eng
University of Tehran
International Journal of Mining and Geo-Engineering
2345-6930
2345-6949
2014-12-01
48
2
115
126
10.22059/ijmge.2014.53087
53087
مقاله پژوهشی
A Novel Integrated Approach to Modelling of Depletion-Induced Change in Full Permeability Tensor of Naturally Fractured Reservoirs
Zahra Izadi
foaexplorator@gmail.com
1
Mohammad Ali Aghighi
m.aghighi@ut.ac.ir
2
Imam Khomeini International University, Ghazvin, Iran
Imam Khomeini International University, Ghazvin, Iran
More than half of all hydrocarbon reservoirs are Naturally Fractured Reservoirs (NFRs), in which production forecasting is a complicated function of fluid flow in a fracture-matrix system. Modelling of fluid flow in NFRs is challenging due to formation heterogeneity and anisotropy. Stress sensitivity and depletion effect on already-complex reservoir permeability add to the sophistication. Horizontal permeability anisotropy and stress sensitivity are often ignored or inaccurately taken into account when simulating fluid flow in NFRs. The aim of this paper is to present an integrated approach for evaluating the dynamic and true anisotropic nature of permeability in naturally fractured reservoirs. Among other features, this approach considers the effect of reservoir depletion on reservoir permeability tensor, allowing more realistic production forecasts. In this approach the NFR is discretized into grids for which an analytical model yields full permeability tensors. Then, fluid flow is modelled using the finite-element method to obtain pore-pressure distribution within the reservoir. Next, another analytical model evaluates the change in the aperture of individual fractures as a function of effective stress and rock mechanical properties. The permeability tensor of each grid is then updated based on the apertures obtained for the current time step. The integrated model proceeds according to the next prescribed time increments.
https://ijmge.ut.ac.ir/article_53087_5893b5121bf3e1576a7fdd868c5495cb.pdf
depletion effect
fracture aperture
naturally fractured reservoirs
permeability tensor
eng
University of Tehran
International Journal of Mining and Geo-Engineering
2345-6930
2345-6949
2014-12-01
48
2
127
137
10.22059/ijmge.2014.53093
53093
مقاله پژوهشی
Application of Geostatistical Modelling to Study the Exploration Adequacy of Uniaxial Compressive Strength of Intact Rock alongthe Behesht-Abad Tunnel Route
Mohammad Doustmohammadi
doustmohammadi@ut.ac.ir
1
Ahmad Jafari
ajafari@ut.ac.ir
2
Omid Asghari
o.asghari@ut.ac.ir
3
School of Mining, College of Engineering, University of Tehran, Iran
School of Mining, College of Engineering, University of Tehran, Iran
School of Mining, College of Engineering, University of Tehran, Iran; Simulation and Data Processing Laboratory, School of Mining Engineering, University College of Engineering, University of Tehran, Iran
Uniaxial compressive strength (UCS) is one of the most significant factors on the stability of underground excavation projects. Most of the time, this factor can be obtained by exploratory boreholes evaluation. Due to the large distance between exploratory boreholes in the majority of geotechnical projects, the application of geostatistical methods has increased as an estimator of rock mass properties. The present paper ties the estimation of UCS values of intact rock to the distance between boreholes of the Behesht-Abad tunnel in central Iran, using SGEMS geostatistical program. Variography showed that UCS estimation of intact rock using geostatistical methods is reasonable. The model establishment and validation was done after assessment that the model was trustworthy. Cross validation proved the high accuracy (98%) and reliability of the model to estimate uniaxial compressive strength. The UCS values were then estimated along the tunnel axis. Moreover, using geostatistical estimation led to better identification of the pros and cons of geotechnical explorations in each location of tunnel route.
https://ijmge.ut.ac.ir/article_53093_03b99fde9fffe286b0d4d2d9b8bb4414.pdf
Behesht-Abad tunnel project
Uniaxial compressive strength
Geostatistical estimation
SGEMS
eng
University of Tehran
International Journal of Mining and Geo-Engineering
2345-6930
2345-6949
2014-12-01
48
2
137
146
10.22059/ijmge.2014.53098
53098
مقاله پژوهشی
Application of Thermal Modelling for Geochemical Characterization of Gadvan Formation, Persian Gulf, Iran
Ahmad Vaezian
a.vaezian@shahroodut.ac.ir
1
Mansur Ziaii
m.ziaii47@gmail.com
2
Mohammad Reza Kamali
kamalimr@ripi.ir
3
Ali Kadkhodaie-Ilkhchi
kadkhodaie_ali@tabrizu.ac.ir
4
Faculty of Mining, Petroleum and Geophysics, Shahrood University, Shahrood, Iran
Faculty of Mining, Petroleum and Geophysics, Shahrood University, Shahrood, Iran
Exploration and Production Research Division, Research Institute of Petroleum Industry, Tehran, Iran
Geology Department, Faculty of Natural Science, University of Tabriz, Tabriz, NW Iran
In the this research, the hydrocarbon generation potential of the Gadvan Formation as a probable source rock was investigated in the central part of the Persian Gulf at the borders of Iran. Type and maturity level of kerogen were investigated in six wells using the results of Rock-Eval pyrolysis and compared with results yielded by the modelling software program known as Pars Basin Modeler (PBM). The cross-plot of hydrogen index (HI) versus maximum temperature suggests that the Gadvan Formation reached early to mid-maturity stages in the studied area, which means that it could act as a gas prone source rock. Furthermore, the burial and thermal history of the Gadvan Formation was determined in one well. Two methods, Easy %Ro and time-temperature index (TTI) were used for the reconstruction of thermal modelling and studying the thermal maturity level in all of the drilled wells reaching the Gadvan Formation. The results of the TTI and Easy %Ro methods were in good agreement and both of confirmed the results of Rock Eval analysis. An integrated approach using different techniques showed that the Gadvan Formation can be classified as a poor gas bearing source rock in the studied area, while its maturity increases towards the southern parts of the Persian Gulf.
https://ijmge.ut.ac.ir/article_53098_97b1a28b492d1c6609a97f58fcf0a57f.pdf
Gadvan Formation
Iran
pars basin modeller
source rock evaluation
Thermal modelling
eng
University of Tehran
International Journal of Mining and Geo-Engineering
2345-6930
2345-6949
2014-12-01
48
2
147
157
10.22059/ijmge.2014.53100
53100
مقاله پژوهشی
Numerical Modelling of the Segmental Lining of Underground Structures
Akbar Salemi
akbar.salemi@gmail.com
1
Fathang Sereshki
farhang@shahroodut.ac.ir
2
Morteza Esmaeili
m_esmaeili@iust.ac.ir
3
Department of Mining, Petroleum and Geophysics, Shahrood University, Shahrood, Iran
Department of Mining, Petroleum and Geophysics, Shahrood University, Shahrood, Iran
School of Railway Engineering, Iran University of Science and Technology, Tehran, Iran
There are several methods for analysing the behaviour of underground structures under different loading conditions. Most of these methods have many simplifications; therefore, in some cases, the results are too conservative and a very high safety factor, usually of more than 2 is needed. On the other hand, for stability analysis and the designing of support systems, these methods consider segmental lining and its joints as a uniform lining or a lining with pin connections. In this study, numerical modelling of the segmental lining of a tunnel was analysed using a sensitivity analysis of the static modelling. The numerical results were obtained by using a finite difference method (FLAC2D). Using this form of analysis, a new simple methodology was introduced so that more reliable results can be obtained. By comparing the frame analysis results obtained by the SAP2000 software with those obtained by the proposed method, it was concluded that the suggested method can be used as a simple and reasonable approach for the segmental lining of underground structures such as tunnels.
https://ijmge.ut.ac.ir/article_53100_06ee6acc1bbe51c03feaf6c1fde3d0f0.pdf
frame analysis
underground structures
numerical modelling
segmental tunnel lining
Sensitivity analysis
eng
University of Tehran
International Journal of Mining and Geo-Engineering
2345-6930
2345-6949
2014-12-01
48
2
159
172
10.22059/ijmge.2014.53102
53102
مقاله پژوهشی
Proposing New Methods to Enhance the Low-Resolution Simulated GPR Responses in the Frequency and Wavelet Domains
Reza Ahmadi
r_ahmadi@arakut.ac.ir
1
Nader Fathianpour
fathian@cc.iut.ac.ir
2
Gholam-Hossain Norouzi
norouzih@ut.ac.ir
3
Mining Engineering Department, Arak University of Technology, Arak, Iran; School of Mining, College of Engineering, University of Tehran, Tehran, Iran
Mining Engineering Department, Isfahan University of Technology, Isfahan, Iran
School of Mining, College of Engineering, University of Tehran, Tehran, Iran
To date, a number of numerical methods, including the popular Finite-Difference Time Domain (FDTD) technique, have been proposed to simulate Ground-Penetrating Radar (GPR) responses. Despite having a number of advantages, the finite-difference method also has pitfalls such as being very time consuming in simulating the most common case of media with high dielectric permittivity, causing the forward modelling process to be very long lasting, even with modern high-speed computers. In the present study the well-known hyperbolic pattern response of horizontal cylinders, usually found in GPR B-Scan images, is used as a basic model to examine the possibility of reducing the forward modelling execution time. In general, the simulated GPR traces of common reflected objects are time shifted, as with the Normal Moveout (NMO) traces encountered in seismic reflection responses. This suggests the application of Fourier transform to the GPR traces, employing the time-shifting property of the transformation to interpolate the traces between the adjusted traces in the frequency domain (FD). Therefore, in the present study two post-processing algorithms have been adopted to increase the speed of forward modelling while maintaining the required precision. The first approach is based on linear interpolation in the Fourier domain, resulting in increasing lateral trace-to-trace interval of appropriate sampling frequency of the signal, preventing any aliasing. In the second approach, a super-resolution algorithm based on 2D-wavelet transform is developed to increase both vertical and horizontal resolution of the GPR B-Scan images through preserving scale and shape of hidden hyperbola features. Through comparing outputs from both methods with the corresponding actual high-resolution forward response, it is shown that both approaches can perform satisfactorily, although the wavelet-based approach outperforms the frequency-domain approach noticeably, both in amplitude and shape of the outputted hyperbola response.
https://ijmge.ut.ac.ir/article_53102_ae8db8d2de6056b82ea44ad4ac0a7734.pdf
forward modelling
Fourier transform
Ground-Penetrating Radar (GPR)
high resolution
Wavelet transform
eng
University of Tehran
International Journal of Mining and Geo-Engineering
2345-6930
2345-6949
2014-12-01
48
2
173
190
10.22059/ijmge.2014.53105
53105
مقاله پژوهشی
A Comparative Study between a Pseudo-Forward Equation (PFE) and Intelligence Methods for the Characterization of the North Sea Reservoir
Saeed Mojeddifar
saeid_miner64@yahoo.com
1
Gholamreza Kamali
kamali@uk.ac.ir
2
Hojjatolah Ranjbar
h.ranjbar@uk.ac.ir
3
Babak Salehipour Bavarsad
babaksalehipour@gmail.com
4
Department of Mining Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Department of Mining Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Department of Mining Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Geopardazesh Petroleum Exploration Services, Ahvaz, Iran
This paper presents a comparative study between three versions of adaptive neuro-fuzzy inference system (ANFIS) algorithms and a pseudo-forward equation (PFE) to characterize the North Sea reservoir (F3 block) based on seismic data. According to the statistical studies, four attributes (energy, envelope, spectral decomposition and similarity) are known to be useful as fundamental attributes in porosity estimation. Different ANFIS models were constructed using three clustering methods of grid partitioning (GP), subtractive clustering method (SCM) and fuzzy c-means clustering (FCM). An experimental equation, called PFE and based on similarity attributes, was also proposed to estimate porosity values of the reservoir. When the validation set derived from training wells was used, the R-square coefficient between two variables (actual and predicted values) was obtained as 0.7935 and 0.7404 for the ANFIS algorithm and the PFE model, respectively. But when the testing set derived from testing wells was used, the same coefficients decreased to 0.252 and 0.5133 for the ANFIS algorithm and the PFE model, respectively. According to these results, and the geological characteristics observed in the F3 block, it seems that the ANFIS algorithms cannot estimate the porosity acceptably. By contrast, in the outputs of PFE, the ability to detect geological structures such as faults (gas chimney), folds (salt dome), and bright spots, alongside the porosity estimation of sandstone reservoirs, could help in determining the drilling target locations. Finally, this work proposes that the developed PFE could be a good technique for characterizing the reservoir of the F3 block.
https://ijmge.ut.ac.ir/article_53105_dcdcacc0cd448c6424e15782c537d588.pdf
ANFIS
clustering algorithms
experimental equation
Porosity
seismic attributes
eng
University of Tehran
International Journal of Mining and Geo-Engineering
2345-6930
2345-6949
2014-12-01
48
2
191
199
10.22059/ijmge.2014.53107
53107
مقاله پژوهشی
The Use of Robust Factor Analysis of Compositional Geochemical Data for the Recognition of the Target Area in Khusf 1:100000 Sheet, South Khorasan, Iran
Majid Keykha Hoseinpoor
majidkeykha@yahoo.com
1
Ahmad Aryafar
aaryafar@birjand.ac.ir
2
Department of Mining, Faculty of Engineering, University of Birjand, Iran
Department of Mining, Faculty of Engineering, University of Birjand, Iran
The closed nature of geochemical data has been proven in many studies. Compositional data have special properties that mean that standard statistical methods cannot be used to analyse them. These data imply a particular geometry called Aitchison geometry in the simplex space. For analysis, the dataset must first be opened by the various transformations provided. One of the most popular of the applied transformations is the log-ratio transform. The main purpose of this research is to identify the anomalous area in the Khusf 1:100000 sheet which is located in the western part of Birjand, South Khorasan province. To achieve the goal, a dataset of 652 stream sediments geochemically analysed for 20 elements was collected. In practice, the geochemical data were first opened by CLR transformation and then the range correlation coefficient (RCC) ratio was calculated and mapped. In consequence, the robust factor analysis for compositional data was used to separate the elements, mostly in the high-value regions obtained by the method of RCC. Finally, the priority of anomalies was specified using weighted catchment analysis. The above procedures led to the recognition of some anomaly zones for elements of Cu, Bi, Sb, Ni and Cr in the study area. Such results can be useful for designing an appropriate exploratory plan for semi-detailed and detailed exploration steps.
https://ijmge.ut.ac.ir/article_53107_da80a840287281bce0fbf5069b57d0f8.pdf
compositional data
Iran
log-ratio transform
RCC
Stream Sediment