Logging-While-Coring

Abstract

One of the main challenges during coring, particularly in exploration wells, is the possibility of unidentification of the right coring point/depth. Typically, this can be noticed only at the surface using gamma-ray logging or geology study. In such cases, the retrieved core sample is already obtained from the undesired formation or interval and thus, the success of the operations has been seriously challenged as a lot of money and efforts have been wasted. Facing this challenge, coring may be repeated (this time trying to be in the right depth interval). Ignoring to core and just relying on subsequent wireline logs for formation evaluation is not an option in an exploration well (because the logs would remain uncalibrated without core data and of limited value). Another challenge of coring (and generally formation evaluation) is that coring and wireline logging are taken under different times and thus well and formation conditions causing some adverse mud invasion or mechanical changes, and even depth matching issue (refer to Chap. 8).