Faults play a significant dual role in oil and gas reservoirs. Faults cause the migration and mixing of oil from separate horizons in one field, and also cause secondary porosity in the rocks and the release of hydrocarbons from the system. Fault plays a fundamental role in the formation of oil traps indirectly. It may block and prevent the fluid in one  direction, as well as transfer and providing a permeable passage for the fluid in  another direction in oil and gas reservoirs. Different types of faults such as normal fault, reverse fault, straight fault, slip fault and thrust fault can cause the formation of oil trap. Identification the  faults  in hydrocarbon reservoirs are very important for  enhanced oil recovery and development of oil fields. Correct description and drawing of faults can facilitate development projects in the oil industry. In this paper, the role of geological faults in oil and gas reservoirs will be discussed. 

Folding is a geological process in which the rock layers of the earth's crust are bent and deformed under enormous tectonic pressures, without significant fracture occurring. This phenomenon usually occurs as a result of the movement of tectonic plates and creates structures such as mountains, valleys, and domes. Folding shows the flexibility of rocks in certain conditions and tells a part of the history of the earth's evolution. Folding causes the formation of anticlines that can form good oil reservoirs. But folds, like faults, can cause hydrocarbon migration. Understanding the geometry and pattern of folds in thrust belts is an important part of the knowledge required in the exploration of hydrocarbon reserves. In addition, understanding the geometry and pattern of folds helps to better understand the physical aspects of reservoirs and provides a basis for advancing in other fields of reservoir studies. In this paper, the role of geological folds in oil and gas reservoirs will be discussed. 

A formation is a set of layers that have a specific lithological composition and spread and extend over a relatively wide area. By examining sediments and deposits, geologists find out the sedimentary environment. The formation boundaries with the lower and upper layers is clearly defined. The top and bottom of a formation is defined, but its thickness has no definite limit. The junction of each formation with its upper and lower formations is called formation boundary. This border can be in different forms. Specific and sudden boundaries, gradual, discontinuity, between fingers, etc. make all kinds of boundaries of formations. In any case, the boundaries of the formations are clear and distinguishable from their upper and lower formations, whatever their state. When two adjacent formations cannot be separated due to their similarities, they can be named together. In this paper, determining the boundary of a geological formation in a sedimentary basin will be discussed. 

The structure of a geological formation is determined by several factors that can be divided into two main groups: internal factors and external factors. Internal factors include the composition of rocks, type of sediment, thickness and arrangement of layers, while external factors include erosion, re-deposition (repeating deposition), movement of geological plates and climate changes. These factors interact and contribute to the unique structure of each formation. Different compositions of rocks resist weathering, erosion and other geological processes differently. The type of sediment determines the physical and chemical properties of the formations and in turn affects the processes of deposition, weathering and erosion. The type of sediments forming the formation (such as sand, clay, limestone) affects its structural characteristics, such as density, shell and particle size. Erosion can lead to deformation, reduction of height and even complete removal of formations. In this paper, parameters affecting  the structure of a geological formation will be discussed.

The phenomenon of formation damage refers to any harmful process that, by affecting the reservoir formation especially the reservoir rock permeability, reduces the production capability of an oil or gas well or the injection capability of a well compared to its natural state. Therefore, formation damage is an undesirable phenomenon that, if it occurs, can cause many operational problems and economic losses. Reduction in production rate or flow rate of oil and gas from the well, reduction in the rate of water and gas injection into the formation, increase in pressure drop as a result of production and shortening of the life of the reservoir, and finally reduction of hydrocarbon reserves, which can be produced with economic efficiency, are all effects of formation damage. But it should be seen how severe these effects are and whether their effect on the performance of the reservoir and well is significant? In fact, the severity of damage to the formation depends on factors such as the type of damage and the method of completing the well, which we will discuss further in this paper.

In geology, the pressure of a formation means the fluid pressure inside the pores of a geological formation, usually known as pore pressure. This pressure in the formation can be lower or higher than the hydrostatic. Pore ​​pressure is determined based on factors such as depth, temperature and type of sediments of the formation and can affect the behavior of the formation. The pressure of the formation is caused by the weight of fluids inside the underground permeable rocks. By increasing depth, the pressure will be increased. The water accumulated inside the porous and permeable formations gets more pressure with increasing depth, just like the pressure increases with increasing water depth in the seas. As the depth increases, the vertical distance increases the fluid pressure. The formation pressure is directly related to the subsidence rate of the bed of the sedimentary basin as well as the rapid sedimentation rate of particles in it. If the bottom of the sedimentary basin has continuous subsidence due to tectonic factors and the rate of sedimentation in such a basin is fast, it causes a large thickness of sediments to form in a short period of time. In this case, increasing the weight of the upper layers to the lower layers causes an increase in the formation pressure.

Surfactant-gas flooding is one of the new methods for enhanced oil recovery. In this method, the simultaneous injection of gas and surfactant solution leads to the formation of foam. Foam reduces the mobility of injected fluids and improves the displacement efficiency of enhanced oil recovery process. Currently, surfactant is used to produce and stabilize foam. Surfactants generally lose their desirable physical properties at high temperature and salinity and are wasted due to adsorption on the rock surface in the porous medium. The most important weakness of foam formed with surfactant is its short-term stability; Nevertheless, if nanoparticles are used instead of surfactant or together with it to produce and stabilize foam, it can eliminate the limitations of using surfactant. By using nanoparticles, a stable foam which have long-term stability in reservoir conditions can be designed to use it as a control agent for the mobility of injected fluids in enhanced oil recovery.                              

The formation of heavy oil in a reservoir rock is influenced by many factors, including temperature, pressure, and the type and composition of hydrocarbons. Factors such as temperature and pressure can drive hydrocarbons to heavier weights, while hydrocarbon composition and reservoir rock type can also affect oil density and migration. Increased pressure can push hydrocarbons toward heavier molecules, thus accelerating the formation of heavy oil. The presence of heavier and carbon-rich hydrocarbons alone can contribute to the formation of heavy oil. Some reservoir rocks, such as sandstone and limestone, are more suitable for heavy oil accumulation due to their permeability and ability to pass heavier hydrocarbons. The processes of primary and secondary migration of hydrocarbons, in which oil and gas move from the source rock to the reservoir rock and accumulate there, play an important role in the formation of heavy oil too. In this paper, we will discuss about factors related to the formation of heavy oil in a reservoir rock.

The behavior of oil wells in salt formations is complex and different from wells drilled in other geological formations due to the unique characteristics of these formations, such as dissolution and sedimentation cycles, changes in salt volume and potential. They show non-linear and complex behaviors due to their low resistance to compressive forces. Salt formations are known as important oil traps, and drilling in these formations and maintaining wells during production are important challenges in drilling engineering. Salt easily dissolves in water and this can cause gradual erosion of the formation and changes in the surface of the earth. The volume of salt changes with temperature and pressure changes. This can cause changes in phase and mobility in the formation and wellbore. Salt can act as an electrical conductor and affect the electrochemical activity in and around the well. Salt formations have little resistance to compressive forces due to their crystalline structure. This makes it possible to encounter large holes during drilling. Salt formations show nonlinear behaviors. For example, due to changes in temperature or pressure, the formation may contract or expand. This makes it difficult to predict well behavior over time.

Factors affecting erosion in geological formations include internal and external factors. Internal factors include the characteristics of the rocks themselves, such as their strength and discontinuities, and external factors include climate, vegetation, slope, and weathering processes. In addition, the type of lithology of the region plays an important role in erosion. Some rocks are easily eroded and others are more resistant. For example, in areas with limestone, chemical erosion is greater than mechanical erosion due to the high solubility of lime. While in areas with sedimentary rocks, mechanical erosion plays a more important role. The behavior of different rocks against erosion is different and some lithological units are sensitive to erosion and prone to produce sediment. The behavior of Quaternary rocks and deposits against weathering and erosion depends on several factors, some of which are related to the nature of the rock and other factors related to the external environment including the rock.

Foam in a porous medium is a gas phase within a liquid phase, which is mainly made of thin layers. These thin layers are stabilized by surface adsorption at the gas/liquid interface. Foam injection into oil wells is an effective method to control gas-oil ratio (GOR), especially in heterogeneous and carbonate reservoirs with natural fractures that are prone to gas ingress. This method is effective because the foam can act as a barrier to gas passage and thus reduce the gas-to-oil ratio. Foam can be used to improve the condition of the production wells that have high values ​​of gas-oil ratio (GOR) in an oil carbonate reservoir. Foam is injected through perforations that produce large amounts of gas to block the path of gas production and cause more oil to be produced from the rest of the well holes at the same time. The foam compensates for the lack of pressure near the well to calm the water and gas coning in thin oil layers, which is called anti-water and gas coning foam technology.

Foam injection is used in oil reservoir to reduce surface tension between gas and oil and also between water and oil. Foam is an intermediate state between gas and liquid that can reduce surface tension and thus increase oil production. This method is usually used for reservoirs with heterogeneities in reservoir rock properties or fractured reservoirs, where gas injection alone is problematic. Foam injection can be done with the aim of delivering the surfactant to the oil inside the matrix and reducing the surface tension between the gas and oil. In this case, with the reduction of capillary forces, the existing balance between capillary and gravity forces will be more in favor of gravity forces, oil recovery will be increased. This method reduces surface tension on the liquid surface and improves gas flow in non-homogeneous areas in an oil reservoir. Foam injection causes uniform displacement of the fluids in the reservoir and prevents the occurrence of fingering.

One of the methods that has recently received attention in oil recovery and the topics of increased extraction is foam injection in the tank, which partially improves the defects of the mixed and non-mixed gas injection method and leads to more oil recovery. Based on the main goal of foam injection and the characteristics of the reservoir fluid and rock, it is necessary to design its structure and type. One of the most important parts of these designs is choosing the appropriate surfactant. Foam injection can be done with the aim of delivering the surfactant to the oil inside the matrix and reducing the surface tension between the gas and oil. In this case, with the reduction of capillary forces, the existing balance between capillary and gravity forces will be more in favor of gravity forces, oil recovery will be increased. In this paper, oam Injection into an oil carbonate reservoir to increase the viscous forces against the capillary forces will be discussed.

In recent years, the increase in oil consumption has caused a strong need to improve the technologies of enhanced oil recovery. One of the common methods for enhanced oil recovery is the gas injection method. However, when gas is injected into the reservoir, problems such as gravity rise due to the low density of gas compared to oil and the high mobility of gas compared to oil reduce the efficiency of this method. Foam can improve mobility and increasing oil recovery by reducing gas permeability. Today, for foam stability, polymers are added to the solution containing foam. In injecting water into the reservoir, adding polymer to the injection water increases the viscosity of the injection water and the mobility ratio of water to oil also decreases. As a result, the sweeping operation is done better and the efficiency of oil production increases. It's better to use polymers that have dual properties, so, in addition to regulating the mobility of water, they create foam and limit the mobility of gas.

Artificial intelligence is one of the most advanced and widely used technologies in various scientific and industrial fields, which is widely used in various industries due to its capabilities. In the meantime, the oil and gas industry is also one of the industries that using artificial intelligence can help to improve and increase productivity in various processes and activities of this industry. One of the main applications of artificial intelligence in the oil and gas industry is forecasting and data analysis. With the help of artificial intelligence algorithms, it is possible to analyze information related to oil and gas reservoirs in a more accurate and reliable manner and make better decisions for production from these reservoirs. Through data analysis, it is possible to improve the quality and achieve zero error. Also, artificial intelligence helps with intelligent decision-making and control in automation processes in the oil and gas industry. By using artificial intelligence systems, the processes of production, drilling, transportation, refining and sale of oil and gas can be performed automatically and with higher quality. This work reduces errors and costs and increases productivity and efficiency in the oil and gas industry.

Foam injection can be used to change the wettability of the reservoir rock, especially in reservoirs with a high degree of heterogeneity where gas injection is associated with problems. Foam can help the production of residual oil in the matrix by reducing the surface tension, changing the wettability of the rock and directing the surfactant solution towards the matrix. Based on the main goal of foam injection and the characteristics of the reservoir fluid and rock, it is necessary to design its structure and type. Among the other important mechanisms that have a great effect on the increase of oil recovery using foam, it is possible to change the wettability of the reservoir rock. Foam injection in carbonate reservoirs to change reservoir rock wettability is one of the effective methods to increase oil recovery. In this regard, the use of additives such as nanoparticles in order to improve the quality and stability of the foam can lead to positive effects of the properties of reservoir rocks and fluids.