Patent ID: 7617052
Filing Date: 2009-11-10
Classification: E21B

Abstract:
1. An ultrasonic estimating method for estimating a mud velocity in a casing by means of an ultrasonic estimating apparatus comprising a transducer and adapted to be positioned inside the casing and displaced through the casing at a plurality of azimuth and a plurality of depth, the method comprising the steps of: a) for a first depth and a first azimuth of the ultrasonic measuring arrangement: a1) emitting an emission ultrasonic wave towards the casing for exciting the casing with a sensibly normal incidence, a2) receiving a reflection ultrasonic wave reflected from the casing, a3) measuring a transit time between the emitting step and the receiving step, a4) determining the casing thickness for the first azimuth, and b) repeating the emitting step a1), the receiving step a2), the measuring step a3) and the determining step a4) for the first depth and at least a second azimuth of the ultrasonic measuring arrangement, wherein the method further comprises the steps of: c) calculating an intermediate mud velocity value based on the measured transit time, the determined casing thickness, a diameter of the transducer and a casing outer diameter for the first depth, and for the first azimuth and at least the second azimuth, and d) calculating an estimated second depth mud velocity value based on the intermediate mud velocity value and an estimated first depth mud velocity value.