Stimulating oil production from Algeria's Hassi Messaoud oil field has proven to be a difficult proposition. Sonatrach is now achieving substantial production increases from non-producing assets with an aggressive re-entry well program. The key to success is a combination of new technologies. Some 600 of the vertically drilled wells are candidates for reentry and rework to drill horizontal laterals, however to be eligible they must meet the following basic criteria which Sonatrach have established:

  • They must be open hole completions.

  • They must have been shut in for a long time – effectively since being drilled.

The zone of interest is the Upper Cambrian, an extremely hard and abrasive sandstone and quartzite formation that are extremely difficult to drill. Kicking off laterals in these re-entry wells is therefore challenging and required the development of new tools in order to do so effectively. Additional challenges were posed by the requirements to be able to isolate the laterals, tie them back to the original cased hole and provide for thru tubing re-entry capabilities.

This paper addresses the milling, drilling and completion issues relevant to these wells and discusses the solutions arrived at. Using a typical well re-entry case history, it details the steps taken to create a TAML1  level 1 open hole multilateral (or a psuedo type level 3 with mechanical integrity) combined with either through tubing completion or conventional tubular completion. It will describe how a combination of liner hanger and inflatable packer technology, together with a large bore completion allowing for selective thru tubing re-entry, has led to several successful installations. Future installations will consist of level 3 multilateral junction hardware that will be utilized to provide formation support and simpler reentry and where required the addition of lateral isolation to cut off gas encroachment. An extensive gas injection program (and in some cases water injection) is utilized in the field to assist in production recovery. The use of annular casing packers in conjunction with liner or tubular plugs will allow for isolation shutoff of either lateral at some later date when gas or water influx offsets oil production gain.

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