Shell Global Solutions

Shell Global Solutions has started to explore alternative, innovative options for well abandonment materials after tests carried out for Phillips Petroleum Company Norway on the long-term performance of commercially available polymers gave disappointing results. Phillips had been hoping to use one of the commercial products on its Ekofisk 1 North Sea field, which is currently being decommissioned.

Encouraging results are now coming from a novel fluorinated polymer that offers long molecular lengths with extensive crosslinking. This has now been created in field conditions from the two components needed for practical storage, handling and installation, particularly offshore. The new generation of possible plugging material is currently performing well in sustained trials.

Many of the world's oil and gas fields onshore and offshore are ageing. Conventionally, to meet tough statutory environmental standards, abandoned boreholes are back-filled with injected concrete. However, tests have shown that the formation of micro-cracks around the periphery of the concrete cores with time allows hydrocarbons to escape into the environment.

The search is on for more effective fill materials that can be installed through retractable coiled tubing rather than the expensive rig abandonments that are needed when using concrete. Success will also mean shorter fill lengths, with commensurably lower installation costs.

Enhanced performance integrity from these materials will also obviate the need for the difficult, complex and extremely costly drilling that is often needed to reseal leaking abandoned wells.

However, the performance criteria for new materials are rigorous, according to Frans Janssen, of Shell Global Solutions' upstream materials engineering services.

"They must be able to withstand temperatures of 150°C with no shrinking. High tensile strengths are preferable, with some elasticity. At the same time, materials must be viscous in installation, with an appropriate curing time, but with low extrusion characteristics once they are in place. We are currently looking for suitable partners to work with us and carry out long-term performance trials on the fluoropolymer."

Shell Global Solutions is a network of technology companies of the Royal Dutch/Shell Group with an extensive network of offices around the world all linked to its centers of excellence in Europe, the USA, and the Far East, and serving a wide range of industries, including: exploration & production, gas & LNG processing and storage, refining, and chemical production.