October 2010 Vol. 237 No. 10

Features

Bolivian Pipeline Project Presents Special Construction Challenges

Transredes, the transportation branch of Yacimientos Petroliferos Fiscales Bolivianos (YPFB), is building a natural gas pipeline in Bolivia between Carrasco and Cochabamba at a cost of $US168 million. Known as the Gaseoducto Carrasco Cochabanba (GCC) pipeline, it is designed to ensure natural gas supply to the western part of the country.

The GCC will be the largest pipeline project built to date in Bolivia and will generate 3,000 jobs and guarantee a supply of natural gas to La Paz, El Alto, Oruro, Cochabamba and Santa Cruz for industrial, domestic and vehicular use. It will also diversify the energy matrix of the country. This pipeline, which will transport 140 MMcf/d of natural gas, will increase capacity from the current 95 MMcf/d.

According to technical and economic projections, the natural gas demand in the country’s western market was estimated in 2008 to be 122.2 MMcf/d, the major markets being Cochabamba with a demand of 71.6 MMcf/d, La Paz, 41.7 MMcf/d and Oruro 5.9 MMcf/d.

In addition to supplying the before-mentioned markets, this natural gas pipeline is intended to indirectly supply the markets of Chuquisaca and Potosi. For this reason the GCC will function in a parallel capacity with the already existing Gasoducto al Altiplano (GAA) and transport gas from the fields located in Cochabamba and the northern part of Santa Cruz.

The GCC pipeline is approximately 250 kilometers and has a diameter of 16 inches with ANSI 600 specifications and a MAOP pressure of 1440 PSI and estimated useful service life of 30 years.

The pipeline has its starting point at the juncture with the Carrasco-Yapacani pipeline in the town of Entre Rios in the province of Carrasco in the city of Cochabamba. The gas pipeline follows the Santa Cruz-Cochabamba highway during most of its route until it reaches the village of Sacaba. Here, it turns south toward the village of Huayñacota and connects with several existing pipelines.

The pipeline will carry 125 MMcf/d of natural gas in its first phase and 175 MMcf/d in the second phase, until a compression station is installed. Another possibility which has been studied is to expand the capacity to 210 MMcf/d through the addition of a compression station. The pipeline has a diameter of 16-inch OD and is in accordance to API 5LX 65 specifications, with a wall thickness of 0.281.

The difficulties to construct the GCC pipeline were enormous due to the complicated morphology of the terrain.

To simplify construction, the engineers from the IPE Bolivia firm have opted to divide the project into three sections. The first, which traverses the flat eastern area and has a length of 110 km was built by a consortium made up of IST Ltda and Conpropet Ltda. The first section was inaugurated on June 20. Located in Villa Tunari in the province of Chapare, this region presented many topographical challenges due to its diversity including plains in its lowest altitudes, foothills, and mountainous areas with sharp drops and changes in elevation of thousands of meters.

Another challenge was the weather, since this area is the most humid in the country with an average rainfall of 500 mm per year.

The most critical areas and where construction proved most difficult was in Rio Sajta where 1,600 meters of horizontal drilling was required in order to cross the river and the Rio Paraiso which had a breadth of 36 meters.

The second section, which traverses the Andean foothills, will be built by Bolinter Ltda and Petrosur. It will have a length of 80 km and be completed in February 2012.

The selection of the route for the second section of the pipeline was particularly complicated due to the geological and geotechnical problems caused by large rivers in the area. The engineers opted for a 500 meter-wide right-of-way for this section as well as in the first and third sections where the pipeline went through several indigenous communities. The engineers did recognizance in the field to determine the final route with a team of specialized topographers. The pipeline is located entirely underground with the exception of the river crossings and in some area of El Sillar, where the geological instability did not permit burying of the pipeline.

Finally, the second section, which is projected to be finished during the second half of 2011, has to overcome the challenge of crossing El Sillar, the most unstable area during the rainy season (December-February) where mudslides are common, which requires much technical precision to select the best route.

For the second section, which encountered geological instability during the preliminary stage, geological and geophysical studies had to be conducted to determine the risk to the pipeline. As a result, several sections were built above ground that rest on “H” type supports.

However, the most critical factors that delayed construction were of a social nature when technicians of IPE were barred from entering several settlements that were affected by the construction of the pipeline. Due to these local conflicts, the company had to alter the route of the pipeline several times.

The third and final section, built by a consortium made up of Serpetbol Ltda and Bolinter Ltda, traverses the valleys and highlands of Cochabamba and is 60 km.

Obstacles to the third section, completed in May 2009, were due to the crossing of the high mountains to Cochabamba. The altitude ranges from 200 meters above sea level in the tropics to 4,000 m.a.s.l. at the top of the mountains, where the steep inclines made the use of heavy machinery difficult and the placement of the pipes for welding difficult as well.

The descent from the Tuty Mayu mountain to the valley of Cochabamba was another technical and logistical challenge, where the design called for an exposed pipe resting on 6-inch metallic supports.

Commissioning of the GCC pipeline is scheduled in mid-2012.