CORRELATION BETWEEN MWD DATA AND LITHOLOGY IN THE PARISIAN BASIN

The use of Measurement While Drilling (MWD) technology during geotechnical investigations provides a large amount of data to engineers in a quick and efficient manner. This method of drilling can be deployed in any kind of soil, from soft clays to soft rocks, and the data acquired is more detailed than what could be acquired through SPT or pressuremeter tests. The machine parameters are systematically collected during the drilling operation and these logs are known to correlate well with local lithology as large variations are usually seen in the data at the transition point between two soil layers. However, interpreting these data in isolation can be challenging as there can be a large difference in performance depending on the machine configuration, drill bit and stabilizing fluid chosen for a given project. For this reason, case studies typically analyse a few drillings in a small area, and there are no widespread correlations that can be used as a basis for interpretation. In this paper, a series of 91 MWD drillings of up to 75 m in depth along a linear path about 11 km long in the suburbs of Paris have been statistically analysed to determine a correlation between the various geological formations encountered and the data collected.