Measurements of borehole diameter are made using acoustic pulse-echo sensors.

The sensors measure the transit time of acoustic waves between the sensor and the borehole wall and transmit the results to the surface in real time.

The surface computer system uses this information to derive the corresponding stand-off distance and borehole diameter, based on the calculated acoustic velocity of the borehole fluid under downhole conditions.

The acoustic sensors also record detailed data in memory, which is processed after the run to derive measures of borehole shape, ellipticity and ellipse orientation.

Applications

•Environmental correction of LWD gamma ray, resistivity and neutron data.

•Quality control for LWD logs.

•Real-time assessment of wellbore stability

•Evaluation of hole cleaning and hydraulics.

•Accurate location of tight spots or ledges.

•Enhanced assessment of directional drilling tendencies.

•Cement volume calculations.

•Allows measurement of time-lapse borehole effects over multiple pipe runs.