Articles tagged with: Study Management

Underground Feasibility Forecasts vs Actuals

underground costing
I recently attended a CIM Management and Economics Society presentation here in Toronto discussing the differences between actual underground production versus the forecast used in the feasibility study. The presenter was Paul Tim Whillans from Vancouver Canada.
His topic is interesting and relevant to today’s mining industry.  Paul raised many thoughtful points supported by data. He gave me permission to share his information.
The abstract for his paper is inerted below.  The paper can be downloaded at this LINK and here are the presentation slides.

ABSTRACT

An underground mining study that is done in accordance with NI43-101, JORC or similar reporting code is generally assumed by the public to be representative, independent and impartial. However, it has been well documented by academics and professionals in our industry that there is a sharp difference between the forecasts presented in these underground studies and the actual costs when a mine is put into production.
For underground mines, the risks associated with obtaining representative information are much greater than for surface mining and the cost of accessing underground ore is also proportionally much greater. There is a pressing need to align expectations, by improving the accuracy of projections. This will result in reduced risk to mining companies and investors and provide more reliable information to government agencies, the public, and more importantly, the communities in which the proposed mine will operate.
The objective of this article and an article currently being written titled “Mining Dilution and Mineral Losses” is to:
– Discuss the dynamics of intention that lead to over-optimism;
– Provide simple tools to identify which studies are likely to be more closely aligned with reality;
– Identify some specific points where underground mining studies are generally weak;
– Discuss practices currently in use in our industry that lead to a composite or aggregate effect of over optimism;
– Describe the effects of overly optimistic studies;
– Outline specific changes that are necessary to overcome these challenges; and
– Stimulate discussion and awareness that will lead to better standards.”

Conclusion

I agree with many of the points raised by Paul in his study. The mining industry has some credibility issues based on recent performance and therefore understanding the causes and then repairing that credibility will be important for the future.
Credibility ultimately impacts on shareholder returns, government returns, local community benefits, and worker health and safety; so having a well designed mine will realize benefits for many parties.
If you need more information Paul’s website is at http://www.whillansminestudies.com/
Note: You can sign up for the KJK mailing list to get notified when new blogs are posted.
Share

Resource Estimates – Are Independent Audits A Good Idea?

mining reserves
Question: How important is the integrity of a tailings dam to the successful operation of a mine?
Answer: Very important.
Tailings dam stability is so important that in some jurisdictions regulators may be requiring that mining companies have third party independent review boards or third party audits done on their tailings dams.  The feeling is that, although a reputable consultant may be doing the dam design, there is still a need for some outside oversight.
Differences in interpretation, experience, or errors of omission are a possibility regardless of who does the design.  Hence a second set of eyes can be beneficial.

Is the resource estimate important?

Next question is how important is the integrity of the resource and reserve estimate to the successful operation of a mine?
Answer: Very important.  The mine life, project economics, and shareholder value all rely on it.     So why aren’t a second set of eyes or third party audits very common?

NI 43-101 was the first step

In the years prior to 43-101, junior mining companies could produce their own resource estimates and disclose the results publicly.  With the advent of NI 43-101, a second set of eyes was introduced whereby an independent QP  could review the company’s internal resource and/or prepare their own estimate.  Now the QP ultimately takes legal responsible for the estimate.
Nowadays most small companies do not develop their own in-house resource estimates.  The task is generally awarded to an independent QP.

Resource estimation is a special skill

Possibly companies don’t prepare their own resource estimates due to the specialization needed in modelling and geostatistics. Maybe its due to the skills needed to operate block modeling software.   Maybe the companies feel that doing their own internal resource estimate is a waste of time since an independent QP will be doing the work anyway.

The QP is the final answer..or is it?

Currently it seems the project resource estimate is prepared solely by the QP or a team of QP’s.   In most cases this resource gets published without any other oversight. In other words no second set of eyes has taken a look at it.  We assume the QP is a qualified expert, their judgement is without question, and their work is error free.

Leapfrog Model

As we have seen, some resources estimates have been mishandled and disciplinary actions have been taken against QP’s.   The conclusion is that not all QP’s are perfect.
Just because someone meets the requirements to be a Competent Person or a Qualified Person does not automatically mean they are competent or qualified. Geological modeling is not an exact science and will be based on their personal experience.

What is good practice?

The question being asked is whether it would be good practice for companies to have a second set of eyes take a look at their resource estimates developed by independent QP’s?
Where I have been involved in due diligence for acquisitions or mergers, it is not uncommon for one side to rebuild the resource model with their own technical team.  They don’t have 100% confidence in the original resource handed over to them.   The first thing asked is for the drill hole database.
One downside to a third party review is the added cost to the owner.
Another downside is that when one consultant reviews another consultant’s work there is a tendency to have a list of concerns. Some of these may not be material, which then muddles the conclusion of the review.
On the positive side, a third party review may identify serious interpretation issues or judgement decisions that could be fatal to the resource.
If tailings dams are so important that they require a second set of eyes, why not the resource estimate?  After all, it is the foundation of it all.
Note: If you would like to get notified when new blogs are posted, then sign up on the KJK mailing list on the website.  Otherwise I post notices on LinkedIn, so follow me at: https://www.linkedin.com/in/kenkuchling/.
Share

Measured vs. Indicated Resources – Do We Treat Them the Same?

measured and indicated
One of the first things we normally look at when examining a resource estimate is how much of the resource is classified as Measured or Indicated (“M+I”) compared to the Inferred tonnage.  It is important to understand the uncertainty in the estimate and how much the Inferred proportion contributes.   Having said that, I think we tend to focus less on the split between the Measured and Indicated tonnages.

Inferred resources have a role

We are all aware of the regulatory limitations imposed by Inferred resources in mining studies.  They are speculative in nature and hence cannot be used in the economic models for pre-feasibility and feasibility studies. However Inferred resource can be used for production planing in a Preliminary Economic Assessment (“PEA”).
Inferred resources are so speculative that one cannot legally add them to the Measure and Indicated tonnages in a resource statement (although that is what everyone does).   I don’t really understand the concern with a mineral resource statement if it includes a row that adds M+I tonnage with Inferred tonnes, as long as everything is transparent.
When a PEA mining schedule is developed, the three resource classifications can be combined into a single tonnage value.  However in the resource statement the M+I+I cannot be totaled.  A bit contradictory.

Are Measured resources important?

It appears to me that companies are more interested in what resource tonnage meets the M+I threshold but are not as concerned about the tonnage split between Measured and Indicated.  It seems that M+I are largely being viewed the same.  Since both Measured and Indicated resources can be used in a feasibility economic analysis, does it matter if the tonnage is 100% Measured (Proven) or 100% Indicated (Probable)?
The NI 43-101 and CIM guidelines provide definitions for Measured and Indicated resources but do not specify any different treatment like they do for the Inferred resources.
CIM Resources to Mineral Reserves

Relationship between Mineral Reserves and Mineral Resources (CIM Definition Standards).

Payback Period and Measured Resource

In my past experience with feasibility studies, some people applied a  rule-of-thumb that the majority of the tonnage mined during the payback period must consist of Measure resource (i.e. Proven reserve).
The goal was to reduce project risk by ensuring the production tonnage providing the capital recovery is based on the resource with the highest certainty.
Generally I do not see this requirement used often, although I am not aware of what everyone is doing in every study.   I realize there is a cost, and possibly a significant cost, to convert Indicated resource to Measured so there may be some hesitation in this approach. Hence it seems to be simpler for everyone to view the Measured and Indicated tonnages the same way.

Conclusion

NI 43-101 specifies how the Inferred resource can and cannot be utilized.  Is it a matter of time before the regulators start specifying how Measured and Indicated resources must be used?  There is some potential merit to this idea, however adding more regulation (and cost) to an already burdened industry would not be helpful.
Perhaps in the interest of transparency, feasibility studies should add two new rows to the bottom of the production schedule. These rows would show how the annual processing tonnages are split between Proven and Probable reserves. This enables one to can get a sense of the resource risk in the early years of the project.  Given the mining software available today, it isn’t hard to provide this additional detail.
Note: If you would like to get notified when new blogs are posted, then sign up on the KJK mailing list on the website.  Otherwise I post notices on LinkedIn, so follow me at: https://www.linkedin.com/in/kenkuchling/.
Share

3D Model Printing – Who To Contact?

One of the technologies that is still getting a lot of press is 3D printing.  It seems new articles appear daily describing some fresh and novel use. Everything from home construction, food preparation, medical supplies, and industrial applications, 3D printing continues to find new applications in a wide range of disciplines.

Mining can take advantage of 3D printing

In a previous blog “3D Printing – A Simple Idea”, I discussed the helpfulness of printing 3D topographic models for the team members of a mining study. I was recently contacted by a consulting firm in Texas that specializes in printing 3D mining models. Here is their story and a few model images as provided to me by Matt Blattman of Blattman Brothers Consulting. (www.blattbros.com/3dprinting)

Blattman Brothers Consulting

Their 3D printed models are used in the same way geologists and mining engineers have employed models for decades. In the past we saw the physical models made of stacked mylar or plexi-glass maps, wood or foam core. We recognized that there is value in taking two dimensional sections or plan maps and making a 3D representation.  This provides more information than those viewed on a computer screen.
Physical models convey scale, interactions and scope in ways that no other method can. Technology like 3D printing improves the model-making process by allowing the addition of high def orthophotos, reducing the model cost, increasing its precision and delivery time.
Currently 3D models can be made in a variety of materials, but the primary three are extruded plastic, gypsum powder, or acrylics.
  • Plastic models (ABS or PLA) are cheap, fast and can created on relatively inexpensive, hobbyist printers. The downside to these models is that the number of colors available in a single model are limited, typically a single color.
  • Powder-based printers can typically print in 6.5M colors, allowing for vibrant, photo-realistic colors and infinite choices for title blocks, logos and artistic techniques. However, gypsum models can be as fragile as porcelain and require some care in handling.
  • Acrylic models allow for translucent printing (“looking into the ground to see the geological structure”) and are more durable than the gypsum. Nevertheless, acrylic models are significantly more expensive than the other two types and the color palettes are limited.
Here are some examples.
Leapfrog Model

Leapfrog Model

Geological Model in Acrylic

Acrylic Model

Powder Based 3D Model

Powder Based 3D Model

Powder Based 3D Model

Powder Based 3D Model

Besides having another toy on your desk beside your stress ball, why not print off your mine plan, or print the geology shapes and topography? It’s all about communicating highly technical data to a non-technical audience, whether that audience is a permitting authority, the general public, or maybe even company management.
The ability to grasp a map or technical drawing is a learned skill and not everyone has it. If you’ve just spent $20M on a feasibility study, why assume that the attendees in a public meeting will fully appreciate the scale and overall impact of your proposed project with 2D maps?
That message can be better conveyed with a model that is easily understood. One of Blattman’s clients, Luck Stone, recently described how they use their 3D printed models in this video.

Blattman’s models are created from the same 3D digital data already in use by most companies involved in geological modeling and mine design. Other than the units (meters versus millimeters), the triangulated surfaces created by the software are no different than those created by mechanical or artistic 3D modeling programs.
While many 3D printing services are available on the market, not all of them are able to speak “mining”. They may not be able to walk the skilled geologist or mining engineer through the process of creating the necessary digital formats and that’s where Blattman comes in. With more than 20 years of mining experience and having already gone through the 3D printing learning curve, they can assist any natural resource company through the process, either as a full-service/turn-key project or just to advise the client on how to prepare their own files.

Conclusion

The bottom line is that 3D printing is here to stay and its getting better each year.   Go ahead and check out the technology to see if it can advance your path forward .
We would be interested in hearing about any experiences your have had with 3D modelling, pro’s and con’s.
Note: You can sign up for the KJK mailing list to get notified when new blogs are posted.
Share

Constraints: Use Them to Your Advantage

mining study management
I recently read a business book called “A Beautiful Constraint: How to Transform Your Limitations into Advantages, and Why It’s Everyone’s Business” by Adam Morgan and Mark Barden. It describes how to use constraints, like lack of time, or money, or resources and use them to help transform your company for the better.
Here’s an Amazon link to the book.  Beautiful Constraint Book Cover
The book discusses how to shift away from the typical “victim” role by understanding how our routines control things, ask the right questions, and focus on “how” and not “if”.

Focus on HOW and not IF

A good example: one of the recommendations in the book is in your team meetings no one on your team is allowed to utter the words “we can’t because…”.  They must replace those words with “we can if…”.   This forces the generation of ideas and promotes a positive attitude rather than a victim attitude.
The book describes how many innovative ideas are due to constraints and those innovations would never have come about without those constraints.
To force innovation in your organization you can create artificial constraints for your team.  This will foster innovative thinking and push for “outside the box” ideas.  The tougher the constraint, the greater the challenge for your team.  Possibly the greater the final outcome too.
The term Theory of Constraints may be common to some.  However that concept is different than what is being discussed in the book.  The TOC essentially relies on managing a constraint or eliminating it, and then addressing the next constraint in sequence.
The book authors instead propose to exploit the constraint or leverage it to create a new possibility.  Hence the title “beautiful constraint”.

Mining has no shortage of constraints

We all know the mining industry has more than enough constraints placed upon it today. It may be lack of funding, lack of skilled talent, environmental pressures, supply-demand issues, social issues, or security issues.  Each mining project may have additional constraints, so one probably doesn’t need to create artificial constraints for the team.
The mining industry has no option but to try to use these constraints in a constructive manner.  Miners must not let them pull the industry down nor simply wait until they go away.  When people say “Mining is cyclical and it will all turn around soon.”, that’s an example of waiting for the constraint to go away.

How long do you wait before taking your own action?

The bottom line is that the book is an eye opener and enlightening.  It may be telling some of us what we already know deep inside but don’t acknowledge openly.  Don’t wait any longer, start innovating, and don’t be afraid of grand innovations.
Note: If you would like to get notified when new blogs are posted, then sign up on the KJK mailing list on the website.  Otherwise I post notices on LinkedIn, so follow me at: https://www.linkedin.com/in/kenkuchling/.
Share

Meetups and Mining Millennials

mining millenials
Over the last year I have had many encounters with the Toronto tech start-up community.  I have noticed some similarities with the junior mining industry but some differences also.
The tech start-up model is similar to the junior mining business model as it relates to early stage funding followed by additional financing rounds.  One obvious difference is that mining mainly uses the public financing route (IPO’s) while the tech industry relies on private equity venture capital (VC’s).
There are also some less obvious differences.
Generally the tech industry is young, vibrant, technology-savvy, and applies the latest in social technology to collaborate.  The mining industry seems to be lagging behind on many of these aspects.
The following article will describe a few of my observations. As you read through this, ask yourself “Should the mining industry be doing these things?”

Tech Meetups and Networking

My first experience with the tech industry was associated with the many after-hours networking meetings called “meetups”.  They are held weeknights from 6 to 9 pm  and consist of guest speakers, expert panels, and for general networking purposes.   Often guest speakers will describe their learnings in starting new companies and failures they had along the way.
The meetups may also provide “how-to” advice for techniques like Google Analytics, Facebook advertising, Google Adwords, email marketing, etc.).
Attending these meetups is usually free.  They are typically held after hours at different tech company offices and they often provide free beer and pizza. One can see the entire industry working together for the betterment of the industry.

How to Organize Meetups

Scheduling of meetups is done via the online software platforms Meetup or eventbrite.  Both of  these work well for announcing the meeting notice and tracking signups and attendees.
By the way, meetups are not only tech-related; they are also held for interest groups for hiking, theatre, writing, yoga, business marketing, etc.  The platforms provide a good way to manage communities.  Unfortunately here in Toronto there are no geology or mining related meetups so the mining industry may be missing out on a good way to build a more collaborative community.
The mining industry does have some local meetings, as far as I know there are mainly three after-hour mining events.  The CIM has a monthly luncheon with a cost of $50-$65 (not exactly inclusive to everybody).   There is a Toronto Geological Discussion Group that holds monthly meetings and seems to be comprised of the older geologist demographic.  The third event is Mining 4 Beer, which a small group that meets intermittently at a local bar.  These few events limit the amount of buzz for those working in the mining industry.  There are a lot of mining companies here with a lot of mining people but not a lot of vibrancy.

Where to hold an event

Most of the tech meetups are held in local tech offices.  These offices are great. They have an open concept, pool tables, ping pong, video games, fully stocked kitchen. Who wouldn’t want to work there?
The last time I was in the offices of a large engineering firm I felt like a lab rat in a cubical maze.   I’m not saying engineering offices can switch to a tech office layout, but more enjoyment of the office environment might help draw more people to the mining industry.
Perhaps it’s easier to have a positive work attitude when money is being thrown at you (as is happening in the tech world) rather than having to scratch and claw for funds like mining must do right now.   However I suggest if one wants more smart young people to come into the industry then one needs to adapt.  This means more than just buying the latest 3D geological software.  It means creating an environment that people want to work in.
In the late 1990’s I was working in the Diavik  engineering office in Calgary.  They provided a unique office layout whereby everyone had an “office” but no front wall on the office so you couldn’t shut yourself in.  There were numerous map layout tables scattered throughout the office to purposely foster discussion among the team.
A similar type philosophy is used by Apple in their office layout design where even the kitchen placement has a purpose.  People should mingle and run into one another to promote conversation.  Discussion is good. Camping out in an office is not good.

Keep it short and to the point

Another thing I noticed with the tech industry is that when start-up tech companies are given an opportunity to tell their story, typically they only have 5 to 10 minutes to pitch.  No long winded thirty page PowerPoint presentation to explain what they are doing.
The tech industry is also big on the “elevator pitch”, a one minute verbal summary of what they are doing.  The tech people are taught to be concise.  If you can’t explain it in plain language in one minute then it’s too complicated.
For comparison, many mining investor presentations can be long, highly technical, and tailored to other technical people and not the average person.   One must ask who is the real target audience for those presentations?

Communication methods

The tech industry relies a lot on remote workers.   They might be overseas or spread around Canada. For communication and collaboration, they use various online systems such as Slack, Google Hangout, Trello.  No more  long email threads with five people cc’d on each email.   Slack uses a chatting approach, similar to text messaging, which makes it easier to follow the conversation and share files.
Can the mining industry be taught to use something new like Slack?  I don’t see a problem with that as long as one honestly wants to learn it. It’s really not that complicated.
For interest, another blog provides some more discussion on online collaboration software “Online Collaboration and Management Tools“.

Conclusion

The bottom line is that I can see a great difference in the attitude and atmosphere in the tech industry compared to the mining industry.  The junior mining game was the precursor for the tech start-up industry but has not kept pace with evolving work techniques.
As senior personnel retire from mining, the loss of this mining experience will be felt.  However the new ideas that may follow could be a positive outcome.
Share

New Mining Software and 43-101 Legal Issues

43-101 issues
NI 43-101 puts a fair amount of legal liability on the Qualified Person preparing a resource or reserve estimate or sign off on an advanced study.  The QP is to be responsible for the accuracy of their work and take legal responsibility.
Every so often some new mining software comes along and I often wonder what are the risks in using it? Some examples of new mining software that I have heard about (but not personally used) nor have seen mentioned in any 43-101 studies are SimSched, the ThreeDify’s software packages, NPV One, and Bentley.

Is the software doing everything correctly?

Given that as a QP I am legally responsible for my work, I am  bit apprehensive about how I can be assured the new software will provide reliable and accurate results for which I accept legal liability.  The last thing I would want to do is issue a public technical report which is found to be in error due to a software bug.
Irrespective of 43-101, if you are working at a mining operation the last thing you want to do is present management with an incorrect reserve, pit design, or production plan.
If you are a consultant, how agreeable will your client be when you tell him that his study was done using a novel software package and not one of the industry standard packages, and there was an error in it?
I recall working with a major mining company and there was a reluctance to adopt any new software that was unproven and not an industry standard.  Money was not the issue; the company’s concern  was with the risk in using unproven software.

What if you have a limited budget?

How do you view new software if you have a limited budget?   The new software may be cheaper, may appear to be be great, and may be a technological improvement and all at a lower cost.  However the software risk still remains.  There is no guarantee that all software output is correct simply because it comes from a computer.
As a QP, I suggest the onus is on the software developers to demonstrate that they can produce reliable and comparable results under all conditions.  They need to be able to convince the future users that their software is accurate.
Perhaps over time the new software will gain wider adoption and be generally accepted.  We may see more 43-101 reports that use it and hence it will get more overall acceptance.
Another question when developing a market for new software is whether it is better to focus on more consultant adoption or more mining company adoption?
Will mining companies use the software if their consultants are using it, or will consultants use it if more companies adopt it?  It’s an interesting discussion that new software vendors must deal with in trying to grow their market share.

 

Note: If you would like to get notified when new blogs are posted, then sign up on the KJK mailing list on the website. The entire blog post library can be found at this LINK with topics ranging from geotechnical, financial modelling, and junior mining investing.
Share

Independent Consultants Are Growing

I have read quite a few articles indicating that the mining industry is seeing a shortage of experienced people, on both the technical and management side of the business.  Apparently the baby boomer generation is now nearing their retirement or early-retirement stage and there is a gap in the number of experienced people following behind.
Many of these retirees enter the “independent consultant” stage of their careers.
I also hear from recruiters that there is a shortage of engineers willing to take remote or international assignments.  This is particularly difficult when a senior level candidate has a growing family.

Can the independent engineers help out?

In a previous article (14. Miners – Why Have Your Own Independent Consultant?) I discussed why mining companies (or even consulting firms) should make use of the independent engineers as advisers or Board members.
I understand from colleagues in the mining industry that many of the people nearing retirement are willing to take on consulting assignments or board or directors roles or other management roles.  They are often willing to work part time and independently.  Or they may work as “associates” with engineering firms.
So there likely is a significant network of experienced people out there.  It’s just a matter of being able to tap into that network when someone needs specific expertise.
So how can one do this?
LinkedIn currently seems to be the only global network for technical people.  It is a great way to connect with engineers and geologists industry wide.
LinkedIn members work everywhere, at mine operations, consulting firms, financial houses,  as independents, or even retired. Almost every technical person I know is registered on LinkedIn.
The question is how to find these people when you are looking for a specific independent expertise for a short term or over the longer term.

Networking

Networking with people you already know is the most common approach.  However what if you need someone with particular knowledge?
LinkedIn is a great search mechanism for technical experts.  With a keyword search one can identify a lot of experts with very specific skill sets.  The problem is that many of the experts highlighted by the LinkedIn search may be fully employed at mining operations or with large consulting firms and may not be the person you are looking for.
To my knowledge, there is no searchable online registry solely intended for independent geologists and engineers.  It would be in the interests of the mining industry to have some type of easily searchable independent consultant directory to be able to tap into the expertise that is out there.  I understand that MineLife.org  is attempting to build such an online service but it still appears to be early in the development stage.
Share

Mining Cashflow Sensitivity Analyses – Be Careful

cashflow sensitivity
One of the requirements of NI 43-101 for Item 22 Economic Analysis is “sensitivity or other analysis using variants in commodity price, grade, capital and operating costs, or other significant parameters, as appropriate, and discuss the impact of the results.”
The typical result of this 43-101 requirement is the graph seen below (“a spider graph”, which is easily generated from a cashflow model.  Simply change a few numbers in the Excel file and then you get the new economics.  The standard conclusions derived from this chart are that metal price has the greatest impact on project economics followed by the operating cost.   Those are probably accurate conclusions, but is the chart is not telling the true story.
DCF Sensitivity GraphI have created this same spider graph in multiple economic studies so I understand the limitations with it.   The main assumption is that all of the sensitivity economics are based on the exact same mineral reserve and production schedule.
That assumption may be applicable when applying a variable capital cost but is not applicable when applying varying metal prices and operating costs.
Does anyone really think that, in the example shown, the NPV is $120M with a 20% decrease in metal price or 20% increase in operating cost?   This project is still economic with a positive NPV.
In my view, a project could potentially be uneconomic with such a significant decrease in metal price but that is not reflected by the sensitivity analysis.  Reducing the metal price would result in a change to the cutoff grade.  This changes the waste-to-ore ratio within the same pit.  So assuming the same size mineral reserve is not correct in this scenario.
Changes in economic parameters would impact the original pit optimization used to define the pit upon which everything is based.
A smaller pit size results in a smaller ore tonnage, which may justify a smaller fleet and smaller processing plant, which would have higher operating costs and lower capital costs.
A smaller mineral reserve would produce a different production schedule and shorter mine life.  It can  get quite complex to examine it properly.
Hence the shortcut is to simply change inputs to the cashflow model and generate outputs that are questionable but meet the 43-101 requirements.
The sensitivity information is not just nice to have.   Every mining project has some flaws, which can be major or minor. Management understandably have a difficult task in making go/no-go decisions. Financial institutions have similar dilemmas when deciding on whether or not to finance a project.   You can read that blog post at this link “Flawed Mining Projects – No Such Thing as Perfection
So if the spider chart isnt he best way to tackle the risk issue, what way is better?  In another blog post I discuss an different approach using the probabilistic risk evaluation (Monte Carlo).  Its isn’t new but now well adopted yet by the mining industry.  You can learn more at “Mining Financial Modeling – Make it Better!
Note: If you would like to get notified when new blogs are posted, then sign up on the KJK mailing list on the website.   
Share

Open Pit Optimization – How I View It

Mining feasibility study
One of the first steps in an open pit design is the pit optimization analysis.  Pit optimization is used to define the most profitable pit shell for a given set of economic parameters.  The economic parameters include the metal prices, processing recoveries, and site operating costs. Normally when optimization is done, a range of metal prices or Revenue Factors (“RF”) is used to develop a series of nested shells to understand how the pit will expand or contract with increasing or decreasing metal prices.
Once the optimization step is complete, mining engineers will then design the pit inside that shell, introducing benches and ramps.  The pit design should mimic the selected optimized shell as closely as possible.
The pit design may (or may not) closely replicate the optimization shell depending on the slope angles used in the optimization and where the haul ramps are located in the design.
Hence the actual ore and waste tonnages mined may be different that the tonnages defined by the optimizer.
Various experts in pit optimization will use approaches of differing complexity.  Some may apply variable mining costs with pit depth; apply variable process recoveries linked to head grade; apply variable pit slopes by sector or depth, apply dilution and ore losses; etc.   One can make the pit optimization step as simple or detailed as one wants it.
The question is whether detailed pit optimization is warranted.  My view is that overly detailed pit optimization is  not required, other than if one wants to test parameter sensitivity on the resulting pit size and shape.  There are just too many uncertainties in the parameters being used in optimization.

Open Pit Optimization Uncertainties

Some of the uncertainties involved in the optimization approach are listed below:
  • Pit optimization can generate large pits that would have a long mine life.  However one doesn’t really know the metal prices far into the future.   So will that final pit ever get mined, or might it even be larger than shown.
  • Pit optimization is typically done at the start of a study, so one doesn’t have the detailed operating costs yet. The size of the project may be unknown and one has to use rough estimates for future costs and possibly even assume preliminary process recoveries.
  • Operating costs will also change in the future, and the optimization step is just a snapshot using current information.
  • Sometimes the optimization includes the use of Inferred resources, which are uncertainty.   Sometimes optimization is done only using Measured and Indicated resource, yet there may be areas if Inferred resource that ultimately convert to M &I and these will have been ignored.  So, either way you do it, you are not sure what ore the pit can captured and will  to shape the pit.
  • The smaller pits, if developed, would consist of smaller operations and may have different operating costs than assumed in the optimization.   Similarly larger pits may have different throughput rates and  operating costs than assumed in the optimization.
  • The ore and waste split reported within the pit will be based on a specific life-of-mine cutoff grade.  This is based on the fixed metal price and operating cost assumptions applied.
  • Overall pit wall slopes may differ for shallow pits versus deep pits.  Slopes may vary above the groundwater table and below it.  In many instances during pit optimization the wall angles are maintained at the same angle irrespective of the pit depths.   Sometimes geotechnical programs have not yet been completed, so optimization slope angles are simply educated guesses.
  • Dilution may be applied globally during pit optimization (unless one is working with a diluted block model).  In reality, dilution may differ in different parts of the ore body, and that may not be considered in the optimization stage. For more discussion on dilution in general, read the blog “Ore Dilution Prediction – Its Always an Issue“.

Conclusion

The bottom line is that pit optimization should be viewed as a guide to the pit design, but not as a highly precise calculation.  There are too many uncertainties in the parameters used.
There is always opportunity for future miner operators to examine pushback to grow the pit larger than initially envisioned.  Having said all that, one should still understand how future changes in metal prices can impact on the pit size, and then assess whether practical pushbacks are possible.   Thin sliver pushbacks are operationally difficult so this should be understood at the start.
While open pit optimization is not a precise science, there is still merit in examining how the pit size and shape reacts to changes in different parameters.  There are many ways to examine this and help select which shell should be advanced into the design stage. It can be more than just looking at the NPV versus Revenue Factor chart.   You can read this post at this link “Pit Optimization – More Than Just a “NPV vs RF” .
Note: If you would like to get notified when new blogs are posted, then sign up on the KJK mailing list on the website.   Follow us on Twitter at @KJKLtd for updates and insights.
Share