Formation Permeability Determination by Micro or Mini-Hydraulic Fracturing

This paper presents a theory and its application for post-fracture pressure-transient analyses. The proposed procedure, known as “impulse fracture test,” is an injection/falloff test designed for the determination of formation permeability and reservoir pressure. The hydraulically induced fracture can pass the near wellbore damaged zone and expose a larger formation area to flow. The permeability and reservoir pressure determined are therefore more representative of the reservoir. The theory is based on the distribution of sources with variable intensity along the fracture trajectory. For field applications, asymptotic solutions are derived to give the “type-curve” capability for the estimation of formation permeability and reservoir pressure. Assorted slope behaviors, such as −1, −2, +1/2 and +1 slopes, are predicted from various pressure and pressure derivative plots. Analyses of data from two wells which were inadvertently fractured support these behaviors.