فهرست مطالب

Chemical and Petroleum Engineering - Volume:46 Issue: 1, 2012
  • Volume:46 Issue: 1, 2012
  • تاریخ انتشار: 1391/07/18
  • تعداد عناوین: 6
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  • Arezoo Sadat Emrani, Mohammad Saber, Fatola Farhadi Pages 1-11
    In this paper, modeling and optimization of Fischer-Tropsch Synthesis is considered in a fixed-bed catalytic reactor using an industrial Fe-Cu-K catalyst. A one dimensional pseudo-homogenous plug flow model without axial dispersion is developed for converting syngas to heavy hydrocarbons. The effects of temperature, pressure, H2 to CO ratio in feed stream, and CO molar flow on the mass flow rate of the desired product (C5+) are investigated. Since the Fischer-Tropsch synthesis produces a wide range of hydrocarbon products, it is important to optimize the reactor operating parameters and feed conditions to maximize yield of reactor. Genetic algorithm was used as the optimization algorithm in this study. The processing variables are defined in the following ranges: Temperature: 493-542 K, Pressure: 10.9-30.9 bar, CO molar flow: 0.0815-0.3074 gmole/s and the H2/CO feed ratio: 0.98-2.99. A reactor model was developed and along with appropriate reaction kinetics, the performance of the reactor was investigated. Model results were in good agreement with experimental data. After validating the model, the production of C5+ was optimized. The results indicated that the production of C5+ increased with increasing pressure while it decreased with increasing temperature, H2/CO ratio, and CO molar flow rate in the feed stream.
    Keywords: Fischer, Tropsch synthesis, Fixed, bed reactor, Genetic algorithm, Modeling, Optimization
  • Hossein Fazeli, Reza Fathi, Abbas Atashdehghan Pages 13-29
    In oil industry, spontaneous imbibition is an important phenomenon in recovery from fractured reservoirs which can be defined as spontaneous uptake of a wetting fluid into a porous solid. Spontaneous imbibition involves both cocurrent and countercurrent flows. When a matrix block is partially covered by water, oil recovery is dominated by cocurrent imbibition i.e. the production of non wetting phase has the same direction of flow as the wetting phase. However if the matrix block is completely covered by water then countercurrent flow takes place, and the production of non wetting phase has an opposite direction of flow to that of the imbibing wetting phase. Each of these processes can be described by a nonlinear partial differential equation (PDE). In this paper, the homotopy perturbation method (HPM) which is a powerful series-based analytical tool, is used to approximate the solutions of cocurrent and countercurrent equations. HPM decomposes a complex partial differential equation under study to a series of simple ordinary differential equations that are easy to be solved. The solutions obtained by HPM are compared with that found using a common numerical method applied by MATLAB software. The difference between the two is seemed to be virtually negligible. A good agreement is also achieved from the comparison of the solutions obtained by HPM with those of a numerical method (NM).
    Keywords: Fracture porous media, Homotopy perturbation method (HPM), Cocurrent imbibition, Countercurrent imbibition, Spontaneous imbibition
  • Jaber Taherishakib, Hossein Jalalifar, Mansour Fatehirad Pages 31-39
    The main task of drilling the formation by the bit is done via scraping, crushing and grinding. Discharging the fluid from the bit nozzles is done with high pressure which assists to break the rocks. Different parameters affect the bit selection and design for each drilling formation, but the most important one is drillability that depends on hardness of the formation. In this paper, the design of continuous gauge near-bit stabilizer and a novel drill bit design was evaluated by optimizing the hydraulics and gauge geometry. It was found that the design is appropriate for the Aghajari and Mishan formations as the drilling efficiency could be increased. Moreover, some problems of drilling in this formation such as bit balling and high wearing were largely reduced by the presented model.
    Keywords: Bit, Drilling, Failure, Gauge, Hydraulic, Soft formation
  • Monir Taherkhani, Peyman Pourafshary Pages 41-52
    Diffusivity equation commonly used for pressure distribution prediction in porous media results from substituting equation of state and continuity equation in Navier-Stokes momentum equation. From mathematical point of view this equation format shows infinite propagation speed for pressure pulse through porous media, which is physically impossible. This issue may caused by numerous assumptions that has been implemented for developing diffusivity equation. However, if we omit two main assumptions of steady state condition and constant velocity and consider linear approximation for velocity field, the pressure propagation differential equation would be hyperbolic which is called Telegraph Equation. The propagation speed is limited for this equation. In this work, these equations are compared in prediction of pressure pulse propagation in Cartesian coordination with different parameters. The results show that the telegraph equation has minor correction in some cases as: far distances from pressure pulse source, when the fluid has high viscosity and for the rocks with low porosity and permeability; so considering common parameters in hydrocarbon reservoirs, the diffusivity equation has sufficient accuracy for reservoir engineering applications.
    Keywords: Diffusivity equation, Darcy equation, Pressure distribution equation, Porous media, Telegraph equation
  • Mohammad Hosein Zareenejad, Azim Kalantari Asl, Hamid Reza Nasriani Pages 53-62
    Decline curve analysis has some advantages over transient well test analysis in which it is not required to shut-in the well and also wellbore storage effects do not exist. Few studies have been done on decline curve analysis of naturally fractured reservoirs but there are even some limitations with available models. On the other hand well test could be expensive and in some operational conditions shutting the well to obtain reservoir parameters is almost impossible. Therefore, investigating the applicability of homogenous reservoir decline models for production data analysis of naturally fractured reservoirs is necessary. In this paper the most important decline models have been used to evaluate reservoir parameters in three Iranian naturally fractured reservoirs and the results have been compared to transient well test analysis. A useful and applicable procedure is also introduced to correct the initial production data when they do not have necessary conditions. The results show that Agarwal-Gardner and Blasingame type curves predict acceptable values for permeability compared to transient well test analysis while Fetkovich type curve cannot predict accurate values. Determined skin values in all wells of the three studied reservoirs are negative. Negative values can be considered to be affected by existing fracture networks in the vicinity of producing wells and also periodic well stimulations. The results also show that Neglecting produced condensates of gas condensate reservoirs with Liquid-Gas Ratio (LGR) less than 100 bbl/MMscf cannot significantly affect decline curve analysis results.
    Keywords: Decline curve analysis, Naturally fractured reservoir, Permeability, Skin factor, Type curve
  • Hamid Sharifi G., Kazem Saadat, Ezatallah Kazemzadeh, Hassan Mahmoudian Pages 63-72
    Application of Archie equation in carbonate reservoirs is not easy due to high dependence of its parameters on carbonate characteristics. Carbonates are very heterogeneous in nature and hydrocarbon reserve estimation in these reservoirs of mostly oil-wet and intermediate-wet is highly influenced by the input values of saturation exponent. To our knowledge, non representative oils have been used in most saturation exponent measurements and not many cases have used live oil for carbonate cores at full reservoir conditions. Performing these experiments at laboratory conditions which differs from reservoir ones would not yield reliable results. The main effort of this study was to properly measure saturation exponent on some carbonate core plugs of an Iranian reservoir at reservoir conditions using live oil by porous plate technique. Resistivity index and capillary pressure by drainage process on some plugs from pay-zone and resistivity index by imbibition process on some plugs from near and within transition zone of studied reservoir were measured. Regression fits by using Archie equation were not satisfying. Hence, the regressions were also obtained without taking into account the origin point which insisted the use of a “b” (saturation distribution) factor in the Archie equation.
    Keywords: Archie equation, Drainage, Imbibition, Resistivity index, Saturation exponent