فهرست مطالب:

چکیده
مقدمه
منطقه ی مورد مطالعه
تئوری
ژئواستاتیک
کوکریجینگ
مقاومت الکتریکی
روش مطالعه ی ژئوفیزیکی و نتایج

بخشی از ترجمه:

یک توده ی سنگی برای کاربرد بالقوه ی ریکاوری یا بازیابی ثانویه مطالع شد. روش های تعیین و مطالعه شامل داده های سخت از حفاری و داده های ژئوفیزیکی نرم از مقاومت الکتریکی بودند. نمونه های مربوط به حفاری در فواصل 1.5 متر ارتفاعی از 29 مکان چاهی حاصل شدند اما چاه ها فاصله ی خیلی زیادی از هم داشتند تا به این طریق بتوان یک تفکیک پذیری جانبی کافی حاصل کرد. داده های مقاومت در امتداد 12 لاین خط موازی با طول 400 متر حاصل شدند و سپس در 3 بعد تحت مدل سازی معکوس قرار گرفتند.روش کوکریجینگ به عنوان مکمل داده های رطوبت اندازه گیری شده با مقاومت الکتریکی برای تولید نقشه ای از نقاط خشک بالقوه درون توده استفاده شدند.

نتایج کوکریجینگ مزیت های زیادی را نسبت به کریجینگ داده های رطوبت به تنهایی و رگرسیون حداقل مربعات در برابر اسکاتر پلات رطوبت اندازه گیری های هم مختصات نشان داد.طول همبستگی شاخص های اندازه گیری رطوبت کوتاه تر از فاصله ی میانگین چاه ها بود.که باعث شد تا رطوبت کریج شده در دور از نقاط نمونه برداری نسبتا همگن شود. تقریبا درفاصله ی 40 متری از چاه ها رطوبت براورد شده به مقدار میانگین داده های نمونه برداری شده رسید این خود باعث شد تا رطوبت کریج شده در حول چاه ها توزیع یکنواختی به خود بگیرد روش کوکریجینگ میانگین را برای درون یابی های بین چاهی در اختیار گذاشت.

بخشی از مقاله انگلیسی:

INTRODUCTION Modern mining relies on the heap leaching process to extract metal from rock
e.g., Burkin, 2001; Han, 2002. Heap leaching is a method of applying a dilute aqueous ionic solution to the surface of a pile of prepared ore
Juvonen and Kontas, 1999. Ore preparation can include crushing, agglomeration, or run-of-mine
ROM, depending on the geology and amount of fine-grained material. The leachate is allowed to percolate through the pile to solubilize and mobilize the metal
Crundwell and Godorr, 1997; De Andrade Lima and Hodouin, 2005;Bouffard and Dixon, 2007, and the leaching solution is either acidic or basic, depending on the metal. A basic sodium cyanide solution, for example, is used to extract gold by forming aurocyanide
Habashi, 1966; Marsden and House, 1992. Gold extraction can be enhanced also by pretreatment with biological agents or through roasting
Iglesias and Carranza, 1994. Beneath the heap, a liner and drainage pipe network collects the pregnant leach solution
PLS for final processing, including solvent extraction and electrowinning. The application rate of leaching solution to the surface of a heap is approximately 5 to 15 L/h per square meter of surface area, and effective leaching of the ore is impacted greatly by the types of geologic materials used in the construction, how they were placed, and the degree of fines. In general, heaps are large heterogeneous rock piles of differing geologic media taken from various parts of an open pit
see Kennedy, 1990. The heap at the Round Mountain Mine in central Nevada, for example, spans approximately 1600 m by 800 m and is more than 150 m tall, with gold occurring in tuff, limestone, and quaternary alluvium
Mills, 1985. These different types of deposits have their own grain-size distribution and controlling factors for lixiviant flow. Manuscr Ineffective leaching within the heap typically is the result of factors that can include the tendency of finer-grained material to compact into confining zones, wetting front instability, and channeling along “fractures” of well-sorted, coarse-grained material
Kunkel and Arnold, 2008. The creation of confining zones, for example, causes pooling and shading. The pooling of lixiviant occurs when solution accumulates above the confining zone, where the hydraulic conductivity of the zone is sufficiently low that percolation through the zone occurs at very large time scales. The pooling then causes additional water to cascade around the confining zone and create a shading effect immediately below. The shaded region remains relatively dry, reducing the total volume of leached ore. Large confining zones therefore reduce the total effectiveness of the heap and leave large metal inventories in place. Targeting the dry zones with a secondary leaching application, such as Hydro-Jex
Seal, 2004, 2007, increases the yield and effi- ciency of a heap. The secondary leaching process consists of drilling and casing holes within a heap, perforating the casing at specific depth intervals, and injecting leachate at high pressures within each depth interval using a straddle packer. The challenge then becomes the characterization of the heap and effective well siting. Given the cost of well drilling and assaying, indiscriminate well placement could absorb the additional profit gained through secondary recovery. Heap characterization can be conducted through direct and indirect means. Direct characterization includes hard information obtained from assay results during drilling. Indirect characterization can include inexpensive geophysical surveys, and the mining industry has relied traditionally on geophysics, primarily for the initial exploration of mineral resources. Geophysics, however, can be applied to near-surface problems to understand more fully the distribution of resources and moisture in an engineered earth. Examples of geophysics applied to engineered structures include levees
Asch et al., 2008, dams
Osazuwa and Chinedu, 2008, and foundations
Dong et al., 2008. The geophysical data usually are considered soft, as unique relationships between the geophysical property and the desired heap property
water content, gold concentration, and so on are rare. Many competing factors can give rise to similar values of the measured geophysical property, and it is necessary to combine the hard and soft data to form a complete conceptual model of the subsurface. In this study, we present a method of combining hard assay data and soft geophysical data for characterizing an active heap using geostatistics. The assay data include gravimetric water content
mass-based moisture content as defined in Topp and Ferré, 2002, and the geophysical data include electrical resistivity, acquired along transects on the surface of the heap and inverse modeled using a 3D resistivity code. This study follows an approach similar to Parks and Bentley
1996, whereby several geostatistical methods are tested and compared, including kriging of the assay data alone, least-squares regression
LSR of the assay and resistivity data, and cokriging of the assay and resistivity data. Although geophysical characterization of waste rock piles is shown in the literature
e.g., Campos et al., 2003; Gloaguen et al., 2007; Poisson et al., 2009, this study explores an active heap to help increase gold production by providing the means for better well siting for secondary recovery methods.

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فهرست مطالب:

چکیده
مقدمه
روش
تعیین خصوصیات مقاومت الکتریکی
پایش مقاومت الکتریکی
نتایج و بحث
نتیجه گیری

بخشی از ترجمه:

آزمایش ژئوفیزیک مقاومت الکتریکی برای تعیین خصوصیات توده بعد از انتهای سیکل فروشویی اولیه استفاده شد. بعد از کامل شدن سیکل فروشویی اولیه بر روی پد، مقاومت الکتریکی در امتداد 12 خط موازی استفاده شد. مقاومت سنج SuperSting R8TX برای انجام اندازه گیری ها با استفادخ از یک آرایه گرادیان و Schlumberger استفاده شد. هر لاین تقریبا دارای طول 1370 پا بوده و متشکل از 140 الکترود12 با فاصله 10 فوت بود. لاین ها با فواصل تقریبی 55 فوت از هم جدا شدند.شکل 1 آرایش را به طرف راس توده نشان می دهد. با 1680 الکترود، تعداد اندازه گیری های ولتاژ بیش از 81000 بود.
منطقه با مقاومت بتالا به طرف نیمه شرقی پد برای فروشویی ثانویه با Hydro-Jex هدف یابی شد. شرکن استخراج نیومونت یک فناوری Hydro-Jex را برای بهبود بازیابی فلز اختراع کرده است که شامل تزریق حجم های بالای سیال با فشار بالا در چاهک ها می باشد. شبیه سازی Hydro-Jex در هر 20 فوت از 190 تا 30 فوت زیر سطح پد اتفاق می افتد و شبیه سازی درون یک تک چاه در دو روز انجام شد.حجم کل مایع تزریق شده به توده می تواند بیش از 750000 گالن باشد. بعد از توقف تزریق مایع، یک سیکل آب کشی طی چند روز برای خارج کردن از فضای منفذی انجام می شود. تعیین خصوصیات مقاومت الکتریکی به مکان یابی چاه ها با هدف یابی منطقه با مقاومت بالا و رطوبت پایین کمک می کند.

برای پایش کارایی فناوری Hydro-Jex، روش مقاومت الکتریکی در نزدیکی چاهک تزریق اعمال شد. طی دوره شش روزه تزریق و آب کشی در چاه  STIM-1 117 عکس از مقاومت تهیه شد. از این تعداد شش عکس برای آنالیز های بعدی کنار گذاشته شد. تغییرات در مقاومت مربوط به مقدار رطوبت بوده و مقادیر 10، 20 و 30 درصد کاهش مقاومت  نقشه یابی شد. کاهش در مقاومت از 100 تا 80 اهم بر متر و 10 تا 8 اهم بر متر موجب کاهش 20 درصد در مقاومت شد.

بخشی از مقاله انگلیسی:

INTRODUCTION Heap construction and effective leaching is greatly impacted by the types of geologic materials used in the construction. The ineffective leaching within the heap is typically the result of finer-grained material to agglomerate into confining layers, which create the two main concerns of pooling and shading. The pooling effect is created when solution accumulates above the confining layer, where the hydraulic conductivity is sufficiently low that percolation through the layer occurs at very large time scales. The pooling will then cause additional water to flow around the pooled solution and create a shading effect immediately below the confining layer. The shaded zone remains relatively dry reducing the total volume of leached ore. Large confining zones will therefore reduce the total effectiveness of the heap and leave large metal inventories in the heap. The Hydro-Jex technology was developed for the secondary stimulation of heap leach pads to augment the extraction of the metal inventory [Seal, 1994; Seal, 2007]. The Hydro-Jex process consists of drilling and casing holes within a heap, perforating the casing at specific depths, and injecting lixiviant at each depth using a straddle packer. This secondary leaching application is extremely effective if the drilling targets are the areas left dry by ineffective primary leaching. Lixiviant volumes and injection pressures of the Hydro-Jex system have been based on cylindrical models and refined by field testing. Actual flow paths of lixiviant within a heap are strongly dependent on the directional hydraulic conductivity of the heap which is, in turn, dependent on the heap construction and variability in particle sizes within the pad. The variability in particle size generally ranges from crushed material (3/4” minus) to run-of-mine (ROM [6” plus]). Any cost-effective characterization technology that will offer insight into the heterogeneity of the heap and locate the dry areas would optimize the Hydro-Jex technology and ensure an even distribution of lixiviant in the zone of stimulation. The characterization technology should be capable of sensing large volumes over broad areas and be non-obtrusive to the drilling and pumping operations. Borehole-based sensors, such as pressure transducers, water content probes, or logging tools, are handicapped in this regard based on 1) disturbance of the zone near the borehole, and 2) the sensing volume is a relatively narrow band near the borehole. Interpolation between boreholes from these small-volume measurements can be misleading. Electrical resistivity geophysics has previously been demonstrated in a number of mining operations to aid in defining heap characteristics [Versteeg et al., 2005]. The dry zones are electrically resistive and are assumed to represent volumes of minimally leached ore-grade material. Fortunately, these dry zones can be imaged inexpensively and non-invasively from the surface of the heap. In addition to characterization, the resistivity technique can be used to monitor time-dependent processes such as the solution migration during Hydro-Jex stimulation. As the saturation of the pore space increases, the electrical resistivity of the material decreases and the effect can be monitored to ensure complete saturation of the desired area. We demonstrate a field application of electrical resistivity to characterize the confining zones and preferential flow paths of lixiviant in a heap after primary leaching from the surface. The characterization effort was then used to help locate wells for secondary stimulation by Hydro-Jex. During injection of lixiviant, the resistivity system was used to monitor the fluid migration away from the Hydro-Jex well in real-time. The electrical monitoring of fluid movement allowed fieldbased decisions to be made regarding the order of stimulation and the potential for optimizing the process for increasing production.

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