PCA) and back-propagation neural networks (BPNN), which can interpret nonlinear and complex relationships between predictors (input variables) and predicted values (target variables). Specifically, 63 samples and their corresponding well logging data were collected from the Wufeng-Longmaxi and Baota formations at the periphery of Sichuan Basin. Experimentally measured brittleness index (BI_(core)) values (from 0.18 to 0.88) derived from compression test stress-strain curves, were considered as the target parameter. Based on the results of linear regression and sensitivity analysis, five types of well logging, including gamma ray (GR), density (DEN), compressional wave slowness (DT), neutron porosity (CNL) and spontaneous potential (SP), were selected as appropriate well logging techniques. Three principal components were extracted from the five well logging datasets using PCA. Following PCA, the back-propagation neural network (PCA-BPNN) model exhibited excellent prediction accuracy according to statistical and graphical error analysis. The established PCA-BPNN model was then applied to forecast the BI profiles of the intervals of interest in well Yl in the study area and the predicted BI values were found to be in agreement with the laboratory measured BIcore values. Therefore, the established PCA-BPNN BI prediction method can be applied to accurately locate suitable hydraulic fracturing intervals for economic and technical practicality.
      原文链接:
    • NSTL

    Proppant transport in scaled experiments;; Effect of drainage configuration and fracture wall roughness

    Lucas BasiukFrederico Irou RoschzttardtzMatias E. Fe rnandez
    8页
    查看更多>>摘要：In recent years, there has been a number of experimental and numerical studies on the transport and settlement of proppant in scaled laboratory fractures that are of interest to understand hydraulic stimulation in hydrocarbon reservoirs. The results from these studies are generally taken with skepticism by the industry. Part of this is due to the perception that results must be very sensitive to the boundary conditions. Small changes in the experimental configuration are expected to lead to very different results. In particular, little is known on how the actual roughness of the fracture walls and the way the slurry is drained from the laboratory cell affect the results. Here, we report experimental results on the proppant transport in a scaled vertical rough cell that mimics a vertical fracture induced during stimulation. We compare results with those obtained in a smooth wall cell, which is more common in laboratory tests. We found that a rough wall allows for a significant increase in the amount of proppant deposited in the cell at high pumping rate. However, the effect of roughness seems to be marginal for low pumping rates, suggesting that most previous studies in the literature which use of a reduced pumping rate were not significantly affected by the use of smooth walls. We also designed different flow configurations at the fracture tip (where the slurry drains form the cell) to study their effect on the way in which the proppant is deposited in the fracture. We found that, in general, the deposited dune is fairly independent of the particular boundary conditions. This suggests that most results reported in the literature are also robust against changes in the selected outflow configuration.
      原文链接:
    • NSTL

    Preparation and properties of nano-silica hybrid hydrophobic associated polyacrylamide for polymer flooding

    Jiawen LiuShibin WangLe He
    9页
    查看更多>>摘要：Polymer flooding was one of the most commercial enhanced oil recovery (EOR) methods. It was the key to study novel polymer which had special properties for improving the oil displacement efficiency. In this study, a nano-hybrid polymer (PAAM@SNP) for polymer flooding was synthesized by in situ polymerization with monomers and silica nanoparticles (SNP). The composition, micro-morphology and rheological properties of PAAM and PAAM@SNP were characterized by FT-IR, 2H NMR, TEM, and rheometer. Compared with pure PAAM, the nano-hybrid polymers showed excellent viscoelastic, temperature resistance and shear resistance properties. The nano-hybrid polymer with the nanoparticle content of 1.5% w/w had the best performance. Improved performance of PAAM@SNP could be attributed to the rigid SNP was dispersed into the polymer to interact with the polymer molecules, which enhanced the network structure of PAAM@SNP and made the network structure of PAAM@SNP more complex. PAAM@SNP could make rocks tend to be water wet, which was good for oil displacement. In the enhanced oil recovery tests, nuclear magnetic resonance (NMR) visualization technology was combined with traditional core displacement experiments to study the effect of polymer flooding. The solution with a concentration of 0.1% w/w PAAM@SNP-1.5 increased oil recovery by 7.82% contrasting only 2.53% for the solution with a concentration of 0.15% w/w PAAM. Observation of cores during displacement by nuclear magnetic resonance imaging revealed that PAAM@SNP~(-1).5 reduced the mobility ratio oil to water and increased sweep efficiency notably. PAAM@SNP~(-1).5 had more obvious advantage in performance and more economical than PAAM, which made PAAM@SNP~(-1).5 have a better application in EOR.
      原文链接:
    • NSTL