Corrosion Analysis of API 5L Gr. Three Phase Crude

Abstract

The safest and most economical way of transporting crude oil is the
use of steel pipes; however, pipelines have continually failed from
corrosion as a result of the poor analysis of data recorded from the
intelligent pigging of the pipeline. In this work, two ultrasonic
Pipeline Internal Gauge PIGs and one magnetic flux leakage PIG
were used to obtain data from three phase crude (carrying a mixture
of crude oil, water and gas) from Mimbo to TMMP. The pipelines are
located in the Niger Delta region of Nigeria. The ultrasonic PIG uses
the pulse-echo principle to determine the wall thickness of steel pipe
walls while the magnetic flux leakage PIG measures the changes in
the magnetic field close to the pipe wall. A cleaning PIG” was first
run through the pipelines to ensure that the pipelines were free of
debris that may alter the signals and data collected by the intelligent
PIGs (smart PIGs). The collected data from the smart PIGs runs
were analysed using Dacon Technology Software and the results
obtained was compared with the line pipe design data obtained from
international standards and codes to determine the status of the
service condition of the operating pipeline systems. The Estimated
Repair Factor (ERF) results were the basis for determining the
service condition of the pipeline. The result showed that MFL
intelligent pigging reduced the metal loss in the pipeline transporting
three (3) phase crude from Mimbo to TMMP by 17.11% between
2005 and 2015 pigging periods. The metal loss peak data showed
that the pipeline transporting three phase crude from Mimbo to
TMMP passed through three separate environments which have
different corrosion rate on the pipeline. From the data collected and
analyzed, it was observed that the internal conditions of the pipeline
have more effect on the ERF. It was also observed from the data
obtained that the points on the pipeline from Mimbo to TMMP
transporting liquid crude with ERF ≥ 0.2 have anomalies at the
internal wall of the pipeline.