Illustration : Thierry Cap de Coume
Despite the economic slowdown, petrol reserves are still threatening to dry up, given that three-quarters of fields have been exploited for the last twenty tears. In this context, major petroleum groups such as BP, Exxon Mobil, Petrobras, Saudi Aramco, Shell, and of course Total, have had no other choice but to discover new fields, often in hostile or difficult-to-access regions. Namely hydrocarbons from ultra-deep offshore areas. This extremely expensive research (costing several tens of millions of dollars per study) can pay off, as in the case of the Tupi fields discovered in the Santos Basin to the southeast of Brazil, the Cascade and Chinook fields in the Gulf of Mexico, or sites located off Congo and Angola, in the Gulf of Guinea…
A number of these petrol fields share the feature of being located at water depths greater than 1,400 m, underneath layers of salt. Such conditions further increase the cost of drilling that is already 5 to 10 times greater than those in the past, notably due to heavy demand and the depth of drilling, going as far deep as 4,000 and 5,000 metres. Or even more. Drilling at such depths raises real technological challenges for equipment manufacturers in the petrol sector who invest an average of 3% of their turnover in research and development. Standard setters in this domain include Géoservices, an expert in drilling surveillance and Schlumberger, the world leader in measurements and metrology. Not forgetting CGGVeritas, a leader in the seismic industry which, though its Wide Azimuth, has brought drastic improvements in 3D imaging of reservoirs hidden under salt. Used for the first time in the Gulf of Mexico, the method consists in mapping out zones explored by boats that either emit seismic waves or receive echoes of waves with the help of specialised detectors enclosed in long flute-like vessels that stretch ten kilometres or so long. “This method is four to five times more complicated than other solutions, but the high cost of drilling, particularly deep offshore, makes it worthwhile,” explains Romain Soubeyran, Technology Manager for CGGVeritas.
By improving the clarity of underground images, the Wide Azimuth allows better visualisation of the inside of the reservoir. An improvement that promises to help companies raise their petrol recuperation rates – an average of only 30%. This level can be improved by injecting polymers inside the oil well – an innovation to be used by Total in 2009 on the Dalia field (Angola) – which sweeps out the reservoir and pushes the oil towards the oil-producing well. SNF Floerger, one of the leaders in this domain, furthermore intends to develop new polymer compositions that must be able to withstand the conditions characterising ultra-deep wells: temperatures between 100 and 120 degrees and pressure as high as several hundred bars.
These extreme conditions also have an impact on the design of exploration and drilling tools, which have to strike a balance between shape restrictions and mechanical resistance. Vallourec, a drill pipe producer, has thus developed expandable carbon-enriched steel tubes capable of bearing extremely strong deformations. By placing lathes inside the tubes, their diameter can be increased between by 15 and 20% in order to optimise well productivity. Thanks to this innovation, petrol group Saudi Aramco has apparently increased its average production by 2,600 barrels per day as well as production per well.
Another restriction specific to great depths: the need to reduce the weight of piping by using lighter-weight metals such as aluminium or titanium, or even composite materials. “In the next 20 years, we can imagine using underwater hoses that will transport LNG (liquefied natural gas, editorial note) from floating gas liquefying plants on gas tankers,” indicates Gérard Momplot, Manager of the GEP (Grouping of companies in the oil and gas services industry). This hose may be made of synthetic rubber in elastomer, with heat insulation to prevent the risks of breakage, hardening or heating, on the basis that it should transport fluids with temperatures of minus 160 degrees.
Brazil, a new Eldorado
Brazil is in the midst of becoming one of the major petrol producers thanks to the discovery, at the end of 2007, of one of the largest petrol deposits, expected to allow it to multiply its reserves by five. On condition that it pays the necessary price. 600 billion dollars, in other words 475 billion euros, is the sum of investments that the Brazilian national company Petrobas must agree to make in order to mine the new petrol fields uncovered in the Bay of Santos, to the southeast of the country. An impressive manna that will bring the country’s reserves of 14 billion barrels up to 50 billion barrels plus. Including 5 to 10 billion of light crude in the Tupi field alone. The mining of this field will necessitate considerable technological advances.
Indeed, this field is buried at a depth of 6,000 metres, where it is protected by a thick saline crust. Apart from sea ground drilling and petrol extraction, the transformation and transport of gas associated with the petrol represent real technological challenges. Rather than constructing pipelines all along the depths of the sea until the Brazilian coast, the company will probably bring the gas and petrol to the surface via a network of supple tubes called risers, which will have to withstand difficult marine conditions, with strong winds and significant underwater currents. After numerous tests – set to begin in Spring 2009 on the Tupi field – production tests should commence in the second half of 2010. If results prove encouraging, production will begin in 2013, with an initial daily rate of 100,000 barrels of petrol and 5 million m3 of gas.
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