Journal of Gas Technology
Volume:1 Issue: 1, Summer 2016

Properties and chemical composition of plus fraction in a petroleum fluid have a considerable impact on the fluid phase behavior. Understanding the trend of changes in molecular weight of successive single carbon number (SCN) groups in a plus fraction requires an accurate and reliable distribution function. Different distribution function models proposed so far may be applicable for certain types of reservoir fluids. In this work, analysis of 30 representative fluid samples in a supergiant gas condensate reservoir indicated a discontinuity in molecular weights of SCN groups at SCN=8, and SCN=13. The exponential, gamma, four-coefficient, and modified four-coefficient distribution functions were applied to these samples to predict the composition of SCN components. Results showed that the exponential distribution function does not predict the distribution of SCN composition accurately, especially in the aforementioned compositional discontinuities. Furthermore, the gamma distribution function was successful in predicting the jump in SCN=8 but failed at SCN=13. On the other hand, the modified four-coefficient model did predict the jumps in both SCN=8 and SCN=13. The overall error of calculations was 37.19%, 12.04% and 10.71% for exponential, gamma and modified four-coefficient models. Comparing four-coefficient and modified four-coefficient prediction results showed that the model parameters are strongly dependent on the fluid nature and need to be optimized based on available field data.

In the last two decades, various modifying techniques have been employed to improve membranes performance including mixed matrix, cross linking, grafting, polymer blending, making composite or hybrid membrane. Blending of polymeric membrane is a cost and time effective approach and an advanced technique for gas separation, where two or more polymers are mixed to produce a new material with different and desired physical, chemical and mechanical properties. This work reports on the separation performance of a novel polymeric blend membrane based on poly(amide-bethylene oxide) and polyethersulfone blends. These flat sheet membranes were synthesized using solution-casting in different ratios (10-40%) in order to improve membrane separation performance of CO2/CH4 gas mixtures. Prepared membranes were then characterized by Fourier Transformed Infra-Red Spectroscopy (FTIR) where spectral changes indicated existence of molecular interaction among the polymeric blends, highlighting their compatible nature. Permeabilities of pure gases (CO2 and CH4) were also examined at room temperature. Results indicated that increasing wt.% PES in the Pebax®/PES blend membranes increased selectivity of CO2/CH4 and decreased pure gas permeabilities.

One of the most important goals of gas engineering is to optimally distribute gas in gas transmission and distribution networks; however, this process often suffers from some inevitable distribution network problems such as errors caused by inaccurate estimates of pressure at various points in the network. Recently, statistical optimization methods have been proposed to solve this problem. Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) are common methods for this purpose. The purpose of this study is to compare the performances of these two procedures. If similar constraints and computational loads are applied to both methods, PSO can provide more accuracy and speed compared to GA, although repeatability of GA was found to be better.

To evaluate the hydrocarbon potential of coal seams (D and E horizons) and their country rocks of Hojedk Formation (Middle to Upper Jurassic) at Kerman Coaly Syncline (KCS), 32 coal and 46 shale samples were collected. These samples were studied geochemically, and their quantity, quality and thermal maturity of organic matter were studied as well. According to Rock-Eval pyrolysis data, it was found that the total organic carbon (TOC) content of coal samples is in excellent condition. Such a situation is, more or less, the same for the shales. Genetic potential (GP) also indicated that the majority of the samples have acceptable potential for gas and oil generation. Therefore, the organic matter quality of Hojedk Formation was evaluated as good to excellent generally. The use of hydrogen Index (HI) as one of the most important factors determining the quality of source rocks showed that the coal and shale samples of Hojedk formation have fewer than 50 to over 600 mgHC/g rock, and majority of the samples fall in 50-200 and 200-300 mgHC/g rock category and therefore, it can be stated that the quality of organic matter varies from without potential to gas and oil potential. The existing kerogen types in these samples are mainly of the III and II-III and consequently, gas and oil generation in the region is likely. Relative high values of S2/S3 (3.70 to 402.36) confirmed the above-mentioned products. In order to evaluate the thermal maturity of organic matter, two different methods (Tmax and vitrinite reflectance) were used. Tmax values revealed that most samples of KCS are in the early to late oil generation window conditions. The highest Tmax (overmature condition) is related to the Tikdar stratigraphic section and this is probably due to its proximity to the Kuhbanan fault. Measurements of vitrinite reflectance also showed that Ro% ranges from 0.5 to 2% and the mean value of this factor is 1.18% and therefore, corresponds to the condition of oil generation window. Finally, based on the quantity, quality and thermal maturity of organic matter at KCS, it can be said that the region has adequate potential for gas and to a minor extent oil generation. Moreover, coal seams, because of enough liptinite contents (up to 22%), are in a better condition in general.

The concentration of H2S in the inlet acid gas is an important factor that sulfur plant designers must consider when deciding on the right technology or configuration to obtain high sulfur recovery efficiency. Using sterically-hindered solvents such as promoted tertiary amines and various configuration for gas treating unit are several alternatives for acid gas enrichment (AGE) to reduce the concentration of carbon dioxide and heavy aromatic hydrocarbons while enriching the H2S content of SRU feed stream. The present article uses combinations of Aspen-HYSYS software and two distinct networks (namely, Regularization network and adaptive neuro-fuzzy inference system) to compare the AGE capability of sulfinol-M (sulfolane MDEA) solvent at optimal concentration to traditional MDEA solution when both of them are used in a conventional gas treating unit (GTU). The simulation outcomes demonstrate that the optimal concentration of Sulfinol-M aqueous solution (containing 37 wt% Sulfolane and 45 wt% MDEA) will completely eliminate toluene and ethylbenzene from the SRU feed stream while removing 80% of benzene entering the GTU process. Furthermore, mole fraction of H2S in the SRU feed stream increases the conventional 33.48 mole% to over 57mole%. Increased H2S selectivity of optimal Sulfinol-M aqueous solution will elevate the CO2 slippage through sweet gas stream at around 4.5mole% which is still below the permissible threshold.

This investigation attempts to evaluate and compare the effect of packing type on the mass transfer and pressure drop along the gas sweetening absorption column. To this aim, modern packings such as Super Ring, Ralu Ring, Ralu Flow and the second-generation packing (Pall Ring), have been used in simulated columns by using of Aspen HYSYS modeling software. Flooding calculation is made possible by linking Aspen HYSYS with MATLAB programing. The selected models validity is checked by comparison to empirical data from a real gas plant. It should be noted that empirical data is available just for second-generation packing. Comparison of these packings performance shows that Super Rings provide low pressure drop, Ralu Rings lead to high mass transfer and Ralu Flow packings can provide high mass transfer and low pressure drop in absorption columns. According to results, the capacity of gas treatment units can be significantly increased by replacing Pall Ring with Ralu Flow.