فهرست مطالب

Oil & Gas Science and Technology - Volume:8 Issue: 4, Autumn 2019
  • Volume:8 Issue: 4, Autumn 2019
  • تاریخ انتشار: 1398/07/09
  • تعداد عناوین: 7
  • Majid Alipour *, Bahram Alizadeh, Scott Ramos, Behzad Khani, Shohreh Mirzaie Pages 1-17
    Chemometric methods can enhance geochemical interpretations, especially when working with large datasets. With this aim, exploratory hierarchical cluster analysis (HCA) and principal component analysis (PCA) methods are used herein to study the bulk pyrolysis parameters of 534 samples from the Persian Gulf basin. These methods are powerful techniques for identifying the patterns of variations in multivariate datasets and reducing their dimensionality. By adopting a “divide-and-conquer” approach, the existing dataset could be separated into sample groupings at family and subfamily levels. The geochemical characteristics of each category were defined based on loadings and scores plots. This procedure greatly assisted the identification of key source rock levels in the stratigraphic column of the study area and highlighted the future research needs for source rock analysis in the Persian Gulf basin.
    Keywords: Chemometric Classification, Source Rock Geochemistry, Rock-Eval Pyrolysis Data, HCA, PCA
  • Ahmed Zoeir, Mohammad Chahardowli *, Mohammad Simjoo Pages 18-34

    Fractured carbonate reservoirs account for 25% of world’s total oil resources and for 90% of Iranian oil reserves. Since calcite and dolomite minerals are oil wet, gas oil gravity drainage (GOGD) is known as the most influencing production mechanism. The most important issue within gas injection into fractured media is the channeling problem which makes the efficiency of gas injection process extremely low. As a solution, foam is used to change the mobility ratio, to increase volumetric sweep efficiency, and to overcome the fingering problem. In this work, we inspected three main influencing mechanisms that affect oil extraction from matrix, namely foam/oil gravity drainage, viscous pressure drop  due to foam flow in fractures, and foaming agent diffusion from fractures into the matrixes. Foam injection simulations were performed using CMG STARS 2015, on a single matrix unit model and on some vertical cross section models. A number of sensitivity analyses were performed on foam strength, injection rate, fracture and matrix properties, matrix heights, and the initial oil saturation within matrixes. The results show that the roles of the mass transfer of the foaming agent and viscous pressure drop  are significant, especially when matrix average heights are small. Moreover, the mechanism for viscous pressure drop  remains unchanged, which continues to aid oil extraction from matrixes while the other two mechanisms weaken with time.

    Keywords: Foam, Fractured Reservoir, Gravity Drainage, Gas Invaded Zone, CMG STARS
  • Ali Nemati Kharat *, Ali Akbar Ghaffari Pages 35-49
    The aim of this research was to produce a convenient additive for enhancing the properties, especially the fluid loss, of oil well cement slurries. In this regard, a variety of drilling/cementing chemical additives known as fluid loss controllers were prepared through derivatization and chemical modification of lignite. Lignite-based graft copolymers were synthesized using different groups of acrylic monomers via aqueous the free radical polymerization method. Then, it was allowed to react with sulfomethylating agents to enhance its water solubility. Subsequently, a comparative sulfomethylated lignite was prepared and employed as the backbone in the free radical polymerization. ATR-FTIR and elemental analyses were performed to demonstrate the structures of the fluid loss controller and incorporated elements. The performance of these additives in improving the properties of oil well cement slurries was investigated through analyzing the quality of fluid loss controller in saline saturated slurries. Under similar desired well conditions, i.e. a compressive strength of 800-1100 psi, a thickening time of 400 minutes, and a viscosity of 25 cP, a fluid loss below 130 ml API was obtained. The best standard performance was assigned to the cement slurry which employed sulfomethylated lignite graft copolymer.
    Keywords: Lignite, Sulfomethylation, Graft Copolymers, cement slurry, Fluid Loss Controller
  • Naser Akhlaghi, Siavash Riahi * Pages 50-63
    One of the tertiary methods for enhanced oil recovery (EOR) is the injection of chemicals into oil reservoirs, and surface active agents (surfactants) are among the most used chemicals. Surfactants lead to increased oil production by decreasing interfacial tension (IFT) between oil and the injected water and to the wettability alteration of the oil reservoir rock. Since surfactants are predominantly expensive materials, it is required to consider an appropriate and high-performance plan for project economics when they are injected into oil reservoirs. One of the operational issues in surfactant flooding is the critical micelle concentration (CMC), which is usually achieved by the injection of surfactant at concentrations higher than CMC. Therefore, the lower the CMC is, the lower the amount of the material needed to be injected into the reservoir becomes, so it will help to economize the project. The salinity of the aqueous phase is a factor affecting the CMC, and with its optimal design, it can reduce the CMC. In this study, the variations of Triton X-100 CMC’s as a nonionic surfactant were measured by altering the concentration of three salts with divalent ions (CaCl2, MgCl2, and Na2SO4) and a single-capacity ion salt (NaCl), as the predominant salts in the porous medium of oil reservoirs, using surface tension (ST) method at ambient temperature and pressure. Each of these salts was dissolved at three concentrations of 0.1, 0.5, and 1 wt.% in distilled water containing specific concentrations of surfactant, and the surfactant CMC in the presence of these salt concentrations was measured. The results showed that increasing the concentration of each salt resulted in a decrease in the CMC, and, in the studied salts, NaCl produced the lowest CMC.
    Keywords: CMC, Triton X-100, Salinity, Surface tension, Micelle, EOR
  • Gholamreza Roohollahi, Mohammadreza Ehsani * Pages 64-84
    Several mesoporous nickel-based catalysts with MgO-Al2O3 as the catalyst support were prepared using a co-precipitation method at a constant pH. The supports were prepared from the decomposition of an Mg-Al hydrotalcite-like structure which had already been prepared with Mg/Al=1. Prior to impregnating 10 wt.% nickel on the supports, the precursor was decomposed at several temperatures of 500, 600, 700, and 800 °C in order to elucidate the effect of calcination temperature on the physical and chemical characteristics of Mg-Al mixed oxides and the ultimate catalytic performance of the synthesized catalysts in the combined steam and dry reforming (CSDRM). The catalyst the precursor of which was calcined at 700 °C shows an excellent nickel dispersion and the highest activity among the other samples. It also exhibits the most stable performance during the long-term 36-hour run with high resistance against coke formation in the harsh condition of CSDRM.
    Keywords: Combined Steam, Dry Reforming, MgO-Al2O3, Mesoporous, Hydrotalcite-derived Catalysts
  • Mohsen Keshavarz, Ahad Ghaemi *, Mansour Shirvani, Ebrahim Arab Pages 85-105
    In this work, the dispersed phase holdup in a Kühni extraction column is predicted using intelligent methods and a new empirical correlation. Intelligent techniques, including multilayer perceptron and radial basis functions network are used in the prediction of the dispersed phase holdup. To design the network structure and train and test the networks, 174 sets of experimental data are used. The effects of rotor speed and the flow rates of the dispersed and continuous phases on the dispersed phase holdup are experimentally investigated, and then the artificial neural networks are designed. Performance evaluation criteria consisting of R2, RMSE, and AARE are used for the models. The RBF method with R2, RMSE, and AARE respectively equal to 0.9992, 0.0012, and 0.9795 is the best model. The results show that the RBF method well matches the experimental data with the lowest absolute percentage error (2.1917%). The rotor speed has the most significant effect on the dispersed phase holdup comparing to the flow rates of the continuous and dispersed phases.
    Keywords: Solvent extraction, Kühni Extraction Column, Dispersed Phase Holdup, Multilayer Perceptron, radial basis function
  • Mehdi Mahmoodi, Mofid Gorji Bandpy * Pages 106-121
    When a natural gas pipeline ruptures, the adjacent upstream and downstream automatic control valves (ACV) should close quickly to prevent leakage or explosion. The differential pressure set point (DPS) at each valve location is the main criteria for value setting in ACV actions. If the DPS is not properly adjusted, the ACV may mistakenly close or it may not take any actions at a proper time. In this study, the effect of characteristic parameters such as pipeline operational pressure (POP) and pipeline pressure drop rate (ROD) due to rupture or a major leak was experimentally investigated on DPS. 25 different conditions with the double set of the mentioned typical characteristic parameters were chosen. In each condition, the differential pressure (DP) was measured over a period of 180 s by statistically analyzing the experimental results, so 25 maximum DP values (DPSs) were obtained. The DPS rises by an increase in ROD or a decrease in POP. Because of using nitrogen gas instead of natural gas for safety reasons and the uncertainties, the DPS results can be practically applied by adding a safety factor of 15%. Finally, the diagram of DPS with respect to ROD and that of non-dimensional DPS (DOP) versus non-dimensional ROD (RTP) were provided for different POP’s.
    Keywords: Automatic Control Valve, Gas Pipelines, Operating Pressure, Pressure Drop Rate