Stimulation

In many oil and gas wells, one additional step is required—stimulating 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. Proppant—a hard substance, such as sand, ceramics or resin-coated material—is 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.