Sharif Digital Repository

Constant drilling in the shale formation causes many problems such as shale swelling and well instability. Annually many costs are spent dealing with these problems in the drilling industry. Many factors can affect this issue. The most important factor is the type of drilling fluid and its additives. The use of oil-based mud is the best option to deal with the clays instability but, due to environmental problems resulting from OBM, their use has been banned in most parts of the world. Therefore, the water-based mud is the only option for the oil industry that can modify its property by use of additives. In this study, the muds contain Nano silica have been introduced. Silicate as shale... 

Wax deposition is one of the main problems in the oil industry. The formation of wax deposition causes problems such as reducing the effective tube radius, increasing pressure, reducing the flow capacity and etc. Even crude oil waxes can block the pipeline due to deposition of wax during crude oil production and transportation operations. If wax deposition is well predicted and effective parameters are well known and studied, they can be useful in reducing the deposition of wax, and consequently its problems and wax deposition costs will be significantly reduced. In this research, wax deposition has been investigated in Underbalanced drilling by OLGA software. In the first part, by... 

MPD technique manages drilling pressure to keep bottom hole Pressure balanced in the well. The objective to this studs, is to approximate the well pressure to formation pressure to prevent entry of fluid into the well. MPD is a new method drilling in which, driller controls the annulus pressure in order prevent drilling problems. the circulating fluids system employed by MPD technology is more akin to that of a pressure vessel. In this thesis, using in laboratory-made machine, reacts with sudden changes in pressure at the bottom hole in the shortest possible time. Basically, this system is a system where well bore pressure management is obtained by adjusting the pressures along the well bore... 

Nowadays, one of the most challenges in drilling and production engineering, is the formation damage caused by fluid filtration while drilling and completion operations. This damage would cause serious problems in pay zone and besides influencing the well performance during its life time – due to permeability reduction in near wellbore area- and cause economic expenses such as workover and stimulation operation. Therefore, considering the aspects of formation damage minimization during drilling and completion operations, the fluid selection for these purposes would be crucial. It requires the knowledge of interactions between these fluids and the reservoir rock. In this thesis, using the... 

Chemical flooding such as surfactant flooding in oil reservoirs can change the wettability and interfacial tension between oil and water and so reduce the residual oil saturation in the reservoir. Some of these materials can be adsorbed a lot on the surface of carbonate rocks, so it is difficult to predict the oil recovery factor in such process. Therefore it is necessary to survey the adsorption amount of surfactants in chemical EOR injections.In this thesis, the adsorption of a nonionic surfactant on the surface of carbonate rock is experimented and the proper model is obtained. Then the surfactant is injected in a core saturated with oil to observe the efficiency of this surfactant in... 

Aphron drilling fluids or CGA fluids are the wellknown updated drilling fluids in recent years.this kind of drilling fluids can control the mud loss into the formation and thus reduce formation damage and drilling costs. its structure consists of two phase fluid (gas and liquid) that the aphrons are the micro bubbles with 10 to 100 micrometer diameter that have strong stability in liquid phase compared to foamy drilling fluids. Generally aphron drilling fluids are made of base drilling fluid and surfactants, for more stability, mixed surfactant-polymer additive is so beneficial. in the last two decades, the Lattice-Boltazmann method is introduced for computational fluid dynamic area and... 

Two phase flow through porous media is one of great interests which have been studied for decades in petroleum sciences and even other fields, e.g. hydrology and physics, to solve problems such as enhanced oil recovery, contaminated groundwater or CO2 sequestration projects. Flow in porous media typically predict by means of Darcy’ law which in two phase flow lead to equations such as Buckley-Leverett or Koval, but today it is well approved that compact prediction of flow pattern by these equations may be accompanied by enormous errors and it’s because flow in certain condition is fractal. In this work a new mechanistic model has been used for simulating of immiscible drainage process and... 

Nowadays, one of the major challenges in the oil and gas industry is sand production, which creates many problems and can complicate the oil and gas production process, so modeling sand production and using models to estimate the start of sand production and also the amount of sand produced can help a lot in the proper management of the reservoir.In this study, first, how to obtain the critical wellbore pressure using the Mohr-coulomb failure criteria and also the Mogi-coulomb failure criteria in different cases, it is explained, that knowing the critical wellbore pressure can be helpful in estimating the start of sand production. Then, how to build a one-dimensional geomechanical model of... 

The aim of this research is to model the separation and transport of multi-component gas mixture through a nanoporous membrane by using pore network models (PNM).
The first part of this project represents the membrane simulating by means of the PNM. A three-dimensional network is used to represent the membrane’s pore space and it consists of two parts; pore and throat. The pores are the main parts of the network and their diameter is characterized according to the pore size distribution of the membrane. Every throat connects two pores and the number of throats which is connected to each pore is named "coordination number". Using a variety size of pores and throats leads to production of... 

The purpose of this research is to model transport and separation of single and gas mixtures through pore network modeling in dense membranes. In the first part of the project, the mass transfer and governing mechanisms of transport are investigated. In the second part of the project, simulation of membrane pore network in 3D of Cartesian coordinate is done. In the third part of the project permeability of single gas and ideal selectivity of binary gases for an actual membrane by desired mechanism are calculated. Then the results of pore network modeling were compare with the results from molecular dynamic simulation for single gas in polyurethane membrane with reasonable agreement. In this... 

The study of porous media, especially in pore-scales (micro and nano scales), is of particular importance in various sciences such as petroleum engineering, chemical, and civil engineering. Determine the physics of the pore scale to understand it better, identify the conditions for it to enforce the laws better, and explain some of the phenomena unknown so far, and finally obtain the parameters performed in the laboratory for specific samples are the main goals of these studies. One of the most well-known methods for analyzing porous media is pore network modeling. These models are always affected by the macroscopic structure of porous media, such as their multiscale state. In this study, an... 

Underbalanced drilling is a type of drilling operation in which the pressure of the drilling fluid is less than the pressure of the formation. This pressure difference has created advantages for this method. Less formation damage, reduction of pipe stuck, increasing rate of penetration and production during drilling are the advantages of this method compared to traditional methods. To reduce the pressure of the drilling fluid, very low density fluids should be used. One way to reduce density is to mix a compressible fluid such as gas into water. Due to the difference in density and surface tensile strength of water and gas, these two phases do not combine, so a stable combination of these... 

One of the most important EOR methods in oil reservoirs is surfactant and polymer flooding. Surfactants cause decreasing in interfacial tension between oleic and aqueous phases. However, polymers give us efficient mobility control in displacing oil by increasing the viscosity of aqueous phase. Therefore, oil is displaced in aqueous phase by viscous forces.
One of the most important challenges in surfactant flooding is adsorption. The net surface charge distributed on the rock surface depends strongly on pH. When we inject surfactant in reservoir, electrostatic charge on rock surface causes the first-layer adsorption. After that we have had second-layer adsorption.
In this thesis we... 

Poor hole cleaning while drilling due to problems such as pipe sticking and ROP reducing will increase drilling cost. It is almost impossible to optimize the hole cleaning during the well planning due to the large number of effective parameters, so it is very important to monitor the hole cleaning conditions while drilling. The best way to monitor the well condition during drilling is using the real time drilling data (RTDD). Hook load (HKL) is one of many RTDD parameters that measured at the surface during drilling operations so it can be used to evaluate the hole cleaning condition. In this research, how to process the raw data recorded while drilling has been investigated. In the next... 

Transport of drilling cuttings at the bottom of the well has always been one of the common problems of oil and gas drilling, which causes stock pipe or reduce the penetration rate and other problem. For this reason, the design of drilling fluid is one of the important drilling problems to be considered in order to optimally transfer drilling cuttings to surface. So far, many papers have been devoted to optimizing the drilling fluid for the transport of cuttings, but these papers focus on the state of drilling fluid static and less to model the dynamics and to examine the interaction between the cuttings and drilling fluid. At this end this study will modeling the drilling fluid flow using... 

Carbonate matrix acidizing using hydrochloric acid which causes CO2 generation is one of the most popular well stimulation techniques in recent decades. Lots of the wormhole propagation models developed for laboratory scale, assumes that the cores are fully saturated with aqueous solution and no CO2 gas is produced. Final purpose of this research is to develop a geochemical model describing equilibrium composition of a 3 phase system of acidic solution-gas-rock accurately in common pressure and temperature conditions of carbonate matrix acidizing to obtain main inputs of acid reactive flow in porous media from it. In this regard, concept of the “extent of the reaction” is defined and after... 

One of the major problems in directional and extended reach wells is poor hole cleaning. Directional and horizontal drilling is more complex than vertical wells. Ineffective particles transport leads to several undesirable issues during drilling. This thesis analyzed all parameters which have directly affected directional hole cleaning. The thesis is based on an experimental set-up designed in Sharif University. In the experimental work, two types of drilling fluid, Newtonian and Non-Newtonian with numerous rheological parameters, three different flow rate, three various nozzle sizes and three individual RPMs in three distinct inclinations 30°, 60° and 90° were used to simulate. Also, to... 

Any factor that causes an additional pressure drop to the reservoir is called damage. Damages due to drilling, well completion and production can cause additional pressure drop to formation. In this study, damage caused by mechanical damage, well deviation from vertical (angled well), partially completed well and horizontal well and formation damage behavior during the occurrence of water and gas coning phenomenon have been investigated by simulation and the results have been verified with the analytical models available for calculating the formation skin factor. Also, by studying and examining the data and the results obtained from the simulation of the horizontal well skin factor in a data... 

One of the best stimulation methods for oil and gas wells is matrix acidizing in order to increase the near wellbore permeability. in acidizing, good acid coverage in different layers is one the main goals. so, various methods have been presented. important part in using these methods is to not damage formation and economic matters. modern methods utilize VES acids for this purpose. viscoelastic characteristics of these materials by formation of miscellaneous, increases the apparent viscosity by a large degree. for this reason, VES fluids can be used to improve acid divergence in acid injection operation. acid system based on viscoelastic surfactants that is changed to gel instantly, can be... 

Casing design is one of the most expensive parts in the drilling of oil wells, and any cost reduction with the basic design of these casing strings will significantly reduce the total cost of the operation. In recent years, occurring scenarios-based casing design has become popular; Because in many cases, it eliminates non-occurring scenarios such as gas kick and saves on drilling costs. In this study, we have tried to investigate all scenarios that may occur during the lifetime of the well, whether drilling or production, and for each well, based on its own field information, possible scenarios for each casing part are selected separately and the applying loads are calculated. For this...