GB1299843A - Investigating a well to determine sand entry - Google Patents

Abstract

1299843 Acoustic inspection devices MOBIL OIL CORP 2 Nov 1970 51937/70 Heading H4D A producing well penetrating a subterranean fluid-bearing formation is investigated by monitoring, for at least two different flow rates, the sound generated by impingement of the fluid flow on an interface within the well, for determining the flow rate above which sand is produced in the flow or for determining the location where sand is produced from the formation. In one embodiment a measured first production flow rate from a formation is established by a valve at the well head. A sound detector hung from a cable is passed through tubing within the well and the detector output, due to fluid impingement on the outside of the tubing, is fed to an uphole amplifier, filter and strip chart recorder. The pass is repeated for second and further production flow rates. A log-log graph of the mean sound amplitude (averaged over one pass) against flow rate may be plotted and exhibits an abrupt change in slope (from a known value) where the flow rate is sufficient to entrain sand in the fluid, thereby abruptly increasing the sound amplitude. Instead of a continuous depth log of sound amplitude, the amplitude as a function of flow rate may be monitored for one or more discrete depth increments. It is thus possible to ensure that the well is operated with a production flow rate below the sand-producing flow rate, or that steps are taken to consolidate the formation if production is to be above that rate.