Ringraumabdichtungen durch plastische Formationen im Bereich von nicht zementierten Verrohrungen in Norddeutschland

摘要

Where wellbore integrity has to be prouen as an important aspect in enuironmental and groundwater protection, methods are required to proue annulus sealing against unwanted migration of hydrocarbons or salt water. This is possible by uarious borehole measurement methods that can be used to distinguish cemented from uncemented annular spaces in the casings. For economic reasons, a complete measurement is ojten not carried out, but instead only a measurement is made up to an expected cement head. Howeuer, in order to ensure to pull the casing in the uncemented area, the casings of all boreholes were measured up to the surface during a special P&A campaign at the Dutch border. During the borehole measurements, attention was taken to a particular characteristic where, surprisingly, an exceptionally good attachment of material" to the casing was obserued in the uncemented areas. The measurements made here showed recurring, identical characteristics in certain geological sections. By taking samples, evidence of formation sealing was obtained by determining the shear strength of the clay material present. It was possible to show that a hydraulic seal of the formation with the uncemented pipe has deueloped here ouer time due to the lithological properties characterized by plastic behauior (e.g. day/salt).