Abstract
The influence of CO2 partial pressure on the corrosion properties, including corrosion rate, morphology, chemical composition, and corrosion depth, of J55 carbon steel in 30% crude oil/brine at 65 °C was investigated. A corrosion mechanism was then proposed based on the understanding of the formation of localized corrosion. Results showed that localized corrosion occurred in 30% crude oil/brine with CO2. The corrosion rate sharply increased as the CO2 partial pressure (P) was increased from 0 to 1.5 MPa, decreased from P = 1.5 MPa to P = 5.0 MPa, increased again at P = 5.0 MPa, and then reached a constant value after P = 9.0 MPa. The system pH initially decreased, rapidly increased, and then stabilized as CO2 partial pressure was increased. In the initial period, the surface of J55 carbon steel in the CO2/30% crude oil/brine mixtures showed intense corrosion. In conclusion, CO2 partial pressure affects the protection performance of FeCO3 by changing the formation of corrosion scale and further affecting the corrosion rate.
Highlights
In recent years, the carbon dioxide flooding enhanced oil recovery (CO2 -EOR) technology has been widely applied worldwide [1,2,3] and has made a positive contribution to the geological reserves of carbon
Mass loss during CO2 corrosion is generally related to environmental conditions, such as temperature, pressure, salt concentration, solution pH, and CO2 partial pressure
Many studies demonstrated that the CO2 corrosion rate of carbon steel increases with increasing CO2 pressure [10,11,12]
Summary
The carbon dioxide flooding enhanced oil recovery (CO2 -EOR) technology has been widely applied worldwide [1,2,3] and has made a positive contribution to the geological reserves of carbon. CO2 -EOR is expected to significantly increase the corrosion failure risk of tubes [4,5]. The acceptable rate of wellbore corrosion in China is less than 0.076 mm·year−1 [6], and the qualitative categorization of carbon steel corrosion rates for oil production systems in the US includes low (0.25 mm·year−1 ) [7]. When water cut is greater than 50%, the corrosion rates of carbon steel Mass loss during CO2 corrosion is generally related to environmental conditions, such as temperature, pressure, salt concentration, solution pH, and CO2 partial pressure. CO2 partial pressure and protective scale considerably impact corrosion rate. Many studies demonstrated that the CO2 corrosion rate of carbon steel increases with increasing CO2 pressure [10,11,12].
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