Fracture-Close Pressure Mean?
Fracture-close, also known as fracture-closure pressure, is the pressure at which a fracture closes without the presence of a proppant or the minimum pressure required to keep the fractures open. At closure pressure, the width of the fracture becomes zero. Fracture pressure on the other hand is the pressure required to make a fracture in a rock.
The pressure required to create a fracture is equal to the pressure required to resist stress in a rock perpendicular to the fracture and hence, the closure pressure is equal to the minimum in-situ stress.
Trenchlesspedia Explains Fracture-Close Pressure
During treatment of a hydraulic fracture, closure stress in the pay zone must be more than the bottom hole treating pressure (BHTP) to increase the existing fracture i.e. BHTP should be greater than the closure stress of the pay zone. Therefore, it is recommended that the wellbore should land in a zone with higher closure pressure to keep the fractures contained.
In design of hydraulic fracture, closure pressure is very important to determine the type of sand needed for the job.