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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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    Fracability evaluation of the upper Cretaceous Naparima Hill Formation, Trinidad

    Uwaila Charles IyareOshaine Omar BlakeRyan Ramsook
    14页
    查看更多>>摘要: The upper Cretaceous Naparima Hill Formation, a primary source rock for conventional oil and gas reservoirs in Southern and Columbus basins, Trinidad is now considered an unconventional reservoir. Effective fracability evaluation is critical to the entire process of unconventional reservoir exploitation. At present, there exists no information on the fracability of the Naparima Hill Formation. A recent study have shown that the Formation consist of four lithofacies (siliceous-calcareous mudstone, calcareous mudstones, carbonate-rich mudstone and siliceous mudstone) that are highly brittle, implying that they are easily fractured. This is debatable because brittle rocks can have a higher fracture toughness, making them more difficult to fracture. In this study, an existing fracability evaluation model that incorporates brittleness, fracture toughness, and minimum horizontal insitu stress was used to evaluate the fracability of the four lithofacies within the Naparima Hill Formation. Through a series of laboratory testing (measurements of P- and S-wave velocities, uniaxial compression tests and Brazilian tests) of the dry outcrop samples, elastic properties (Young's modulus and Poisson's ratio), uniaxial compressive strength and tensile strength were determined. X-ray diffraction analysis (XRD) was also performed on the outcrop samples to determine their mineral compositions. Brittleness indices based on the rock elastic properties, rock strength and mineral compositions were used to evaluate the rock brittleness, and the fracture toughness was estimated from the tensile strength. The study results indicate that all lithofacies are highly brittle, which is consistent with the previous study. The fracability evaluation results showed that the siliceous calcareous mudstones and siliceous mudstones are more fracable than the calcareous and carbonate-rich mud-stones. The key factors that control the fracability of the Formation were found to be the amount of quartz, and the rock strength that is influenced by calcite cementation.

    Thixotropy research of laponite-hydrogel composites for water shutoff in horizontal wells

    Lifeng ChenGang LiYadong Chen
    12页
    查看更多>>摘要: The thixotropy of the hydrogel determines the ultimate hydrogel filling shape in the annulus between the slotted liners and wellbore in horizontal wells. But the common hydrogel cannot be successfully applied for water shutoff in horizontal wells due to its poor thixotropy. In this work, the nanoparticle laponite (LAP) was introduced into the chemically cross-linked acrylamide gelling solution to develop an excellent thixotropic hydrogel. The effect of LAP concentration on thixotropy was investigated through the hydrogel rheometer at 50 °C. It was found that the increase of LAP concentration in gelling solution is advantageous for enhancing the thixotropic performance. At the same time, the freeze-etching scanning electron microscopy (SEM) examinations indicated that the LAP hydrogel had a uniform grid structure, which can be broken easily by shear and restored quickly. The high concentration of inorganic salt in gelling solution will reduce the ability of LAP to improve the thixotropy of the gelling solution. Particle size distribution experiments demonstrated that the effect of CaCl2 on the particle size distribution of LAP is more remarkable than that of NaCl when their concentrations are the same. The effect of temperature on thixotropy was also investigated by the hydrogel rheometer. It shows that the increase of temperature will reduce the shear thinning effect of LAP hydrogel. This is because increasing the temperature leads to an increase in the dissociation of hydroxyl groups on the side surface of the LAP particles, which not only increases the pH of gelling solution but also increases the positive charge on the side to facilitate the aggregation of particles. The research results can enrich the Theological theory of nanoparticle/polymer. This study also provides technical guidelines for further increasing the thixotropy of polymers that are commonly used in enhancing oil recovery.

    Application of Janus nanoparticles in enhanced oil recovery processes: Current status and future opportunities

    Zahra TohidiAlireza TeimouriArezou Jafari
    12页
    查看更多>>摘要: Janus nanoparticles (JNPs), as a new and special type of nanoparticles (NPs), have a great potential to use in enhanced oil recovery (EOR) processes. The surfaces of JNPs have two or more distinct physical properties which allow them to have different chemical behaviors at the same time. Nowadays, this type of nanoparticle has drawn much attention in EOR. In this study, the application of JNPs in EOR processes is reviewed and JNPs are compared with common NPs. Special features, synthesis methods, advantages, and disadvantages of the JNPs for use in oil recovery methods are discussed. Also, the influence of the JNPs on the viscosity alteration, interfacial tension (IFT) reduction, wettability alteration, and oil recovery factor are discussed by reviewing previous conducted experimental and numerical studies. Despite all the studies conducted in this field, many challenges are facing these materials for use at field-scale operations that are discussed in this study. Producing JNPs with different bases such as metal oxides bases, synthesize a new JNPs at an industrial scale, the effect of reservoir's pressure and temperature, and development of new strategies are still needed to investigate in future studies to find the mechanism of JNPs in oil reservoirs and utilize them in real EOR operations.

    Effects of methane hydrates on two-phase relative permeability in sandstone: Numerical simulation of laboratory experiments

    Alejandro Bello-PalaciosPer FotlandStian Almenningen
    11页
    查看更多>>摘要: To identify the challenges and limitations in measuring and modelling gas relative permeability in hydrate bearing sandstone, we simulate a series of experiments. Experimental and numerical results are used to examine the amount of hydrates formed as well as how the flow of gas is affected by the hydrate formation. The reservoir simulator TOUGH+HYDRATE was used. The system is represented numerically in both 1-dimensional and 2-dimensional grids. The 1-dimensional simulations are used to check the system consistency by keeping track of the amount of hydrates that are formed, given the initial and boundary conditions. The 2-dimensional simulations are used to measure the effects of heterogeneity in the distribution of hydrates, and its impact on both relative permeability and capillary pressure. The results reveal complexities when comparing experimental and simulated permeability in hydrate-bearing systems. The results from the 1-dimensional calculations show that most experiments have not been able to form the amount of hydrates that is theoretically possible by the initial mix of brine and gas. This indicates that early growth of hydrates can limit mass transfer to inner parts of the core shielding the system for further nucleation. This is supported by the 2-dimensional simulations. These show how a heterogeneous pattern of hydrates can limit fluid flow by (a) reducing the intrinsic permeability, (b) scaling down gas relative permeability, and (c) and scaling up capillary entry pressure of portions of the core. Although these effects do not fully explain the experimental results, the results provide insight to hydrate induced flow restrictions and how these can affect experimental result.

    A novel pressure and rate transient analysis model for fracture-caved carbonate reservoirs

    Xin DuQingyu LiPeichao Li
    16页
    查看更多>>摘要: Fracture-caved carbonate reservoirs (FCCRs) have been developed worldwide and contribute significantly to world's hydrocarbon reserves. Numerous models for FCCRs were proposed in the previous works. However, with more and more exploitations, some kinds of FCCRs are observed from the field geological information but not reported in the existing literature. In this paper, a novel model for FCCRs is proposed and its corresponding pressure transient analysis (PTA) and rate transient analysis (RTA) solutions are presented. This model has a wider applicability than the previous models proposed by our research team. First, the geological model is established based on the geological information. Sequentially, the simplified physical model and the mathematical model are developed. Through Laplace transformation, Duhamel's principle, and Stehfest numerical inversion, the solutions of dimensionless bottom-hole pressure and dimensionless flow rate integral are derived. Then, the RTA type curves of two-cave model are plotted to recognize the flow characteristics, which can be divided into five regimes comprehensively. In addition, two concaves are observed on the derivative curve. The RTA type curves of three-cave model are also presented. A comparison between the RTA type curves of two-cave model and three-cave model shows that when one more cave exists in the formation, one more concave will be added to the derivative curve. Furthermore, the differences between the proposed model and previous models are presented through comparing the PTA type curves. Next, the effects of key parameters on the RTA curve behavior of two-cave model are demonstrated. Results indicate that the RTA curves are controlled by the friction and fluctuation coefficients, mobility, storage ratio, region radius, and cave storage constant. The friction and fluctuation coefficients influence the depth of first concave, while the storage ratio, region radius, and cave storage constant dominate the middle flow period, and the mobility has an impact on the boundary dominated flow regime. Finally, the application of proposed model on a field well from Shunbei Oilfield, western China is presented to calibrate its accuracy and reliability.

    Experimental and numerical investigations of particle plugging in fracture-vuggy reservoir: A case study

    Zhu BaiyuTang HongmingYin Senlin
    16页
    查看更多>>摘要: Fracture-vuggy reservoirs commonly occur in carbonate rock and volcanic rock, leading to a significant loss of circulation. With both vugs and fractures, a fracture-vuggy reservoir is somewhat different from a fracture reservoir in pore structure and the plugging mechanism of particle materials. Based on the visualization model of a microfluidic chip and CFD-DEM numerical simulation, a set of methods was established to evaluate the effect of particle plugging in a fracture-vuggy reservoir. First, the influence of vugs on the particle bridging mechanism in the fracture-vuggy reservoir was analyzed using CFD-DEM numerical simulation. The results showed that vugs aggravated particle retention and reduced plugging efficiency. The particle plugging of the fracture-vuggy reservoir and fracture reservoir were compared through microfluidic experiments. This study provides a new evaluation method for characterizing particle plugging near a wellbore, and provides an intuitive understanding of the plugging mechanism of a fracture-vuggy reservoir.

    A comprehensive review on the significant tools of asphaltene investigation. Analysis and characterization techniques and computational methods

    Masoumeh HassanzadehMajid Abdouss
    13页
    查看更多>>摘要: After years of research into the heavy components of crude oil, asphaltenes are still one of the most complex and unknown organic molecules. During these years, asphaltene has been the subject of research by chemists, chemical engineers, petroleum engineers, materials engineers and other sciences from various angles. Abstract of research on asphaltenes is a decoding of their molecular structures which is the key to solving the puzzle of predicting the specific properties of asphaltenes, such as self-association, deposition, and surface activity in crude oil. In this regard, a variety of laboratory techniques have been used to identify asphaltenes in the field of the molecular weight, chemical structure, architecture and physico-chemical properties such as MASS, UV-VIS, NMR, EPR, ESR, FL, IR, RA, XPS, UL, XRD, SAS, GC, AFM, STM, TEM and etc. In parallel with molecular characterization research, engineers in this field have made great efforts to predict the properties of asphaltenes to prevent the economic damage caused by the deposition and formation of w/o emulsions in the producdon cycle (Oil well reservoir, production, transmission, storage, refinery, etc.). Numerous modeling and simulation methods have been used to investigate these topics. In this article, a comprehensive review of laboratory techniques for the identification of asphaltene molecules with a brief introduction of these techniques and the most popular and most practical computational models for predicting the properties of asphaltene based on Solubility theory and colloidal theory Has been introduced. Also Recent molecular simulation methods for the study of asphaltenes, such as Monte Carlo and especially molecular dynamics (MD) and useful tools for the study of asphaltene have been reviewed.

    Displacement flow of yield stress materials in annular spaces of variable cross section

    Pedro J. Tobar EspinozaPriscilla R. VargesElias C. Rodrigues
    16页
    查看更多>>摘要: We conducted an experimental study of a yield stress material being displaced upwardly at controlled flow rate by a Newtonian fluid in an annular space whose external wall consists of a sudden expansion-contraction. This system is a simplified representation of the primary cementing process of an oil well, whose bore diameter may present variations. In the experiments, different pairs of fluids were employed. The yield stress materials were Carbopol aqueous solutions at three different weight concentrations, with Herschel-Bulkley viscosity behavior. The Newtonian liquid was a glycerin/water mixture. A wide range of flow rates were explored, varying the dimensionless cavity depth and cavity axial length. A non-monotonic behavior is observed for the dimensionless volume of yield stress material displaced from the cavity by the Newtonian fluid flow. In addition, the Theological properties and geometrical parameters were seen to have a strong influence on the displaced volume.

    Simulation of the deasphalting process of crude oils: Models development and extraction conditions analysis

    Igor De Las HerasJavier DufourBaudilio Coto
    9页
    查看更多>>摘要: Heavy crude oils are under constant investigation due to light oil exhaustion. So, its use is compulsory to meet the world energy demand. Heavy crude oils present several drawbacks as high content of metals, heteroatoms, and asphaltenes, and, therefore, upgrading processes are becoming essential. A deasphalting process, conventionally used for vacuum residue upgrading, can be an interesting pretreatment to eliminate the heavier phases and ease the crude processing in conventional refining facilities. Most of the models developed for deasphalting simulation show problems to be implemented in simulation software packages. In this work, a versatile deasphalting simulation method is developed, composed by the definition of a synthetic crude oil model, formed by discrete pseudo components, and a deasphalting model approaching the process to a liquid-liquid extraction based on the thermodynamic model modified UNIFAC (Dortmund). Both models were satisfactorily validated. The deasphalting method was used to explore the solvent/crude ratio, extraction temperatures, and alternative solvents in substitution of conventional light paraffins. Higher extraction temperatures did not enhance remarkably the deasphalting process and the optimum solvent to crude ratio depends on the solvent type. Alcohols were found as promising compounds as their use is recommended by some studies and they showed great deasphalting results.

    Sensitivity analysis of factors controlling the cement hot spot temperature and the corresponding well depth using a combined CFD simulation and machine learning approach

    Rui WangErgun KuruYifei Yan
    12页
    查看更多>>摘要: Designing a suitable cement system has been a challenging task in high pressure-high temperature wells (e.g., deep oil and gas wells, geothermal wells). Bottom hole circulating temperature (BHCT) is commonly used as the key operating variable in the cement design. However, it has been shown that cement formulations based on the BHCT failed to meet field requirements in many cases (especially in deep wells or geothermal wells). In reality, the temperature of the hot spot, where the highest temperature occurs in a well during the circulation, should be used as the setting temperature criteria for proper cement slurry formulation. However, as there are multiple factors affecting the hot spot temperature and its corresponding depth, it is not a simple task to determine these design parameters. To overcome these design challenges and facilitate optimization of the cement system formulation for the deep, hot wells, a new systematic approach has been developed by coupling a machine learning and a computational fluid dynamics (CFD) simulation technique. In this study, we investigated the effects of the five common design variables (i.e., wellbore depth, geothermal gradient, casing size, hole size and flow rate) on the hot spot temperature and the corresponding depth. Data extracted from the simulation study results were used to train multiple linear regression models, which were developed as part of using machine learning approach for comparing the influences of these five factors on the hot spot temperature and the corresponding depth. The results indicate that increasing casing size (OD), geothermal gradient and the well depth also increased the hot spot temperature and its corresponding depth, while the increasing flow rate and the wellbore size caused reduction in the hot spot temperature and its corresponding depth. Casing size and the cement circulation rate seemed to have the greatest impact. Results also indicated that the effects of these factors on the hot spot temperature and its corresponding depth were synchronized. With the increasing wellbore to casing diameter (i.e., do/di) ratio, both the hot spot temperature and its corresponding depth decreased (i.e., lower maximum cement temperature was observed at the shallower depth). The new numerical method is proven to be a realistic and reliable approach for comparing the influences of different factors on the hot spot temperature and the corresponding depth. Practical guidelines developed from the results of this study can be used for improved cement job design in field applications.