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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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    Mechanical properties of methane hydrate-bearing sandy sediments under various temperatures and pore pressures

    Shi ShenYanghui LiXiang Sun
    11页
    查看更多>>摘要：According to the marine geological survey, marine hydrate reservoir's temperature (T) and pore pressure (P-P) conditions change with water depth and burial depth. Besides, the change in Tand P.P conditions would also occur during the exploitation of hydrate. It is meaningful to study the combined effects of Tand P.P on mechanical behaviors of methane hydrate-bearing sediments (MHBSs) to evaluate the hydrate reservoir's stability. In this work, a set of mechanical experiments were carried out to study the effect of Tand P.P on the mechanical properties of MHBSs. With decreasing Tand increasing P.P, the samples' strength increased, and the stress-strain behaviors also changed. Moreover, with decreasing Tand increasing P.Py the samples' dilatant volumetric strain increased. The mechanical properties of MHBSs were affected by the 'distance' between the test condition point and the phase equilibrium curve. With increasing 'distance', the sample s' strength increased; simultaneously, the stress-strain behaviors also changed. A shift line was introduced in temperature-pressure space, which was the boundary between the hardening and softening behaviors of the MHBSs. Furthermore, we established the numerical relation between strength, T and P.P in this paper. The results of this study can be used for the studies of reservoir stability during methane hydrate productions.
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    A review on parameters affecting nanoparticles stabilized foam performance based on recent analyses

    Shahrul Aida Ab RasidSyed M. MahmoodNor Idah Kechut
    22页
    查看更多>>摘要：In recent years, much attention has been paid to the addition of nanoparticles (NPs) into the surfactant foam structure to form durable foams. Although surfactant foam as an enhanced oil recovery (EOR) technique significantly increases the viscosity of the injected fluid compared to gas injection, it has been observed that the foam structure does not have the required stability in cases such as high temperatures and high salinity. Although NP addition increases stability, the extent of this increase depends on several parameters, including NP properties (i.e., size, type, surface wettability) and reservoir properties (i.e., salinity of formation water, presence of oil, reservoir temperature), process parameters (i.e., NP concentration and flow rate), synergistic effects between the surface charge of NPs and the net charge of surfactant, and NP loss in the porous medium. This study aims to review and summarize the findings of previous studies to conclude the effects of each of the parameters above on foam stability, identify differences, and determine gaps for future studies. Throughout this report, a study background is provided, followed by the concept of stability and how to determine it in different tests for NP-surfactant foam. Next, the mechanisms of increasing stability by NP addition are briefly presented. Lastly, previous findings related to the effect of each parameter on NP foam stability are presented and discussed. Although several detailed reviews of NP-stabilized foam have been published previously, the present study differs from them in that the effects of additional parameters were investigated by reviewing new findings. Moreover, an attempt has been made to discuss the effects of parameters from different angles and according to their role in the mechanisms of NP-stabilized foam, such as particle detachment energy and maximum capillary pressure. The findings of this review show that i) oil presence lowers foam stability, ii) increasing NP concentration as well as decreasing NP size, temperature, NP retention, and salinity lead to increased stability, and iii) for parameters including NP surface wettability, NP types, and shear rate/flow velocity there are optimum points that result in the best foam performance. NP loss in a porous medium is an economically damaging process that occurs through mechanisms including adsorption, mechanical entrapment and log-jamming, and particles settling due to gravity. Depending on the type of mechanism, the strategy for minimizing or removing the influence of these mechanisms differs. However, there is currently no way to determine and measure the contribution of each of these mechanisms to the total retention in dynamic tests, which could be a specific topic for future research.
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    A high performance magnetically responsive Janus nano-emulsifier;; Preparation, emulsification characteristics, interfacial rheology, and application in emulsion flooding

    Lei YueiWanfen PuTianhong Zhao
    11页
    查看更多>>摘要：Recently magnetic nanomaterial has become a research hotspot in many areas due to its environment friendly, low-toxicity, magnetic responsiveness, and excellent reusability. This paper aims to study a novel amphipathic Janus magnetic nanoparticle (MJNP) applied for emulsion flooding, including preparation, emulsification characteristics, interface rheology, and enhanced oil recovery performance. X-ray diffraction (XRD), Fourier transform Infrared spectrometer (FT-IR), Transmission electron microscopy (TEM), Scanning electron microscope (SEM), Thermal gravimetric analyzer (TGA), and vibrating sample magnetometer (VSM) are employed to observe the crystal structure, shape, size, surface components of Janus nanoparticle, and magnetic responsiveness. Results show this high performance MJNP fabricated by Pickering emulsion method has coupled carboxyl and octyl chemical groups on both ends of its surface. What's more, MJNPs have not only sufficiently small particle size for ensuring free flow in reservoir but outstanding magnetic responsiveness for efficient reusability. This hydrophilic MJNP owns excellent emulsion performance to prepare high internal phase O/W emulsion without any additive. Results show 0.3% of MJNP has prepared stable O/W emulsion with 90% of oil content, and 80% emulsion is even stabilized by 0.02% of MJNP and fails to phase inversion. Furthermore, these emulsions fabricated by higher concentration of MJNP own finer stability and anti-temperature. The intensity of interfacial film is evidently enhanced with the aggregation of MJNPs on oil-water interface. When concentration of MJNP is equal to 0.2%, the interfacial dilational modulus has increased to 34.24 niN/m. Moreover, the MJNP interfacial film shows remarkably elasticity. Salinity has a significant effect to the stability of MJNP interfacial film, and this effect is more distinct in the higher concentration of MJNP. 0.08% of MJNP fluid has the best anti-salt performance. Meanwhile, this novel Janus nanoparticle shows an excellent oil recovery capacity for emulsion flooding.
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    Research on convection-reaction-diffusion model of contaminants in fracturing flowback fluid in non-equidistant fractures with arbitrary inclination of shale gas development

    Xiaoxu DongWenjing LiQun Liu
    14页
    查看更多>>摘要：The large-scale hydraulic fracturing technology used in shale gas development will cause major environmental pollution problems. Therefore, determining the concentration of contaminants in the fracturing flowback fluid to reduce surface water pollution caused by shale gas development is one of the main tasks facing shale gas development. This paper mainly studies the convection, reaction and diffusion process of contaminants in fracturing flowback fluid in non-equidistant fractures with arbitrary inclination. Firstly, based on the convection-reaction-diffusion model of fluid and combined with the fracture morphology, the convection-reaction-diffusion model of contaminants in fracturing flowback fluid in non-equidistant fractures with arbitrary inclination is established. Secondly, in order to solve the established model, an unproved fracture equivalent method is proposed, which fully considers all the distributions of the left and right wings of the fractures. Thirdly, the convection-reaction-diffusion model is solved by using coordinate transformation, the Laplace transform method, the characteristic root method, and the Gaver-Stehfest numerical inversion method. Then the concentration of contaminants at the port of the left and right wings of each fracture near the horizontal wellbore in real space is obtained. Finally, taking the chloride ion in the fracturing flowback fluid as an example, the influence of the main controlling factors on its concentration is studied. The results show that the chloride ion concentration increases nonlinearly with the linear increase of backflow velocity and molecular diffusion coefficients, and decreases nonlinearly with the linear increase of rate coefficients and the length of the fracture. This research provides a theoretical basis for the research on the flowback pollution of fracturing flowback fluid.
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    Research on cutting track and working load of directional drilling PDC bit

    Haiping TianHaitao RenDongdong Song
    14页
    查看更多>>摘要：Polycrystalline diamond compact bit directional drilling technology has proven to be an important means to effectively improve drilling efficiency and save drilling costs. Under the directional drilling condition of PDC bit, due to the existence of screw angle or offset mechanism, the center axis of the bit deviates from the center of the borehole, and the cutting teeth of the bit do complex alternating trajectory cutting motion at the bottomhole and the trajectory lines of the cutting teeth themselves intersect in space. (1) The kinematics analysis of directional drilling PDC bit under different working conditions was carried out, including motion analysis at the stage of sliding steering deflection and motion analysis at the stage of composite steering drilling. The kinematics equation of PDC bit under sliding steering deflection and motion space equation of PDC bit cutters at the stage of composite steering drilling were deduced respectively. (2) By establishing the calculation model of cross Angle of cutters under directional drilling conditions, the influences of transmission ratio, tooth placement, offset and deflection Angle on the cross angle are analyzed. The movement law of PDC cutters and the bottom hole morphology formed by bit are studied under directional drilling conditions. (3) Based on the digital simulation system of PDC bit rock breaking, the cutting load under the state of alternating trajectory was studied. On this basis, the cutting mechanics model of PDC bit cutters in directional drilling was established. At the same time, the accuracy of simulation analysis was verified by laboratory unit experiments. It is considered that PDC cutters can form alternate cutting path in directional drilling, which can easily invade rock and improve mechanical efficiency. The larger the intersecting angle of the cutting teeth, the more likely the rock is to form a through crack and then be broken. When the intersecting angle is 90°, the average energy consumption of rock breaking in cross cutting is reduced by about 32.9% compared with parallel cutting. The research results have improved the understanding of the rock breaking mechanism of PDC bit directional drilling, provided a new technical means for bit performance analysis and have also provided a reference for the design of new personalized bits under the discussed working conditions.
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    Spatial assessment of gross vertical reservoir heterogeneity using geostatistics and GIS-based machine-learning classifiers: A case study from the Zubair Formation, Rumaila oil field, southern Iraq

    Amna M. HandhalFrank R. EttensohnAlaa M. Al-Abadi
    15页
    查看更多>>摘要：The study of oil-field reservoir heterogeneity is an important task in the oil industry as it affects waterflooding, developing injection production systems, and optimizing hydrocarbon production. In this study, vertical reservoir heterogeneity was quantified using the Lorenz statistical index, empirical Bayesian kriging, and seven machine-learning classifiers (Classification and Regression Trees, Boosted Regression Trees, Random Forest, Naive Bayes, Logistic Regression, K-Nearest Neighbors, and Support Vector Machine with three different kernels (linear, radial, and polynomial) under the geographic information system platform. The main pay zone of the Zubair Formation in the Rumaila oil field from southern Iraq was used as a case study. The degree of heterogeneity was first quantified using the Lorenz index, and a borehole-heterogeneity inventory location map was prepared according to the determined Lorenz index. Information about five factors influencing the heterogeneity, namely, porosity, permeability, volume of shale, reservoir-unit thickness, and depth to the top of reservoir unit, was collected based on available cores, nuclear magnetic resonance log, gamma-ray logs, and drilling-information logs. Factors from these sources were interpolated to show their spatial distribution using the empirical Bayesian kriging technique. The relationship between the borehole inventory map of vertical heterogeneity and the five factors was examined using the seven machine-learning classifiers. Two statistical-error measures, namely, accuracy and Cohen's kappa, were used to verify the performance of the classifiers in both training and testing stages. Results proved that Random Forest, Support Vector Machine with radial kernel function, and Logistic Regression were the best models. The probabilities of the best performance models were then interpolated and classified into five heterogeneity zones;; Very low, low, moderate, high, and very high. The high-very high classes for each of these models approximately occupy 60% of the oil field and are mainly distributed in the middle and north of the field, whereas the other classes encompass about 40% of the field and mostly occur in the south. This distribution of classes is most likely related to the distribution and complexity of former depositional environments.
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    A comparative study of gas transport in dry and moisturized shale matrix considering organic matter volume fraction and water distribution characteristics

    Fangtao LyuZhengfu NingXiaojun Wu
    18页
    查看更多>>摘要：Understanding gas transport in shale matrix is of great significance for reservoir evaluation and gas well productivity. Up to now, numerous transport models were developed based on the hypothesis of homogeneous confined cylindrical nanopores by coupling with multiple mechanisms. In this work, a new transport model is proposed by coupling different transport mechanisms employing the volume fraction of organic matter (OM) instead of the total organic carbon content (TOC). The signature that the OM density is generally lower than the bulk matrix is also considered. The porosity of OM and inorganic matter (iOM) is determined by rock pyrolysis analysis, respectively. Water distribution in OM and iOM pores in the form of water clusters and adsorbed water films is quantified by water adsorption experiments. Gas transport model in moisturized shale matrix pores is then established considering the difference in water distribution. Meanwhile, both of the proposed models are analytical solutions with the hypothesis that the OM and iOM are arranged parallelly. The impacts of different factors on gas transport capacity are analyzed and discussed. Results indicate that the apparent permeability of the shale matrix decreases with the decline of pore radius. For the same pore diameter, the gas transport capacity of OM pores is much greater than that of iOM pores. The apparent permeability decreases with the increasing OM fraction. The irreducible water within the shale matrix can reduce the gas flow capacity considerably, and the apparent permeability is more sensitive to the change of irreducible water saturation at low pressure comparing with that at high pressure. This study sheds fundamental light on the gas transport distinctions in dry and moisturized shale matrix, which provides insights into the development of water-bearing shale gas reservoirs.
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    Pore-scale study of the anisotropic effect on immiscible displacement in porous media under different wetting conditions and capillary numbers

    T.R.ZakirovM.G. Khramchenkov
    16页
    查看更多>>摘要：This article investigates the effect of anisotropy on two-phase flows in porous media (both drainage and imbibition) under various wetting angles and capillary numbers. The focus is on the applied results useful to petroleum engineering. Mathematical modeling based on lattice Boltzmann equations in combination with multi-relaxation time and color-gradient model is used as a research tool. This paper proposes a new method for creating digital models of porous media, based on a combination of a quartet structure generation set and Monte-Carlo algorithms. The advantage is the ability to control both heterogeneity and anisotropy. This paper presents visual phase diagrams of the invasion patterns in anisotropic samples as a function of wetting angle and capillary number. The results show that the ratio between capillary and viscous forces is highest for the sample with favorable anisotropy, which has the biggest permeability, and decreases on going to unfavorable anisotropy (lowest permeability). This effect leads to the finding that boundary capillary numbers, which determine the transition between crossover mode and invasion patterns (viscous and capillary fingering, and compact displacement), are shifted towards lower values as anisotropy increases. The images of fluid distributions are numerically described using fractal dimension and displacement efficiency. It was found that the anisotropic effect is most pronounced at capillary fingering and does not significantly affect the invasion characteristics in the imbibition mode. The sensitivity of the fractal dimension and displacement efficiency to a change in the wetting angle is maximal at favorable anisotropy and decreases on going to unfavorable anisotropy. During drainage, the fractal dimensions, estimated for favorable and unfavorable anisotropy, show opposite trends depending on the capillary number. In the imbibition mode, there is an increase in the fractal dimension with an increase in the capillary number for all porous structures. In addition, this paper investigates the anisotropy effect on the ?injected fluid-skeleton ? interfacial length under different wetting and dynamic conditions. It was shown that the anisotropy has no significant effect on this parameter, and the best interaction efficiency was found with a compact displacement, and the least with a viscous fingering. Also, the influence of the no-flow and periodic boundary conditions on the invasion characteristics is examined. The results show that boundary conditions do not significantly affect the invasion in the sample with favorable anisotropy for any wetting angles. Periodic boundary conditions negatively influence the displacement efficiency for samples with isotropic and unfavorable structures at drainage, but no noticeable effect was found during imbibition.
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    Geopolymer as the future oil-well cement;; A review

    Stephen AdjeiSalaheldin ElkatatnyWilberforce Nkrumah Aggrey
    8页
    查看更多>>摘要：The petroleum and cement manufacturing industries have been accused of contributing substantial quantities of carbon dioxide (CO2) into the atmosphere. Additionally, Portland cement systems suffer carbonation and degradation in high saline and acidic environments. Geopolymer, a much cleaner cementitious binder, synthesized through the reaction of aluminosilicate materials and alkaline solution has been a leading alternative to ordinary Portland cement (OPC). The feasibility of using geopolymer in oil-well cementing is still being explored. The objective of this review study is to provide a single document that summarizes the findings from these studies. In general, researchers have explored geopolymer application in aggressive environments and well plug and abandonment operations, the effect of temperature, and its compatibility with drilling fluid. Compared to OPC systems, geopolymer is more resistant to acidic environments, performs better in high saline conditions, and is highly compatible with drilling mud. The geopolymer being a green technology coupled with its optimized properties implies that it is the future of oil-well cement. For further studies, we suggest in-depth characterization of lightweight geopolymers.
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    Comprehensive insight into cuttings motion characteristics in deviated and horizontal wells considering various factors via CFD simulation

    Like MaJianqing LaiXinxin Zhang
    25页
    查看更多>>摘要：In extended-reach and directional drilling, cuttings transport is a key issue associated with the efficiency of hole-cleaning and drilling operation. If the cuttings cannot be returned to the surface in time, many technical difficulties may arise such as excessive torque and drag, stuck pipe, and loss of well control. In this study, a computational fluid dynamics (CFD) approach with Eulerian-Eulerian (EE) multiphase model was employed to comprehensively understand and analyze the effect of several drilling operation parameters, mud rheological properties, and specularity coefficient (representing various wellbore wall conditions) on the cuttings transport performance. A commercial CFD software (ANSYS FLUENT? 19.1) was used to implement all simulations, and a sensitivity analysis was executed with an error of less than 5%. Furthermore, the motion patterns of cuttings were observed and analyzed under various factors. The results show that the cuttings transport performance is sensitive to the wellbore wall condition. In the lower side of annuli, the volume fraction of cuttings increases significantly by 28% with increasing specularity coefficients. Additionally, the combined influence of critical shear rate and flow rate on the cuttings distribution was investigated. The relative reduction rate of cuttings concentration decreased by 30% with increasing critical shear rate at the fluid velocity of 0.4 m/s, while that didn't change so obviously at the fluid velocity of 0.8 m/s.
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