Lessons learnt on the Open Hole Completions for the Two HPHT Retrograde Gas Condensate fields using Expandable Liner Hangers, External Sleeve Inflatable Packer Collars and Swell packers for Zonal Isolation

Abstract

Abstract 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. Introduction The FA and FB gas fields are offshore in approximately 85m of water. They are approximately 300 km southeast of Vung Tau, Vietnam (Fig. 1). This high-temperature reservoir (300ºF) is within the Mid-Miocene Dua Formation, which is an anticline with a four-way dip closure, split by three NNW-SSE sealing faults, and overlain by the Thong Formation. Data from three offset wells; i.e., FA 1X drilled in 1994, FB 1RX drilled in 1996, and FA 2X drilled in 1997, were available. Seven initial wells and three in-fill wells were planned for the fields. The production wells scheduled for completion are listed in Table 1.