Two approaches to automating marine geotechnical surveys

By Laurie Thornton · June 2025 · Published in SeaNews ↗

Many marine projects, from extending a harbour wall to installing an offshore windfarm, depend on seabed soil and rock samples to understand seafloor composition and design proper foundations. Drilling cores via geotechnical survey is an expensive and often risky undertaking, but automation can help, says Laurie Thornton, co-founder of marine construction specialist MintMech.

We’ve all heard “automation = good”. In most industries, it reduces risks and improves productivity. But for offshore wind, automating geotechnical drilling is so effective it could be the deciding factor in whether the UK meets its renewable energy targets and the world completes the energy transition.

Subsea drills

Today, subsea drills represent the most advanced levels of automation. Since the drill is sitting on the seabed, it is unaffected by heave. This stability enables recovery of potentially top-quality core samples, without any crew in hazardous situations or manual handling required.

However, compared to traditional topside drilling, subsea systems come with very high financial outlay. They also require multi-skilled operators, proficient in control systems, mechanical engineering and pressure-compensated hydraulics, more common in the oil and gas world than renewables or construction.

The potential for downtime is also higher as subsea drilling involves combining sensitive mechanisms with salt water at extreme pressures. Simply lowering the system to the seabed can take several hours, let alone bringing it back up to diagnose and repair a fault. In addition, after a 24-hour drilling run, you might bring the drill up and find it empty after something went wrong and no cores were collected.

If time and money were no object, a subsea drill would likely be the go-to choice most of the time. They are ideal for a wide range of situations, can be deployed with a wide range of vessels and pose zero risk to vessel or crew.

Topside drilling

By comparison, in topside drilling the drill is at the surface, built into the vessel and the bit is ‘tripped’ down to the seafloor. Tripping can be hazardous if done manually, so at sea is usually automated using an iron roughneck.

After touchdown, the challenge is drilling accurately while the vessel heaves. To combat this, a passive heave compensation system allows movement which keeps the drill bit stationary relative to the seafloor rather than to the vessel.

However, passive systems are imperfect and prevent delicate work. Retrofitting automated heave compensation upgrades like MintMech’s Active Heave Assist, for instance, can make a topside drilling rig comparable to a subsea drill by hydraulically controlling the existing passive cylinders, eliminating virtually all heave.

A major benefit of topside drilling is having access to the drill, which not only aids repairs, but also lets topside drillers analyse cores as they are collected. Instead of waiting until after the drilling run to see recovered cores, like with a subsea drill, a topside driller can inspect each core and adjust factors like RPM, flow of drilling fluid or torque to improve recovery. This creates a feedback loop which is not possible with subsea drills.

Subsea systems may be the future, but automating topside drilling can narrow the performance gap at a far lower cost. Whichever path the industry takes, automating geotechnical drilling can make more projects financially viable and accelerate the pace of offshore construction in time for net zero.