Pushing the Boundaries of Concentric-Coiled-Tubing Technology To Resurrect Subhydrostatic Gas Wells on an Unmanned Offshore Installation

摘要

Ravenspurn North is a mature gas field in the southern North Sea with 42 wells, drilled (and many hydraulically fractured) in the late 1980s. By 2006, more than half of the wells had ceased to flow, and many were flowing intermittently. With ailing wells and consequently falling production rates, the longer-term future for Ravenspurn North field was uncertain. A wireline campaign suggested a common failure mode for many wells: Large amounts of proppant had accumulated in the wellbore. Modeling of the potential range of static and dynamic pressure losses caused by this proppant supported a significant enhancement to the remaining gas potential. However, the depths of the wells combined with subhydrostatic pressure conditions and large-diameter lower completions made achieving cleanout challenging. Furthermore, the target wells were located on unmanned offshore installations with minimal facilities, deck space, and deck loading.