Fracturing

When sandstone rocks contain oil or gas in commercial quantities but the permeability is too low to permit good recovery, a process called fracturing may be used to increase permeability to a practical level. Basically, to fracture a formation, a fracturing service company pumps a specially blended fluid down the well and into the formation under great pressure. Pumping continues until the formation literally cracks open. Meanwhile, sand, walnut hulls, or aluminum pellets are mixed into the fracturing fluid. These materials are called proppant. The proppant enters the fractures in the formation, and, when pumping is stopped and the pressure allowed to dissipate, the proppant remains in the fractures. Since the fractures try to close back together after the pressure on the well is released, the proppant is needed to hold or prop the fractures open. These propped-open fractures provide passages for oil or gas to flow into the well. See figure to the right.

ARTIFICIAL LIFT

After the well has been perforated, acidized or fractured, the well may not produce by natural flow. In such cases, artificial-lift equipment is usually installed to supplement the formation pressure