ABSTRACT

Corrosion is the principal cause of damage to metals in oil and gas storage tanks. Corrosion damages cause a cost impact to maintain these facilities (repairs and replacements) in addition to the loss of production. Corrosion occurs mostly on the storage tanks bottom area, because of the water layer which is generally found on the bottom of the tanks. Moreover, condensation from vapors in the tank creates very sour (dissolved H2S) corrosive environment that can also exacerbate corrosion in the roof plates and central column.

This case study presents and discusses the failure of tank fixed roof center support column of a first stage free water knockout tank within the Wafra Eocene field. The fixed cone roof was supported by several pipe columns on the bottom plate. The tank had been in service for 10 years and it was opened for periodic maintenance activity. It was observed that the center support column had circumferential cross-sectional corrosion damages, one meter from the tank bottom. Root Cause analysis was carried out to know the mode of failure and how this failure can be prevented during design, construction or operation.

INTRODUCTION

In general, tremendous amount of financial loss is incurred every year because of tank integrity failure. The cost to repair such failures far outweighs the initial cost of tank construction, in addition liability may also increase the maintenance time for the necessary repairs to be made during operations. The present paper discusses the case study of catastrophic failure of a column supported roof tank

The Wafra Joint Operation (JO) field is located in the west central part of the Kuwait- Saudi Arabia Partitioned Zone. The main existing Wafra facilities include Sub Centers (SCs), Main Gathering Center (MGC), Pressure Maintenance Plant (PMP), Large Scale Pilot (LSP), Power Generation Plant (PGP), Oil Pumping Station, Bulk Chemical Storage Facility, Export Facilities, and Main Offices

The Wafra field produces two types of Crude Oil, Ratawi (light oil, 20-24 API) and Eocene (heavy oil, 16-19 API), from multiple reservoirs. Crude Production contains 220,000 BBLS/Day and produced water production 1.1 MBBLS/ Day. The wells production is gathered at Sub Centers (SCs) distributed throughout the field. The SCs are designed to remove some of the free water and solution gas and then crude is transported via trunk line to MGC.

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