By Franklin L. Foster, Ph.D.
Cold (as in non-thermal) Heavy Oil Production with Sand (CHOPS) has become one of the main ways that heavy oil is produced in the Lloydminster Region. As documented in numerous other places on this website, the old struggle to produce Heavy Oil without its concomitant sand was solved by producing the sand. A key technology which enabled this was the Progressing Cavity Pump (PCP) which effectively augured to the surface the entire mixture of oil, water and sand. Sand became a medium for greater production of oil. In fact, a slogan was developed which the oilfield oldtimers could not believe – “Sand is Our Friend.”
However, produced sand means extra work and extra costs. In today’s Heavy Oil patch, huge quantities of sand are produced along with the oil. Once it is separated from the oil it has to be stored, often in a central location (which means trucking costs) and ultimately disposed. An increasingly popular method for disposing of the sand is to inject it down into caverns in the salt layers which underlay the local oil bearing formations. It has been estimated that more than 25% of the operating costs of producing heavy oil are related directly or indirectly to sand.
Beyond the costs of the CHOPS process are the environmental hazards. Separating oil, water and sand on the surface means continual possibilities of soil, water, and atmospheric pollution. The frequent need to transport any or all of the constituents, usually by truck, increases the environmental impacts and spreads them over a much wider area. Throughout this process, significant quantities of greenhouse gases, such as methane, are being vented into the atmosphere.
So … what if there was a
way to avoid most of these problems? Enter the innovative idea of
the SuperSump. This would see a number of wells, still using a CHOPS
process, but producing the oil, sand, water mixture downward into a cavern
carved out of a salt formation well below the oil reserves. In this
cavern, natural settling would see the three constituents separate.
Then, one large pump could pump pipeline quality oil to the surface. When
necessary, the water could also be pumped out but the sand would stay
behind, already in the salt cavern far below the surface.
This one simple (once you think of it) concept offers to overcome most of the problems associated with CHOPS. Since the producing wells are not producing to the surface, they have much less environmental impact. Since all the separation is occurring deep underground, all of the environmental and cost elements are greatly reduced or eliminated. Transportation costs are cut significantly. Several wells produce into one cavern and on heavy lift pump can produce the resulting oil into a flowline or pipeline.
Some challenges do remain.
The salt cavern must be designed to facilitate the separation, and storage
of the sand, all while maintaining its structural integrity. As
production continues, the size of the cavern needs to grow to accommodate
the increased volumes of sand. As well, since the producing wells
are producing to the cavern, it is more difficult to monitor the
productivity ( or even the operational status), of each producing well.
However, preliminary economic evaluations indicate that despite initially
higher capital costs, the SuperSump system has the potential to recover
these costs in a two year period and since ongoing operating costs will be
significantly lower, the wells can produce at a profit for much longer
periods of time and also recover a higher proportion of the available oil
than the current CHOPS methods.
So, our friendship with sand may be coming to an end. We are looking at a production process that will leave sand far underground – out of sight, and out of mind.
Figures courtesy: "SuperSump Heavy Oil Recovery Evaluation" by Brian Wagg & Yi Fang, C-FER Technologies, 2007.