SPWLA Glossary

Afterflow or afterinjection, continuing for a short time after the well bore is shut in at the surface, in the form of wellbore loading or unloading due to the compressibility of fluids inside the well bore. The well bore has storage capacity equal to the volume within the well bore in direct communication with the porous and permeable formation. When the well bore is shut in at the wellhead, fluid will continue to flow into or out of the well bore until pressure is equalized between the well bore and formation. No wellbore storage effect can occur if the well bore is shut in at the bottom of the well at the face of the formation.