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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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    A multifractal-based method for determination NMR dual T2 cutoffs in coals

    Sijian ZhengShuxun SangYanbin Yao
    14页
    查看更多>>摘要：An accurate classification of pore fluid typing in coals is critical for understanding and assessing fluid flow characteristics during coalbed methane production, but the widely used nuclear magnetic resonance (NMR) single T2 cutoff (T_(2C)) model remains some apparent defects. In this study, we proposed a novel NMR dual T2 cutoffs model for fluid typing classification based on the multifractal theory. Firstly, the NMR and high-speed centrifugal combined measurements were performed for twenty-one coals with strikingly different ranks. Secondly, the multifractal analysis theory was introduced to investigate multifractal characteristics of the fully water-saturated NMR spectra. Thirdly, the correlations between dual T2 cutoffs and multifractal parameters were systematically analyzed. Fourthly, a multifractal-based model was established to evaluate the NMR dual T2 cutoffs values in coals. Results show that the pore fluid typing was re-divided into: absolute irreducible- (T2 < T_(2C1)), absolute movable-(T2 > T_(2C2)), and partial movable-fluid (T_(2C1) < T2 < T_(2C2)) based on dual T2 cutoffs. The values of T_(2C1) and T_(2C2) were in the range of 0.049-0.455 ms and 36.12-102.34 ms, respectively. Multifractal numerical simulations indicate the coals have typical multifractal characteristics. The minimum multifractal dimension (D_(min)), singularity strength subtraction (α_(max)-α_(min)), and singularity strength proportion (α_(max)/α_(min)) were linearly correlated with dual T2 cutoffs, that can be further used for model-building. The dual T2 cutoffs calculated from the proposed multifractal-based model qualitatively agree with those obtained from complicated laboratory experiments, indicating the accuracy of the established multifractal-based model in this study - from the validations of six non-modeling coals. It can be concluded that the proposed multifractal-based model in accurate and convenient, also be scalable in the applications of other rocks such as shales.
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    Upgrading of Mackay River bitumen through co-aquathermolysis with lignin under mild conditions

    Xiao QuGuangqian ZhouChen Wang
    6页
    查看更多>>摘要：In the present work, the catalytic co-aquathermolysis of Mackay River bitumen and lignin was performed at the temperature of not higher than 300 °C. The heteropoly acid (HPA) catalysts was used as the catalyst for co-aquathermolysis. The bitumen to lignin ratio, lignin solvent, and reaction temperature have been optimized. The properties of oil samples before and after reaction including viscosity, API°, SARA contents and average relative molecular weight have been determined. The results confirmed the synergistic effect in bitumen and lignin catalytic co-aquathermolysis. Compared with the bitumen aquathermolysis alone, the viscosity-reducing ratio and heavy fraction conversion ratio increased by 42.6 and 9.15 percentages, respectively, API° increased by 1.3, and molecular weight of asphaltene decreased by 199. The synergistic mechanism of co-aquathermolysis has been analyzed through Fourier transform infrared spectroscopy (FTIR) and oxygen content changes of aromatics. More oxygen-containing groups have appeared in the FTIR spectra, and the oxygen element content of aromatics increased. The complementation of endothermicity of bitumen thermal cracking and exothermicity of lignin pyrolysis provided the co-aquathermolysis with synergistic viscosity reduction effect. We hope that the results will cast a new light on Mackay River bitumen in situ or ground upgrading for its transportation and refining.
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    In situ dynamic X-ray imaging of fluid-rock interactions inside tight sandstone during hydraulic fracturing: fluid flow process and fracture network growth

    Zizhuo MaYibo WangYikang Zheng
    11页
    查看更多>>摘要：Hydraulic fracturing plays a fundamental role in unconventional hydrocarbon production and the development of enhanced geothermal systems. Thus, studying the fluid flow process and fracture network growth during hydraulic fracturing is necessary to provide guidance for creating and sustaining fracture networks in target reservoirs. The actual formation stress state and hydraulic fracturing process can be simulated in the laboratory for small-scale rock samples in hydraulic fracturing experiments. High-energy industrial X-ray computed tomography (CT) has been used to directly track the fracture propagation in millimeter-scale samples under triaxial stress loading. In this study, a large-scale fracture network with economic benefits for unconventional energy exploitation was the target of the experiment; therefore, centimeter-scale samples were used. A hydraulic fracturing simulation experiment was conducted on tight sandstone by applying triaxial compression and injection pressures. With the assistance of the PEEK core holder and third-generation medical X-ray CT scanner, in situ dynamic X-ray imaging of the fluid-rock interactions inside the sample was conducted for the first time. The fluid-rock interactions and fracture network growth can be dynamically observed, revealing the fluid-rock interactions during the hydraulic fracturing process and how macroscopic failure develops from the microfracture.
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    Development of an NMR workflow for determining nano-petrophysical properties of marine and lacustrine mudrocks

    Na YinQinhong HuSamuel J. Becker
    12页
    查看更多>>摘要：Nuclear Magnetic Resonance (NMR) is a powerful method of pore structure and fluids characterization for a wide range of porous media due to its fast and non-destructive capabilities, but its utilities of nano-petrophysics (the properties of rocks and fluids, as well as their interactions, in the presence of predominantly nm-sized pores) for tight oil formations warrant more studies. In this work, a total of four cylindrically-shaped tight reservoir samples at 2.54 cm in diameter with four different lithologies in USA and China were selected for systematic NMR analyses with T2 relaxation time, T1-T2 mapping, NMR cryoporometry (NMRc), and magnetic resonance imaging (MRI) techniques, along with other supplemental tests of X-ray diffraction (XRD), mercury intrusion porosimerry (MIP) and vacuum-assisted water immersion porosimetry (WIP), to characterize their petrophysical properties. The results show that the effective porosity obtained from NMR was highly consistent with WIP. Three samples characterized by MRI showed that T2 spectra had a good response to the fluid distribution in the samples. In this study, T2 time was converted into the pore size by combining corrected NMR T2 spectrum and MIP pore-throat size distribution. Finally, The Katz-Thompson model was applied for NMR data to calculate the permeability at different inflection points (connected pore networks) to quantitatively evaluate their individual permeabilities and porosities. Furthermore, except for sample N9 (carbonate-rich Wolfcamp A mudrock), a satisfactory agreement was achieved between the results of K2c (cut-off time at the second inflection point) and helium method for permeability analyses.
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    Micromechanism of partially hydrolyzed polyacrylamide molecule agglomeration morphology and its impact on the stability of crude oil-water interfacial film

    Zhihua WangYunfei XuYifan Gan
    11页
    查看更多>>摘要：Based on the background of oilfield chemical flooding produced liquid treatment projects, to achieve new insight into the micromechanism of the impact of polymer molecules applied to enhanced oil recovery (EOR) technology on the crude oil-water interface behavior, different 'crude oil/HPAM/produced water' interface simulation systems were constructed by regulating the polymerization degree and hydrolysis degree of partially hydrolyzed polyacrylamide (HPAM) and combining the composition and physical properties of oil and water phases. The simulated results showed that all simulation systems have a stable layer order and clear crude oil-water interface after dynamic relaxation equilibrium. HPAM molecules were agglomerated in different forms at tie crude oil-water interface depending on the inorganic cations in the water phase and their own degree of polymerization and hydrolysis, and the order of inorganic cations aggravating the agglomeration was Ca~(2+)>Na~+>K~+>Mg~(2+). The stability of the interfacial film was positively correlated with the gyration radius of the HPAM molecules. Unlike the continuous increase in the gyration radius of HPAM molecules with increasing polymerization degree, the effect of increasing hydrolysis degree on the stability of the crude oil-water interfacial film is concentrated in the range of 15-35%, the gyration radius of HPAM molecules no longer increases when the hydrolysis degree continues to increase, and the interfacial film stability no longer significantly changes.
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    The influence of heterogeneous proppant pack on fracture closure and productivity

    A.M. SkopintsevE.V. DontsovA.N. Baykin
    13页
    查看更多>>摘要：Even though hydraulic fracturing is a common and well adopted well stimulation method in petroleum industry, there are still open scientific questions in the area, mainly due to complexity of the phenomena involved in the process. In this paper, we particularly address the problem of fracture closure and productivity in situations, when proppant distribution inside the fracture is strongly heterogeneous. This can happen, for instance, during pulsed injection, in which a pulse of clean fluid is alternated with a pulse of slurry with proppant. Such a combination leads to Saffman-Taylor instability and, consequendy, to spatially heterogeneous distribution of proppant. To address the problem, a coupled hydraulic fracturing and proppant transport model is utilized to simulate proppant placement in a fracture. After that, a three-dimensional finite element model is used to compute fracture closure and fluid inflow or productivity. Several numerical examples with various pumping schedules are presented to better understand the influence of proppant heterogeneity on fracture closure and the resulting production. In addition, to get insights about the observed behavior, an analytical model for fracture closure between two proppant pillars is presented. The model provides a single dimensionless parameter that quantifies the degree of fracture closure between the pillars of proppant. Numerical results are analyzed and discussed in relation to this dimensionless number.
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    Depositional environment, age determination and source diagnose of oils from the western Chepaizi Uplift (Junggar Basin) constrained by molecular biomarkers

    Liu ZhongquanChang XiangchunXu Youde
    13页
    查看更多>>摘要：The western Chepaizi Uplift of petroleum-enriched Junggar Basin hosted multiple oil-bearing intervals, i.e., Neogene Shawan Formation (N1s), Lower Cretaceous Tugulu Group (K1tg), and Upper Carboniferous Xibeikulasi Formation (C2x). However, their origins had always been debated, due to the occurrence of Jurassic, Cretaceous and Paleogene source rocks in the neighboring Sikeshu Sag. In this paper, two oil groups, i.e., group A (N1s and K1tg oils from the west margin of western Chepazi Uplift), and group B (oils from the east margin of the western Chepaizi Uplift). The latter can further subdivided into family B1(Upper Jurassic Qigu Formation (J3q) oil and N1s oils from east margin of western Chepaizi Uplift close to the Sikeshu Sag, and oil sands from the Sikeshu Sag) and family B2 (N1s and C2x oils from eastern margin of the western Chepaizi Uplift away from the Sikeshu Sag) can be defined. Age-specified biomarker ratios (24-norcholestane, Oleanane index and extended tricyclic terpane ratio) implied Jurassic and Paleogene source ages with minor Cretaceous contributions. Depositional environment-diagnosed biomarkers (Pr/Ph, Pr/nC_(17), Ph/nC_(18), methyldibenzothiophene/methylphenanthrene, C_(22)/C_(21) tricyclic terpanes, C_(24)/C_(23) tricyclic terpanes, C29αβ/C30αβ hopane, C31 hopane (22R)/C30αβ hopane, and gammacerane/C30 hopane) showed lacustrine source input with high hypersalinity for family B1 but freshwater lacustrine facies for group A and family B2. C_(27)-C_(28)-C_(29) regular steranes and triaromatic steroids distributions indicated ascending order of high plant contribution from family B1 to family B2 to group A. Combined with stable carbon isotope, the uplift-scale petroleum contribution to multiple oil-bearing intervals by multiple source intervals were lined out. Group A oils implied origins from source rocks deposited in freshwater lacustrine facies under weak oxidation conditions with predominant organic input of high plants, and genetically matched with the Lower Jurassic Badaowang Formation (J1b) mudstone source rock. Family B1 oils showed provenance from source rocks occurred in reducing source facies with high hypersalinity and great contribution of lower organisms, and well corelated with both J1b and Paleogene Anjihahe Formation (E_(2-3)a) source rocks. However, where away from the generating Sikeshu Sag, especially for family B2 oils, the hydrocarbon contribution of E_(2-3)a source rocks was decreased, mainly controlled by their variable distribution and thermal evolution.
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    Chemometric investigation of oil families and geochemical characterization of crude oils in the Northern Dezful Embayment Zone, SW Iran

    Ahmad Reza RabbaniJalil SadouniMorteza Asemani
    11页
    查看更多>>摘要：Chemometric analysis was performed on 19 crude oil samples from 14 different oil fields to reveal oil families and their distributions in the Northern Dezful Embayment Zone. The geochemical characteristics and candidate source rock(s) of the defined oil families were also investigated in this study. The chemometric classification revealed three different oil families in the studied area. Group I includes Naft Sefid, Ramin, Kupal, Martin and Aghajari oil fields. Group II comprises Ziloie, Masjid-e Soleyman, Karanj, Haftkel, Balarud, Qale Nar, and Karoun oil fields, and group III contains Azar and Dehluran oil fields. All studied samples were expelled from open marine settings with anoxic conditions, type II kerogen, and marine organic matter inputs. The group I oil held, have C29/C30 > 1, TAR<1, moderate C22/C21 and C24/C23 tricyclic terpanes, an insignificant amount of Oleanane, mid-oil window maturity, and an average carbon isotope of -26.98‰, which were charged from the Kazhdumi source rock. The group II oil family has C29/C30H < 1, moderate C22/C21 tricyclic terpanes, TAR<1, moderate C24/C23 tricyclic terpanes, and a high Oleanane Index (average of 22%), mid-oil window maturity, and average carbon isotope of -25.35‰. These oils were originated from the Pabdeh Formation. The group in samples have C29/C30H > 1, high C22/C21 tricyclic terpanes, TAR<1, low C24/C23 tricyclic terpanes, mid-oil window maturity, and an average carbon isotope of -27.67‰, which were originated from the Garau or Sargelu settings.
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    Mixture of relevance vector regression experts for reservoir properties prediction

    Guangzhou ShaoCheng YuanXingye Liu
    12页
    查看更多>>摘要：One of the most indispensable works in the oil and gas exploration and exploitation is reservoir properties forecast. We develop a reservoir properties prediction method based on the mixture of relevance vector regression (RVR) experts. For reservoir properties prediction, an individual machine learning model is probably insufficient with limited training data. The mixture of experts can decompose a complicated problem of reservoir properties prediction into several relatively simple sub-problems by incorporating multiple learning models, where each model processes specific parts of the data. In the proposed method, RVR has been chosen as the expert because it results in sparser regressors and determines hyperparameters automatically. It can also project data into a high-dimensional space through kernel functions to resolve the non-linear problem and avoid the curse of dimensionality. At first, a mixture of RVR experts model is trained on the well data samples. The input features are elastic properties and the output is a reservoir property. Then, the learning model is applied to test dataset and the corresponding reservoir properties are generated. The proposed method is applied to two field data, in which the learning model is obtained by training on the well data and is tested on the well and seismic data, respectively. Compared with an individual RVR expert, some metrics, such as mean absolute derivation (MAD), root mean square error (RMSE), coefficient of determination (R~2) and Akaike information criterion (AIC) etc., are effectively improved. The successful implementation of the method demonstrates its feasibility, certifying the superiority of the new method in the aspect of likelihood of fit and accuracy again.
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    Occurrence characteristics of the movable fluid in heterogeneous sandstone reservoir based on fractal analysis of NMR data: A case study of the Chang 7 Member of Ansai Block, Ordos Basin, China

    Qibiao ZangChenglin LiuRizwan Sarwar Awan
    20页
    查看更多>>摘要：In the Ordos Basin, Chang 7 sandstone is considered an essential tight sandstone reservoir. In this research, the occurrence characteristics of the movable fluid, fractal characteristics, and their relationship in Chang 7 reservoir of the Ansai Block, Ordos Basin, have been quantitatively evaluated through nuclear magnetic resonance (NMR) and fractal theory. Moreover, the factors influencing the fractal dimensions and movable fluid distribution have been determined through a series of experiments, i.e., conventional physical property, cast thin section, scanning electron microscope (SEM), high-pressure mercury intrusion (HPMI), and X-ray diffraction technique (XRD). It has been noticed the movable fluid distribution in the tight sandstone reservoirs is greatly affected by the pore structure heterogeneity. Results show the main pore types in Chang 7 are the intergranular dissolution pores, intragranular dissolution pores, residual intergranular pores, and inter-crystalline pores. The pore size chiefly ranges from 0.1 nm-5 pm, while the main fluids storage spaces are nanopores and submicron pores. The reservoir has been divided into three types (type I, II, and III) based on the distribution of the T2 spectrum and petro-physical parameters. Moreover, these reservoirs have various movable fluid distributions and fractal structures, Multiple factors such as pore structure, pore size distribution, and mineral compositions are discussed, which influence the fractal dimension and movable fluid saturation. The reservoirs having more nanopores are often associated with strong heterogeneity and low movable fluid content. The fractal dimension is weakly affected by pore structure parameters and mineral compositions. The movable fluid saturation is significantly affected by pore structure while weakly affected by mineral compositions. The relationship between heterogeneity and movable fluid distribution varies with reservoir types. The inhibition of heterogeneity on the movable fluid of different reservoirs is mainly reflected in various pores. Movable fluids controlled by throats are primarily distributed in different pores, resulting in diverse effects of heterogeneity on controlling the effect of different throats in various reservoirs. The findings of this research can help better understand the occurrence characteristics of the movable fluid in tight sandstone reservoirs with different fractal features.
      原文链接:
    • NSTL