Risk Assessment for Implementation of Chemical Treatment Programs on Production Wells within the Wafra Oilfield Partition Zone (Kingdom of Saudi Arabia and Kuwait)

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Authors

Tariq Kamshad (Kuwait Gulf Oil Company) | Ravi Shankar Siriki (Oil Support Services) | A/Rahman Al-Ghamdi (Saudi Arabian Chevron Inc.) | Douglas Kellow (Weatherford Engineered Chemistry)

Publisher

NACE - NACE International

Publication Date

March 6, 2016

Source

CORROSION 2016, 6-10 March, Vancouver, British Columbia, Canada

Paper ID

NACE-2016-7115

Abstract

The chemical treatment of reservoir fluids within the wellbore is essential for the control of associated corrosion and scale deposition issues that adversely affect the integrity of the downhole pumping systems as well as casings and production tubing strings. Corrosion and scale deposition issues within downhole pumps and production tubing strings can lead to major losses in production and costly workovers, which adversely affects operational economics.

The production tubing strings and casing materials within the Wafra Field production wells consist mainly of API Specification 5CT L80 carbon steel(1). API 5CT L80 is used commonly in many oil and gas fields because of higher strength than API 5CT J55. API 5CT L80 is satisfactory for SSC resistance in all conditions but may incur weight-loss corrosion. Although corrosion resistant alloys (CRAs) have good resistance to corrosion, API 5CT L-80 is still thought to be the most cost effective material used for the downhole tubing strings in Wafra.

Due to the aggressive nature of the highly sour and high carbonate salinity brine, the workover rate for downhole pump and tubing failures was frequent. The Wafra Risk Assessment was developed with the Likelihood of Failure (LoF) based on historical corrosion well workover failures and the Consequence of Failure (CoF) directly tied to oil daily oil production. Identification of the higher risk wells (RISK = LoF x CoF) became a direct relationship between the failure frequency and the higher producing oil wells.

Further consideration was given to the reservoir fluid characteristics as well as the downhole artificial pumping systems being utilised within the individual wells. Future chemical treatment and monitoring programs would then be designed with consideration given to downhole pumping systems (SRP, PCP and ESP) vs. effective chemical treatment and delivery system economics.

Introduction

The Wafra oilfield was discovered in 1953 and lies in the western part of the Kuwait-Saudi Arabia Neutral Zone in the northeastern part of the Arabian Peninsula. The Wafra producing formations consists of a northwest - southeast trending anticlinal fold and produces from four main reservoir formations consisting of the Eocene-1, Eocene-2, Burgan (Wara) and Ratawi zones.