Definition - What does Hydraulic Fracturing mean?
Hydraulic fracturing is a well activation process, which involves pumping of Chemicals, water and sand under pressure high enough to crack a formation. The purpose of this process is to create controlled cracks or fractures within the rock formation in order to improve the permeability, thus allowing the formation fluids to flow more easily.
This is simply called “fracking” or “hydrofracking”.
Petropedia explains Hydraulic Fracturing
The flow of hydrocarbons from a formation mainly depends on properties like porosity and permeability of the rocks. Fracking process is implemented in reservoirs like shale. This process involves the pumping of chemicals at a higher pressure than the strength of the rock, so as to create fractures in the formation. Once the fractures are created a propping agent such as ceramic beads or sand is pumped to keep the cracks open.
Once the well is drilled and cased it is hydro tested for integrity before the fracking process can begin. This process involves the use of surface equipment like storage tanks for chemicals, proppants, piping, pressure control equipment and frack monitoring unit. This process is carried out in several stages.
Stages of fracking:
- Acid stage: In order to clear the debris and to provide a clear pathway for fracking fluids a mixture of diluted acid and water is pumped into the wellbore for cleaning purposes.
- Pad stage: without the use of proppants a batch of treated water along with variety of chemicals like corrosion inhibitors, scale inhibitors, oxygen scavengers are used to clear the formation and allow the placement of the proppant.
- Proppant stage: In this stage a mixture of water and proppant (quartz, silica, plastic pellets, resin-coated sands, sintered bauxite, etc.) are fed into the wellbore. The size and type of the proppant depends on the wellbore conditions. Once the pressure is bleed off the water flows back keeping the proppant inside the formation, thus enhancing the permeability of the formation.
- Final flush stage: Fresh water is pumped to clean out excess proppants.