Thursday, 27 November 2014

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It's the economics, stupid

John McKenna, Editor

Shell hits million-barrel mark from ultra-deep water field off Brazil

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London – Shell has now produced over one million barrels of oil at the Parque das Conchas fields 120 kilometres off the coast of Brazil, where ultra-deep water and a constant swell makes for tough operating conditions, the company has announced. The 2km-deep operation, it said, has involved a series of technology firsts and remote-controlled submarines used to install the equipment needed to produce the oil from deep beneath the seabed.

The field encompasses a vast network of wells and pipelines connect reservoirs scattered up to 20km apart. Claiming a double technical first, Shell described how oil and gas are separated on the seabed before powerful electric pumps push the oil upwards from the low-pressure reservoirs to a specially converted production vessel on the surface that stores it for shipping to shore. Meanwhile, lilometres-long umbilical cables from the vessel channel continuous power and chemicals to the production machinery far below.

To develop the fields economically, the reservoirs of Parque das Conchas were connected through a single production process centred on the converted vessel. Production from the fields — currently ramping up — is the latest step in Shell’s strategy of delivering an additional 1 million barrels per day of oil and gas production in the coming years.

Central to the Parque das Conchas project is a floating production, storage and offloading vessel (FPSO) with the capacity to produce up to 100,000 barrels of oil and 50 million cubic feet of natural gas a day. Shell is the operator with a 50% share with partners Petroleo Brasileiro (Petrobras) holding 35% and India’s ONGC Campos Ltda. 15%.

To combat the low pressure in the reservoirs, Shell installed 1,500-horsepower electric submersible pumps on the seabed. Each pump uses the thrust of a Formula 1 car engine to drive the oil to the surface. The oil travels through specially-developed steel pipes that are flexible enough to move with the ocean’s persistent swell.

Production comes from the Abalone, Ostra and Argonauta B-West fields lying at depths of between 950 to 2,500 metres below the seabed, south-east of the city of Vitória.The first phase of the project now on-stream involves nine producing wells. A second phase currently in planning will focus on the Argonauta O North field.

The pressure of water on the seabed is about 180 bar – 180 times the average pressure at sea level – and too much for a human diver to bear. Temperatures are near-freezing and the sun’s rays cannot penetrate. Remotely operated submarines steered by crews at sea level installed the pumps, well-head machinery and other equipment piece by piece.

Adding to the challenges, the resources lie in small to medium-sized reservoirs under a seabed terrain made unstable by shifting sands. To prevent sand, mud and shale from falling back into the well while drilling, Shell pumped in a mix of synthetic oil with additives under high pressure to hold the hole open. And the geological make-up of each reservoir varies, with the density of oil ranging from very heavy in the Ostra field to light in Abalone.

Some of the oil at Parque das Conchas has a high gas content. To prevent this gas from entering the pumps and damaging them, Shell installed machines to separate the oil from gas on the seabed, rather than on a surface platform or onshore. Instead of burning this gas off, it is being pumped back into the Ostra field for storage until construction of a gas export pipeline system is complete.

Oil is pumped up to an FPSO because of the remote location of the fields, far from any pipelines, The vessel — a converted tanker — can store nearly 1.5 million barrels of oil for shipment to shore, from where tankers take it to markets.

In a further technical breakthrough, Shell developed huge steel umbilical cables to connect the FPSO to the seabed equipment in each of the reservoirs over a 270-square kilometre area. The electrical and hydraulic power they supply, along with the anti-freeze chemicals, keeps operations running around the clock.

 

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