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Oil and gas production field requirements to maintain asset integrity and scale control are very diverse. In an operator’s field in Latin America, the conditions across several wells required the co-injection of corrosion and scale inhibitors. The brine composition of these wells is challenging due to relatively high concentration of calcium ions as well as the presence of iron. The selected scale and corrosion inhibitors need to be compatible with brine and with each other without negatively impacting the absolute performance of the individual products. An additional practical challenge for product selection was imposed by the extreme remote location of the field requiring the product to perform at an optimal dosage without increased transportation and logistics costs.
This paper describes the results from screening studies conducted with a series of corrosion inhibitor product formulations using different static and dynamic lab performance evaluation test methods. As the primary corrosion inhibitor actives are oil-soluble by nature, focus was given to formulating the product with an appropriate selection of solvents, such as methanol and isopropanol, and surfactants to achieve the desired compatibility with the brine and scale inhibitors. The final products were identified, and an optimal product dosage was arrived at based on tests conducted under typical and aggressive conditions representative of the field. However, due to the diversity of conditions and corrosion severity levels across multiple wells in this field, corrosion prediction simulations were run for unmonitored wells to estimate a baseline corrosion rate and build confidence in the recommended corrosion inhibitor product dosage. The validation of the prediction for monitored wells with ER probes will also be discussed in this study.
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A lot of oil and gas facilities face corrosion problems because the production fluid contains some corrosive components represented by CO2. Generally, corrosion inhibitors are used in order to mitigate corrosion problems of tubing and pipeline. Imidazoline is known as one of the active ingredients of corrosion inhibitors and widely used in the oil and gas industries. However, imidazoline-type inhibitor is easily hydrolyzed to amide if water mixes into it.
In the oil and gas industry, long-distance transportation of petroleum and related products is usually carried out in large-diameter carbon steel pipelines. Water present with the oil, along with corrosive species such as CO2, H2S and organic acids, causes severe corrosion of the inner pipe walls.1 An effective method of controlling corrosion is to continuously inject corrosion inhibitors into pipelines conveying oil-water mixtures. As corrosion occurs on water wetted metal surfaces, corrosion inhibitor (CI) molecules form protective films which retard electrochemical reaction rates at the water-metal interface,2 thereby protecting carbon steel pipes against CO2 ("sweet") corrosion and H2S ("sour") corrosion. Most commercial CIs are a complex mixture of several compounds that contain surfactant-type active ingredients, such as imidazoline, amine, phosphate ester, and quaternary ammonium derivatives.
Traditionally, oil recovery operations are subdivided into primary, secondary and tertiary stages. EOR is commonly classified as tertiary recovery, where gases, liquid chemicals and thermal energy can be used to enhance the displacement of reservoir fluids. Different sources divide EOR into two to five categories, one particular method, polymer flooding, is based on increasing the fluid viscosity by adding a polymer to the injected water. Polymer EOR is a mobility-control process using a polymer-augmented waterflood, typically a solution of partially hydrolyzed polyacrylamide (HPAM) or polysaccharides, which is injected to displace oil towards production wells.
In metalworking processes, contaminants can interfere with future processing steps and may accelerate corrosion on metal parts. As such, a cleaning step is often implemented prior to coating or packaging finished parts. Industrial cleaners are typically water-based with blends of surfactants, co-solvents, chelating agents, and/or flash rust inhibitors. While accelerated corrosion tests such as humidity and salt fog exist, they are typically too aggressive for the evaluation of flash rust inhibitors in cleaners which are not meant to provide long-term corrosion protection. There is a need in the industry for a quick and reliable way to select a cleaner that meets the needs of the application and is compatible with the overall process. A screening method to compare the flash rust protection ability of various water-based cleaners was investigated. Modified vapor inhibiting ability (VIA) testing and linear polarization resistance (LPR) tests were performed on carbon steel plugs treated with several cleaners. Industry standards currently recommend that any detergent or cleaner be removed from metal surfaces prior to applying coatings. When evaluating cleaning processes where coatings will be subsequently applied, adhesion testing should be paired with the screening test. The effects of various cleaners on adhesion of a waterborne acrylic coating were investigated.
A new water-soluble quaternary ammonium compound, didecyldimethylammonium bicarbonate/carbonate (DDABC), has been evaluated as a corrosion inhibitor via standard electrochemical tests on steel and shown to be highly effective. At the proper dilution, the inhibitor migrates to the metal/solution interface and forms a monomolecular film on the anodic sites.
Laboratory testing of corrosion inhibitors under high temperature high pressure (HTHP) conditions is challenging. HTHP testing has been traditionally performed in closed systems with fixed liquid/gas volume and testing results are usually influenced/compromised by the accumulation of ferrous ions and corrosion products. The aim of the work is to optimize corrosion inhibitor testing conditions at HTHP to generate results of better reliability. The corrosion of carbon steel by CO2 at HTHP was assessed using small working electrodes of large liquid volume-to-sample surface area in autoclaves. The effect of CO2 partial pressure was also investigated. The blank and inhibited corrosion rates were monitored by linear polarization resistance (LPR) and the morphology of coupon surface was measured by vertical scanning interferometry (VSI). The testing results were deemed to be more representative of the field service environment when the amount of ferrous ions and corrosion products was reduced due to the usage of small working electrodes.
Impact of pre-existing corrosion (pre-corrosion) on Corrosion Inhibitor (CI) performance was evaluated in conditions unfavorable of protective scale formation. CI protectiveness was significantly reduced after a 3-day pre-corrosion period.
The effect of carbon steel coupon surface finishing processes on corrosion in a carbon dioxide environment with high and low salinity. The system was also tested with and without chemical inhibitors.