Drilling Technology Influence on Boreholes Quality with Geophysical Measurements Implications

The drilling techniques and operations performed during drilling can affect the borehole’s shape and quality, with direct repercussions on the quality of geophysical records, both LWD and wireline. However, wireline measurements are more affected than LWD, due to the operations that occur after drilling the well (e.g., reaming trips, etc.) and the “aging borehole” phenomena (breakouts and fractures become larger, invasion becomes deeper).

The most affected by borehole’s quality and shape are the pad-type geophysical tools: Imaging, Litho-density or Microresistivity, which require a good contact with the formations. Also, the sonic logging readings can be affected by the occurence of quasi-horizontal or inclined fracture systems, due to a strong attenuation of the signal, causing the “time stretch” or even “cycle skipping” phenomena (abnormally long transit time readings).

Different types of fractures induced by drilling operations can create a false invasion appearance, since the resistivity tools with short investigation radii are influenced by the drilling fluid penetrating in these fractures.