HOUSTON—When Petrobras and partners began the Lula NE pilot project offshore Brazil, they had a tall order to fill—implementing new technologies as part of a fasttrack project facing several technical challenges.

These include reservoir fluid variations, the presence of fluid contaminants such as CO₂, a high gas-oil ratio and water depths of 2,120 m (7,300 ft) with no “off-the-shelf” proven subsea technology capable of handling such field conditions.

Add to this the pressures of being a fast-track project in the early development stage of the Santos Basin Presalt Cluster, a new frontier in 2009, charged with not only gathering data that could prove beneficial in future field developments but also for generating revenues to help finance other nearby presalt fields while doing its part to help the company reach a 1-MMbbl/d target from presalt fields in 2017.

But the mission was accomplished as Rafael Cruz, reservoir engineer for Petrobras, explained during a technical session on overcoming challenges on offshore field developments. In February 2015, production reached 950,000 bbl/d of oil and hopes are to reach the 2017 target one year ahead of schedule.

“Lula has successfully met its business objectives so far. First oil was only nine days away from the three-year milestone,” Cruz said, adding a new subsea concept was developed and the FPSO unit is currently producing at its maximum capacity.

One of the goals of the project was to gain presalt experience through data acquisition, Cruz said. Work included two seismic acquisitions, including a high-resolution one, along with a drillstem test program, extended well tests and an interference test along with production logging tests, fluid samples, special fluid analysis, large computer cluster and people to get the work done.

“Most of the wells are intelligent completions, and the whole process involves eight producers, five water-alternating-gas (WAG) wells, two subsea manifolds and one gas injector well,” Cruz said.

As detailed in an OTC paper about the project, the reservoir data acquisition and drainage plan studies provided guidance on artificial lift, flow assurance, gathering system and fluids processing concepts. A downhole fluid sampling and laboratory experiments program was established to “identify critical aspects of flow assurance, such as wax, gelation, hydrates, asphaltenes and inorganic scale.”

There were also challenges with the gathering system, considering “there were no off-the-shelf proven technologies that could handle this amount of contaminates, at this water depth and pressure,” Cruz added. The strategy was to run a design competition to find solutions, Cruz said, targeting seven major prequalified subsea providers.

The winning proposal, he said, had two submerged buoys for riser support. The proposal also included eight buoy foundations, 16 tethers, 15 catenary risers ending up with pipeline ends terminations, production clad lines and gas injection lines (steel catenary risers) and riser anchoring piles.

To reduce costs and gain flexibility, standardized christmas trees were incorporated into the well design. The design also included two WAG injection manifolds, which lowered the number of injection risers.

However, the greatest risk of the project was the subsea construction, gathering system and installation, Cruz said. Subsea system fabrication delays prompted the consortium, which included BG E&P Brasil and Petrogal Brasil, to use flexible risers to connect the first producer well to start up the FPSO unit as scheduled. Other delays forced changes in the drilling campaign, adding value to the importance of having contingency plans. But installation of FPSO Cidade de Paraty was quick.

Completing such a large fast-track while developing new technology required putting focus on key information, Cruz said. The first well was drilled in 2009, and first oil was reached in 2013 with plateau production hit in 2014.

“We work in a risky business so there will always be uncertainties,” he said. “It’s a matter of strategy” and finding key information. Companies involved also set up what Cruz called a “war room” to enable fast decision-making and communication among stakeholders.

Velda Addison can be reached at vaddison@hartenergy.com.

Offshore