Diagnostic Fracture Injection Testing Mean?
Diagnostic fracture injection testing (DFIT), also called mini-frac, mini fall-off or data frac is a pressure transient test conducted for ultra-low permeability shales to provide valuable information about the reservoir, and also hydraulic fracture treatment parameters.
The test in effect is a short duration, small volume fracturing operation where small quantities of clear fluid i.e. 2 or 3% of potassium chloride (KCl) water is injected in small quantities to create a fracture before the wellhead is shut-in and pressure is released.
Since the shift towards unconventional, ultra-low permeability reservoirs, DFIT has proved to be the most economical method to determine reservoir and frac properties.
Trenchlesspedia Explains Diagnostic Fracture Injection Testing
DFIT is primarily conducted to obtain essential reservoir properties in a short time frame. It helps determine fracture design parameters such as closure time, closure stress, fluid efficiency, net pressure, etc. which are important variables in a fracture model.
The DFIT is performed before the stimulation treatment of a formation. Small volumes of KCl, i.e. 5 to 30 bbls for shale reservoirs and 50 to 100 bbls for unconventional low permeability sands, are pumped into the formation at a rate of 1 to 6 bpm to induce a small fracture.
A clear indication of breakdown during the pump-in is necessary and the rate of injection and volume of injection is recorded for analysis. After the procedure, the well is shut-in and the pressure is allowed to decline and recorded.
The test is conducted after casing or cementing of the well, and before the scheduled date of stimulation.