Cost-Effectively Modernizing Offshore Drilling Line-Ups with DC Power Grids and Energy Storage

This paper outlines an approach/solution which enables offshore operators to economically upgrade (i.e., modernize) drilling drive lineups with direct current (DC) based power grids and energy storage. Many legacy drilling rigs in operation (and ones that are currently stacked/idled) utilize drilling drive technology that is currently obsolete or will be in the near future. Modernizing these rigs can often be an arduous and expensive undertaking. Most drilling setups feature lineups of individual variable frequency drives (VFDs) equipped with dedicated rectifiers, which control power output to motor/consumers, such as mud pumps, the top drive, draw works, rotary table, etc. These alternating current (AC) based setups have been used with success for decades. However, as fuel consumption and emissions, as well as space and weight, have become priorities, DC grid systems have gained interest. The solution described in this paper is designed to enable drilling rig operators to upgrade to a modern DC power distribution system using the same footprint as the existing drilling line-up and with minimal modifications to cabling. Energy storage, such as batteries or supercapacitors, can also be integrated within the footprint to enhance the performance of drilling operations – for example through peak shaving and blackout prevention. The solution/approach is highly flexible/modular and is derived from proven concept that has been deployed on hundreds of marine vessels worldwide. The paper provides a description of a solution that is being implemented on a jack-up rig in the Middle East. The new integrated drilling drive setup uses the same footprint, cable network, and communication principles as the rig's existing system and will be comparatively less costly and complicated to implement than simply swapping out existing drives (i.e., one for one replacement).