An Engineering Approach to the Treatment of Constant Pressure Boundary Condition in Block-Centered Grid in Reservoir Simulation

Abstract

Block-centered grid and point-distributed grid are the most widely used grids to describe a petroleum reservoir as units in reservoir simulation. In the point-distributed grid, the boundary grid point falls on the boundary, whereas the point that represents the boundary grid block is half a block away from the boundary. As a result, the point-distributed grid gives accurate representation of constant pressure boundary condition. In the block-centered grid, the approximation of a constant pressure boundary is implemented by assuming the boundary pressure being displaced half a block coincides with the point that represents the boundary grid block and by assigning boundary pressure to boundary grid block pressure. This is a first-order approximation. A second-order approximation was suggested, but it has not been used because it requires the addition of an extra equation for each reservoir boundary of a boundary grid block. Furthermore, the extra equations do not have the form of a flow equation.

This article presents an engineering approach for the representation of a constant pressure boundary condition in a block-centered grid. The new approach involves adding a fictitious well term per boundary to the flow equation of a boundary grid block. This treatment is valid in both rectangular and radial-cylindrical grids. The flow toward a fictitious well is linear in rectangular coordinates and radial in radial-cylindrical coordinates. The flow rate equations for fictitious wells were derived from the inter-block flow rate term between a boundary grid block and the grid block that falls immediately outside reservoir boundary. These flow rate equations are presented and tested. With the new treatment, both block-centered grid and point-distributed grid produce pressure profiles with comparable accuracy. In other words, the use of the point-distributed grid does not offer any advantage over the block-centered grid in rectangular and radial-cylindrical coordinates for the case of constant pressure boundaries.     

Reducing Dangerous Effects of Unsymmetrical Dimethylhydrazine as a Liquid Propellant by Addition of Hydroxyethylhydrazine—Part I: Physical Properties

In this work, the effect of low volatile hydroxyethylhydrazine (HEH) as a solute on unsymmetrical dimethylhydrazine (UDMH) has been studied in order to reduce harmful effects of UDMH vapors. Desirable physical properties of binary mixtures UDMH/HEH have been measured and compared to pure UDMH. These properties include boiling point, viscosity, density, and vapor pressure that are important for using binary mixtures of UDMH/HEH as less dangerous liquid propellants. Due to the formation of strong hydrogen bonding between UDMH and HEH, the volatility of UDMH has been reduced appreciably upon the addition of HEH. It is indicated that the measured physical properties may deviate significantly compared to corresponding predicted values. Binary mixtures of UDMH/HEH can also react spontaneously in contact with nitrogen tetroxide (NTO) and red fuming nitric acid (RFNA), so they can be called hypergolic propellants.     

ALUMINA SUPPORTED Co-Mo OXIDES AS A CATALYST FOR HYDRODESULPHYRISATION OF ORGANIC SULFIDES AND DISULPHIDES (PART-I) USING STOPPED FLOW GAS CHROMATOGRAPHY

ABSTRACT

A model study on the hydrodesulphurization of dimethyl sulphide, di n-prophyl sulphide, di n-butyl sulphide and dimethyl disulphide on Co-Mo-A1₂O₃ surface was conducted using stopped-flow chromatographic technique. The plots for the rates of hydrocarbon formation agreed well with the first order reaction at the surface of the catalyst.

Activation energies for the hydrodesulphurization of (C₂H₅)₂S, (C₃H₇)₂S, n-(C₄H₉)₂S and (CH₃)₂S₂ are 57.55, 70.67, 72.74 and 37.80 Kj mole^?1 respectively.     

RAPID PYROLYSIS OF EASTERN CANADIAN COALS BY FREE FALL REACTORS

Abstract

The effect of temperature was investigated on the rapid pyrolysis of Prince, Lingan and No. 26 coals in the temperature range of 525^° to 750^°C using a 600 cm high stainless-steel free fall reactor at atmospheric pressure.

The yields of char, condensibles and gaseous products were determined at 25^°C intervals. Gaseous products were analysed for H₂, CO, CO₂, CH₄ and C₂+.

Volatile product (condensible and gas) yields exceeded the volatile product in the A.S.T.M. methods at and above 700^°C.

Some experiments using Prince coal were repeated at reduced pressure (50 mm mercury) in both the 600 cm height stainless-steel and a 140 cm height quartz reactor in order to find out the effect of pressure and retention time.

The experimental results indicated that the condensable yield was higher at the lower pressure and at the shorter retention time. The effect of retention time was far more pronounced.     

Performance and thermo-economic assessments of geothermal district heating system: A case study in Afyon,Turkey

In this study energy, exergy and exergoeconomic analysis of the Afyon geothermal district heating system (AGDHS) in Afyon, Turkey is performed through thermodynamic performances and thermo-economic assessments. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, exergy losses and loss cost rates. Energy and exergy losses throughout the AGDHS are quantified and illustrated in the flow diagram. The energy and exergy efficiencies of the overall system are found to be 37.59% and 47.54%, respectively. The largest exergy loss occurs in the heat exchangers with 14.59% and then in the reinjection wells with 14.09%. Besides, thermo-economic evaluations of the AGDHS are given in table. Energy and exergy loss rates for the AGDHS are estimated to be 5.36 kW/$ and 0.2  kW/$, respectively.     

Highly reflective coatings for interior and exterior steel cladding and the energy efficiency of buildings

The effect of surface heat-radiation properties of coil-coated steel cladding material on the energy efficiency of buildings in Nordic climate is addressed by parallel temperature and energy usage measurements in a series of test cabins with different exterior solar reflectivity and interior thermal reflectivity. During one year, a number of one- or two-week experiments with air conditioner cooling and electrical floor heating were made while logging air-, radiation- and surface temperatures, energy consumption and weather conditions. Measurements show significant energy savings in the test cabins by the use of high thermal reflectivity interior surfaces both during heating and cooling and a strongly reduced cooling demand by the use of high solar reflectivity exterior surfaces. Results are interpreted within the context of a steady-state energy flux model, to illuminate the importance of surface resistance properties (radiation and convective heat dissipation).     

An investigation on renewable energy education at the university level in Turkey

In the present study, to discover how teaching of renewable energy sources in Turkey is carried out at the university level, a questionnaire was developed and applied at different universities in Turkey. The analyses conducted on the data obtained from the questionnaire revealed that education about geothermal, solar and wind energy is given at master’s level, other renewable energy sources are taught at the undergraduate level within the curriculum of some engineering courses. The teaching performed about renewable energy sources is in Turkish and at encyclopedic level. As preparing and obtaining the required materials are costly, some problems are encountered in the teaching of renewable sources. In Turkish universities, no degree about renewable energy sources is granted. Hence, the country must make use of the people having engineering degree to capitalize on its renewable energy sources. As there is no program specializing on providing training about the renewable energy sources, it seems to be difficult to find experts about this issue. The current state of renewable energy sources education seems to be inadequate and it should be expanded and strengthened.     

Biodiesel from mutton fat using KOH impregnated MgO as heterogeneous catalysts

The use of MgO impregnated with KOH as heterogeneous catalysts for the transesterification of mutton fat with methanol has been evaluated. The mutton fat (fat) with methanol (1:22 M ratio) at 65 °C showed > 98% conversion to biodiesel with 4 wt% of MgO–KOH-20¹ (MgO impregnated with 20 wt% of KOH) in 20 min. The reaction conditions optimized were; the amount of KOH impregnation (5–20 wt%), the amount of catalyst (1.5–4 wt%, catalyst/fat), the reaction temperature (45–65 °C), fat to methanol molar ratio (1:11–1:22) and the effect of addition of water/oleic acid/palmitic acid (upto 1 wt%). Although, transesterification of fresh fat (moisture content 0.02 wt% and free fatty acids 0.002 wt%) with methanol in the presence of KOH (homogenous catalyst) resulted in the complete conversion to biodiesel, but in the presence of additional 1 wt% of either free fatty acid or moisture content, formation of soap was observed. The MgO–KOH-20 catalyst was found to tolerate additional 1 wt% of either the moisture or FFAs in the fat.     

PETROLEUM GEOLOGY AND HYDROCARBON POTENTIAL OF THE GUBAN BASIN,NORTHERN SOMALILAND

The Guban Basin is a NW‐SE trending Mesozoic‐Tertiary rift basin located in northern Somaliland (NW Somalia) at the southern coast of the Gulf of Aden. Only seven exploration wells have been drilled in the basin, making it one of the least explored basins in the Horn of Africa – southern Arabia region. Most of these wells encountered source, reservoir and seal rocks. However, the wells were based on poorly understood subsurface geology and were located in complex structural areas. The Guban Basin is composed of a series of on‐ and offshore sub‐basins which cover areas of 100s to 1000s of sq. km and which contain more than 3000 m of sedimentary section. Seismic, gravity, well, outcrop and geochemical data are used in this study to investigate the petroleum systems in the basin. The basin contains mature source rocks with adequate levels of organic carbon together with a variety of reservoir rocks. The principal exploration play is the Mesozoic petroleum system with mature source rocks (Upper Jurassic Gahodleh and Daghani shales) and reservoirs of Upper Jurassic to Miocene age. Maturity data suggest that maximum maturity was achieved prior to Oligocene rift‐associated uplift and unroofing. Renewed charge may have commenced during post‐ Oligocene‐Miocene rifting as a result of the increased heat flows and the increased depth of burial of the Upper Jurassic source rocks in localised depocentres. The syn‐rift Oligocene‐Miocene acts as a secondary objective owing to its low maturity except possibly in localised offshore sub‐basins. Seals include various shale intervals some of which are also source rocks, and the Lower Eocene evaporites of the Taleh Anhydrite constitute an effective regional seal. Traps are provided by drag and rollover anticlines associated with tilted fault blocks. However, basaltic volcanism and trap breaching as a consequence of the Afar plume and Oligocene‐Miocene rifting of the Gulf of Aden cause considerable exploration risk in the Guban Basin.     

APPLICATION OF MULTICOLUMN VALVE SWITCHING GAS CHROMATOGRAPHY FOR THE ANALYSIS OF NAPHTHA AND KEROSENE FRACTIONS OF SAUDI ARABIAN LIGHT CRUDE OIL

The straight run naphtha and kerosene fractions of Saudi Arabian Light crude oil were analyzed for paraffins, olefins, naphthenes and aromatics (PONA) using a gas chromatographic technique. This method is based upon group type separation according to carbon numbers using a programmed multiple valve switching sequence and employing multicolumn approach. The chromatographic operating conditions and carrier gas flow rates were selected to determine PONA contents of naphtha and kerosene fractions. These straight run fractions were produced by an automatic true boiling point (TBP) apparatus. Boiling range distributions of these fractions were determined using a standard ASTM method of simulated distillation. PONA results were compared with the literature. Total paraffins, naphthenes and aromatics agreed with each other.