A new report commissioned by Shell Canada shows it would be safer and easier for the company to abandon a multi-million-dollar two-kilometre pipe at the bottom of the ocean, instead of retrieving it.

The huge pipe — called a "riser" — crumpled to the sea floor eight months ago off Nova Scotia's coast.

The riser had been used by the Stena IceMAX, a specialized ship hired by Shell Canada, to drill an exploratory well to search for oil.

In bad weather and rough seas on March 5, the riser disconnected from the ship. Shell has been weighing its options for whether to retrieve its equipment ever since.

Buoyancy Modules

Buoyancy modules made of styrofoam and plastic (similar to the ones shown here) broke free from a pipe used for offshore drilling by Shell Canada. (Balmoral Offshore Engineering)

This latest report, obtained by CBC News, analyzes the safety and feasibility of each option.

Retrieving the riser would "present a considerable health and safety risk to offshore personnel related to the complexity and highly specialized nature of offshore recovery operations," the report says.

Contrarily, leaving the riser in the ocean presents very little risk to offshore personnel. The report also says abandoning it "would not likely result in adverse environmental effects."

As big as 250 school buses

Retrieving the riser would be challenging because of its size, weight and dimensions. The riser and "lower marine riser package" together weigh approximately 2,400 tonnes.

Recovering the dropped equipment would be equivalent to lifting 250 school buses from the ocean floor.

Shell Lower Marine Riser Package

Shell Canada's 'lower marine riser package' is a 115-tonne piece of equipment that connected the riser to the well head on the sea floor. This two-storey-tall device plunged to the bottom of the ocean and is now buried beneath an estimated 40 to 50 tonnes of silt. (Stantec)

Still no set plan; regulator must weigh in

Although two reports have indicated that leaving the equipment on the bottom may be the better option, Shell has not said what it will do.

Once Shell has a plan, it must then present its case to the Canada-Nova Scotia Offshore Petroleum Board (CNSOPB).

The board will work alongside the Department of Fisheries and Oceans and Environment Canada. Together, the agencies will decide what regulations govern abandoned equipment.

There is no set timeline for when Shell will conclude its internal investigation, or when the CNSOPB will make a decision on the future of the riser.