مجله پژوهش نفت
پیاپی 56 (پاییز و زمستان 1386)

Nowadays, numerous studies are carried out to convert natural gas into valuable products, such as syngas method. In this study, a syngas production pilot plant was designed and produced to study the process, reaction and catalyst optimization/performance and technology development which will be discussed in full. Various techniques including modeling and simulation were applied and commercial data were employed to design the process. In order to control system performance; an advanced PLC system equipped with proper softwares of reading, controlling and recording data was used. 

Lower diamondoids, methyl and ethyl derivatives are commonly present in gas condensation reactions. In this study, all samples were collected from Gonbadly, Shourijeh, Mozdooran (North-East) gas fields. Column  chromatography and urea adduction techniques were applied for clean up. Also a precise GC/MS instrument was used for separation and identificaton of lower diamondoids. The identified lower diamondoids and their  derivates were compared in terms of mass spectra, retention times and mass chromatograms. The concentration of lower diamondoids was quantified and calculated within the range of 0.07-4.85 mg/l.

Estimation of the applied stress is the main factor in designing transmission pipelines. Since the anchor is subject to different loads, controlling the intensity of stress is very significant. In this study, the axial loading of transmission pipelines has been studied in terms of operating pressure, temperature and other conditions. Finally an analysis and design has been presented for the anchor block to balance these loads. The anchor block system is the key factor in this regard. This study presents a method to design and analyze planar anchors. Using plate theory and finite element analysis; properties and dimension of anchor flange were also determined according to pipeline diameter and the applied loads.

The gravitational drainage of oil in gas-invaded zone is identified as the major production mechanism in carbonate reservoirs. Oil is kept in a matrix block surrounded by gas and then subject to two distinct and opposing forces. Due to the difference between oil and gas densities, gravitational forces tend to expel oil through the lower part of the block, while oil-rock adhesive force acts to peneterate within the rock. Drainage arises when “gravitational” and “capillary” forces coincide. In this study, the mathematical modelling of gravitational drainage in naturally fractured reservoir is presented which involve capillary, gravitational, and infiltration processes. A simple approach was proposed to simulate gas-oil gravity drainage process in fractured porous media using an appropriate fracture capillary pressure. The permeability value is approximated by the location of fracture in the stack block. The capillary pressure in horizontal fracture is related to height of fracture in stack block to gas-oil interface. Numerical simulation results revealed good agreement with experimental data. This study revealed that capillary continuity and fracture transmissibility are the most important factors in oil recovery by gravitational drinage mechanism.

Fluid behavior is very important in reservoir engineering regarding process design and field management and plays a key role in predicting hydrocarbon reservoir performance simulations. Dissolution of gas in oil may be the result of gas injection at pressures above the saturation pressure of a given oil provided that the system (gas-oil) is given enough time to reach equilibrium conditions. Gas injection into an under-saturated oil reservoir is a typical situation in which both gas dissolution and oil swelling are observed. Since the dynamic behavior of a reservoir under such a process can only be simulated using compositional reservoir model. Therefore oil swelling test should be carried out. The result of this test along with other PVT data were used to propose an equation of state (EOS). Due to precision of laboratorial procedures and also the hysteresis effect; a certain percentage of errors were inevitable. This study was done by applying an EOS to simulate oil-gas PVT changes.

Compact heat exchangers have a significant impact on energy transfer and therefore optimization of heat exchangers increases the efficiency of thermal energy transfer and gas cooling degrees. Such heat exchangers are also cost-effective. Condenser and evaporator of refrigeration vapor compression cycles supplied with R-134 are both compact heat exchangers which play a significant role. In this study, the compact heat exchangers were investigated in terms of thermal efficiency. Laminated evaporator and parallel flow condenser (as the most important types of compact heat exchangers), were designed for refrigeration cycle. The formulation was based on effectiveness method and a computer analysis was carried out for optimization. Also a model was presented for the whole refrigeration cycle. Finally results were compared to experimented data and revealed a very good agreement.

In this study, problems concerned with kinetic experiments of intrinsic rates in heterogeneous catalytic reactions were first discussed and then a software was designed to facilitate the design of kinetic experiments, estimation of kinetic parameters and discrimination among competing kinetic models. Suitable selection of a kinetic model is essential in reactor designing, scale-up, material selection and minimizing the capital expenditures. The software designed in this study, consists a database that offers various information such as: process information, process flow diagrams, commercial catalysts used in industrial processes, the major manufactures, type of reactors, etc. The kinetic parameters are estimated using a non-linear regression algorithm and discrimination among rival models was done using statistical data of Bartlett’s χ2 test.

The main part of oil produced in Middle East is supplied from carbonate reservoirs, the majority of which are fractured ones. These reservoirs produce higher rates at their early ages which is followed by lower rates   afterwards, leading to low overall recovery values. The purpose of most drillings is to increase production over longer periods. A reservoir simulation study was carried out on a fractured Middle Eastern carbonate field to determine the optimal production strategy. The three possible methods - natural depletion, gas injection and water injection- were then compared. Results indicated that water injection exhibits better recovery values than gas injection and natural depletion. This is expected since rock exhibits intermediate oil-wetting values, meaning that higher recoveries are achieved due to water flooding. The presence of fractured rocks led to early breakthrough and lower recoveries in gas injection method. The different physical mechanisms affecting oil recovery values are discussed and a few suggestion were presented for other fields possessing the same fracture properties and wet-abilities.

Changes of Strontium isotopic ratios (87Sr/86Sr) of oceanic waters are not detectable, since they occur over millions of years. Strontium exists in calcareous shell of marine organisms. 87Sr/86Sr ratio of oceanic waters at different geologic times can be estimated by calcuting this value in calcareous shells of living organisms. Similar to conventional techniques, age correlation can be based on 87Sr/86Sr changes. By applying this study method, geologists, paleontologists and oceanographists have been able to clarify many ambiguities. In this study, the strontium isotopic ratios of 158 samples from Well Gurpi#1 located in East of Dezful, Iran  (from upper Cretaceous to lower Jurassic period) were measured and a 87Sr/86Sr profile was created and then compared to the global profile. Comparing 87Sr/86Sr values of upper Cretaceous to lower Jurassic sediments to those of evolutionary ones from Phanerozoic seas revealed a good agreement.

Sulfolane is normally used for Recovery of aromatic compounds. In the present study, Sulfolane was produced from Butadiene and SO2 via two steps. In the first step, Sulfolene was synthesized from SO2 and Butadiene in a gas phase. The second step involves hydrogenation of Sulfolene (as solvent) in the presence of a catalyst. According to previous studies, hydrogenation of Sulfolene might take up to 20 hrs and may require high pressures [1]. However lower pressures and shorter durations were used hydrogenation of Sulfolene in this study.

Although some researchers have claimed Garu Formation in West of Iran as a potential source rock, no documented analytical result has been reported yet in this regard. Since identification of source rock(s) in any exploratory area is essential, a geological section containing the Garu Formation from Kuhe-Sefid (80km S-E of Kermanshah, Iran) was sampled. Seventy nine samples were analyzed by Rock-Eval Pyrolysis based on TOC measurements. As the samples of the mentioned locality contained the minimum required TOC values required for a potential source rock, 12 samples were selected for organic-petrographical investigations. After extracting the Kerogen of the selected samples, their Vitrinite Reflectance (Ro%) was measured. Elemental analysis of Kerogen was also carried out on 6 samples. The mean vitrinite reflectance values ranged between 0.80 to 1.10% which indicates existence of organic maturation level at the end of oil window. The results of elemental analyses and Rock-Eval data indicate the presence of Kerogen (mainly type III and partially type II). Although the TOC content is low (due to considerable thickness of the source rock), this formation is potentially capable of producing large quantities of gaseous and liquid hydrocarbons.

A certain carbonate reservoir in southwest of Iran provides the opportunity to validate LMR (Lambda Mu Rho) as a characterization technique, while lithological is still the main characterization method. In an area where reservoir is poorly imaged by amplitude changes and where acoustic impedance alone fails to separate high porosity-permeability reserves from lower ones, LMR can be an important tool. The significance of this method has not been examined in carbonate reservoirs.  Lambda is an elastic parameter relating to incompressibility and is sensitive to pore fluid type. Shear modulus (Mu) is an elastic parameter corresponding to rigidity which is sensitive to rock matrix type. These two variables, were calculated bases on rock physics measurements and 2-D seismic experiments. Rock physics lab studies were carried out on 40 samples which were collected from 4 wells of the reservoir. Initial LMR values around the reservoir were based on rock physics lab measurements. Porosity and permeability studies of these 40 samples, helps detection of high porous samples from lower ones. Then according to LMR values; samples were categorized into two groups: those exhibiting a good potential for being a reservoir and ones with lower reservoir properties. The next step was calculating LMR values from seismic data, therefore P-wave and S-wave reflectivity were extracted from prestack seismic P-wave gathers. Inversion of reflectivity estimates may lead to calculation of P- and S-impedance, density, and also lame parameters (λ.ρ, μ.ρ). The variation of Mu rho (μρ) across the field reveals that this is an efficient method for detection of high porosity-permeability zones from lower ones in the carbonate reservoirs, and a good agreement exists between results of rock physics lab and seismic data, however Lambda rho (λρ) is not a reliable technique for discrimination between oil and brine saturation.

The texture of rock has a significant effect on production rate of hydrocarbon reservoirs and controls the   required pressure drops in fluid movement and production. In the reservoir zones that possess poor pore  connections, an inadequate network is formed and therefore the recovery factors are relatively small. The study of capillary pressure curves and thin samples reveals that rocks with vuggy porosities exhibit a good flow behavior and can be categorized as good reservoir rocks. It was also found that a full or partial reservoir rocks with inter-crystalline porosity possess low fluid recovery which is due to the weak connection between pores and their connecting throats.