Concept, Design and Implementation of a Halite Scale Mitigation Completion in a Gas Well

A North Sea operator was planning to sidetrack an existing gas well to access untapped reserves with an extended reach, sub-horizontal reservoir target. The well was expected to deposit halite scale in the lower part of the completion and across the sandface based on experience from other wells in the field and a production chemistry desk study, possibly from initial production. The project team investigated completion concepts for the well that would address the scaling issue and selected the most appropriate concept prior to designing and planning a practical installation. Several concepts were examined for practical application, including a detailed risk review, before a capillary water delivery system was selected. This involved running 3 capillary lines through the production packer to chemical injection valves deployed on a pre-perforated tailpipe inside the lower completion. As this lower completion was a 5” perforated liner, significant tolerance challenges had to be overcome. The well was completed with the selected concept in January 2013, with the water delivery system injecting 8 bbls of water per day from initial production. The well is on stream and producing at higher than expected rates, with no halite scaling issues identified. By identifying potential flow assurance issues at the concept stage, innovative applications of existing technology can be considered and applied. A multidisciplinary project team is required to meet the demands of such a challenging project. With halite scaling becoming increasingly problematic in the North Sea, the application of water delivery completion concepts may become key to future developments.