July 2017, Vol. 244, No. 7

Features

Brazil Advancing Natural Gas Initiative in Lula Norte Field

With the discovery in 2006 of the Tupi gas field (now known as Campo Lula), Brazil began a new era in the national petroleum industry.

In December 2016, the volume of gas and oil produced reached 1.5 MMboe/d, which represents 46% of the total production of hydrocarbons at the national level. Petrobras’s strategic plan for 2030 is to achieve a production of 3.7 MMbpd.

The plan suggests that with completion of Rota 1, 2 and 3, Brazil will achieve a total natural gas capacity of 44 MMcm/d, which breaks down as 10 MMcm/d for the pipeline of Rota 1, 16 MMcm/d along Rota 2 and 18 MMcm/d for Rota 3. Doubling the natural gas supply, which responds to continuous demand growth, will allow Brazil to reduce imports from other countries.

The main objective of the new Rota 3 pipeline is to expand the natural gas supply of the Lula Norte field, located in the Pre-salt Santos Bay, which has a length of 353 km –  307 km corresponding to the maritime section and 48 km to the terrestrial part –  in addition to installing five pipeline end manifolds (PLEMs) and three pipeline end terminations (PLETs) for future connections. They will transport 18 MMcm/d of natural gas to the petrochemical complex of Comperj in the region of Rio de Janeiro, with an investment of $1 billion.

For installation of the pipeline, Petrobras contracted construction company Allseas, which used the vessels Calamity Jane, Solitaire and Lorely, beginning in September 2016, and completing the job within 18 months.

The first obstacle for Petrobras was approval for its environmental permit which took two years to obtain. In July 2016, the licenses were granted for 1123 and 1124/2016, the maritime stretch containing protected fauna at 58 and 2,200 meters of depth.

To carry out the exhaustive study from the seabed to the beach of Jaconé, which is of geological interest due to environmentally important beach rocks, it was necessary to implement specialized teams and a considerable amount of economic resources. The engineers decided the arrival of the duct to the beach would be executed through a 1-km-long horizontal directional drilling, along which different pigs will be installed 250 meters apart. The terrestrial section of the gas pipeline will cross 16 rivers, five highways and a deactivated railroad track.

A second major concern was preventing the pipeline from passing through heavily populated, industrial, and protected areas by implementing variable rights-of-way between 20-50 meters to cross about 480 private properties that had to be compensated under national law.

The manufacture of the API 5L X70 steel pipe has been assigned to Tenaris and its subsidiary in Brazil. It is equipped with an external anti-corrosive coating with three-layer polyethylene, while the internal coating is made of epoxy resin, in accordance with the API RP 5L2.

The UO forming presses produce pipes of greater thicknesses and higher steel grades, capable of withstanding the hostile environments of ultra-deep waters which include high pressure, the transportation of hydrocarbonates in sour environments and high levels of corrosion.

The project includes an induced cathodic protection system and monoblock-type electrical insulation joints at all points of upwelling along the pipeline. The pipeline is equipped with a measuring station at both ends, each with two measuring sections monitored by a computer that calculates the flow of gas transported in real time. flhe installation method of the gas pipeline used by Allseas is the S-Lay technology, which allows work at any depth required.

Onboard the Solitaire, each pipe joint is welded, inspected and protected in a horizontal workshop (firing line). As the boat advances, from the bow the pipe is laid by curving it downward through the water until it reaches the touchdown point on the seabed. As more pipe is laid out under its own weight, it assumes the S‑shaped curve.

The curvature of the upper section of the pipeline is controlled by a stinger, a steel structure with rollers protruding from the end of the firing line to prevent buckling of the pipe. The curvature in the lower section of the pipeline is controlled by pipe tensioners – caterpillar tracks that grip the pipe. The amount of tension is among the most important factors in the capabilities of the vessel.

Finally, protection is provided by mattresses consisting of concrete blocks connected by steel or synthetic material. The concrete blocks are covered with special pads to prevent the pipeline from being damaged. Since the crossing protrudes above the level of the seabed, it is covered either by rocks (rock dumping) or by additional mattresses for protection.

The vessel Calamity Jane is responsible for installing concrete mattresses using her remotely controlled subsea installation frame and her ROV-operated mattress installation frame. Additionally, in some areas pipelines must be buried to protect them from near-shore wave forces, ship anchors and commercial fishing activities.

Specialized equipment is used to dig a trench and cover the pipeline. Allseas’ mechanical trencher creates a V-shaped trench underneath the pipeline using mechanical digging arms. The pipeline gradually sinks into the trench behind the machine. Remedial passes clear soil that has fallen back into the trench by means of strong jets of water.