A Comprehensive Study of a Water Treatment Plant in one of the Iranian Oil Fields to Increase Yield and Productivity

Shokrolahzadeh, Sakineh; Ashoori, Samaneh; Zahedzadeh, Mohammad; Radmehr, Mojgan; Roayaei, Emad

A Comprehensive Study of a Water Treatment Plant in one of the Iranian Oil Fields to Increase Yield and Productivity

Document Type : Research Article

Authors

National Iranian Oil Company, IOR Research Institute, Tehran, I.R. IRAN

Abstract

Water injection is one of the most effective methods for enhanced oil recovery or reservoir pressure maintenance. The quality of the water is an important factor in the success of a water flooding. The major problem may be associated with water injection is corrosion and plugging of the reservoir that cause injectivity loss and increase in operational cost. The main objectives of sea water treatment plants are to control of important factors such as, oxygen level, bacteria, scaling and suspended solids.This paper presents an overview of optimization of water treatment steps for a seawater injection plant by focusing on corrosion and chemical management. To approach this purpose, a step-by-step review has been implemented on the plant consisting of 40km pipelines, 3-stage filtrations, a deaeration tower, and treatment chemicals. The plant treats seawater for injection into two of Iranian offshore oilfield. That has been in operation for 28 years. During these years, damages have been occurred in the system and relatively in the reservoir due to corrosion and poor control of suspended solids. Besides, it suffers from lack of corrosion monitoring system and has never been inspected for corrosion potential, even though pig cleaning has been run frequently. Field data and laboratory tests indicated that one of the major problems associated with seawater injection in this oilfield results from inadequate filtration and presence of scales, as well as Sulfate Reducing Bacteria. The finest filter size is determined to be lower than 2µm according to the permeability of productive reservoir layer while it is 10µm on the site. Use of poor quality oxygen scavengers in over dose concentration beside the deaeration tower raises the concentration of sulfate and consequently shows up as CaSO₄ precipitate. Application of scale and corrosion inhibitor and biocide, as well as their efficacy, are discussed in details. Having NACE TM0299-99 Standard in mind, a corrosion monitoring system has been proposed for the plant. It was proved that with few replacements in chemical injection points, the system efficiency increased by 30%. The outcome of the study was, more effective treatment, less formation damage, as well as reduced cost and quantity of chemicals used per volume of oil produced and treated injected water.

Keywords

References

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