By Dozith Abeinomugisha & Naboth Mugyerwa
Pipelines are widely used for bulk transportation of hydrocarbons (oil and gas) because they are safe, environmentally friendly, require the least energy, have the lowest maintenance costs, have less impacts on land-take, have negligible loss of commodity in transit and are highly reliable, compared to trucking.
Uganda discovered commercial quantities of crude oil in 2006, and being a land-locked country, three routes were evaluated at feasibility stage to access the sea: (i) Hoima – Lokichar – Lamu and (ii) Hoima-Mombasa, both in Kenya and (iii) Hoima-Tanga in Tanzania. The evaluation of the routes was based on best pipeline routing principles which include social, environmental, safety and economic considerations. The Hoima – Tanga route was selected as the best route for Uganda after careful evaluation based on best pipeline routing principles.
The East Africa Crude Oil Pipeline (EACOP) project has, therefore, progressed from conceptual, feasibility, and Front End Engineering and Design to the ongoing detailed engineering stage, through a careful process that takes care of the social, environmental, and safety concerns.
The EACOP System
The 1443km long (296km in Uganda and 1,147 km in Tanzania) EACOP is designed to deliver crude oil discovered in the Albertine Graben, to international markets, through a Marine Storage Terminal (MST) at Tanga, in Tanzania. It has six pump stations that will boost the oil pressure to ensure continuous flow, and two pressure reduction stations that will control the pressure in the pipeline to ensure that it is within safe limits as it moves within the pipeline. At the MST, the oil will be stored in tanks with capacity of two million barrels, before it is dispatched to the Load-Out Facility (LOF), approximately 2.8km offshore.
The EACOP has 76 block valves that are strategically located. The valves automatically close, to isolate different sections of the pipeline to limit the impacts of any leakage, especially to isolate ecologically sensitive areas. The EACOP shall be fitted with a fiber optic cable, which shall relay real time information to enable monitoring of the pipeline. The information can be used to detect and mitigate any leaks, damages, third party interference, corrosion, and blockage.
During the design of the EACOP, a risk assessment was carried out to ensure mitigation of identified threats. For primary protection, mitigation measures that have been implemented in the design include the following.
A wall thickness assessment was carried out to ensure that the pipeline can withstand both internal and external pressure arising from its operations, and any chemical composition to which it may be subjected. The pipeline wall thickness is varied depending on the areas that it traverses. In environmentally sensitive areas, the pipeline wall is made thicker for extra strength to eliminate the possibility of failure.
The pipeline will be coated with fusion bonded epoxy to guard against external corrosion or deterioration during its lifetime.
Throughout its length, the pipeline will be buried up to 1.0m below the surface. The depth will be increased to 1.5m in locations where it crosses critical sensitive areas such as roads, rivers, and wetlands.
In addition to wall thickness, additional corrosion allowance has been added through coating. This is required to contain the pressure and to compensate for the metal expected to be lost over the life of the project.
Reliable and accurate pipeline control and leak detection systems are critical for safe operations of any pipeline system. These play an important role in reducing consequences of any spillage. The EACOP will be installed with a robust leak detection system, based on two technologies: (i) Real Time Transient Model (RTTM) and (ii) fiber optic. These two will be capable of accurately detecting the smallest possible leakage, pinpointing the leak location, estimating the leak volumes, and relaying the information to the operator and Government in real time. The block valves will then be used to immediately isolate the leak location.
The EACOP will be installed with 76 block valves. The number and location of these valves were determined after a comprehensive risk analysis to ensure that they will sufficiently isolate any section of the pipeline in case of failure.
In addition to wall thickness, the pipeline will be coated with a thick layer of concrete slab at the wetland crossings, to ensure it always remains below the ground and provide additional protection from external impacts that may otherwise damage the pipeline.
The EACOP is designed to use Horizontal Directional Drilling (HDD) for the crossing of major rivers. The pipeline will, therefore, be below the riverbed and not in contact with water. The smaller rivers will be crossed with pipeline concrete slabbing.
Roads, especially tarmac roads will be crossed by boring under the road so that the traffic flow is not impacted. Slabs will be installed at the crossings of murram roads that are earmarked for upgraded to tarmac in future.
To protect the pipeline from external damage, a fiber optic cable with intrusion detection capabilities will be installed along the pipeline to provide a warning to the operators and Government in case there is any excavation attempt within the right of way. A warning tape will be laid within the pipeline trench, to notify any person accidentally attempting to excavate within the right of way of the pipeline.
At seismically active areas, the pipeline design is strain-based, using a steel grade that is more ductile to withstand earth movements. This is further facilitated by a special trench design, using sand to increase ductility.
To minimize greenhouse gas emissions, EACOP will be powered by hydro electricity from the National grid in Uganda and a solarization project has been inbuilt into the project in Tanzania.
The EACOP system has, therefore, not only been specifically designed for Uganda’s crude oil, but has also utilized recent technological advances to ensure it is safe, during construction and operations.
By Dozith Abeinomugisha is the Director Midstream and Naboth Mugyerwa, Manager Pipelines, Petroleum Authority of Uganda