نشریه روش های تحلیلی و عددی مهندسی معدن
پیاپی 23 (تابستان 1399)

Identification of deep ore deposits is one of important subjects in exploration field. Discrimination of dispersed mineralization zones and blind mineralization area is an important challenge in exploration of mineral deposits. Geochemical Zonality method and alteration models are traditional method that utilized for exploration of deep ore deposits specially Cu porphyry and Au veiny deposits. In this study, the anomaly thresholds have been determined using the fractal method for calculating the Zonality indexes in Tanurcheh area and then 4 important Zonality indexes have been used. In addition to these traditional methods, suitable information in this field can be achieved using interpretation of geochemical data in frequency domain. The situation of deep deposits and dispersed zones can be surveyed using interpretation of frequency anomaly in frequency coefficients of elements method. In this study, the potential of deep mineralization in one part of Kashmar Au and Cu mineralization area has been surveyed by frequency coefficients of elements method and obtained results have been compared to Zonality method and information of deep exploratory boreholes. The results of frequency coefficients method have properly been confirmed using the results of deep drillings unlike Zonality method.

In the first stages of study exploration of hydrocarbon resources, geophysical methods and exploration well drilling are considered costly. Therefore, using of organic geochemical methods, it is possible to analyze the hydrocarbon resources in the region as well as Khouriyan Desert located in southern Semnan. The exploratory activities in this region have begun in 1927 by Russians to search for hydrocarbon resources. In this study, 15 samples of surface soils have been taken to a depth of 1-2 meters from this area. Surface samples taken are analyzed under the Rock-Eval pyrolysis analysis. In this analysis, the results obtained from peak S1 express the presence of free hydrocarbons in soil samples. Also, XRD analyzes and determination of soil pH in the region have been performed as surface geochemical methods. The existence of environmental alterations in the studied area has necessitated an examination of the sulfur isotope and the presence of iron ion in this region. The results of this study indicate the presence of migrated hydrocarbons on the ground, which has led to the development of hydrocarbon contaminants in this area. This issue, coupled with the existence of a hydrocarbon system of lower red, Qom and upper red, can indicate the presence of hydrocarbon reserves in this area.

Summary Using rock physics models, it is possible to simulate the reservoir more precisely and as a result, the risk of exploration and production of oil and gas will be reduced significantly. In this study, three models of Self-Consistent-Gassmann, Xu-Payne and Xu-White model was investigated in a two wells in a carbonate reservoir in southwest of Iran. Then, two fused model was proposed to improve the accuracy and improve the efficiency by using the Sugeno fuzzy integral fusion method and Simple Additive Weighting (SAW) Model, respectively. The compressional wave velocity and shear wave velocity were estimated using 5 mentioned models. The results show that in Xu-White and Sugeno fuzzy integral models, the estimation of compressional and shear velocity in well A have the lowest (79 and 81) and the highest correlation coefficient (99 and 98) with real data, respectively. This indicate that the Sugeno fused model is the best estimate. Introduction Since the seismic reservoir characterization have a very important role in all stages of exploration up to the development and production of hydrocarbon reservoirs, it is important to identify the relationship between reservoir properties and their elastic behavior, using rock physics model. In order to improve the rock physics models, researchers proposed different methods, which in this study Sugeno fuzzy integral fusion method has been used. Methodology and Approaches The study of the elastic properties of rock physics on carbonate rock was carried out through of Self-Consistent-Gassmann, Xu-Payne and Xu-White rock physics models. All these models were built to derive optimal elastic properties to obtain reliable estimates of compressional wave velocity, shear wave velocity. The main step consisted of modeling each of the seismic rock properties over a specified porosity, pore space system and hydrocarbon type. At the end, these two models are fused by the Sugeno fuzzy integral fusion model and SAW model. All the models have been evaluated by measured (observed) data. Results and Conclusions Three models of Self-Consistent-Gassmann, Xu-Payne and Xu-White rock physics were evaluated and compared using petrophysical and geological data, in a carbonate reservoir of an Iranian oil field. By examining the results of compressional and shear wave velocity estimation using two fusion methods (SAW and Sugeno) and three models of rock physics, it is determined that the methods and models used for the studied carbonate reservoir have given a satisfactory result, but the Sugeno fusion model has improved the results. The reason for this could be related to the use of optimization algorithms in the Sugeno.

One of the most advanced methods of cutting materials is water jet cutting. Due to its advantages over other cutting methods, it has been widely used in recent years. Cutting with a water jet is a subset of fluid and structure interaction issues in which water flows into the boundaries of the rock, and this changes the shape of the rock in the impact area. In order to examine this issue accurately, the boundary conditions of water and rock must be coupled in order to obtain the correct behavior of the collision area, which is the most important and complex part of simulation by theoretical, experimental and numerical methods. In this paper, the rock cutting with water jet is simulated using a smoothed particle hydrodynamics method, which is a lagrangian numerical and meshfree method. For this purpose, firstly, the governing equations for fluid and solid are discretized with the help of the predictive-correct algorithm. Then, using the algorithm based on these equations, two-dimensional collision of water jet and rock and breaking behavior of rock are simulated. With this method, the depth and width of the cut can be determined at different speeds of the water jet and the optimal cutting speed of the stone is obtained. The results of the simulation have acceptable accuracy compared to the experimental results and shows that the smoothed particle hydrodynamics method is a suitable method for the analysis of rock cutting with water jet.

The clustering analysis is a method for data classification based on the similarity, so that the most similar data are placed in the same cluster. The cluster analysis of petrophysical data is able to determine the quality of sandstone reservoir based on the different existing lithologies. Since the most sandstone reservoirs have different kinds of interbedded shales as well as different detrital and chemical minerals due to their sedimentation environment, they show a variety of lithologies and consequently different reservoir qualities. The determination of the most effective petrophysical logs based on the environment understudy has a significant effect on the clustering quality, lithology determination, and the reservoir quality evaluation. In this research, to determine the most effective logs in the two stage and k-means methods, the GR, LLD, LLS, MSFL, DT, URAN, THOR, POTA, CALI, NPHI, RHOB logs were chosen as the input in IBM SPSS, Statistic version 24. Based on the obtained results, the GR, LLD, LLS, NPHI, and RHOB logs are the most effective logs for two stage clustering method. This result was in agreement with the k-means method findings. Based on the clustering results, the understudy sandstone formation with a thickness of 222 meters were classified to three lithological groups of carbonate-anhydrite, shaly and clean sandstone with the thickness of 44.40, 73.26, 104.34 meters, respectively. The clean sandstone had the best quality with regards to the average porosity and permeability in compare to the other subsections.

Summary The Middle Jurassic Sargelu Formation consists of gray shales and argillaceous limestones in the southwestern Iran. According to lithology, petrophysical and geochemical characteristics, Sargelu is considered as a probable active source rock in the southwestern Iran. The purpose of this paper is to evaluation of hydrocarbon generation potential of Sargelu Formation and its distribution of quantity, quality and maturity in Lorestan, Abadan plain, Dezful embayment, and northwestern Persian Gulf. The evaluation is based on Rock-Eval and vitrinite reflection results of 365 samples from 16 fields and outcrops. Geochemical parameters indicate very good hydrocarbon generation potential for Sargelu during the geological time in different parts of study area. IntroductionSeveral petroleum systems are active in the southwestern Iran and different formations are considered as first or secondary source rock for them. Sargelu Formation is one of the richest source rocks for Jurassic petroleum system in the southwestern Iran and Arabian adjusting areas. Although several researches have been evaluated petroleum potential of Sargelu in the south-west of Iran, none of them study Sargelu in a regional scale. This work assesses hydrocarbon generation of Sargelu (quantity, quality and maturity) in the regional scale in the southwestern Iran and northwestern Persian Gulf. The study area is approximately 725 km long and 350 km wide. Methodology and ApproachesThis study discusses the petroleum potential of Sargelu Formation in south west of Iran, based on data collected from different studies carried out previously. 365 Rock-Eval and 31 vitrinite reflectance data from 16 fields and outcrops were uploaded and evaluated by p.IGI.3.5.1 software. Results and ConclusionApproximately 95% of the samples have a TOC content > 1%, which is consistent with good to very good source rock potential. TOC and HI vary from 0.13 to 26.42 and from 0.9 to 1168, respectively. Samples from eastern Lorestan basin (Gashoon, region 1 to 5) indicate good to very good petroleum potential with kerogen type II, while samples from Dezful embayment and Abadan plain indicate fair to good petroleum potential with kerogen type III and II/III. Moreover, samples selected from western Lorestan basin have kerogen type III/IV. The trend of maturity of Sargelu source rock in the study area is exactly in inverse relation to TOC and HI distribution indicating Sargelu in western Lorestan basin, Dezful embayment and Abadan plain generates high amount of oil and gas during geological time with increasing its maturity.

Two-stage centrifugal separators are the most novel generation of gravity separators that are increasingly used in the beneficiation of coal and minerals. The flow pattern and behavior in these separators is very complex. In this research, computational fluid dynamics (CFD) and discrete phase model (DPM) were used to investigate the influence of medium viscosity on the flow field and on the performance of a two-stage centrifugal separator. Volume of fluid (VOF) and Reynolds stress model (RSM) were used to tack the liquid-liquid interface and turbulence modeling, respectively. With increase in the medium viscosity, the performance of the separator was decreased as a consequence of decreasing the tangential velocity, and the air volume fractions inside the separator. Moreover, a high viscosity increases the drag force and consequently the medium recovery into the float stream. Such an effect consequently increased the separation density of the separator. When the medium viscosity was changed from 1×10-3 to 3.09×10-3 Pa.s, the medium recovery of the first and the second stages of the separator were increased about 56% and 23.7 %, respectively. Ecart probable (Ep) values for the first and second stages were also increased 98% and 131%, and the air volume fractions were decreased about 38.73% and 29.35%, respectively.

Wellbore instability and drilling fluid loss in fracture formation is one of the main issues in deep drilling. In order to determine an efficient drilling methodology it is necessary to investigate the effect of fracture on instability and fluid loss mechanism. In this article in order to evaluation of the vertical wellbore stability and fluid loss in fracture formation, three dimensional simulation of of a wellbore in the Persian Gulf was carried out using Discrete Fracture Network (DFN) and Distinct Element Method (DEM). Validation of the model and stability analysis of wellbore was carried out using maximum allowed movement, normalized yield zone radius criteria and caliper log data. The initial analysis of the model showed that the wellbore is in an unstable state for kakhdumi formation. In order to investigate the hydromechanical mechanism in fracture formation, drilling fluid was injected by rate of 25 BPH and viscosity of 1.08 cP to the wellbore. Slip in fractures, shear displacement and the volume of fluid loss was determined as main parameters for wellbore stability analysis. The effect of in-situ stresses ratio (σ_H/σ_h ) on instability mechanism and fluid loss was carried out based on six different scenarios for in-situ stresses ratio. By increasing in-situ stresses ratio and in an anisotropic (σ_H/σ_h =2) satat, slips and shear displacement along the discontinuity increased. In this case, for 25 BPH drilling fluid flow ratio the fluid pressure decrease along the discontinuities. The parametric study for five different fluid flow ratio showed that in (σ_H/σ_h =1.06) the fluid expansion in fracture increased. Moreover, tension failure and shear displacement decreased in low fluid flow ratio. In 5 BPH fluid flow ratio, the fluid pressure in fractures decreased compared with higher fluid flow ratio. This is because of less shear displacement and fluid expansion along fracture in lower fluid flow ratio.

Production scheduling is the most important and influential issue in open pit and underground mining design and planning. The main purpose of mine production planning is time scheduling and determination of mine activities sequencing under some technical and extraction constraints in order to achieve one of the following goals: maximizing Net Present Value (NPV), the amount of ore extraction or mine life. Underground mine planning optimization which is used to determine the sequence of stopes extraction, is difficult due to the complexity of decision making and the interaction between existing constraints. Since, mathematical programming techniques are capable for solving complex and multi-limiting problems, they can be used for optimization purposes. In this study, after reviewing previous studies on the design and planning of underground mine production, the step by step explanation of a proposed model based on Integer Programming (IP) has been addressed. In order to validate proposed model, an example of 9 stopes was considered. First, the sequence of extraction was carried out using manual design and then using extended mathematical model in GAMS/CPLEX software. The current NPV obtained by manual production scheduling was 8.211 million dollars. While, this value for mathematical model was 8.331 million dollars. In other words, NPV value in mathematical model was 1.46% higher than manual method which indicate the power of mathematical programming for solving complex problems.

The analysis of geochemical samples of several elements and the relevance of the location and extent of mineralization area in an exploration region with the mineralization, pathfinder and indicator elements, makes it possible to determine the composite anomaly (multi-element anomaly) on a single element. The purpose of this paper is to introduce ranking methods for the determination of composite geochemical anomalies. For this purpose, three ranking methods namely that of characteristic analysis, VIKOR and FDAHP-VIKOR methods are used. 365 geochemical samples taken in the epithermal Ag-Au Chah-Zard deposit have also been used. Ranking results in R mode indicate that As criterion is the most important element related to mineralization and Au, Ag and Sb elements take the next positions. Also, the ranking of geochemical samples show that the anomalies obtained from all three methods are similar to cumulative anomalies. The result obtained with the FDAHP-VIKOR algorithm is due to conformity of the location and extent of the anomaly area with the geochemical anomalies of the main mineralization elements, Ag and Au elements, and the median area of this range, as compared to the other two methods which is introduced as a potential mineralization area. An area of 0.42 Km2 is proposed for the design of a borehole drilling network in a detailed exploration phase and a smaller area of 0.10 Km2 within it is proposed for designing a density drilling network. Therefore, ranking methods can be introduced as a new method for determining the composite anomalies.

In this paper, the extended Euler deconvolution method is studied for interpreting magnetic and gravity anomalies. This method, overcoming some limitations of the conventional Euler deconvolution method, is utilized for simultaneous and automatic estimate of the depth, structural index and horizontal location of potential field sources. The main limitation of the conventional Euler deconvolution method is non-linear dependency of structural index and background field; hence a simultaneous estimation of these parameter is not possible. For overcoming this problem, a value of structural index is presumed and the obtained results are evaluated according to various criteria. A wrong structural index affects the final results. In the extended Euler deconvolution, the Euler differential equation is solved for Hilbert transform of the field and its derivatives. Since the Hilbert transform of a constant value is zero, the linear dependency of structural index and background filed will be removed, and therefore the automatic calculation of structural index will be possible and the presumption of structural index is not required anymore. Moreover, since Hilbert transform has two components of x and y, the number of equations to be solved at each point is increased, and consequently the solutions are more reliable. In this paper, firstly, a background theory of the extended Euler deconvolution is discussed in detail. Then the method is applied to a magnetic anomaly produced over eighteen magnetic sphere (dipole) having different magnetic properties. Finally, the method is used for interpreting a Bouguer gravity anomaly of Noranda in Quebec province of Canada and also a magnetic anomaly of an area located near Anar city of Kerman province of Iran.