A group in the United States recently launched the “Rethink Alberta” campaign which urged tourists to avoid Alberta until the Province cleans up and minimizes the environmental impact of oil sands production operations. The initiative focuses on the environmental impact of oil sands related activities, including mining and the tailings produced as a by-product. This type of campaign along with the associated rhetoric and the high operating costs associated with traditional bitumen extraction, provides ample incentive for significant investment in oil sands technology. The motives behind the development of more efficient technology are a combined desire to improve the industry's public image, produce a more environmentally acceptable product, and extract as much usable bitumen as possible.
Tailings ponds and their environmental impact have become an easy target for public criticism. Developing economically sound and environmentally friendly tailings ponds related technology has become imperative to oil sands mining. Fiscal and public policy concerns now compel industry participants to invest in research and development to increase extraction efficiencies and decrease the environmental impact of tailings ponds.
Many of the largest oil sands operators have, as recently as December, 2010, reached an agreement to collaborate more broadly in a sharing of tailings technical information. The parties further agreed to collaborate on tailings-related research, to eliminate monetary and intellectual barriers to the use of tailings technology and to develop a framework so that tailings information is both kept current and verified through peer review.
The introduction of the Energy Resources Conservation Board’s Directive 074 (April 3, 2009 Energy@Gowlings) aims to reduce fluid tailings and mandates the formation of trafficable (solid) tailings deposits, while holding oil sands operators accountable for tailings management. As a consequence, the pressure on oil sands operators to effectively reduce the environmental impact of oil sands mining has increased significantly. Ideally, this reduced environmental impact will be achieved through innovative clean technological advances, which will be both economically viable and environmentally friendly. Most of the technologies are intended to speed up the reclamation process while recycling more water. A description of some of these technologies follows:
Canadian Natural Resources Limited’s (CNRL) Horizon project has implemented a technology by which CO2 emissions are captured and then injected into the tailings slurry lines before the tailings enter the tailings pond. The reaction creates carbonic acid, which changes the pH (acidity) of the tailings mixture and allows for better settling of the tailings and cleaner water which can then be reused in the extraction process.
CNRL also intends to use another process in the next phase of the Horizon project, where mechanical cyclones will remove water from the coarse tailings sand and thickeners will remove water from fine tailings, clays, silts and sand. These two streams will then be combined with waste CO2 emissions. Resultant tailings will be deposited in a tailings disposal area where more water will be released from the tailings and subsequently recovered for reuse. The CO2 is expected to react with, and effectively attach to, the minerals in the tailings to create more stable mineral carbonates.
Suncor has initiated a process that it calls Tailings Reduction Operations (TRO) where mature fine tailings (MFT) are mixed with a polymer flocculent and deposited over sand banks. The flocculent adheres to the MFT clay particles, causing them to bundle together, and aids in separating water from the clay. The separation occurs on a slope, encouraging the water to drain out of the MFT mixture more quickly. Implementation of TRO on a larger scale would not only speed up the reclamation of MFT, but should also result in the creation of dramatically smaller tailings ponds and a more efficient mining regime.
Shell Canada Ltd. has developed a technology called “atmospheric fines drying”. This technology, currently being demonstrated at Shell’s Muskeg River Mine, first collects MFT, transfers the MFT to a drying area and then mixes the MFT with flocculants, which bind to the clay particles in the MFT. This mixture is then placed on a sloped surface, which speeds up the release of water to a collection area. This collected water is then reused in the extraction process, while the remaining MFT-flocculent deposits are further dried to increase strength and solidify sufficiently to meet and exceed reclamation requirements.
Syncrude Canada Ltd. is using a multipronged technological approach to address tailings ponds issues. These technologies include “water capping”, “composite tails” and “centrifuge.” Water capping involves layering fresh water over a deposit of fine tails to form a lake. Tests have shown promise that these ponds will evolve into natural ecosystems supporting healthy plants, animals and fish. Composite tails combines fine tails with gypsum and sand. The combination causes the tailings to settle faster and accelerates the development of reclaimed land. Centrifuge involves spinning water out of fine tailings and then recycling this water for use in facility operations.
The dedication of oil sands producers to developing practices that speed up reclamation and recycle water is indicative of the commitment of the industry to taking ownership of and attempting to minimize the impact that oil sands mining practices have on the environment. The reality is that it takes time and money to research and develop technologies that work. The “perfect” technological solution is unlikely to arise instantaneously. Oil sands miners have made great strides in developing more efficient reclamation practices and reducing water consumption. Giving the oil sands industry credit for the technological advances that have been made, while continuing to encourage further improvements, is far more important than focusing on the errors of the past.
In-situ Extraction Methods
There are currently five common methods of in-situ (in-place bitumen) extraction. The two most common methods are Cyclic Steam Stimulation (CSS) and Steam Assisted Gravity Drainage (SAGD). CSS, also known as Huff-and-Puff, consists of three stages: injection, soaking, and production. Steam is initially injected into the oil sand formation. The heat from the steam causes a softening of the oil sands and a liquification of the bitumen. Once saturated, the well is closed and the steam-charged oil sand is left to soak. After a short period the well is reopened and the bitumen begins to flow into the same piping from which steam was initially injected. Flow is natural at first because of the built-up pressure from the steam injection; flow is then encouraged through mechanized (vacuum and pumping) removal. This cycle is then repeated until the return becomes marginal because of decreased pressure in the production zone and increased steam (water) usage. At this point steam flooding (of which SAGD is a variation) can be initiated to increase pressure in the well and resume production.
In SAGD two parallel horizontal wells are drilled into the same oil sands formation. Steam is injected through the upper well into the oil sand. The steam heats the bitumen, reducing viscosity and allowing heated bitumen to gravity flow into the lower well. Once in the lower well, the raw bitumen is forced to the surface either through natural pressure or the use of pumps. SAGD can typically recover about 60-70% of the bitumen in place. SAGD is almost twice as thermally efficient as CSS because less energy is required to maintain the heat in the well. SAGD is currently the in-situ oil production method of choice because of its lower energy requirements and higher oil output.
Despite the advantages of CSS and SAGD technologies, both have ecological and financial drawbacks. The initial difficulty is that tremendous amounts of energy are used in both processes. In other words, a significant amount of natural gas is being used to produce the steam required for bitumen extraction. These methods also require significant amounts of water to create the steam that is being injected. In addition, the surface boreal forest must, to a limited degree, be disturbed or destroyed to allow for the placement of wells and surrounding infrastructure. Recognition of these negative impacts has resulted in further investments in newer, more efficient technologies, or improvements to existing technology, that has increased production while simultaneously reducing the environmental impact. Some of these innovations and improvements are described below:
a) The Vapour Extraction Process (VAPEX), developed by Vapex Technologies International Ltd., is an extraction method similar to SAGD, but does not use steam in the in-situ extraction process. Instead of steam, hydrocarbon solvents are injected into the upper portion of the parallel wells, diluting the bitumen, and thereby enabling it to flow into the lower well where it is pumped to the surface. VAPEX is more costly than SAGD and CSS, but has its own benefits. The developer claims cost is offset by the lack of heat and non-usage of water and that an upgraded oil/bitumen is extracted because of the injection of lighter hydrocarbons. VAPEX can also be combined with other in-situ extraction methods. Cenovus has launched a pilot project at Christina Lake where VAPEX is being used in conjunction with steam to aid in extraction. Upon the completion of the extraction process, the solvents are then separated from the bitumen with the vast majority being reused. The higher cost of VAPEX has made the industry reluctant to adopt widespread usage, but if bitumen yields can be shown to increase as a result of its use, it will become a more likely choice for oil sands producers, especially in combination with other extraction techniques.
b) Petrobank Energy and Resources Ltd. (Petrobank) has patented a method for in-situ extraction called Toe-to-Heal-Air-Injection (THAI). With THAI, two wells are drilled into the oil sands formation– a horizontal and a vertical well. Steam is injected through the vertical well until what is effectively a lighter oil is heated to a critical point. The lighter oil is then ignited, the steam halted, and air is injected. This causes the lighter oil to burn, heating the remaining heavier oil and bitumen, decreasing its viscosity and allowing it to more easily flow into the horizontal well. The gases created by the combustion then actively drive the oil and bitumen up the well to the surface.
Although THAI has yet to be commercially developed, it is significant for a number of reasons. It reduces the amounts of both water and energy necessary to extract in-situ bitumen, minimizing the environmental impact of the extraction process while decreasing the overall cost of extraction to the producer. Through the use of THAI, Petrobank claims a 70-80% recovery of the original bitumen in place. This is consistent with SAGD and is particularly efficient given that about 10% of the lighter oil in place is actually burned off during the extraction process!
c) The remaining in-situ extraction method is known as Cold Heavy Oil Production with Sand (CHOPS). This is the cheapest method of extraction, but also the least effective, as only about 10 % of the bitumen is recovered. CHOPS uses progressive cavity pumps to force out bitumen and the surrounding sand without heat. By also extracting sand, holes are created in the oil sand formation, allowing for increased flow of heavy oil and bitumen to the extraction pumps resulting in increased production. CHOPS is only viable in areas where oil and bitumen are sufficiently fluid to be pumped. It also requires large amounts of energy to carry out the pumping process and developers must also somehow dispose of the sand after it is separated from the oil and bitumen. Despite these drawbacks, CHOPS is still the cheapest method of extraction and requires no water or heat to extract product. However, given its limited application, it is doubtful whether CHOPS will become a primary extraction method in the Alberta oil sands.
While the optics of these commonly used in- situ extraction methods are better than those of mining, none are perfect or achieve the ultimate goal of the producer, which is to maximize hydrocarbon recovery and reduce costs while lowering the environmental impact and improving the perception of the producer and the industry as a whole. This quest for higher recovery rates and lower cost production has resulted in the development of new initiatives and implementation of some of the new technologies referred to below to augment and improve extraction methods.
Similar to VAPEX, many companies are currently experimenting with the addition of hydrocarbon solvents to CSS and SAGD operations. Imperial Oil (Imperial) has developed Liquid Addition to Steam for Enhanced Recovery (LASER) technology where lighter hydrocarbons are injected with steam into oil sands formations. To quote Imperial, the object of the process is to “enhance the field application of CSS by increasing the mobilization of and contact with bitumen while using the same amount of steam.” This would have both environmental and economic benefits as less water and energy is required to extract increased amounts of oil and bitumen. Imperial describes the results of LASER-CSS as “quite positive.”
Expanding Solvent SAGD (ES-SAGD) and Steam Alternating Solvent (SAS) have been introduced by Cenovus to improve the efficiency of SAGD operations. In ES-SAGD, similar to LASER-CSS, the SAGD process is augmented by the addition of solvents to the steam and co-injection during the steaming process. The solvents are selected based on their compatibility with the evaporation temperature of the steam, the preferred outcome being a solvent that behaves similar to the steam in terms of evaporation and condensation. Alternatively, the SAS method requires that the solvents be injected at alternate intervals from the steam. The purpose of both of these methods is to increase the production of the well without increasing the amount of steam required to extract the bitumen and oil. Cenovus has conducted trials of ES-SAGD at its Christina Lake project and has found a significant increase in the production levels of its trial wells.
Environmental Impacts: A Narrower Footprint
Recent technological innovations have, in some instances, had the effect of reducing the environmental impact without increased hydrocarbon production being the ultimate goal.
One of the major problems associated with in-situ drilling and pre-drilling activities, is the impact on the boreal forest. In recognition of this “invasion,” several Alberta oil sands companies have begun using Low-Impact Seismic exploration, which has resulted in more than a 60% reduction in the footprint associated with the laying of seismic lines. In Low-Impact Seismic exploration, helicopters are used to deploy recording equipment reducing the need for trucks or other heavy equipment access. Existing clearings are then used as staging sites for temporary equipment storage. While in the past cutlines would simply cut straight through mature trees directly to a particular site, Low-Impact Seismic lines are routed along the path of least resistance – avoiding trees, creeks, and animal dens. The ultimate goal of this initiative is to minimize impact on wildlife habitats and reduce the amount of timber loss associated with seismic exploration.
Water use in the oil sands has become a major concern for environmentalists and northern Alberta residents. A number of industry initiatives are responding to these concerns, which are aimed at reducing the amount of water being used and using less fresh water as the in-situ extraction primary water source.
Imperial’s Cold Lake operation has significantly reduced water requirements for its SAGD extraction. In 1985 about 3.5 barrels of fresh water was required per barrel of recovered bitumen. Presently, about ½ a barrel of water is required per barrel of recovered bitumen. Imperial currently recycles 95% of the water it uses. When recycled water is insufficient, Imperial uses brackish water from deep saline aquifers and minimal fresh water to supplement the required water. In addition, while still in its early stages of development, Imperial is working on a new technology aimed at separating bitumen from mined oil sands without adding any water at all!
Suncor’s MacKay River in-situ facility employs Zero Liquid Discharge (ZLD) technology. This is the same technology that Shell Canada is considering for use at its Scotford Upgrader. In SAGD production, the flow of oil and bitumen into the lower well is accompanied by steam and water with high saline content. Regulations require that saline water be disposed of in a “suitable well.” As Mackay River does not have a suitable disposal well nearby, ZLD is used to remove the salt from the saline water and to recycle the water as steam; 90% of the saline water is recycled in this manner. By expanding ZLD technology, Suncor has minimized its fresh water usage, while simultaneously increasing the productivity of its in-situ facility through more efficient output and reduced energy usage. In addition, Suncor is able to reduce costs associated with third party disposal of saline water.
The University of Calgary has announced it is making great strides in using bacteria to “densify” oil sands tailings ponds. This research aims to increase the sedimentation of tailings, utilizing nitrate-reducing bacteria to prevent the release of methane gas associated with the activity of other bacteria. While this technology is in the early stages of development, it is an example of the advances being made to ensure that tailings ponds settle and are remediated with as little environmental impact as possible. Should this technology prove to be a feasible and effective option for oil sands producers, it could become a faster and more efficient means to reclaim tailings-affected lands without increasing methane emissions.
To reduce the effects of greenhouse gases, Carbon Capture and Storage (CCS) is being explored. CCS involves capturing CO2 emissions and storing them kilometres below the ground. While CCS is not only a concern of the oil and gas industry, captured CO2 is considered an excellent source material for injection to increase pressure under somewhat depleted conventional oil fields to encourage enhanced oil recovery. The Alberta government has committed $2 billion to CCS funding which it intends for use in 4 different “pilot” projects.
Technological advances in the oil sands industry are a variety of initiatives that attempt to address and balance environmental considerations, economic factors and the public perception of the industry. In the 40 years of its existence, the industry has become far more economically efficient, produces a cleaner and better upgraded product, and does so in a more environmentally conscious manner. The implementation of sound technological advances, while sometimes frustratingly slow, does indicate the industry’s commitment to becoming even better. This is evident by industry improvements in reclamation and water recycling in oil sands mining, and improvements in in-situ processes.
As producers experiment with technologies that are intended to produce proportionately more hydrocarbon from the same volume of oil sand so as to increase producer profits, the result may be the creation of extraction methods that are cleaner, less environmentally invasive and more efficient. The by-product of new technologies and techniques may go some way to maximizing hydrocarbon production and producing cleaner fuel. It is not simply the desire to protect the environment or the desire to increase profit that drives the industry. It is a combination. As a result, it is a very reasonable and attainable expectation that the oil sands industry will, in the foreseeable future, be both cleaner and more productive and as a result attract less attention.