Successful Dual Casing Exits are becoming more commonplace in today's oil field. However, there are still many challenges involved with this type of work. This paper will outline the successful completion of a two well campaign carried out in the Arabian Gulf along with the problems encountered, lessons learned, the post job conclusions and the recommended way forward for future jobs.
The task for this campaign was to design, build and supply a system that would be able to set inside 4 ½″ casing and successfully mill a window out of this smaller pipe into the surrounding cement then mill out through the larger 9 5/8″ casing. Having milled the window through both sizes of casing, a rat hole would have to be drilled deep enough to suit the subsequent drill ahead BHA. Although these window milling BHA's were to be conveyed using pipe, like traditional TTRD exits, this campaign would utilize PDM motors to provide the rotation for sidetracking the wells.
On both occasions, the sidetracks were completed and the customer was able to continue the drill ahead operations as planned. There were many lessons learned throughout the campaign. From the initial design stages, through the manufacturing phase and finally onto the operational issues, the lessons learned were significant and will be used in the future advancement for this type of work.
This technical paper will show the importance of this campaign which, with the lessons learned, will lead to many more successful dual casing exits being carried out.