Andrei Baev & Christopher Wilkins discuss advances in abrasion resistance and mitigating corrosion
Before the first US oil well was drilled, large amounts of oil came from whales. Whale oil was burned in everyday lamps, and by the 1840s the industry was large enough that several hundred fleets sailed the world’s oceans hunting for whales. Very small amounts of petroleum oil were also burned. That oil was skimmed from the lakes it had seeped into from below. All that changed when the first US oil well was drilled on August 27, 1859 by Edwin L. Drake.
For eight years Drake had worked as a conductor for the New York and New Haven Railroad, but retired for health reasons. He retained his conductor’s license, though, which allowed him free rail travel. For this reason a group of investors recruited him to visit a farm in Titusville, Florida, and report on oil said to be seeping up from the earth there. Seneca Oil Company was created, and Drake employed as its general agent.
To find the source of the oil, Drake had to dig deep. However, the well began to collapse at 16ft. He began to use 10ft pipes to lien the borehole, connecting them one by one and driving them into the earth to keep the wellbore from collapsing. At 69ft, he struck oil. It pooled in the 16ft dugout, and Drake came up with the idea of using a pump to extract oil from the well. He used a common hand pump for water wells, and collected the oil in a bathtub. This pumping application is commonly seen in today’s rod pump technology.
Roughly two million oil wells are producing worldwide, over half using some sort of lift technology, 750,000 of them rod pumps. This total includes 350,000 rod pump wells in the USA. However, the technology is imperfect. Deviations and doglegs in wellbores often cause rod wear, which can result in failure. This occurs when a sucker rod rubs against the tubing wall, eventually wearing a hole through it. The more deviations and/or the greater severity of doglegs in the wellbore, the more frequently rod wear will occur. Many technologies have been developed to increase the mean amount of time between these failures, including rod guides, abrasion-resistant internal plastic coatings, poly liners and others, but none provided satisfactory increased life of downhole tubulars.
A new coating system outperforms many others. Majorpack’s duplex coating consists of intermetallic and polymer coatings. The intermetallic layer is a diffusion zinc coating, chemically more active than iron, which works as a protective layer against the corrosive atmosphere within wells. It covers 100% of the pipe’s internal and outer diameters, and its threads and connections. Its micro-hardness is several times higher than Grade E steel, which provides excellent resistance to mechanical wear.
The top layer is a liquid epoxy-phenolic that provides an additional layer of corrosion resistance, as well as deposit mitigation. This duplex coating system is the best solution for oil wells, protecting against CO2 and H2S corrosion, high temperatures and abrasive wear. On average, tubulars with the MPAG coating systems last three to five times longer than non-coated tubulars.
According to NACE International, the cost of corrosion in the US oil and gas industry is US$27 billion. Other sources show that microbiologically influenced corrosion (MIC) accounts for over 20% of the total. MIC constantly increases as reservoirs become sour from water injection systems that increase oil production. When pipe is exposed to water containing microorganisms, they attach themselves to the surface of the pipe and create a biofilm. Electrochemical conditions at the point where the biofilm meets the metal can change, which may induce corrosion due to acid production, iron oxidation, and the creation of H2S.
In a prolonged third-party lab test, water samples were collected from three US basins known for MIC. The lab measured the levels of adenosine triphosphate (ATP), acid producing bacteria (APB), and sulphate reducing bacteria (SRB) at different times. ATP is a nucleotide that is the primary source of energy in all living cells. New discoveries were made after each measurement. The first is that the ATP levels began to reduce, which could suggest that the diffusion zinc intermetallic layer is killing living cells. The second discovery was that the levels of APB didn’t fall. However, the coated samples remained completely intact. This could suggest that the zinc layer is impervious to APB. The third discovery was that the SRB levels in each sample either declined drastically or were eradicated, suggesting that it killed the SRB.
The system extends the life of tubulars in all types of corrosive environments. Many field trials have shown the coating system to improve the life of tubing by up to four times (which significantly reduces operational expenditure and project downtime, thereby enhancing revenue streams). In a test in five wells located in Russia, coated wells operated for an average of 992 days, compared to 324 for uncoated tubulars. Finally, oil producers have a solution to the problem of pipe corrosion and Majorpack is working to develop its business portfolio and establish manufacturing plants in Texas and also to expand its product sales network both in the USA and internationally.
Andrei Baev is CEO & Christopher Wilkins is Vice President at Majorpack