مجله پژوهش نفت
پیاپی 108 (آذر و دی 1398)

Water injection especially low-salinity water injection has provided a low-cost EOR method for more oil recovery. In recent years, most of the studies on low-salinity waterflooding have been focused on the investigation of the effect of water injection on rock/oil/water interaction. The purpose of this study is to investigate the fluid/fluid interaction which has received less attention in comparison with the rock/fluids interaction. In this experimental work, a series of bottle tests have been performed with 20 percent of crude oil and 80 percent of saline water (for five different common salts in the seawater) with different salinities from 6,000 to 40,000 ppm. By sampling the emulsified portion at the oil/water interface, the size distribution of the water droplets in oil has been obtained. Moreover, the size of water droplets have varied from 0.02 to 1.65 mm, and relative frequency of categories was 0.73 at its maximum. The size of water droplets decreases with a decease in the salinity. Among the salts, calcium chloride is more effective in comparison with others as the water droplet size is the lowest among three other salts, and consequently it could attract more natural surface active materials from oil to water-oil interface. The sorting of salts from highest to lowest stable emulsion is calcium chloride, magnesium chloride, sodium sulfate and sodium chloride. Ultimately, this is due to the interactions of ions in saline water with oil, charge density of ions and their surface activity.

Thermal conductivity of a partially saturated rock sample depends on several parameters such as matrix properties, pore structure, pore filling fluids and their saturations. Indeed, complex pore structure of the rock causes many problems in prediction of its thermal conductivity at different saturation conditions. Numerous investigators presented different correlations and mechanistic predictive models to predict thermal conductivity of porous media. But, most of these models have focused on the prediction of thermal conductivity of single phase saturated porous medium. Analogy between electricity transmission and heat transfer through a rock can be considered as a basis to develop a model for prediction of thermal conductivity. In this paper, thermal conductivity of six carbonate plug samples from one of the Iranian reservoirs has been measured at vacuum condition. Also, for four samples of these six plugs, thermal conductivity has been determined at fully water saturated condition and four different water saturations using divided bar steady-state apparatus; in addition, the second phase has been air. This apparatus has been designed and constructed in Petroleum University of Technology (PUT). Finally, according to the results, it is obvious that rock thermal conductivity at vacuum condition decreases with an increase in porosity. Furthermore, thermal conductivity of partially saturated rock increases with an increase in water saturation. Moreover, a new model for predicting rock thermal conductivity of partially saturated rock has been presented based on the analogy between electricity transmission and heat transfer through the rock. Our experimental results confirmed the suitability of the proposed model.

Permeability, skin factor, and wellbore storage coefficient are three essential parameters for well and reservoir. Moreover, well testing is the conventional method for determining these parameters. In this method, pressure data are plotted versus time in semilogarithmic and logarithmic scales, and specified relations determine well test parameters. In this study, a new approach is introduced to obtain well test parameters using artificial intelligence. First, using endpoints related to two real wells, pressure data are produced by reservoir simulator software. Because the data have a lot of noises, the additional data are removed, and analyzing the data is more comfortable. Then, with the combination of a genetic algorithm and the Levenberg Marquardt algorithm, the basic parameters of the reservoir have been calculated. In the last step, the pressure data are entered into standard software, and their values are calculated. Finally, the combined algorithm with excellent accuracy has been able to calculate these parameters in comparison with the conventional Saphir 4.10 well testing software.

It is probable to take into account the presence of liquid hydrocarbon in case studies related to hydrate formation risk. Hydrate formation kinetic may be influenced by liquid hydrocarbon in result of mass and heat transfer resistance of phases. In this fundamental research, the effect of liquid hydrocarbon presence on nucleation and growth  steps of methane hydrate formation has been investigated. For this purpose, the experiments have been carried out considering two different cooling rates and volume ratios of liquid hrydrocarbon to water, and then parameters like induction time, induction temperature, percent conversion of water to hydrate and growth  time of hydrate completion have been measured and/or calculated. Regardless of different cooling rate, it is observed that the presence of liquid hydrocarbon has lowered induction time and induction temperature, that is moderating the nucleation step. Moreover, the presence of liquid hydrocarbon has shown a significant effect on the percent conversion of water to hydrate and the growth  time of hydrate completion. Generally, dispersion of water droplet through liquid hydrocarbon has increased water interface followed by a layered hydrate formation mechanism around the water droplets, this led to a decrease in percent conversion of water to hydrate and the growth  time of hydrate completion in comparison with blank experiments. Finally, hydrate formation kinetic and water to hydrate conversion have been more limited by increasing the volume ratios of liquid hydrocarbon to water.

During the production of hydrocarbon reservoirs and the injection process, pore pressure changes lead to reservoir compaction, which directly affects the petrophysical properties of the reservoir rock. Therefore, it is very important to recognize the changes in rock behavior and reservoir properties such as porosity and permeability which are significant. In this study, the effect of hydrostatic loading on petrophysical, geomechanical and structural properties of carbonate reservoir is investigated, which the investigation is followed by analyzing the porosity, permeability and pore size distribution. In order to investigate the changes in the geomechanical behavior of the carbonate reservoir, the compressional and shear wave velocities of two reservoir rock samples with similar geometrical and physical properties have been measured under different loading conditions. Scanning electron microscopy (SEM) images have also been used to examine the structural changes of rock samples. The results of this study show that under loading, permeability and porosity have a decreasing trend in 36.14% and 7.39% respectively in the last loading step. The study of compressional and shear wave velocities demonstrate that there is an increasing trend by increasing pressure, which it is due to the volume ratio of rock matrix to pore space. Combining the analysis of SEM images and pore size distribution shows that pores have become compacted, and the mean pore size has been reduced, in which this pore collapse and the placement of smaller particles among coarse particles have decreased porosity and permeability. Ultimately, understanding the changes in petrophysical properties along with their corresponding structural and geomechanical changes is very important in production planning of hydrocarbon reservoirs.

In this work, a nanostructured/mesoporous p-type, low-price, stable mangranese sulfide semiconductor was synthesized and employed under ambient temperature and pressure conditions, to produce hydrogren and sulfur through photocatalytic transformation of an H2S-containing alkaline solution. X-ray diffraction (XRD), field emission scanning and transmission electron microscopy (FESEM, TEM), and adsorption-desorption isotherm (BET) analyses proved a nanostructured morphologry for the synthesized energry material. Moreover, usingr diffuse reflectance UV-vis. spectroscopic (DRS) and electrochemical impedance data (Mott-Schottky diagram), bandgap energy and flat-band as well as valence and conduction bands’ potentials were determined for this semiconductor material. Photocatalytic investigations revealed a good potency for the synthesized material to produce hydrogen fuel and sulfur element [quantum yield: 12% measured at 434 nm]. Furthermore, after 3- hours operation of the reactor containing 0.2 g photocatalyst, the extent of hydrogen gas and sulfur product were obtained 1350 µmol and 42 mgr, respectively.

The high amount of trapped crude oil in carbonate reservoirs is the main objective of the various Enhanced Oil Recovery techniques. However, the harsh conditions of these reservoirs, such as high temperature, incompatibility of formation brine and sea water ions, as well as oil-wet conditions, are among the factors which face the desired approach with serious challenges. Therefore, in this study, the stability, interfacial tension, wettability alteration, and microvisual flooding experiments have been investigated using two types of anionic surfactants [DSS and SDBS] and two types of cationic surfactants [CTAB and CPC]. The amount of recovered oil was 63%, 48%, 44% and 35% respectively. The highest recovery factor was due to implementation of the DSS surfactant. Also, in order to investigate the effect of surfactant on the wettability alteration, the reservoir rock samples were aged for two weeks. Contact angle measurement of 160 degree has proved the oil wetness condition. Wettability alteration has been investigated using treating solutions of anionic surfactants DSS, SDB and cationic surfactants [CTAB and CPC]. Obtaining results demonstrate contact angles of 100, 90, 60 and 48.7 respectively. Finally, the highest wettability change is due to the application of CPC which alters the contact angle from 160 degrees to 48.7.

Due to the importance of measuring multiphase flows in the oil, gas, refining and petrochemical industries, in this study, the feasibility of different two-phase flow measurement methods has been investigated. Two-phase flow loop and measurement equipment including orifice plate flow meter and mercury manometer have been designed according to the international standards. Flow rates of water and air phases in two-phase flow loop have been measured using electromagnetic and turbine flow meters respectively before entering the mixing section and forming two-phase flow. Total mass flow rate of two-phase flow passing through the orifice flow meter has been equal to the total mass flow rate of water plus the total mass flow rate of air that has been measured by electromagnetic and turbine flow meters respectively. The orifice pressure drop for different flow rates of water and air and various volume fractions of air in two-phase flow has been measured. Reynolds number and air volume fraction of two-phase flow were in the range 744 – 10000 and 15 – 40% respectively. Effects of Reynolds number and air volume fraction of two-phase flow on the orifice plate performance have been investigated. For low Reynolds numbers of two-phase flow that the plug flow pattern has been dominant, the slope of changes for discharge coefficient has been more in comparison with upper ranges of Reynolds number where the flow pattern is changed from plug flow to stratified. Orifice plate flow meter has been simulated using CFD approach. The standard K-Epsilon turbulence model has predicted better results than other turbulence models. The present study provides the basis for measuring two-phase flows in the oil and gas industry.

Nowadays, oil spill to the seas and oceans is one of the most critical factors in the sea-based pollution in the world. On-time recognition and prevention of oil spills to the marine environment and decreasing of its harmful effects on sea ecosystems are necessary. Remote sensing technology is suitable for early recognition of oil pollution from the air because of the data-collecting in various ranges of Electromagnetism and a broad view of the region. In this study, after evaluation of the scientific sources and the comparison of various sensors and about the time and place of the oil pollution, the images of the second level of MODIS sensor, from 2005 to 2015, have been used. So that a new method for monitoring of the oil spill has been developed. Moreover, the suggested method has focused on enhancment of sensor data. In this study, in order to enhance the bands 1 or 2 oil spill of MODIS sensor, the mean long-term statistical parameters and standard deviation of time-series data have been applied. Therefore, the undesirable data sets for each pixel have been deleted through the initiative process. Then, the mean and the long-term standard deviation of the data have been acquired from the long-term data. Moreover, finally, the value of each pixel has been standardized by utilizing those parameters. The oil spill event has been simulated by this method. Afterward, the normal frequency distribution method was applied to screen the oil patches, and the polluted pixels have been screened by applying  the appropriate threshold. In this way, the oil pollution happened in 2007, and 2010 have been screened by the designed model, and their accuracy has been compared to the real land map. The results of the map for each oil spill event have been acquired as follows: 96% total accuracy and 0.95 Kapa co-efficient for August 2007, 95% total accuracy and 0.92 Kapa co-efficient for July 2010. Finally, the overall results of the study have shown that the designed model has enough accuracy in recognition and screening of oil spills events.

Nowadays, the natural energy of the reservoir is not capable of producing remained oil in reservoirs due to the drop in the bottomhole pressure in oil reservoirs. Hence, oil industry professionals are always searching for new ways to recover remained oil in reservoirs. Chemical injection has been used extensively for EOR purposes in recent decades. But this method has always been subject to limitations. The waste of surfactant and polymer during injection operations in reservoirs is considered as the most important issue in the feasibility of chemical injection operations. Many efforts have been made to reduce the absorption of surfactants on rock surface for the economic operation. Adding polymer to injectable chemicals is used as the most practical method, due to a better control of the water-oil mobility ratio and also the impact on the absorption of surfactants in different ways. In this study, the effect of temperature on the adsorption of chemical surfactant, Triton X100, has been investigated. In addition, the effect of hydrolyzed polyacrylamide polymer on the absorption of this surfactant has also been evaluated.

In bio-desulfurization (BDS) process, microorganisms are used for fossil fuel sulfur elimination. The goal of this project is the isolation of thermophilic microorganisms which are able to support bio-desulfurization activity from DBT as the sole sulfur source and to find an optimized media culture for growth and bio-desulfurization activity. To identify the cell growth and bio-desulfurization activity, Basal Salt Medium containing DBT has been used. For optimization of the culture medium, different carbon and nitrogen sources and also different concentrations of sulfur source were used. Moreover, the findings illustrate that the maximal cell growth was achieved after 96 h incubation. In addition, the Gibbs results have shown that this strain eliminates the sulfur in DBT by 4S pathway and 2-hydroxybiphenyl, as the end product of the desulfurization process has been produced at the maximal concentration (26.1 mg/L) at 72 h. Finally, the results of research illustrate that the isolated thermophilic strain is capable of eliminating sulfur in DBT, and this process may be improved by optimizing the culture media.

Lithofacies investigation has an important role in hydrocarbon exploration and development stage. Several methods and studies have been done about reservoir properties based on geostatistical knowledge in hydrocarbon fields up to now, but some limited studies have been done about lithofacies propagation and modeling. In this study, data from 21 wells (petrophysical logs, cutting and core) in one of the hydrocarbon fields in Persian Gulf have been investigated. In the studied field, the Carbonate-Evaporate Kangan succession has been divided in two zones (A and B) and six sub zones (a1-a2-a3 and b1-b2-b3) based on petrophysical evidences and indications from cutting. For modeling lithofacies, six lithofacies codes have been presented; the codes are as folllows: anhydrite, limestone, dolomite, shale, dolomitic limestone, dolomite with anhydrite. After variography analysis, identified codes have been propagated based on sequential indicator simulation method by considering depositional environment of Kangan Formation (Early Triassic) in the studied area. The results of this study which have been confirmed by new drilling wells data, show that this method has a good accuracy and can be used in related sequences to predict the lithofacies and good reservoir properties.