With recent announcements from the International Energy Agency and the U.S. National Petroleum Council predicting a looming energy crunch as early as 2012, and with diversity in fuel supply such as ethanol and biodiesel not widely available to lessen dependence on gasoline, it has come to the attention of the world that oil producers simply need to produce more oil. The only other alternative, and one that is not politically easy to attain, is to dramatically alter energy consumption patterns across the globe.

Although the U.S. Department of Energy's fossil-fuel office suggests that more than 60% of all oil remains stranded in reservoirs, producers often face numerous technological challenges when it comes to maximizing production and ultimate recovery. With world energy demand predicted to increase between 50% and 60% by 2030 and the U.S. becoming increasingly dependent on foreign supplies, any technology that can boost production and recovery will in great demand.

In the life of an oil field, initial production typically results in 10% to 30% recovery. Secondary efforts, such as waterflooding, can increase recovery between 10% and 20%, and tertiary recovery, which can be fluid injection such as CO2, can increase recovery an additional 15% to 25%.

A newly popular method that is an optimization process for both CO2 flooding and waterflooding is forced fluid injection via pressure pulsing.

CO2 flooding has attracted a lot of attention as a viable tertiary-recovery method. The process begins with CO2 being injected into an oil reservoir via injection wells. Water is then injected to drive the oil and CO2 to producing wells.

The use of CO2 in flooding can thin the solution, which can result in non-uniform or preferential flow (fingering) and poor recovery of the hydrocarbon. The injection of water helps reduce chances of this.

An adverse effect of this solution alternation is that, when CO2 is mixed with water, it forms a highly corrosive carbonic acid. Operators may need to equip wellheads with stainless steel seals, bolts and other trimmings if considering CO2 injection. The CO2 can then be extracted from the oil and reused.

Though it can be difficult to fully combine CO2 with heavy oils, CO2 is still soluble in oil, causing the fluids to swell. This trait of CO2 makes it far more efficient than liquefied petroleum and natural gas. The CO2 that is injected can come from naturally occurring reservoirs and industrial sources, but new technologies are being developed to produce CO2 on-site for use in areas without access to the CO2.

Waterflooding is the most widely used and successful secondary oil-recovery process. In many oil fields, waterflooding is initiated well before any significant depletion takes place, to avoid gas coming out of solution and to maintain well productivity. Waterflood oil recovery depends on a number of important geological and fluid properties and operating factors, but the most common problem observed in waterflooding is the injection water seeking zones of highest flow (permeability). Simply stated, water travels a tortuous path of least resistance.

For a production company, the ability to inject larger volumes of water more uniformly into a producing reservoir is an important operational objective as processing rate or water throughput and processing efficiency (uniformity of flow) directly affects production volumes. Volumetrically, where input equals output, increasing input by a factor of two also increases output by a factor of two.

If the proportion of water and oil of the output tends toward more oil because of uniformity of flow, the production company would recognize greater overall production. If a formation is not volume-balanced with respect to input/output and the reservoir is in a stage of "filling" the pore space to reestablish pressure drive, then the ability to increase injectivity beyond rates typically modeled and measured in the field would also be beneficial as a production company may realize improved production sooner.

Forced fluid injection via pressure pulsing is an injection process in which, with each impulse, a volume of liquid is forced at high accelerations by downhole devices into the reservoir. Akin to a beating heart, the process works by elastically expanding and contracting the pore networks typically found in all oil-bearing reservoirs and forcing liquids to travel outside nature's path of least resistance.

Pressure pulsing is not a stand-alone technology but rather an optimization process that gives rise to more uniform injection and faster injection rates. The major applications of pressure pulsing are in flooding processes, such as waterflooding, surfactant and CO2 flooding.

The history of pressure puling in the oil sector dates to 1998 where it was first implemented in the Canadian heavy-oil sector. Given the nature of the process, in 2000 it was also introduced to the environmental groundwater-remediation sector where it has been routinely implemented to aid in the placement of remedial fluids used to neutralize groundwater contaminants.

The U.S. is hoping to reduce its dependence on foreign oil, the U.K. and Norway have launched several initiatives to maximize recovery, and even Saudi Arabia is looking to increase its oil production using improved and enhanced oil-recovery methods. Pressure pulsing is one key to unlocking stranded oil.

With so many new technologies, like pressure pulsing, being used and developed, it is clear that the world is on the right track to maximizing recovery in existing oil reservoirs.



Brett Davidson is president, chief executive and a founder of Alberta-based Wavefront Energy and Environmental Services Inc., which provides oil-well stimulation, secondary recovery and groundwater remediation services.

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