Pipelines have proven to be the most reliable and efficient means of transportation of hydrocarbons. Different fluids from numerous sources have different physical, chemical and operational properties, thereby separate pipelines were laid for most of the fluids. However, laying of new pipelines is becoming more and more challenging with vast and complex network of existing pipelines and topographies being faced in both onshore as well as offshore. Moreover considering the huge laying costs and risks of damaging the delicate balance of flora and fauna by entering the unchartered territories, a point does arise to optimally utilize already existing massive pipeline infrastructure.
In this technical paper a method has been formulated to achieve such a cause. A case study from an existing subsea pipeline project of M/s ADOC (Japan) has been presented. Existing 8 inch subsea pipeline of M/s ADOC (Japan) from Hail Site Terminal (HST) to Mubarraz Island in UAE was originally designed for gas service. However, the client intended to use the same for treated sea water service. A thorough design adequacy check was performed to convert the existing subsea gas pipeline into a liquid pipeline. In such a case it is mandatory to check the adequacy of the pipeline for the intended service and design parameters which includes checking for suitability of already selected pipe wall thickness, on-bottom stability and free spans under the action of hydrostatic and hydrodynamic forces.
The methodology adopted for this project can be generalized in order to create a framework to establish a basis to use an existing pipeline for different services.