Sidetrack Trajectory Success Indicator

Abstract

The drilling of a secondary wellbore departing from a primary wellbore, known as a sidetrack, is used for many reasons during wellbore construction. Sidetrack techniques and procedures are well established with all the major service companies. A typical sidetrack operation would consist of setting a deflector (whipstock), cutting a hole in the existing casing (window), and then drilling into the formation at the desired exit angle and direction (kick off) to produce a starting hole (rathole) for subsequent drilling. The sidetrack milling assembly would then be Pulled Out of Hole and the drilling bottom hole assembly (BHA) run in hole to continue drilling the secondary wellbore trajectory. If for some reason, the casing exit and desired departure of the sidetrack is not obtained, this will remain unknown until the subsequent drilling operation with Logging While Drilling (LWD) tools are run in hole and have extended the rathole. The failure to obtain and recognize the desired kickoff departure prior subsequent drilling operations can lead to significant Non Productive Time (NPT) and subsequent rectification costs. This paper describes the development and successful testing of a compact sensor package located near the front of the sidetrack milling assembly. The sensor package is activated at surface and records inclination data during the sidetrack operation. When the sidetrack milling assembly is pulled out of hole the sensor is read wirelessly using a handheld reader once the milling assembly is at surface. The reader gives the operator a visual confirmation, or otherwise, that the desired sidetrack kick off departure has been achieved allowing informed decisions to be made on the next operational stage.