A Case History of the First Drilling with Liner Application in Romania

Abstract

Drilling a creeping salt formation at a depth of more than 4,200 mMD can be a challenging task, especially when the mud weight cannot be increased enough because of losses in zones above. A stuck pipe can often be released by pumping water pills; however, after drilling through salt while running casing, the hole can close in (time-dependent creep), making it impossible to run casing across this interval. In such situations, innovative ideas to drill and isolate such an interval can help save the day.

One such idea was implemented in a deep well in Romania. While drilling at a depth of 4,237 mMD, the bit encountered an aggressive salt layer, causing stuck pipe that could not be released with water pills and eventually resulted in three sidetracks. On the third attempt, the well was drilled to the top of salt layer, and then the 7-in. liner, a casing bit, and a hydraulic set, rotating liner hanger system were run together on drill pipe. The bit drilled through the 17-m salt layer and died out immediately after achieving its objective. The liner was cemented in place, and the salt layer was successfully isolated. Drilling then continued through the reservoir section below.

This was OMV Petrom's first application of drilling with liner (DwL) and proved to be successful in terms of meeting its objective (i.e., isolating the salt layer). Because the DwL operation was not in the original well design, the DwL system and operating procedures were designed, planned, and delivered on short notice. Considered instrumental to the success of the operation, the collaboration between OMV Petrom and the integrated service provider enabled the engineering and subsequent execution of the DwL operation to move forward in a seamless manner, which contributed greatly to the success of the DwL operation.

The operation proved that DwL can be implemented to case off problematic zones, which increases the likelihood of meeting well objectives. Had this technology not been implemented, the available alternate solution could have resulted in additional time and cost with a low probability of success. This paper will present the experience of the first ever application of drilling with liner in Romania and the associated lessons learned, as well as a discussion of the circumstances under which it became the foremost technology on the way to reaching the target reservoir.