Although drilling technology is now able to deliver ultra-long horizontal wells, completion technology has been slower to evolve. Running long liners, effective stimulation and completions are some of the areas that require more attention.
The paper discusses some of the challenges in the development of the Al Shaheen reservoirs offshore Qatar and how they were overcome. Some of these wells have a step-out in excess of 30,000 feet with a TVD of 3,100–3,500 feet and thus they offer some unique challenges.
Running and cementing liners to these depths is difficult and some of the methods to effectively achieve this are discussed. Perforating guidelines are presented that allow sand control without having to resort to conventional sand control practices. Stimulation of such long reservoir sections is a particular challenge and a fine balance must be struck between acid coverage and cost, both for barefoot and perforated intervals. The so-called Q-CAJ technique of acid distribution is presented, which has allowed acceptable stimulation despite these conditions. The technique also offers opportunities to stimulate long horizontal boreholes more effectively and at lower cost.
Some of the wells are completed with multi-zone selective completions, which push the design limit of equipment. A number of such intelligent wells have been completed successfully and more aggressive wells are planned. In order to optimize the development cost, dual-lateral wells have also been drilled with complete control over each lateral. Discussed are some of the underlying completion techniques such as running completion in stages, use of mechanical latches, hydraulic control line wet connects, interval control valves and limitations imposed by control lines. The paper concludes with some of the challenges that have yet to be overcome.