Evaluation of Casing Exit Setting Depth Criteria for Whipstock

Abstract

Baker Hughes GE has conducted several hundred whipstock operations over the last years on the NCS with a high success rate. This work will go into detail on some of the operations that were less successful, particularly in terms of where and how the whipstock was set inside the wellbore. One whipstock operation was set with a KOP right in the area of oval casing issues. Hence, five cases with the potential of being analyzed with regards to setting depth of the operation were chosen. The main criterions that have been analyzed are: • Casing ovality • Dogleg severity of the wellbore • Casing eccentricity • Lithological formation around casing wellbore • Favorable whipface angle After analysis of the cases in question, it was found that a casing ovality of 10% at the KOP is detrimental for a whipstock operation, while one case showed 5% and were successful. This shows there to be a cut-off percentage somewhere 5 and 10% ovality when planning a whipstock setting depth. Several whipstock operations had also been set in areas of a DLS in excess of 3 °/30 m, where the chances of compromising the operation is greater.