ABSTRACT

Oil and gas facilities can be subjected to faster deterioration during period of shutdown than those in operation; hence replacement of damaged equipment or piping can be very costly. Among the myriads of short-term preservation methods available, chemical treatment preservation program represents one of the most effective method to minimize the risk of continuous deterioration, hence safeguard the overall integrity of the facility.

This paper details the unique challenges encountered within the Al-Wafra oilfield when implementing chemical treatment method under the stagnant and highly corrosive conditions, as a result of unscheduled shutdown. These conditions alongside the entrapped sludge and accumulation of fluids at low spots is expected to lead to the dominance of under-deposit (UDC) and microbial induced corrosion (MIC), hence any chemical program should be designed to effectively mitigate these damage mechanisms. Consequently, the methodology developed involved initially flushing the facilities with less saline water to remove deposits and sediments, and subsequently treating the entire facility with a mixture of corrosion inhibitor, oxygen scavenger and biocide in brackish water. This is expected to significantly reduce the corrosion rates in comparison to uninhibited system. A range of corrosion monitoring techniques alongside fluid chemistry analysis was implemented for the field monitoring to ascertain the overall efficacy of the program as per key performance indicators (KPI).

INTRODUCTION

The Joint Operation (JO) Al-Wafra Oilfield is located in the west central part of the Kuwait-Saudi Arabia Neutral Zone. The Al-Wafra oilfield reserves were first discovered and wells drilled in 1954. The Al-Wafra field produces two types of crude oil, Ratawi (light oil, 24 API) and Eocene (heavy oil, 18 API), with average water cut 80-85% from multiple production wells. During operation, the production wells produce the oil emulsion through coated flowlines to sub-centres (SC) where the sour oil, water and gas is separated. Joint Operation has two gathering fields; Eocene and Ratawi. Eocene has 2 phase separation, whilst Ratawi has 3 phase separation. The sour gas flows to the Main Power Generation Plant, whilst the oil is produced to the Main Gathering Centre (MGC) and the produced waters are routed to the Pressure Maintenance Plant (PMP) for treatment and eventual re-injection for secondary recovery.

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