Commissioning of oil and gas pipelines (both onshore and offshore) includes operational activities such as cleaning, odometry, pigging, flooding, testing, dewatering, purging, drying and chemical cleaning. Horizontal dewatering is an activity by which water is extracted through drains. The horizontal drainage system is applied primarily for large areas and long stretches of trench typically found in construction. The hydrostatic testing requires water as test medium, to demonstrate that the pipeline has the strength required to meet design conditions and to verify that the pipeline is leak free. After dewatering, the residual moisture observed at internal walls of pipeline poses a problem and is necessary to dry the pipeline. Some pipelines may require drying to protect the pipe from internal corrosion caused by the formation of corrosive acids, such as carbonic acid in the case of carbon dioxide pipelines. Drying with super dry air provides internal corrosion protection if the line is to remain out of service for some period of time before it is placed in service. This paper identifies the potential drying problems and calculation procedure occurring with residual water formation at the interior of hydrocarbon pipelines during drying processes.