Mini-frac / DFIT
A critical component of determining caprock integrity is the determination of in-situ stresses. Mini-fracs and DFIT’s are common and reliable techniques for indirectly measuring the formation’s minimum in-situ stress. During a mini-frac, test fluid is pumped in a short pulse into the reservoir to create a small fracture that cuts through near- wellbore damage to establish communication with the true formation.
Hydraulic fractures naturally follow the path of least resistance, thus propagating perpendicular to the formation’s minimum principal stress. After the fracture is opened, the pumps are shut down. As the downhole pressure declines, test fluid leaks off into the formation and the induced fracture closes. This pressure decline can be analyzed to determine when the fracture closes. The pressure at which a hydraulic fracture closes is equivalent to in-situ stress of the formation.
To detect when the fracture closure occurs, BGES believes that a single unique closure event should satisfy multiple diagnostic plots or methods. Therefore, a combination of analytical methods are used in concert to arrive at a consistent interpretation of fracture closure. This is also known as the “holistic fracture diagnostics” methodology.