Global carbon emission reduction targets and how to meet them are high on operators’ agendas. Quantifying greenhouse gas (GHG) emissions created across every segment of the hydrocarbon extraction and production value chain is an essential step in this process.

It's already widely acknowledged by operators on the UK Continental Shelf that drill cuttings treatment at the well site can materially reduce costs and improve safety by avoiding the need to collect, contain and transfer cuttings by sea and road freight to a specialist processing facility onshore, as required using the traditional "skip and ship" method. It's also widely accepted that by reducing the transport and logistics involved in skip and ship processing, carbon emissions are also greatly reduced, but by exactly how much had not been precisely quantified.

In order to support operators’ understanding of their carbon footprints towards drilling waste management specifically, TWMA performed a study to establish the comparative carbon footprint for a portable thermal processing drill cuttings processing unit, treating drill cuttings on a standard offshore platform, versus that of a typical skip and ship to shore operation.

The study investigated the carbon footprinting process, interpreted recognised guidance and set system boundaries and emission scopes. The carbon footprint associated with each method of treatment was then calculated, based on carbon dioxide equivalent (CO2e) per tonne of drill cuttings functional unit. Furthermore, a carbon calculator was created to establish a carbon footprint comparison capability for any well within the North Sea.

The results revealed that the carbon footprint of the current skip and ship operation is 53% higher than that of a portable unit treating drill cuttings at typical North Sea well site. Furthermore, and based on the lower estimate of drill cuttings produced on the UK Continental Shelf, additional benefits will include: the diversion of 28,000 tonnes of waste powder from landfill; the recovery of 6000 m3 of produced oil for re-use in the offshore drilling system; and 6000 m3 of water that requires no further wastewater treatment.

This study is the first of its kind to show a direct CO2 comparison between offshore processing and the skip and ship cuttings disposal method. It has increased the awareness of the CO2e emissions associated with each process. As the industry moves towards a lower carbon future, it provides a solution to significantly reduce the carbon emissions of drilling operations whilst also improving safety and reducing well cost.

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