Exploration drilling projects in arctic and northern regions often take place in remote, cold, isolated and demanding locations such as lakes, muskeg areas and oceans. One of the major challenges for these projects is the lack of infrastructure making it unfeasible to employ barges or drilling vessels to support project activities.
The cold, however, can be used to one’s advantage. Depending on its temperature and crystal structure, ice can be nearly as hard as concrete. As such, using an “ice pad” provides a cost effective and safe platform for construction and exploratory drilling. With the summer heat, the ice pad melts, leaving no environmental impact.
Ice Pad Design Considerations
Ice pads can be grounded or floating depending on the water depth and the ice thickness required to support the intended loads. The design load should account for all anticipated loads during the project. In addition to the rig dead load, rig live loads and mobile loads - such as trucks and loaders, must also be accounted for in the design.
Floating ice pads can be constructed in stable ice zones where ice cover is not subject to movement during the project. This is typically in lakes or landfast ice zones in the ocean. Floating ice pads should be designed to provide sufficient bearing capacity to support the intended equipment loads and provide sufficient freeboard so that load settlement due to creep is controlled in a way such that it remains above the waterline by an acceptable margin at the end of the project.
In an area where there is a possibility of ice movement during the project, ice pads must be grounded. This is typically in shallow water. In this situation, ice pads are designed to resist the forces exerted by moving ice.
Ice pads can be constructed by free-flooding, with spray ice or with chipped ice. Typically, free-flooding is the most cost effective construction method however the ice build-up rate is the slowest. Ice pads can be built quickly using chipped ice, though this can be costly. Depending on the project needs, a combination of the three ice construction methods can be used to satisfy both cost and project schedule requirements.
Quality Control and Monitoring
The bearing capacity of the ice pad depends on the quality of the constructed ice. Proper construction procedures must be employed to ensure the highest ice quality and thus, the safety of the ice pad. Daily construction progress and procedures should be detailed and verified by an ice engineer. Once the ice pad construction is complete, it is recommended that both ice temperature profile and ice strength measurements are performed in addition to the mandatory ice thickness profiling prior to deploying equipment on the ice pad. For floating ice pads, ice movement and settlement of the pad should be continuously monitored to ensure the safety of the pad. Positive freeboard (the height of the ice cover above the waterline) should be maintained at all areas of the ice pads.
Ask us about our ice pad work for De Beers’ exploratory drilling programs at the Snap Lake, Victor mine (pictured above) and Gahcho Kue projects.
For more information on our arctic engineering services, click here.