GoldSim as a Predictive Tool for Oil Sands Mining Operations

Posted by  Jason Lillywhite

We are pleased to share insights from a recent presentation by Candace Whitten, GIT and Matthew Ryans, P.Eng from WSP.  This work was presented at the 2024 GoldSim User Conference. 

Oil sands mining operations generate multiple tailings types requiring various treatment methods, storage components, and time for tailings maturation. GoldSim was employed to develop a dynamic material mass balance model simulating future tailings production and treatment alternatives.

Figure 1 - Schematic diagram of bitumen extraction and tailings storage and treatment

The model provided insights into the production of coarse and fine solids, informed by ore grade and production schedules. It identified high-sensitivity parameters and ensured compliance with site-specific thresholds, as established by Directive 085. This compliance guarantees that the modeled treatment technologies are sufficient for managing fluid tailings and that there is no net growth of fluid tailings beyond the life of mine (LOM) production. Additionally, the model offered insights into optimizing tailings management to minimize environmental impact and support sustainable mining practices. 

Introduction

Oil Sands mining operations generate multiple tailings types requiring various treatment methods, storage components and time for tailings maturation. For this project, GoldSim was used to simulate an oil sands mining operation to estimate cumulative tailings production by type over the life of mine (LOM). Planned mining operations and tailings generation were modeled to assess if the proposed storage facilities have capacity to store the tailings waste on-site and assess whether the available treatment options would be sufficient for waste treatment. Additionally, the model aims to identify opportunities to reduce environmental impact by optimizing tailings management and treatment processes.

Modeling Approach

GoldSim was employed to develop a deterministic material mass balance model simulating tailings production and multiple treatment alternatives to validate the efficacy of tailings storage components in conjunction with timing complexities for treatment and on-site storage during mine operations. The model was designed to provide a comprehensive framework to evaluate a range of conditions and contingencies unique to oil sands mining, such as pre-treatment fluid tailings storage requirements, for achieving specific geotechnical outcomes. By identifying parameters with high sensitivity and ensuring proposed operations capture desired outcomes within ranges of site-specific thresholds, the model provided clear, visually intuitive results to inform other disciplines designing operational strategies and parameters.

Mature Fine Tailings

Oil sands mining produces multiple tailings streams as a function of various processing methods and ore grade. The tailings streams are segregated into bitumen, coarse solids (sand), fine solids (fines), and water. The initial step in production is to separate these sub-components, maximizing bitumen recovery for upgrading. The solids streams are separated via density into coarse solids or fine solids and are deposited in an external tailings facility to allow for further separation and consolidation of fine tails from coarse tails, and to maximize the recovery of freewater for recycling back to processing. The fine tails, referred to as ‘fine fluid tails’ (or FFT) require significant time to settle and consolidate into a higher solids content, where they can then be treated. 

Within the first few years of tailings deposition, the fines will first settle out as ‘thin fine tailings (or TFT)’, with a solids content or less than 30% (by weight). Following the first few years post-deposition, TFT will increasingly consolidate into ‘mature fine tailings (or MFT) at a higher solids content. Once the MFT reaches a solids content between approximately 30%-35%, it can be treated to achieve maximum dewatering.

Figure 2 - Conceptual cross section of a tailings facility

Tailings Production and Storage

Tailings streams produced from oil sands mining are specific to the ore grade and composition, processing technologies and treatment methods. For modeling tailings production and fluid tailings storage, one key assumption was that the tailings streams segregate and deposit in storage facilities at the desired solids content, which allowed for the most conservative results in terms of available storage and treatment.

Figure 3 - Composition of ingredients of oil sands. (Source: Fine fluid tailings explained: Problems & solutions. Oil Sands Magazine. https://www.oilsandsmagazine.com/news/2023/5/11/fine-fluid-tailings-explained-problems-solutions)

Figure 4 - Simulated ore composition over time

Ore grade and resulting composition was identified as a parameter with high sensitivity.  This specific ore grade demonstrates the need to fine-tune production schedule for fluid tailings storage, as the overall trend shows a higher fines composition compared to available bitumen that can be extracted.

Modeling Outcomes

The model determined the production of coarse and fine solids, informed by ore grade and production schedules. It also identified high-sensitivity parameters. The cumulative production of fluid tailings achieved compliance with site-specific thresholds, as established by Directive 085 (see section below). This compliance ensures that the modeled treatment technologies are sufficient for managing fluid tailings and that there is no net growth of fluid tailings beyond the life of mine (LOM) production. The model provided insights into optimizing tailings management to minimize environmental impact and support sustainable mining practices.

Figure 5 - Solids generated per unit ore V1

Figures 5 and 6 present the cumulative production of solids per unit of ore, highlighting the differences between version 1 (V1) and version 2 (V2) of the ore production schedules. 

Figure 6 - Solids generated per unit ore V2

The comparison of cumulative tailings solids production per tonne of ore factors in different ore grades and production schedules. Coarse solids are used in the construction of dykes and beaches for the external tailings facility, while fine solids are used to estimate treatment methods, rates and timing over the LOM. These results show the difference in solids composition based on ore grade, a key consideration in determining treatment technologies.

Figure 7 - Storage balance V1

The model simulated cumulative fluid tailings production, allowing for comparison of the timing and capacity of site storage facilities based on proposed ore production schedules for the mine life, version 1 (V1) and version 2 (V2). 

Figure 8 - Storage balance V2

The model results were used to provide timeframes for when fluid tailings production could exceed storage capacity and to inform the design team, allowing for fine-tuning of ore production schedules.

Directive 85

This directive, as established by the Oil Sands Conservation Act (OSCA) and enforced by the Alberta Energy Regulator, provides the framework for managing fluid tailings volumes, including tailings dams and impoundments, as well as regulatory benchmarks for permitting and environmental compliance. Operators are required to submit annual reports detailing the profiles of site Tailings Management Facilities and fluid tailings inventories, as well as operational management plans.

The model was used to ensure compliance with site-specific fluid tailings volume thresholds and growth profiles for proposed site operations, specifically:

• Fluid tailings growth matches the rate of treatment
• Treatment technologies for fluid tailings are sufficient and the best available
• The end of mine fluid tailings inventory does not demonstrate net growth exceeding five years' worth of production

Contact Information:

Candace Whitten, Environmental Geologist, Lakewood, CO, USA; Email: candace.whitten@wsp.com

Matthew Ryans, Geotechnical Engineer, Drammen (Strømsøtorg), NO; Email: matthew.ryans@wsp.com