Sharif Digital Repository

Many petroleum engineering operations, such as drilling, well completions, and workover, may cause an alteration in the properties of hydrocarbon-bearing formations, including porosity and permeability. Solid and fluid influx into the reservoir in an overbalanced pressure condition can cause permeability reduction from formation damage in the invaded zone. While the solid invasion is limited to a few inches away from the wellbore, the fluids will invade significantly deeper into the formation. Therefore, the invasion of fluids may be considered as the primary mechanism that causes the near-wellbore damage. Correct quantification of the damage is an important component for predicting well... 

One of the major issues raised in the numerical models is the effects of various input parameters on the model output. Identifying the most important parameters in the output is very important in petroleum engineering, especially in tuning equation of states and history matching. Screening the most important parameters from unimportant parameters is assessable by sensitivity analysis.In this study local and global sensitivity analysis methods are used to identify the most important parameters in tuning EOS for seven different fluid samples. Global sensitivity analysis methods are more successful in correct ranking of tuning parameters. Morris method as a global method can screen the... 

This paper describes the use of Quad-Tree Decomposition for upscaling of absolute permeability 2D geological models. Quad-Tree Decomposition is a data structure and generates an unstructured upscaled model that preserves the heterogeneity of the original geological model. In other words, in high-variability regions of the geological model, the gridblocks of the upscaled model remain small but in other regions that the permeability variation is low, the gridblocks of the upscaled model are coarsened. Quad-Tree Decomposition is a very simple, efficient and robust method that reduces the total number of gridblocks and results to high saving in time and memory required to flow simulation in the... 

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... 

One of the three fundamental methods in reservoir evaluation is coring, other two methods are logging and well test. Coring is an operation during which, samples from formation rock are taken, and used for laboratory tests and examinations. Although coring presents exact information from reservoir rock, its small scale is the reason of some laboratory errors. This operation is fulfilled with special bits. Coring importance shines where it could give us an idea of reservoir conditions; however cannot be develop it, to all of the reservoir. Coring is used to identify rock properties like porosity, permeability, wettability and fluid properties like fluid density or fluid saturation. Rock... 

A genetic-based pore network extraction method from micro-CT images is proposed in this work. Several variables such as the number, radius and location of pores, the coordination number, as well as the radius and length of the throats are used herein as the optimization parameters. Two methods are presented for modeling the pore network structure. Unlike the previous models, these methods are directly based on minimizing the error between the extracted network and the real porous medium. This leads to the generation of more accurate results while reducing required computational memories. Two different objective functions are used in building the network. In the first method, only the... 

Investigation of reservoir performance and long-term production prediction are main goal of numerical simulation. Numerical simulation mainly consists of solving sets of non-linear equations developed by combination of continuity equation, equation of state and Darcy equation. Classical methods such as finite difference method (FDM), finite volume method (FVM) and finite element method (FEM) are widely used for solving sets of fluid flow equations that mentioned above. Researchers have used other methods like boundary element method recently. Each of these methods has their own restrictions. But the main source of error in these methods is due to numerical estimation of spatial derivatives... 

During the drilling process, cutting concentration in vertical and inclined wells is a common problem and major issue in designing hydraulic parameters. This is becoming more important in near bit area. Cutting transport usually is affected by several parameters such as mud rheology, flow rate, nozzle size, rotation speed, and mud weight.
In this work it was aimed to design a new set-up to test all the factors on hole cleaning phenomenon especially in near bit area. The set-up consists of a 16 feet long flow loop, 3.28 feet height of the test section, and 3.33 inches inner diameter of the test section. Each parameter which has an impact on hole cleaning could be varied. The cutting... 

The efficiency of acidizing operation is usually assessed through Build up or Drawdown test (calculation of skin). These methods are performed only after the acidizing operation, so it is impossible to evaluate the efficiency of acidizing during the real time operation. Analysis of the acidizing efficiency during the operation by using the acidizing operation data is a viable approach to this costly and challenging process. In this project, it has been tried to present a well testing method for calculating changes of skin value of a carbonate reservoirs during acidizing operation by using the real field data (surface pressure, injection rate and etc.).
The estimation of skin changes... 

Drilling operation is one of the most important parts of oil production procedure. Therefore, drilling optimization has an effective role in ultimate benefits and total cost reduction. Also formation damage can affect reservoir performance. In this study, a combination of optimization methods for each part of drilling operation has been used and fitness function of total cost is presented. This function includes number of bit runs, bit selection, controllable parameters and drilling mud properties. For prediction of formation damage radius and variable risk analysis, two new methods are proposed and have been used as fitness functions. Finally, by suggesting a multi objective optimization... 

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... 

The static and dynamic properties of a porous medium are highly dependent on its internal geometry. CT scan images are used to obtain porous media geometry. These images are not directly suitable for computational purpose. Because these images are not easy computable, the pore-throat network models are used to geometrical conversation. Extracting these models from CT scans is done using statistical-probabilistic methods based on image processing. In this study, new methods for extracting the 3D pore network model from 2D/3D CT scan images and pore connection detection are presented. In this method, the geometric static parameters of the rock, including the porosity, the porosity-based... 

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... 

In drilling operations, cost, time, and quality are the three factors to consider for evaluation. Drilling optimization means reducing project costs and completing them as quickly as possible while still meeting the standards. Due to the complexity and specificity of directional drilling and the increasing need for this type of drilling, optimizing the directional drilling operation is of great importance. Drilling rate of penetration and hydromechanical specific energy are considered as two main indicators of drilling performance in this thesis. In the first step, drilling rate of penetration is predicted using drilling data and machine learning algorithms and then single-objective 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... 

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... 

One of the most important problem in oil and gas well drilling is well cleaning and pipe sticking. This problem more sensitive when depth is increase. When a well is drilled, cuttings must be transported to the surface. For this reasen use drilling mud to circulate in well and transport the cuttings. Drilling mud exit from bit nozzle, wash and clean the well. Well cleaning depends on this parameter: fluid viscosity, annulas flowrate, well inclination, cutting size and shape, cutting density and mud density.The aim of this thesis is study and simulate of cutting transport phenoimena while drilling is running with comertial software like Fluent and Comsol. We study forces acts on cutting... 

In this study, the green element method is used to model petroleum problems such as oil production due to expansion mechanism, one and two dimensional spontaneous imbibition and water flooding. Despite of boundary element method that its applications in reservoir engineering are limited to simulation of single phase fluid flow in homogenous media, green element method can solve multi-phase flow in heterogamous media. In this thesis, by this method the governing partial differential equation for these processes are modeled and then solved. In one dimensional medium, green element method can successfully simulate the oil production from heterogamous reservoir due to expansion mechanism. The... 

Oil reservoirs, have integrated identity; that is they consist of different parameters such as wettablity, initial water saturation, capillary and gravity forces, etc. which are related to each other and affect ultimate recovery simultaneously. In fractured reservoirs, other parameters such as fractures and complex geological structures are also considered  among  important  parameters  which  affect  ultimate  recovery.  Due  to  large  amount  of reserves,  fractured  reservoirs  are  subject  to  different  studies  and  simulations.  In  this  research, different  parameters  which  affect  ultimate  recovery  in  fractured  reservoirs,  are  studied  and simulated. Different  studies ... 

One of the most important issues in modeling and simulation of reservoirs is determination of different rock types or Rock Typing. In this study, after a brief review of some conventional methods for rock typing, their capabilities have been investigated. In this way, for the first time, pore network modeling is used as a tool for validating the rock typing methods. By using flow simulation in porous medium with pore network modeling approach, similar rock types data have been generated and these artificially data have been used for validating of rock typing methods. To form more realistic pore networks, both regular and irregular pore network have been modeled and analyzed. Pore size...