Well assembly monitoring

A well assembly 1 comprising a sensor 2 and a method of monitoring using the sensor 2. The well assembly may comprise a wellbore 7 and the sensor comprising plural sensing devices 4, wherein the sensor is in a fixed location relative to the wellbore for monitoring the size and/or shape of the wellbore. The method may be a method of monitoring the size and/or shape of the wellbore and comprises: providing the sensor in a fixed location relative to the wellbore and monitoring the size and/or shape of the wellbore using the sensor. The well assembly may comprise a well foundation 6, e.g. a suction anchor, and the sensor, wherein the sensor is in a fixed location relative to the well foundation, and wherein the sensor is for monitoring the earth underneath the well foundation during installation of the well assembly. The method may be a method of monitoring the earth underneath the well foundation and comprises providing the sensor in a fixed location relative to the well foundation and monitoring the earth underneath the well foundation during installation of the well assembly.