In many oil and gas wells, one additional step is requiredstimulating the formation by physical or chemical means so that hydrocarbons can move more easily to the wellbore through the pores or fractures in the
reservoir. This is usually done before installing a pump or when the pump is
removed for maintenance.
Acidizing, one form of stimulation, is the injection of
acids under pressure into the rock formation through the production tubing and
perforations. Hydrochloric acid, for example, is particularly effective in
dissolving portions of limestone and dolomite formations. This creates channels
beyond the perforations for oil and gas to flow back to the well. Acidizing is
often followed by fracturing.
Fracturing or fracing is another common method of
stimulation. A fluid, such as water or an oil product, is pumped down the
hole under sufficient pressure to create cracks (fractures) in the formation. Proppanta hard substance, such as sand, ceramics or resin-coated materialis
injected with the fluid. As the fluid disperses, the material remains to prop
open the fracture.
Petroleum Communication Foundation. Our Petroleum Challenge: Exploring Canada's Oil and Gas Industry, Sixth Edition. Calgary: Petroleum Communication Foundation, 1999. With permission from the Centre for Energy.