abbas hashemizadeh

Considering the extent of unconventional gas reservoirs and the exigency of optimal production from these resources, the design of hydraulic fracturing operation according to the geomechanical aspects is the most important step in the exploitation of these resources. Oil and gas sources differ from each other in many aspects, such as the shape of source and reservoir rocks, mechanisms of formation, penetration, distribution and occurrence. Unconventional reservoirs are resources that cannot be exploited economically with conventional resource extraction methods.

Methodology and Approaches:

Before drilling, the reservoir is in equilibrium, and no special stress causes the reservoir to collapse, but after the drilling operation, stresses are applied to the reservoir as induced stresses, which cause the loss of balance and instability in the wellbore. In this regard, the greater the distance from the center of the well, the stresses will decrease. Knowing the direction of minimum and maximum horizontal stresses helps engineers to predict the possibility of casing collapse.

Due to the low permeability of the unconventional gas reservoirs to achieve optimal production from these sources, geomechanical parameters are of particular importance. To increase production from these sources, one of the most widely used operations worldwide is a hydraulic fracture. One of the important components in studying the propagation of hydraulic fissures is the difference in horizontal stresses. According to what has been obtained based on geomechanical studies in Roseneath and Murteree formations, for reservoir rocks with low horizontal stress such as sandstone reservoirs, the fracture pressure of the formation is much lower. However, the shale reservoir with more horizontal stress has more failure pressure and the fracture in these reservoirs has less expansion. On the other hand, studies in the Montney Formation indicate that Poisson's ratio and Young's modulus affect the characteristics of shales such as their fragility. In this regard, a formation with a lower Young's modulus is more difficult to fracture and is not considered a suitable option for hydraulic fracturing operations.

To avoid drilling damages, it is very important to determine the field stress. Prediction of elastic parameters such as Poisson's ratio and Young's modulus is of great importance in determining in-situ stress and completing geomechanical modeling. These parameters are calculated statically through laboratory tests on drilling cores or dynamically through log data. However, such data may not be available in the oil field data-bank. Therefore, Daily Drilling Reports (DDR) can be introduced as a suitable alternative for predicting rock’s elastic modulus. In this study, for the first time, an attempt has been made to estimate the Dynamic Young’s modulus using DDR data with the application of a variety of conventional machine learning methods. In this regard, linear, support vector machine (SVM), artificial neural network (ANN), Random Forest (RF) LSBoost, and Baysian have been used. Input data to these algorithms also include depth, string rotary speed (RPM), rate of penetration (ROP), weight on bit (WOB), density (RHOB), porosity (Φ), pump pressure (PP), and tangential velocity (TV). Each of these algorithms was then compared in terms of accuracy using correlation coefficient (R2), mean squared error (MSE), and root mean square error (RMSE) criteria. Finally, using conventional experimental correlations and using core data, the resulting values were converted to static values. The results show that using daily drilling reports, based on the above criteria, a good estimate of the elastic parameters can be achieved. Also, among the methods used, Baysian and LSBoost methods have slightly higher and better accuracy than other methods.

The study of factors affecting wellbore stability has become very important in the oil and gas industry because they will save time and costs. In studying the stability of oil and gas wells, different factors such as mechanical properties, in-situ stresses, and pore pressure can be used. Consequently, knowing and calculating these parameters will be helpful in analyzing the wellbore stability. This study evaluated the effects of changing stresses on the wellbore stability and drilling mud weight window using a ratio of different stresses for the first time in one of the wells of the Zireh gas field, located in the southwest of Iran. Due to the lack of laboratory data, each of the parameters of the geomechanical model were determined by empirical correlation. Using Mohr-Coulomb and Mogi-Coulomb criteria, the drilling mud weight window was determined to be 76.99-128.17 (pcf) and 67.56-128.17 (pcf), respectively; however, Mogi-Coulomb provided better results. The wellbore stability is also investigated by using 3D numerical modeling using ABAQUS software and the Mohr-Coulomb criterion. According to the results of the numerical and analytical methods, the well is completely stable. Ultimately, five different in-situ stress ratios were examined to determine how in-situ stress distribution affected wellbore stability. According to the results, the mud weight window range decreases as the stress changes from an isotropic to an anisotropic state, indicating wellbore instability.

In the primary oil recovery, which is done using natural mechanisms in the reservoir, less than one third of the volume of petroleum is produced in the best cases for various reasons, including the process of reducing the pressure caused by production. In addition, by adopting secondary methods of oil recovery, such as water injection, despite the widespread use, due to the high mobility of water relative to oil, a large part of the resources will not be able to be produced. Therefore, in order to meet the demand for crude oil, which is constantly increasing, there is always a need to use EOR methods of overdraft to increase the recycling rate after the start of production. One of the efficient methods to increase the efficiency of the crude oil sweeping process is polymer injection (or flooding), which has been used as one of the chemical methods of oil recovery for many years. Since Case Study is a wide, in-depth, and detailed study of a particular case and thus accesses a wide range of knowledge for the analysis of complex systems, the assurance of case study research that all components have been examined is assured. In this study, after a comprehensive review of successful case studies, EOR by polymer flooding operations, the factors and conditions affecting each of the stages of polymer selection, injection operations and then its impact on the rate of increase in production rate and also the rate of reservoir oil recovery has been studied. The results of this operation in different oil fields show the addition of suitable polymer to water in the flooding process and in different conditions, the potential to reduce water production and also reduce the amount of oil saturation remaining in the reservoirs and thus increases oil recovery factor.

Only 10% of Iran's oil reservoirs have a sandy structure and the rest have a carbonate structure. Therefore, a relatively large part of the oil in these reservoirs is heavy and can not be extracted by conventional methods. For this reason, methods called enhanced recovery are used to increase the recovery factor of oil reservoirs. Enhanced recovery is performed by secondary and tertiary methods, which include thermal and chemical methods and gas injection are among the tertiary methods. One of the chemical methods is polymer flooding. For many years, polymers have been used to control the mobility of injected water and to enhanced recovery of oil reservoirs. By increasing the viscosity of polymers, they reduce the mobility of water, increase the stability of the kinematic profile, reduce the phenomenon of finger injection of the injected fluid, and finally increase the oil production from the reservoir. In this paper, first the application of polymers in oil reservoirs, then the types of polymers used in the discussion of enhanced oil recovery, including polyacrylamides, alkali-surfactant-polymer, xanthanes, polysaccharides, and hydroxyethyl cellulose have been investigated. In addition, destructive factors of polymer structure, factors affecting polymer flooding, different injection patterns, screening criteria, and in general parameters affecting the succesful operation and its general dimensions, as well as, simulation of polymer flooding in one of the Iranian oil fields are investigated.

Petroleum hydrocarbon pollutants are one of the hardest compounds in terms of decomposition and control and classified as stable and important organic pollutants that have adverse effects on human health and the environment and combating environmental pollution caused by them is an important issue for the world and human societies. Although the removal of these pollutants from the environment is a major problem, biodegradation (which uses natural microbial biodegradation activity) is an ecofriendly and economical approach to control these types of contaminants and has become a pivotal method of cleaning up environments contaminated with petroleum hydrocarbons. The present study provides a comprehensive, uptodate and efficient review of the bioremediation of petroleum hydrocarbon pollutants, taking into account the hydrocarbon alterations in microorganisms with a particular focus on the new insights gained in recent years. Also, the metabolism of hydrocarbons in microorganisms has been described by reviewing research presented in recent years. The results of studies show well that petroleum hydrocarbon pollutants are biodegradable using some microorganisms such as oleophilic and their removal by this method is cost-effective and economical. Microbial biodegradation of petroleum hydrocarbon contaminants uses the enzymatic catalytic activities of microorganisms to increase the degradation of contaminants several times more than traditional methods

The magnetic field (MF) affects the corrosion rate of N-80 carbon steel (which is frequently used in petroleum industry) in 3.8 Molar (or 12.5% weight percent). HCl was studied first at different conditions by implementing the potentiodynamic polarization (PDP) and gravimetric weight loss (WL) procedures. Response Surface Methodology (RSM) was next implemented to investigate and simulate the impacts of intensity of the magnetic field, time of magnetization, and elapsed time on the efficiency of corrosion inhibition (η). The test results revealed that acid magnetization considerebly decreases the rate of corrosion of N-80 carbon steel (CS) in the presence of HCl up to 93% so that it can be used as an eco-friendly and cost-effective substitute for the common corrosion inhibitors. The results also revealed that η enhances by enhancing the intensity of magnetic field. The morphology of the N-80 CS surface was also studied using SEM in the magnetized and normal HCl solutions.