A Deep Dive into the Subsea Environment

In 2012, we hosted a workshop at the Brazil Technology Center in Rio de Janeiro for the (then) recently created Subsea Systems Center of Excellence (CoE). A research manager from Petrobras made the interesting observation that the “gold rush” toward pre-salt deep water exploration was much more complicated than the race to the moon in the late 1960s. His reasoning was that we have actual footprints of a man on the moon (ok, several, if one counts all landing parties from Apollo missions), but so far no man has ever set actual foot on  the deep sea floor (James Cameron, and others who made excursions bellow 1000 km [621+ miles] depth, never actually left the subs they were in).

Subsea oil exploration started at very shallow depths and rapidly has grown to astonishing water depths. Take, for example, the following chart that Petrobras uses in 10 out of 11 presentations given in technical congresses.

Brazil_Subsea1
Slide from Petrobras presentation

This chart shows the Christ Redeemer statue (at left) in Rio (note that the statue is not by the shore as depicted this is for visual reference only) and several water depth drilling and completion records along with the year in which those records were achieved.

Pre-salt levels are even deeper than depicted here. A well can easily be 300km (186+ miles) from the shore and the sea bottom might be at 4000m (2,485 miles) below that. But to reach oil, you still have to drill through several kilometers of salt layer and only then will you reach the reservoir, also known as the “pre-salt” layer; shallower wells above the salt layer are called “post-salt.”

Into the darkness

At 4km (about 2.5 miles) depth you can`t see any light. It is as dark (or darker) than deep space. In fact, about 90% of all ocean volume on earth is aphotic, meaning it is not reached by sunlight. It is even hard to find deep sea beauties such as viper fish or angler fish, which can be found typically down to 2km.

Regarding temperatures, after 1km the temperature stabilizes pretty much at 4˚C (39.2F), reaching maybe even -1˚C depending on salinity, without ever reaching solid state (we use salt on streets to melt snow right? But not here in Rio, of course).

Brazil_subsea2

And finally pressure. At 4km you have about 400 bars of pressure (an easy rule of thumb is 1 bar for every 10m). To give you a sense of how much pressure that is, imagine a load of 4000 tons, or 16 locomotives, concentrated on a single square meter. At this pressure you have to design components and equipment that can withstand extreme pressure without crushing in on themselves. Either they can survive at these extreme pressures or you have to shield them within a pressure vessel in which the internal pressure will always be exactly the same as the atmospheric pressure on the surface. This requires a huge and bulky metal chamber with several centimeters of wall thickness. The picture here shows an aluminum cylinder crushed under pressure.

By now I’m sure you realize that operating in a subsea environment is extremely hard, extremely dangerous and extremely expensive. Operating in a subsea environment requires a vast number of resources to prospect, drill, and explore a well. And most importantly, every step must be carried out in a safe manner to assure the risk of any serious accident is kept low, with very tight and conservative control.

Filling the need

GE currently has several business units that produce equipment to be used in harsh environments, with a goal of enabling oil operators to build and extract oil from wells. But many of them are not qualified to reach water depths where pre-salt levels are found. As with the Aviation business, qualifying parts and procedures takes a considerable amount of time and can be costly.

The Offshore and Subsea CoE at the Brazil Technology Center was created specifically to help customers (externals like oil operators such as Petrobras, Chevron, Statoil, BG, BP, Repsol and internals like several GE business units) currently producing or interested in producing equipment for well and subsea exploration. To simulate the harsh pressure conditions, the CoE will use a hyperbaric chamber where components will be pushed to their design boundaries using pressures and temperatures of near real conditions to where these components are intended to work.

The CoE also will collaborate with a material lab to develop a new generation of materials and will design new manufacturing processes to make subsea structures more robust, most durable, and lighter than the traditional metal alloy-heavy structures. The CoE team also has joined forces with several well exploration technical domains such as flow assurance, drilling, production, subsea processing, control and inspection.

In the home stretch

The building of the new BTC research center is very close to being finished and soon we all will see brand new equipment in our CoE lab spaces. There are now more than 110 colleagues at the site, including researchers, our functional team and two co-located groups. These are GE Flexibles (formerly Wellstream), which will be located on the BTC site in a huge building that will house their massive test rigs for flexible pipes (a spool can have a 10m radius!) and GE Measurement & Control, which is building a new Customer Application Center on our site to house several high end inspection devices such as the V-Tomex Industrial CT scan. Please stay tuned for upcoming news on this site.


3 Comments

  1. umar

    Yes but in sub sea environ, distance is perceived as depth, and 10 km is perceived as not below but above 1000 kms. However, yes you got your point across. The atmospheric pressure makes sub sea surface more inhospitable than the surface of the moon. Very informative article. Thanks.

  2. Bruno Betoni

    Absolutely correct Ely, which is yet bellow 1000km

  3. Ely

    James Cameroon deepest trip was at ~10 km. Not 1000 km.