فهرست مطالب yousef mirzaeian

Mining has been always one of the riskiest and most uncertain activities. Although this uncertainty in conventional economic models (traditional method of net present value or NPV) is considered costly due to the risk of forecasting error, the theory of real options, by considering the value of managerial flexibilities in dealing with these uncertainties, has a positive value. Contrary to the theory of real options, traditional methods of financial evaluations, ignore the value of managerial options and the flexibility of the project. One of the management options in mines, which has been studied in this research and a scientific strategy has been presented for its use, is the authority to store the final product of the mine for a specific period. In this study, assuming that the final product price of the mine follows the Mean Reversion Process (MRP), the type of storage option of the final product of the mine is determined as well as its parameters such as the option time to maturity, option Strick price and the cost of acquisition, and then the option value is evaluated using the binomial lattice network. Finally, using optimization methods, the best market price for gold storage and the expected limits for storage profitability have been determined. The results of this study show that at present, for a mine with sufficient working capital for 6 months of production and a storage cost of $ 5 per ounce, storing the final gold product at a market price of less than 1371 $2022/Oz has a positive (profitable) expected value. Also, the highest value of storage decision was obtained at the world price of 670 $2022/Oz and with the value of 130$2022 per ounce. The relative efficiency of storage is estimated to be up to 21%. It is worth mentioning that to use this article in different mines, its results must be updated by changing the assumptions and new market conditions.

The presence of pores and cracks in porous and fractured rocks is mostly accompanied by fluid flow. Poroelasticity can be used for the accurate modeling of many rock structures in the petroleum industry. The approach of the stress to the value of the fracture stress and the effect of pore pressure on the deformation of rock are among the effects of fluid on the mechanical behavior of the medium. Due to the deformation-diffusion property of porous media, governing equations, strain-displacement, and stress-strain relationships can be changed to each other. In this study, constitutive equations and relationships necessary to investigate the behavior and reaction of rock in a porous environment are stated. Independent and time-dependent differential equations for an impulse and point fluid source are used to obtain the fundamental solutions. Influence functions are obtained by using the shape functions in the formulation of the fundamental solutions and integrating them. To check the validity and correctness of provided formulation, several examples are mentioned. In the first two examples, numerical application and analytical solution are used at different times and in undrained and drained conditions. In times 0 (undrained response of medium) and 4500 seconds (drained response of medium), there is good coordination and agreement between the numerical and analytical results. In the third example, using the numerical application, a crack propagation path in the wellbore wall is obtained, which is naturally in the direction of maximum horizontal stress.

Nowadays, hydraulic fracturing is used in various fields such as stimulation of oil reservoirs, measurement of in-situ stresses, extraction of geothermal energy and extraction of conventional and unconventional hydrocarbon resources.Meanwhile in-situ stresses and porosity are the most important factors that affecting the propagation, opening and extension of the crack. In this research, the above parameters have been investigated using analytical and numerical methods. For numerical modeling in this research, the numerical method of displacement discontinuity, has been used, which is one of the methods with high ability in modeling discontinuity and failure. The program used is a quadratic element based on solid mechanics and fracture mechanics. In this research, by addition of the fluid flow module, the fluid mechanics is included in the analysis. In the fluid mechanics module, the effect of fluid flow on crack opening displacement is investigated. This part of the program is created by finite difference method in mode of forward time central space. Finally, after validation of the program, the effects of in situ stress and porosity on crack propagation were investigated. In order to generalize the results, the studied parameters have been presented in dimensionless forms. It is concluded that the best direction for creating a hydraulic fracture is in the direction of maximum principal stress. As the in-situ stress difference increases, less injection pressure is required to propagate the crack. In the crack with a 45 degrees angle relative to the maximum stress, a lower injection pressure is required to propagate the crack; then this crack after several step of growth deviates to the maximum stress direction. Increasing the porosity of the formation reduces the amount of Young's modulus and Poisson's ratio, which leads to increases the crack opening at higher porosity values.

The MIP technique in combination with Piecewise linear function has lead to a method of stope design, which uses a one, two or three-dimensional discretisation of the ore zone (block model). An optimal economic stoping boundary is developed by optimizing the starting and ending locations for mining within each row or column of blocks (a mining panel). To determine these locations, two piecewise linear, cumulative functions are used for each row. The stope boundary model is optimized using a MIP approach that employs a special kind of variables named “special ordered sets type 2”. This paper presents a step by step explanation of the model construction. The optimizing problem is solved using the MIP approach. GAMS/Cplex11 software tool is employed to numerical examples. The model is validated by comparison with similar cases.