The sand that forms the layer containing oil and gas at Parque das Conchas has travelled a short distance in geological terms from Brazil’s coastal mountain ranges, 1,000 metres above sea level, to fill the Campos Basin. But the steep angle of the sand’s flow - which ends 2,000 metres below sea level all of 120 km from its origin - has left the sand relatively little time to settle, making drilling more difficult.
“Drilling down thousands of metres into the uncompacted seabed in the Campos Basin is like trying to dig a deep hole in beach sand,” said Gunnar Holmes, who was Shell Brasil Senior Operations Geophysicist working on the project. "As we drill down thousands of metres, sand and water pour back in.”
To prevent sand, mud and shale from filling the well during drilling, Shell pumped a mix of synthetic oil with additives into the well under high pressure to shore it up before installing a permanent steel casing. Engineers then installed perforated pipes covered by several layers of mesh that act as a sieve to stop sand from flowing into the well, but allowing oil and gas to enter.
Tools that can make electronic and microscopic measurements helped engineers drill with pinpoint precision. For the first time, Shell used technology that gives a detailed picture of geology three to five metres away from the well while it is being drilled. This technology allows engineers to steer drills in response to a continuous flow of geological information.
“That means we can steer the path of the well as we drill and stay in the best reservoir,” said Lee Stockwell, who worked on the project as a Shell Senior Petrophysical engineer.
First oil and gas separators on the seabed
Remote-controlled submarines helped to install 1,500-horsepower electric pumps on the seabed — each with the power of a Formula 1 engine — to push oil to the surface, since the natural pressure inside the reservoirs is too low. Just as a fast-flowing river resists freezing, the six pumps on the seabed help prevent the oil from freezing. They also stop wax from forming under the high pressure and low temperatures in the 78-km network of production pipes. This was the first use of electrical submersible pumps in a full-field development.
In another industry first, machines separate oil and gas on the seabed, rather than on the surface. Without first separating the oil and gas, the electric pumps — designed for liquids — would struggle to force oil to the surface. Any gas entering the pumps could cause damage and lead to pump failure.
The reservoirs in Parque das Conchas are up to 20km apart. Shell developed special umbilical cables to keep the power supply running and to feed chemicals to the seabed production system. The 25 centimetre-wide cables also carry sensors that convey vital temperature and pressure information back to engineers on the surface. The six cables, which stretch for a total of 54km, supply electrical and hydraulic power to the wells, manifolds and pumps. The chemicals prevent frozen solids forming in the oil.