مجله پژوهش نفت
پیاپی 127 (بهمن و اسفند 1401)

Most hydrocarbon reserves are stored in natural fractured reservoirs and such systems can affect significantly on the reservoir performance. Therefore, geomechanical studies, understanding and investigating fracture patterns to optimize hydrocarbon production are of great importance for the geologists and oil engineers. Geomechanical studies generally include size and orientation of the three main axes of stress, including vertical stress (Sv), maximum horizontal stress (SHmax) and minimum horizontal stress (Shmin). Studies related to well logging and geomechanical issues are the main objectives of electrical imaging techniques of the well wall. Electrical, sonic or image log, which record high-quality images are pushed in to the well and provide important information regarding boundaries of bedding, structural elements such as faults, folds, discontinuities, fractures and even secondary porosities. Accordingly, in this study, in one of the west south oil fields of Iran using Fullbore Formation Micro Imager (FMI) regarding natural and induced fractures related to regional folding and faulting, some characteristics of the fracture patterns have been studied. These characteristics include the type of fracture, orientation, density, openness, amount of sleep and their relationship with regional construction of the ground. Despite the geological complexities of understudied field, orientations of sub surface fractures indicated clear relationship with the local folding axis and in some cases, it seems that it relates more the orientation of the maximum horizontal stress to the present location of the local strike slip fault too. Orientation of the maximum and minimum horizontal stress obtained N30E- N60W and N50E- N40W respectively based on two wells data analysis. According to the open fractures observed in the wells, three stages of fracture are proposed: pre-folding, early-folding and post-folding fractures.

gels that have a low viscosity at the time of mixing and form a three-dimensional gel structure after some time delay can be applied successfully in controlling lost circulation. The hybrid gel consists of a cross-linked gel polymer as a continuous phase and an oil as an internal phase. The hybrid gel is cost effective and its properties can be controlled. This study consists of two parts, experimental investigation and empirical modeling using response surface methodology. a number of parameters such as initial gelation time, final gelation time, crosslinking rate and Final viscosity were defined and compared to evaluate the gel behavior under different conditions. First, the effect of pH, temperature and salinity on gel performance as well as the stability of the gel over time were investigated. Then, dynamic stability test for different gels was examined to measure the amount of pressure that the gel in the fractured core can withstand to prevent further fluid loss. Finally, the amount of gel rupture with time in HCL (15 and 28%) was investigated to evaluate the formation of damage of hybrid gel. The experimental results show that hybrid gels can have proper performance and application in industry to combat lost circulation due to their flexible viscosity response and non-damaging properties. response surface methodology(RSM) based on Box-Behnken design was utilized to identify a correlation for prediction of final viscosities of hybrid gel as a function of temperature, pH and salinity. The predicted model was obtained by solving the quadratic regression model. The value of correlation co-efficient (predicted R2 = 0.88) for the present mathematical model indicated good relation between experimental data and predicted values. Therefore, the proposed model predicts the viscosity of gel adequately within the limits of input parameters being used.

An accurate estimation of methane absolute adsorption in nanopores of shale gas is crucial for a good estimation of gas in place (GIP). However, experimental studies would only provide us with the excess adsorption isotherm directly. In this regard, knowing the adsorbed density is necessary to calculate the absolute adsorption. For this purpose, most researchers calculate the absolute adsorption isotherm via the Langmuir adsorption model with a constant value for the adsorbed density. In the present study, using hybrid grand canonical Monte Carlo/molecular dynamics simulations, we explained how to improve the calculation of the adsorbed density in calcite. For this purpose, methane inside calcite mineral with a pore size of 4 nm at temperatures of 30 and 90 °C and pressures up to 50 MPa is simulated, and the effects of temperature and pressure on the amount of adsorption and adsorbed density are investigated. This study showed that adsorbed density increases and decreases with increasing pressure and temperature, respectively. The results verify that the Langmuir adsorption model with constant adsorbed density will underestimate the absolute adsorption capacity, which is exacerbated with pressure. Finally, the adsorbed density obtained from molecular simulations to convert excess adsorption to absolute values can provide acceptable results that can be improved the GIP assessments.

In this research, we studied fracture parameters comprehensively and analyzed their sensitivity by the use of discrete fracture model and finite-element method. This paper seeks to find the most effective fracture parameters on fluid flow behavior in reservoirs. The experiments are conducted in two states of single and multi-fracture networks to analyze the effectiveness of the fracture parameters. During the experiments, all the related parameters were held constant except one, and then that variable parameter was changed step by step. The flow behavior was measured in these steps and the dependency of flow on each of the other fracture parameters was analyzed. Results indicate that the sensitivity interval of fracture intensity is between 6 to 30 fractures per cubic meters. This interval for fracture dip and orientation is 0˚ to 90˚ and 0˚ to 135˚, respectively. Also, high changes in flow behavior occur when the fracture length is between 0.14 to 0.84 meters, and the fracture aperture ranges between 0.01mm to 0.1mm. Quantitative analysis of the obtained results showed that aperture is the only parameter that alters the crack behavior (from improving fluid flow to weakening it). Furthermore, sensitivity analysis revealed that for a single fracture, the aperture and orientation are the most important parameters, while the fracture intensity and aperture are the most effective ones for the multi-fracture network.

To date, various mechanistic models and empirical correlations have been developed to characterize and model two phase oil-water flow systems. However, in the most of these proposed models and correlations, simplified assumptions with the iterative solutions approach have been utilized, which do not have enough accuracy to estimate the flow characteristics. The aim of this study is to overcome this problem by developing a convolutional neural network through the deep learning. For this purpose, 270 flow tests including dispersed water-in-oil, dual continuous and dispersed oil-in-water flow tests have been conducted in the both horizontal and inclined (30o) states. The neural network was trained on 70% of the achieved laboratory data. It is necessary to explain that two-dimensional flow pattern images were used as the input data and flow patterns and liquid holdup fraction values were applied as the output data. The results of this study revealed that the applied flow convolutional neural network model is able to predict the flow regimes with 91% and 96% accuracies in the horizontal and inclined flows, respectively. This model is also able to predict the liquid holdup fraction with a reasonable error of 1.22% and 0.98% in horizontal and inclined flows, respectively. Therefore, it can be concluded that the proposed approach is able to automatically and accurately predict the flow regimes and liquid holdup fractions through flow images in the both horizontal and inclined states.

The separation of benzene and thiophene from petroleum products is one of the most important gasoline production processes in the oil industry. Imidazole and thiocyanate-based ionic liquids have been used effectively to separate benzene and thiophene. This is despite the fact that basic studies, on the other hand, remain important for the identification of this type of ionic fluid. The osmotic coefficient is the most important quantity for the electrolyte system that can be used to describe the behavior and study the interactions that occur in the systems. Therefore, the behavior of ionic liquids as electrolytes is also of special importance because these materials are highly hydrophilic, and this may change the design conditions of the process. Therefore, in thisstudy, the osmotic coefficient of the aqueous solution of ionic liquid 1-butyl-3-methylimidazolium thiocyanate (IL) in the temperature range (298.15 - 328.15) K was measured by steam pressure osmometry up to 1 mol kg-1. Water activity and water vapor pressure reduction are determined. The developed Pitzer-Archer model was used to correlate the experimental osmotic coefficient and obtain the mean IL activity coefficient. The average standard deviation for osmotic coefficient values in the binary system with the Pitzer-Archer model is 0.012. The PC-SAFT and PCP-SAFT equations were also used to predict the osmotic coefficient.

This study aims to investigate the use of hydraulic fracturing in the Bangestan reservoir in one of the major fields, which is in southwest Iran. It is a tight reservoir with natural fractures. Because hydraulic fracturing is one of the reservoir development techniques, it is extremely critical to determine the in situ stresses in order to assess the effectiveness of this technique in enhancing the reservoir’s production. For this purpose, a one-dimensional geomechanical model of the reservoir was developed. Geomechanical modeling was created based on the data available from the studied oil field wells as well as pre-existing experimental and mathematical correlations. The following criteria were determined for the candidate layer for hydraulic fracturing operations in the second stage of the research after determining the required geomechanical parameters: (1) appropriate porosity, (2) low in situ stress, (3) low water saturation, (4) low uniaxial compressive strength, and (5) high difference between the minimum and maximum horizontal stresses. The results of this study led to the selection of layer 3 of the reservoir as the target layer for hydraulic fracturing.

In this study, the catalytic performance of thin layers of Ni-Co/Al2O3-ZrO2 was explored using the dry reforming of methane (DRM) in a microchannel reactor. Physical vapor deposition (PVD) was used for preparing the nanostructures. To this end, first, thin layers of Al2O3-ZrO2 were sputtered on stainless steel plates to form catalyst supports. Then, the combination of Co and Ni were coated on the catalytic support during different deposition times (2, 3, and 4 min) with Co/Ni weight percentages of 2.5%, 5%, and 7.5%. Box-Behnken design was used for the reactor tests, which were performed under certain conditions (i.e., temperature: 700, 750, and 800 ˚C; pressure: 1 atm; and feed flow rate: 10 ml/min) to assess the impact of various parameters (including deposition time, Co/Ni weight percentage, and reaction temperature) on catalytic activity and stability. The results showed that the highest level of activity and stability was registered at the deposition time of 4 min, the Co/Ni weight percentage of 5%, and the reaction temperature of 800 ˚C.

Well integration aims to protect human life and the environment by reducing the risk of uncontrolled oil and gas production release during its life cycle. Well integrity requires safe connections for the casing, tubing, and downhole equipment. In this research, using modeling and simulation software by finite element method, a premium connection has been designed, which is required for the current conditions of oil and gas wells. The connection was loaded according to the international standard ISO 13679 in a triaxial loading, including the axial loads of tension and compression with internal and external pressure. The analysis results were evaluated using the criteria of stress and sealability. The results showed that the designed connection fully meets the standard requirements. The amount of stress created at different loads is lower than the yield strength of the material, while the contact pressure of the sealing surfaces makes reliable sealability. It was found that design by finite element analysis can be a reliable and inexpensive tool and an alternative to physical experiments.

Oily sludges are generally formed from oil residues, effluents and wastes of different stages of separation in the petroleum industry and have various and complex compositions depending on the source of production and storage conditions. In addition to reducing capacity and causing corrosion in storage tanks, these sludges will also cause environmental risks due to water and soil pollution. In this study, using physical methods, the hydrocarbon compounds in the sludge are separated from other compounds including water and solid minerals. Then by adding different percentages of separated sludge and natural bitumen to 60/70 bitumen, were formulated bitumens with different quality. The physical and chemical properties of the resulting bitumen were evaluated in the laboratory and the results show an increase in the desired quality of produced bitumen. In this paper, the surface response method (RSM) was used to optimize the bitumen production formulation.