The Korean National Oil Company (KNOC) has developed seven retrograde gas-producing wells located in offshore Vietnam. The scenarios presented by these wells taught the developers valuable lessons, and the intent of this paper is to share these lessons by presenting the concepts considered for well design, the selection process for the completion equipment and techniques, the preplanning for the installations, and the experiences encountered during the actual installations.

Several completion challenges had to be addressed, including isolation of water production below the casing shoe and control of condensate banking, sand production, and commingling of multiple production zones in the long openhole sections.

A different type of completion that involved an expandable liner hanger (ELH) with an external-sleeve inflatable packer collar (ESIPC) was chosen, and installation and cementing were accomplished in a single trip. The ESIPC was deployed just below the water-producing zone, and cement was pumped up the annulus from the ESIPC to where the expandable liner hanger (ELH) was set above it. It was felt that this design would prevent water from entering the wellbore while enabling optimum production. To prove the concept, a stack-up test was performed at surface before actual deployment on location to ensure that the cement wiper plugs would pass through the expandable-liner-hanger ball seat and that the concept would perform as intended.

Swellable packers were selected from the various proven openhole isolation devices available to the industry to provide the zonal isolation required in the multi-zone intervals.

This was the first openhole completion in Southeast Asia in a high-temperature, commingled gas environment in which isolation would be contained solely by swellable packers.

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