PETROLEUM RESEARCH
Year:2015 | Volume:25 | Issue:83|Papers Count:19

In this study, the polymer flooding’s process in the micro-model with different patterns of fractures is simulated. The sensitivity analysis on effective parameters of a fracture such as length, orientation and number of fractures has been done and the influence of each parameter on the oil recovery has been investigated. Simulations have been performed using Eclipse software and the confirmation of numerical results is checked with experimental data. In addition, results of Polymer flooding have been compared with those of water flooding, which is one of the simplest and cheapest method for enhancing the oil recovery. Comparison of data shows that polymer flooding specially in fractured reservoirs has higher recovery and it is because of fingering effect’s reduction. Also it has been found that in the micro-model with a large number of short fractures, improvement of the oil recovery is more than other situations.

Seismic data are commonly contaminated by noise. Ground roll is one of the most important noises in onshore reflection seismic data acquisition. It is a coherent noise with a lower speed, lower frequency, and stronger amplitude than reflection seismic signals. Due to the dispersive property of the ground roll, it is distributed in fan-shaped zones at near offsets about the source. There are several methods for ground roll suppression such as 1D and 2D frequency filtering and velocity filters. In this paper, a new filtering method based on the generalized S transform and the empirical mode decomposition has been used to attenuate the ground roll coherent noise. In the proposed method, the x-t domain seismic data transformed to t-f-x domain using a generalized S transform. Then, the empirical mode decomposition is applied to the transformed data along the X-direction. The first intrinsic mode function related to high wave numbers is removed to attenuate the ground roll. The denoised seismic data can be obtained by stacking up the remaining intrinsic mode functions and transforming back into the t-x domain using an inverse S transform. The efficiency of the mentioned method has been tested on real seismic data and compared with empirical mode decomposition in the f-x domain. The obtained results show that the proposed method attenuates the ground roll better than the combination of empirical mode decomposition and Fourier transform.

In this work, the separation of disulfides from spent caustic in demercaptanization units has been studied on laboratory and bench scales. The effect of increasing demulsifier on various variables such as chemical structure, concentration, solvent effect, and residence time with regards to the performance of the desulfurization of caustic has been experimentally investigated. The results show that a high efficiency of spent caustic recovery can be achieved using optimal concentrations of demulsifier and solvent. By increasing demulsifier, sulfur compounds in caustic are reduced to about 20 ppm. In this process, the best solvent for caustic desulfurization was the one similar to the original oil cut with low sulfur content. The spent caustic solution will therefore be recyclable. The operation conditions were environmentally friendly and cost effective.

Gas condensate reservoirs are generally deeper and are found at higher pressures and temperatures relative to oil reservoirs. Light hydrocarbon compounds are parts of crude oil and gas condensates, which have different types of structures. 7-carbon hydrocarbons with open chain and branch ring structures can be considered as good indicators for the recognition and origin of organic matters, source rock characteristics, etc. In this study, three fluid samples of three independent gas fields in southern Iran, from Kangan and upper Dalan formations (with similar geochemical characteristics), are subjected to detailed hydrocarbon analysis (with the ability of the identification of molecular components of the organic compounds) and other PVT experiments, and changes in the concentration of specific compounds having 7 carbons or less in different reservoir conditions were studied. The results showed that according to the overall parameters, samples A and C were similar and both were different from sample B, which was attributed especially to the difference of reservoir conditions between samples A and C with sample B. Also, the paraffinicity property of fields initially decreased but then increased from A to C, and, likewise, field B represented vast evidence for the occurrence of biodegradation processes. Figures showed that the source rock of sample C had obviously the terrigenous origin, but understanding the origin of samples A and B were carried out using various diagrams and it was determined that the two fields had the dry origin. It was also found that the mixing process of reservoir contents having organic matters with that of the other formations have probably occurred in sample C.

Soils contaminated with petroleum compounds, especially polycyclic aromatic hydrocarbons (PAH’s), are one of the major environmental problems that threats the ecosystem and human life. This complex mixture of petroleum hydrocarbons is fused and contains various isomers of carbon and hydrogen, which are composed of a double rings or more loops. Today, many well-developed methods have been proposed for the remediation of contaminated soil, which, regardless of the complexity of the process, are very difficult and costly. The aim of this study was to decontaminate polluted soils from pyrene as an index of poly aromatic hydrocarbons (PAH’s). The remediation of PAH compounds like pyrene was carried out by using nano-photocatalysts. In this study, the response surface methodology (RSM) is performed for the formulation of catalyst concentration and UV exposure time. Under laboratory conditions, artificially clean soil samples were sterilized and contaminated with 40 mg/kg pyrene. Then, 5 grams of the soil contaminated with a solution of 40 ppm pyrene (PAH’s compounds) were well mixed with different nano-photocatalyst concentrations of 2, 4, 6, 8, and 10 wt%. of TiO2, ZnO, and SnO2. The soil samples were exposed to UV-C light (15 Watt at a wavelength of 254 nm) in a photo-degradation reactor for 10, 15, and 20 hrs of exposure. Under the photo-oxidation reactions, the removal of pyrene from the soil samples was calculated according to a standard method (ASTM D-5520) of fluorescence UV spectroscopy. The results showed that the degradation of pyrene by the mentioned nano-photocatalysts were possible and the highest rate of degradation (71%) was obtained at a TiO2 catalyst concentration of 10 wt.% during 20 hrs of UV exposure. In this paper, the photocatalytic removal of hydrocarbons was studied by using a nano-photocatalytic degradation process having various factors such as the effect of catalyst type, catalyst concentration, and UV irradiation exposure time. Finally, the removal of pyrene from soil was determined and the corresponding absorption spectra were presented.

The photocatalytic oxidation and mineralization of petroleum refinery wastewater in aqueous catalyst suspensions of titanium dioxide (TiO2), Degussa P25 (80% anatase, 20% rutile) was carried out in a batch circulating photocatalytic reactor. The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). In order to analyze the process, four significant variables viz. pH (2-10), catalyst concentration (0-200 mg/l), temperature (22.5-52.5oC), and reaction time (30-150 min) and TCOD removal as the process response were studied. From the data derived from the factorial design, the ANOVA analysis revealed that the first order effects of reaction time, pH, temperature, and catalyst concentration and second order effect of pH, catalyst concentration, and temperature produced the main effect on TCOD removal efficiency. A maximum reduction in TCOD of more than 83% was achieved at the optimum conditions (pH of 4, catalyst concentration of 100 mg/l, temperature of 45oC, and reaction time of 120 min). The reaction kinetics showed that reactive activation energy for TCOD conversion was calculated to be 19.34 kJ/mol.

The Surmeh formation is hosting important oil reserves in the Middle East and Iran. It is mainly composed of dolostone in the upper part and dolomitic limestone in the lower part with interbedded anhydrite layers. According to this study, in Balal and Salman oil fields, some changes, including changes in facies, type, and the intensity of the diagenetic processes and lithology, have controlled porosity and permeability values. By comparing these factors in fields, one may conclude that dolomitic deposits in the Balal field consist mostly of barrier and lagoon facies. Toward the southeast, the proportion of grain-dominated barrier dolograinstone facies was reduced, while the dolopackstone lagoonal facies was increased. In the Salman mud-dominated tidal flat, dolowackestone and dolomudstone facies are increased but anhydrite cement content is decreased due to dolomite porosity and permeability. Comparing these two fields, they generally suggest the existence of similar facies. However, their main differences that influence the reservoir quality are the abundance of grain-dominated facies and anhydrite conten.

Upper Dalan formation, is a complex of carbonate reefs-evaporite, and Kangan with dominant lithology of limestone and dolomite is associated with anhydrite layers; Permo-Triassic succession of the South Pars gas field hosts the largest none-associated gas reservoir in the world located in the offshore of the Persian Gulf between Iran and Qatar. The geometry and distribution of high energy facies (shoal facies) are the main constituents of field reservoir quality, which is controlled with sedimentary environment. This study deals with the assessment of geological facies and their relation with petrophysical properties in incorporation with wire line logs to propagate the reservoir schemes. Core and petrographic analysis were carried out with the aim of recognizing the distribution of sedimentary facies and facies associations. Twelve microfacies were categorized into 4 major facies associations: tidal flat, lagoon, shoal, and open marine. The reservoir quality of facies associations was evaluated based on core porosity and permeability. In un-cored wells, facies associations were predicted as logfacies based on wire line logs by using intelligent neural networks. The sequence stratigraphic framework in the field was used to correlate facies in a two dimensional model. The 3D distribution of facies associations is assessed as logfacies by geostatistical modeling and sequential indicator simulation.

Large percentages of world hydrocarbon reservoirs are fractured reservoir and fracture distribution in these reservoirs are not distributed randomly. Fracture distribution in fractured reservoir depends on the combination of structures, lithology, reservoir thickness, fault, and other fracture controllers. For accurate fracture modeling, these factors should be integrated with well data. For this purpose, fracture density of three wells in Marun oil field is used. Fracture related seismic attributes such as instantaneous frequency, curvature, and dip is extracted from seismic data. Geological and petrophysical features, which control fracture density, are modeled by the integration of seismic and well data. By the integration of these factors and fracture density in wells, fracture density is modeled by artificial neural network. In this study, the continuous fracture model is properly modeled and the results demonstrate 82% correlation with well data. This continuous fracture model has a relatively good relation with transmissibility map and the transmissibility map satisfies high fracture density in the south limb of anticline. Most fracture densities are located in the southern limb of anticline and this seems to be suitable region for field development.

Nowadays, quantitative methods for seismic data interpretation are mostly used instead of qualitative evaluations for the description of reservoir from exploration to production phase and, over time, it will be more important in upstream oil industry. One of the most prosperous methods is AVO analysis that considers the variation of reflection coefficients versus offset between the source and the receiver. This method uses prestack data to identify hydrocarbon in reservoir and can be used as a direct hydrocarbon indicator in clastic rocks. In this paper, AVO analysis method has been described to detect hydrocarbon reservoir and AVO analysis was applied to the Ghar sandstone reservoir in Hendijan oil field. This study is carried out using 3D prestack data and well logging data. At first, forward modeling has been performed using well logging data from wells. Class 1 AVO anomaly has been recognized for this reservoir. After the forward modeling step, fluid replacement modeling (FRM) in reservoir zone has been applied and the best attributes, which had a great sensitivity to fluid, were distinguished. But FRM shows that the attributes are not sensitive to changes in fluid type. AVO anomaly on upper boundary of Ghar sandstone is affected by changes in lithology. Also, intercept-gradient cross-plot was produced by attributes. Reservoir area and zones has been discriminated with intercept-gradient cross-plots. For seismic data, various AVO attributes and cross-plots have been extracted by different methods and have delineated. Unfortunately, attributes and cross-plots were not able to detect fluids boundaries and fluid boundaries, because of the poor quality of seismic data. The results not only help to select new drilling locations more accurately, but the reservoir parameters can also be modeled with less uncertainty.

In this contribution, a CFD technique has been used to study the effects of operational parameters on the amount of hydrodesulfurization (HDS) and hydrodearomatization (HDA) conversions in the trickle bed reactor (TBR). The Eulerian-Eulerian multiphase approach has been used to simulate multiphase flow conditions with appropriate models to account interphase interactions at TBR. Due to the importance of porosity distribution effect on the hydrodynamics behavior and reaction conversion, an appropriate trilobe porosity model has been implemented in the simulation models. The studied parameters are temperature, pressure, liquid phase velocity, and gas phase hydrogen sulfide concentration. The simulation results show good agreement with the reported experimental data.

Oil generation is a long process of converting oil from organic matters, which takes millions of years. The generated oil migrates and accumulates in reservoir rock and is preserved as an oil accumulation or oil field. In this study, by using basin modeling method, thermal history in a thrusted section is simulated and the hydrocarbon generation history of source rocks is investigated. By means of stratigraphical, geological, and geochemistry data and using 1D basin modeling software, the burial and oil generation histories are reconstructed. In addition, organic matter maturity, oil and gas windows, and the quantity of hydrocarbon generation of Pabdeh, Kazhdumi, Garau, and Sargelu source rocks are obtained. The vitrinite reflectance data were used for the quality control of the model. Based on this study, the thrust fault has increased the depth and maturity of source rocks, and thereby the speed of the oil generation process. When the source rock is at the peak oil generation stage, thrust fault effect would be higher. If the source rock produces hydrocarbons before faulting and loses some potential, the thrust fault effect is far less.

PVC/MWCNT’s and CA/MWCNT’s mixed matrix membranes (MMM’s) were prepared. These membranes were characterized for the investigation of gas separation properties. For this reason, both raw and functionalized multiwalled carbon nanotubes (MWCNT’s) were used. At last, it is understood that membranes filled with functionalized MWCNT’s had better performance. The effects of MWCNT’s loading ratio were investigated on the gas separation performance of the prepared membranes for He, N2, CH4, and CO2 gases. The results represented that all gases permeability had an increasing manner with increasing the nanofiller loading ratio. CO2 permeability were more increased and at 1 wt.% of MWCNT’s for MMM’s based on PVC, and at 5 wt.% of MWCNT’s for MMM’s based on CA, this value reaches 11.48 and 14.21 respectively. Moreover, CO2/CH4 gas separation selectivity showed better results and at 3 wt.% of MWCNT’s reaches its maximum value (52.76). Also, the results of mechanical resistance analysis represented that MMM’s based on PVC have better mechanical properties than MMM’s based on CA.

One of the recently developed methods of enhanced oil recovery in carbonate reservoir is smart water flooding. Smart water can alter the wetting state of carbonate rocks from oil-wet to water-wet and increase oil production. In this study, we have investigated the effect of smart water composition on the carbonate rock wettability at different aging temperatures and pH’s through measuring the contact angle. The response surface methodology was utilized for the design of experiments. The results show that Mg+2, SO4-2, and K+ ions have important roles in wettability alteration due to interaction with carboxylic acids adsorbed on the rock surface. Not only Mg+2 and SO4-2 ions but also, inactive ions such as K+ influenced the wetting state of carbonate rock. Furthermore, an increase in temperature could cause more water wetting state and more activity of ions in solution. In addition, increasing pH could decrease the contact angle because of reduction in positive surface charge of carbonate rock surface. However, when pH was close to 8, the contact angle was raised probably due to the precipitation of Mg+2 ion.

Asmari formation, assigned to Oligocene-Lower Miocene, forms the most important hydrocarbon reservoir in the south and southwest of Iran. In the studied field, Asmari formation constitutes a sequence of carbonate (common at upper part) and clastic (common at lower part) sediments. The carbonate section belonging to early Miocene and being commonly assigned to shallow marine, high energy barrier and lagoon is severely subjected to diagenetic processes. Macro-microscopic studies (core and thin section) along with geochemical and conventional core analysis showed that, in dolostone intervals, the development of intercrystalline pore spaces and the presence of primary interparticle pore spaces on the one hand and the performance of compaction and evaporite mineralization on the other hand caused considerable changes in reservoir quality. This study aimed to investigate the effect of evaporite (anhydrite and celestite) mineralization on the Asmari reservoir properties. This research showed that the quantity and distribution of evaporitic minerals, namely anhydrite and celestite, played a very significant role in controlling the reservoir quality of dolostone intervals. The most common and efficient forms of anhydrite and celestite distribution occur as pore space cement-filling, poikilotopic, replacement, and occasional fracture-filling. Evaporitic cement-filling that occupies about 40% of intergranular (in early burial) and intercrystalline pore spaces, noticed in some samples, have reduced the porosity and permeability of dolostone intervals to nearly zero value. Primary and secondary nodular forms having considerable extent in all facies have not decreased the reservoir quality of Asmari formation.

In this paper, electrofacies in ASMARI formation in Gachsaran oil field were determined using multi resolution graph-based clustering method (MRGC), This oil field is located in the southwest of Iran. The determination of electrofacies in this field is performed by using the combination of image logs and other well logs obtained from one of the wells in the field. In order to obtain an exact evaluation, environmental corrections were performed on the logs. The comparison of lithology results, shale volume, porosity, and water saturation with determined facies, using clustering analysis by applying image logs, shows acceptable agreement between the obtained electrofacies and the corresponding lithological results, and represents a new categorization of the formation. This new categorization has reservoir aspects; the variations of the petrophysical properties in each facies are unique and the variations of these indices are determined in individual facies. Moreover, by considering the span of the identified electrofacies, the reservoir and non-reservoir layers are distinguished based on the performed zoning.