Abstract

This paper presents the well construction results to date of an offshore development drilling campaign, which has delivered record-breaking top-quartile performance throughout every phase of well delivery.

The primary purpose of the paper is to distribute both the techniques and lessons learnt in the Pearl well construction campaign, in order that this information can be built upon and lead to further improvements in well delivery. This is a goal that is equally important to both national governments and IOC's in the current economic climate. Some techniques are specific to carbonate reservoirs but others are valid for any offshore development where wells are pre-drilled in order to meet plateau rate from first gas.

Historically, the development wells in Qatar's giant North Field have taken in the region of 75 days to drill, complete, perforate, stimulate and clean up in preparation for their long-term production. The Pearl Well Engineering team has set a new benchmark for North Field wells, dramatically reducing this time by 40% to an average of 45 days. Every aspect of the well design and construction was examined, challenged, and where possible, optimized. Both small incremental improvements and a step-change innovation contributed to the dramatic reduction in delivery time. The paper presents full details on the incremental improvements, some of which include: cost effective Bottom Hole Assembly (BHA) selection, cement design, driving of conductors with deviated drive shoes and simple, fast and very effective stimulation design.

Focus is also given to a truly innovative approach to perforation, stimulation and clean-up. For the Shell Pearl project, these activities were carried out concurrently with the drilling of new wells. The drilling continued from the rig but at the same time the perforation, stimulation and clean-up of pre-drilled wells was conducted from specially built temporary decks installed on the permanent jacket. Therefore, the 20 days per well required to perform these operations were taken off the critical path giving a corresponding direct saving on rig days.

In conclusion, this paper describes in a section-by-section manner both the main factors that contributed to a top-quartile, 40% reduction in well delivery time, and the possible future opportunities to reduce this time still further based on the experience to date.

This content is only available via PDF.
You can access this article if you purchase or spend a download.