Coupling Geomechanics and Transport in Naturally Fractured Reservoirs
M.R
Jalali
University of Waterloo, Waterloo, Ontario, Canada
author
M.B
Dusseault
University of Waterloo, Waterloo, Ontario, Canada
author
text
article
2012
eng
Large amounts of hydrocarbon reserves are trapped in naturally fractured reservoirs which arechallenging in terms of accurate recovery prediction because of their joint fabric complexity andlithological heterogeneity. Canada, for example, has over 400 billion barrels of crude oil in fracturedcarbonates in Alberta, most of this being bitumen of viscosity greater than 106 cP in the GrosmontFormation, which has an average porosity of about 13-15%. Thermal methods are the most commonexploitation approaches in such viscous oil reservoirs which, in the case of steam injection, are associatedwith up to 275-300°C temperature changes, leading to considerable thermoelastic expansion. Thistemperature change, combined with pore pressure changes from injection and production processes, leadsto massive effective stress variations in the reservoir and surrounding rocks. The thermally-induced(thermoelastic) stress changes can easily be an order of magnitude greater than the pore pressure effectsbecause of the high intrinsic stiffness of the low porosity limestone and bounding strata. Study of thesestress-pressure-temperature effects requires a thermo-hydro-mechanical (THM) coupling approach whichconsiders the simultaneous variation of effective stress, pore pressure, and temperature and theirinteractions. For example, thermal expansion can lead to significant joint dilation, increasing themacroscopic, joint-dominated transmissivity by an order of magnitude in front of and normal to thethermal front, while reducing it in the direction tangential to the heating front. This leads to stronginduced anisotropy of transport processes, which in turn affects the spatial distribution of the heatingarising from advective heat transfer.
International Journal of Mining and Geo-Engineering
University of Tehran
2345-6930
46
v.
2
no.
2012
105
131
https://ijmge.ut.ac.ir/article_51322_dc722861ec4df3261f67b7bc61845117.pdf
dx.doi.org/10.22059/ijmge.2012.51322
A Methodology to Estimate Ores Work Index Values, Using Miduk Copper Mine Sample
Mohammad
Noaparast
School of Mining Engineering, University College of Engineering, University of Tehran
author
S
Rahmati
School of Mining Engineering, University College of Engineering, University of Tehran
author
Golnaz
Jozanikohan
School of Mining Engineering, University College of Engineering, University of Tehran
author
S.
Aslani
School of Mining Engineering, University College of Engineering, University of Tehran
author
A.
Ghorbani
School of Mining Engineering, University College of Engineering, University of Tehran
author
text
article
2012
eng
It is always attempted to reduce the costs of comminution in mineral processing plants. One of thedifficulties in size reduction section is not to be designed properly. The key factor to design size reductionunits such as crushers and grinding mills, is ore’s work index. The work index, wi, presents the oregrindability, and is used in Bond formula to calculate the required energy. Bond has defined a specificrelationship between some parameters which is applied to calculate wi, which are control screen, fineparticles produced, feed and product d80.In this research work, a high grade copper sample from Miduk copper concentrator was prepared, and itswork index values were experimentally estimated, using different control screens, 600, 425, 212, 150, 106and 75 microns. The obtained results from the tests showed two different behaviors in fine production.According to these two trends the required models were then defined to present the fine mass calculationusing control screen. In next step, an equation was presented in order to calculate Miduk copper ore workindex for any size. In addition to verify the model creditability, a test using 300 microns control screenwas performed and its result was compared with calculated ones using defined model, which showed agood fit. Finally the experimental and calculated values were compared and their relative error was equalto 4.11% which is an indication of good fit for the results.
International Journal of Mining and Geo-Engineering
University of Tehran
2345-6930
46
v.
2
no.
2012
133
140
https://ijmge.ut.ac.ir/article_51323_74143567616d24a8ab9fcbf34fa90b4f.pdf
dx.doi.org/10.22059/ijmge.2012.51323
Hydrogeological Issues Concerning the Thar Lignite Prospect
R. N.
Singh
Nottingham Centre of Geomechanics, Department of Civil Engineering, Faculty of Engineering, University Park, Nottingham NG7 2RD, U.K.
author
A. S.
Atkins
Faculty of Computing, Engineering and Technology, Staffordshire University, Beaconside,
Stafford, United Kingdom ST18 OAD
author
F.
Doulati Ardejani
School of Mining, College of Engineering, University of Tehran, Iran
author
text
article
2012
eng
The paper is concerned with the hydrogeological appraisal of the proposed mining operations in theThar lignite field in Sindh, Pakistan. The Thar coalfield covers an area of approximately 9000km2 andcontains three lignite seams lying at depth of 130m to 250 m. In the Thar lignite field, the presence ofthree main aquifers induces pore pressure in the rock mass surrounding the lignite seams and makes highwall slopes potentially unsafe. It is, therefore, necessary to dewater the rock mass before commencingmining excavations. The paper describes the proposed mine dewatering scheme to facilitatedepressurising of the rock mass surrounding the mining excavations. Inflow prediction of groundwater tothe surface mining excavation was carried out using a SEEP/W finite element software package. Thesimulation results show that the ground water inflow from the Top aquifer is 114m3/d, from theIntermediate confined aquifer is 141m3/d and from the Bottom confined aquifer is 1.28 x 105 m3 /d. Theseresults were compared with the analytical solutions which indicated that the relative error of estimation ofinflow quantities varies from 3.4 % to 6.4%.
International Journal of Mining and Geo-Engineering
University of Tehran
2345-6930
46
v.
2
no.
2012
141
156
https://ijmge.ut.ac.ir/article_51324_2309ef7a693c54004f14a2a57a757c18.pdf
dx.doi.org/10.22059/ijmge.2012.51324
Cut-off Grade Optimization for Maximizing the Output Rate
A.
Khodayari
School of Mining, College of Engineering, University of Tehran, Iran
author
A.
Jafarnejad
School of Mining, College of Engineering, University of Tehran, Iran
author
text
article
2012
eng
In the open-pit mining, one of the first decisions that must be made in production planning stage, after completing the design of final pit limits, is determining of the processing plant cut-off grade. Since this grade has an essential effect on operations, choosing the optimum cut-off grade is of considerable importance. Different goals may be used for determining optimum cut-off grade. One of these goals may be maximizing the output rate (amount of product per year), which is very important, especially from marketing and market share points of view. Objective of this research is determining the optimum cut-off grade of processing plant in order to maximize output rate. For performing this optimization, an Operations Research (OR) model has been developed. The object function of this model is output rate that must be maximized. This model has two operational constraints namely mining and processing restrictions. For solving the model a heuristic method has been developed. Results of research show that the optimum cut-off grade for satisfying pre-stated goal is the balancing grade of mining and processing operations, and maximum production rate is a function of the maximum capacity of processing plant and average grade of ore that according to the above optimum cut-off grade must be sent to the plant.
International Journal of Mining and Geo-Engineering
University of Tehran
2345-6930
46
v.
2
no.
2012
157
162
https://ijmge.ut.ac.ir/article_51325_5e0acff134fa8084db947013ca36236a.pdf
dx.doi.org/10.22059/ijmge.2012.51325
Pillar Design in the Hard Rock Mines of South Africa
D.F.
Malan
Department of Mining Engineering, University of Pretoria
author
text
article
2012
eng
This paper gives an overview of the difficulties associated with the design of hard rock pillars in South African mines. Recent examples of large scale pillar collapses in South Africa suggest that these were caused by weak partings which traversed the pillars. Currently two different methods are used to determine the strength of pillars, namely, empirical equations derived from back analyses of failed and stable cases and numerical modeling tools using appropriate failure criteria. It is illustrated in the paper that both techniques have their limitations and additional work is required to obtain a better understanding of pillar strength.Empirical methods based on observations of pillar behaviour in a given geotechnical setting are popular and easy to use, but care should be exercised that the results are not inappropriately extrapolated beyond the environment in which they are established. An example is the Hedley and Grant formula (derived for the Canadian uranium mines) that has been used for many years in the South African platinum and chrome mines (albeit with some adaptation of the K-value). Very few collapses have been reported in South Africa for layouts designed using this formula, suggesting that in some cases it might yield estimates of pillar strength that are too conservative.As an alternative, some engineers strongly advocate the use of numerical techniques to determine pillar strength. A close examination unfortunately reveals that these techniques also rely on many assumptions. An area where numerical modeling is invaluable, however, is to determine pillar stresses accurately and to study specific pillar failure mechanisms, such as the influence of weak partings on pillar strength.
International Journal of Mining and Geo-Engineering
University of Tehran
2345-6930
46
v.
2
no.
2012
163
191
https://ijmge.ut.ac.ir/article_51326_4f42ed56ef81360c34301947221a489e.pdf
dx.doi.org/10.22059/ijmge.2012.51326
An Assessment of Factors Affecting Reactive Transport of Biodegradable BTEX in an Unconfined Aquifer System, Tehran Oil Refinery, Iran
A.
Agah
PhD student in Mining Engineering, Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology, Iran
author
F.
Doulati Ardejani
Professor, Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology, Iran
author
H.
Ghoreishi
Head of Environmental department at Tehran Oil Refining Company, Iran
author
text
article
2012
eng
Risk-based assessment methods are commonly used at the contaminated sites by hydrocarbon pollutants. This paper presents the results of a two-dimensional finite volume model of reactive transport of biodegradable BTEX which have been developed for the saturated zone of an unconfined aquifer in the Pump station area of Tehran oil refinery, Iran. The model governing equations were numerically solved by modification of a general commercial software called PHOENICS. To reduce costs in general, many input parameters of a model are often approximated based on the used values in the contaminated sites with same conditions. It was not fully recognised the effect of errors in these inputs on modelling outputs. Thus, a sensitivity analysis was carried out to determine the influence of parameters variability on the results of model. For this analysis, the sensitivity of the model to changes in the dispersivity, distribution coefficient, parameters of Monod, Michaelis-Menten, first- and zero- order kinetics modes on the BTEX contaminant plume were examined by performing several simulations. It was found that the model is sensitive to changes in dispersivity and parameters of Michaelis-Menten, first- and zero- order kinetics model. On the other hand, the predictions for plumes assuming Monod kinetics are similar, even if different values for parameterization are chosen. The reason for this insensibility is that degradation is not limited by microbial kinetics in the simulation, but by dispersive mixing. Quantifying the effect of changes in model input parameters on the modelling results is essential when it is desired to recognise which model parameters are more vital on the fate and transport of reactive pollutants. Furthermore, this process can provide an insight into understanding pollutant transportation mechanisms.
International Journal of Mining and Geo-Engineering
University of Tehran
2345-6930
46
v.
2
no.
2012
193
208
https://ijmge.ut.ac.ir/article_51327_13a3f9f49f7d98624def05162fc79fd4.pdf
dx.doi.org/10.22059/ijmge.2012.51327
Using Bacillus Cereus as a Geo-Biological Marker For Gold Prospecting in Iran
B.
Tokhmechi
School of Mining, Petroleum and Geophysics Engineering, Shahrood University of Technology
author
M.
Mamarabadi
Department of Plant Protection, Faculty of Agriculture, Shahrood University of Technology
author
text
article
2012
eng
Several methods have been developed for gold exploration in the past, among which biological base method is known to be the most efficient with least expenses. This method can also be used for latent gold prospects exploration. In the present study, the possibility of applying Bacillus cereus frequency in soil as a biological marker was investigated for the exploration of latent gold prospecting in Iran. The study was performed on three gold sources in Iran known as Moteh, Zarmehr and Mahallat, however, the major focus was on Mahallat gold reserve. The results of bacterial cultivation showed that no bacteria have been isolated in samples taken from Moteh soil. On the other hand, the presence of bacteria was observed in cultural media which were prepared from the collected samples from Zarmehr and Mahallat.In Mahallat gold reserve the frequency of bacteria was noticeable, particularly in the soils with in-situ fine-grained. In addition, it was seen that when the gold grad increases the bacterial frequency of Bacillus cereus will also increase. Finally, a linear correlation was developed between bacterial frequency and the gold semi-quantified grad. Using this correlation the monitoring of semi-quantified gold grad can be undertaken.
International Journal of Mining and Geo-Engineering
University of Tehran
2345-6930
46
v.
2
no.
2012
209
221
https://ijmge.ut.ac.ir/article_51328_dfed5ae5b2ac61372a31722d95507a52.pdf
dx.doi.org/10.22059/ijmge.2012.51328