In SituPrepared Nanoparticles in Support of the Oilsands Industry Meeting Future Environmental Challenges
a report by Nashaat N Nassar, Maen M Husein and Pedro Pereira-Almao Department of Chemical and Petroleum Engineering, Alberta Ingenuity Centre for In-Situ Energy, University of Calgary
The depletion of the world’s supply of conventional oil is well accepted. This fact has led to an increased demand on the recovery and upgrading of unconventional oil in order to meet current and future energy needs. The Alberta oilsands industry currently produces oil, known as bitumen, that has to be upgraded into lighter synthetic crude with low sulphur, nitrogen, asphaltene and heavy metal content.1
Environmental Concerns with Oilsand Recovery The most common subsurface bitumen recovery process employs steam-assisted gravity drainage (SAGD) in situ with various stimulation techniques. The current oilsands recovery and upgrading processes face significant environmental challenges.1,2
There are four
major environmental concerns synonymous to all of the oilsands industry, namely:
• Wastewater: Currently for every barrel of oil produced, approximately four to 16 barrels of wastewater are generated that are then discharged into tailing ponds.3
More than 840million cubic
meters of tailing ponds spread out over 170km2 of northern Alberta.4
• Air emissions: During oilsands recovery, a number of chemical reactions between steam and oilsands take place and several
gaseous by-products evolve, including H2S, NH3, CO, CO2, CH4, NOx and SOx.2,5
• Solid waste and by-products of oilsands production: Upgrading and refining may cause serious ecological problems if solid waste and by-products are released into the environment. For each barrel of oil recovered via surface mining, approximately 2tons of solid waste are produced.6
Nonetheless, surface mining is not the best option for oil production in the future.
• Spills during oilsands processing: These are difficult to clean and the extent of irreversible damage to the environment once endured has not yet been fully determined.
Reducing the environmental footprint of the oilsands industry is thus critical for a sustainable future for oilsands operation in Alberta.
The Properties of Nanoparticles
Nanoparticles (NPs) portray unique catalytic and sorption properties due to their exceptionally high surface area-to-volume ratio and active surface sites. Also, NPs are highly mobile in porous media because they are much smaller than the formation pore space, leading to effective transport properties.
The Alberta Ingenuity Centre for In-Situ Energy group focuses on research and development of in situ preparation techniques in which NPs are prepared within the heavy oil matrix. Below are some focus areas of the group’s current research activities.
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In Situ Synthesis and Stabilisation of Colloidal Nanoparticles
Stable metal oxide NPs could be prepared in situ in heavy oil matrices employing water-in-oil (W/O) microemulsion methods as follows. An aqueous solution of the corresponding metal is added to a W/O emulsion, agitated for a period of time. Then an aqueous solution of a base is added to initiate nucleation and growth of the metal oxide/hydroxide NPs, which remain stable in suspension.15–18
W/O microemulsion systems represent heavy oil matrices under SAGD conditions to a good extent. They are attractive media for NP preparation due to their ability to form a wide variety of NPs with controlled sizes (see Figure 2).
The catalytic activity and/or sorption capabilities of the NPs formed depend primarily on the surface area/L of the oil matrix, which is dictated by particle size, colloidal concentration and stability. A comprehensive review summarising the findings on variables
© TOUCH BRIEFINGS 2011
• Applying in situ prepared NP sorbents for the scavenging of potential toxic gases evolving during oilsands recovery and upgrading. The goal is to effectively capture those gases before they seep into adjacent aquifers and/or into the atmosphere. In this research, ultradispersed metal oxide sorbents were successfully prepared in situ within heavy oil. For the first time, the in situ
removal of H2S(g) from the oil matrix under the upgrading conditions was examined.2,5,7,8
• Dispersing NPs with catalytic properties in situ enables the production of upgraded oil by reducing oil viscosity in reservoirs and via bitumen dissolution. In addition to enhancing oil production, in situ upgrading of heavy oil reduces the operating cost and environmental challenges pertaining to on-surface facilities, including emissions of greenhouse gases and nitrogen oxides, solid waste by-products and demand on fresh water. Upgrading can be achieved in two ways: (i) Adsorption of asphaltenes onto NPs with specific affinity towards asphaltenes.9–12
These NPs are also magnetic, allowing for their magnetic separation and removal from the process stream.
(ii) Upgrading of heavy oil in situ into light, utilisable distillates within the reservoir environment with the aid of ultra-dispersed nanocatalyst particles.11–14
A cartoon representation illustrating the potential application of in situ prepared colloidal NPs coupled with the SAGD process is depicted in Figure 1. The discussion below sheds some light on techniques for in situ preparation of ultra-dispersed NPs in oil matrices. It also highlights
the results of H2S(g) scavenging and asphaltene adsorption, gasification and oxidation.
Heavy Oil
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