Shortly after initial rumors emerged about a massive presalt discovery off Brazil’s southeastern coast following the completion of the 1-BRSA-369-RJS well in October 2006 by the Noble Paul Wolff semisubmersible rig, there was substantial disbelief within the wider upstream industry over the early reserve estimates leaking from the excited headquarters of Petrobras and its partners Galp Energia and BG Group. Many observers simply believed that the initial size estimates being issued were for oil in place rather than total recoverable reserves.

Within a year, however, the Tupi discovery, as it was first known, was accepted as being one of the largest offshore fields ever found and Brazil’s first supergiant discovery. It also was the largest find made worldwide since the Kashagan discovery in 2000 offshore Kazakhstan. A second well on the field spudded in May 2007 by the same rig firmed up the first estimates, with the 3-BRSA-496-RJS appraisal probe, drilled 9.5 km (5.9 miles) south of the original well, hitting light oil of 28°API gravity.

Reserves of 8.3 Bboe
Just before year-end 2010 and after the drilling of 11 wells in total, Petrobras, as operator of Block BMS-11 in the deepwater Santos Basin, submitted the declaration of commerciality for the oil and gas accumulations in both Tupi and also the Iracema areas to the country’s National Petroleum Agency (ANP).

In that proposal the names for these accumulations were given as Lula and Cernambi, with the former named in honor of President Luiz Inácio Lula da Silva, who led the country from 2003 to 2011.

The total recoverable volumes for Lula were put at 6.5 Bboe of 28°API gravity oil with Cernambi put at 1.8 Bboe of 30°API gravity oil. These estimates were reached after the drilling of the follow-up wells and the performing of an extended well test on Lula in May 2009.

To put Lula’s significance in perspective, overnight the field essentially added 50% to Brazil’s previously known total recoverable reserves of approximately 14 Bbbl, hence the initial doubt over the first estimates that emerged about the size of the find.

Lula sits approximately 250 km (155 miles) offshore the southern coast of Rio de Janeiro in a water depth of 2,140 m (7,021 ft). Petrobras holds 65% of the concession, while BG has 25% and Galp 10%. The field’s presalt reservoir contains sweet crude sitting under a layer of salt in places up to 2,000 m (6,562 ft) thick.

Energy demand
Lula, of course, is now merely part of Brazil’s burgeoning presalt bonanza, with the region expected to play a significant role in meeting future global energy demand over the course of the next several decades.

The wider presalt area measures some 800 km (497 miles) in length and 200 km (124 miles) in width, stretching from offshore the state of Espirito Santo to the state of Santa Catarina. Other key discoveries in the area have included Jupiter, Carioca, Caramba, Pirambu, Caxareu, Parati, Bem-Te-Vi, Guara and Iara.

The field’s development is a massive undertaking, involving what will eventually be a fl eet of fl oating production platforms, mainly FPSO vessels (up to nine) and multiple billions of dollars of investment. Initially, pilot production began via the Cidade de São Vicente FPSO vessel, followed by the fi rst defi nitive production system, Cidade de Angra Dos Reis, on Oct. 28, 2010. This has since been followed by the deliveries of the Cidade de Paraty, Cidade de São Vicente, Cidade de Mangaratiba and Cidade de Itaguai FPSO vessels, with the Cidade de Marica and Cidade de Saquarema to follow later this year and in 2016, respectively.

Future phases
Future phases will see Lula Alto start producing early in 2016 as well as Lula Central by mid-year, while in 2017 Lula South and Lula Far South are expected to flow. Petrobras’s latest business plan states that in 2018 the Lula North section will start producing, while in approximately 2020 the Lula West section is expected to be brought onstream.

The field’s gas is exported by the 216-km (134-mile) Lula-Mexilhão Gas Pipeline, which connects the Cidade Angra Dos Reis facility to the Mexilhão platform.

Lula has been a game-changer as much for its technological innovation as for its sheer size. This was recognized earlier this year at the Offshore Technology Conference (OTC) in Houston, which highlighted the harsh oceanographic conditions in the presalt area as well as the achievement of production in a location far from shore and with no existing production infrastructure. Development also took place in ultradeep water and below the large salt layer in a high-pressure reservoir.

The OTC Awards Committee gave Petrobras the coveted Distinguished Achievement Award for Companies for its work in the presalt, where it “successfully implemented ultradeepwater solutions and set new water-depth records.”

OTC’s statement said, “Petrobras increased its efforts in technology development to exploit this hard-to-access resource in waters up to 2,200 m [7,218 ft]. By the end of 2014, Petrobras was producing more than 700,000 bbl/d of oil in the presalt layer of the Campos and Santos basins. The oil and gas production in this challenging environment demanded the development of different riser systems, which were successfully applied and are now available for the industry. Additionally, Petrobras achieved a signifi cant reduction in the drilling and completion time for wells.”

Reservoir challenges
Some of the biggest challenges were the heterogeneous carbonate reservoir and seismic imaging complexity, the thick salt layers and very deep reservoirs, and the presence of contaminants (CO2 and H2S) in the reservoirs.

One of the biggest lessons learned from the presalt, according to Petrobras, is the reservoir’s production behavior. When the company started to defi ne the pilot project, its main concern was that the presalt microbialite carbonate reservoirs could behave like most carbonate reservoirs, exhibiting a high initial rate followed by a sharp decline caused by the critical heterogeneities like sealing faults or facies degradation between wells.

In the Lula extended well test and the pilot production phase, despite the heterogeneities, there was good pressure communication across the reservoir, both laterally and vertically. This characteristic supported the main decisions regarding its development.

Other achievements so far have seen the company use steel catenary risers with lined pipes installed using the reel lay method, with the carbon-steel rigid risers supported by buoy supporting risers. The company also has on record the deepest use of fl exible risers (in a depth of 2,140 m [7,021 ft]) and another water-depth record 2,103 m (6,900 ft) for drilling a subsea well using the pressurized mud cap drilling technique, which helps avoid loss of circulation downhole.

Work still goes on, of course. In its efforts to increase the recovery factory, Petrobras is continually increasing the alternating injection of water and gas while also planning to reduce the size but increase the efficiency of its produced CO2 separation systems.

Lula is set to remain a game-changer for Brazil for decades to come. Earlier this year Petrobras’s presalt production topped 800,000 bbl/d just eight years after its discovery. This milestone is particularly significant when one considers that it took the company 31 years to achieve 500,000 bbl/d in 1984. That last figure was achieved via more than 4,100 producing wells, whereas in the presalt the company has achieved its current level with just 411 producers. The presalt now accounts for around 25% of Petrobras’ production in Brazil and by 2018 is expected to make up around half of the company’s total output.