Method for identifying formation fractures surrounding a well casing

Abstract From the Canadian patent

An acoustic borehole logging tool traverses a fluid-filled cased well with an acoustic energy transmitter. Pressure waves created in the well fluid by the transmitter generate tube waves in the well casing. A closely spaced receiver detects tube waves that have travelled along the cased wellbore and been reflected by fracture interfaces. These reflected tube waves are recorded and used to identify the top and bottom of any fracture interval in the formation behind the well casing. This method can also be applied to determination of the effectiveness of a hydraulic fracturing operation in a subsurface formation behind a well casing.