The Ourhoud Field is located in Eastern Algeria and has some 60 producing wells with average production of approximately 600 m3/d/well (3,750 bopd/well). Pressure maintenance and production drive is provided by means of water injection at a total rate of some 55,000 m3/d (345,000 bwpd), and gas injection at 106 mmscfd. One water injection well provided problems to the continued effectiveness of the water injection program, because a thin isolated layer was acting as a thief zone taking some 30% of the injected water. When injection was shut down, the zone would crossflow into the zones above and below it at a rate of some 550 m3/d (3,460 bwpd). In order to correct this problem a straddle system was needed to shut-off this zone, allowing all of the injected water to enter the two desired layers thereby increasing both the volume displaced into these layers and the production rate of surrounding wells.

After a detailed review of available straddle options to shut-off the zone in the 7″ monobore completion, it was decided that a single trip system would provide the best chance of success by reducing the number of well entries required, the installation time, and the likelihood that continued shut-in cross-flow would have an adverse effect on a conventional two-trip straddle installation due to the protracted operation time. The chosen one-trip straddle (to set and retrieve) was a newly designed tool which had a model available in the required 7″ size that had undergone rigorous testing, but had not yet been used in the field. After extensive review of the design and testing of the tool, and evaluation of the risks associated with deploying a new design straddle against the advantages of a single trip installation, it was decided to run the first 7″ one-trip straddle on electric line in the well. In this paper the authors will review the well specifics, the design and operation of the single trip straddle, and the decision making process which resulted in its first installation. They will go on to describe the installation process in detail, and review the positive results achieved by the successful shut-off of the cross-flow situation.

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