One of the main corrosion problems faced by the oil and gas industry is HTHP (high temperature, high pressure) corrosion at both sour and sweet conditions. HTHP oil and gas fields are increasing for both onshore and offshore production. The dosage rate of HTHP corrosion inhibitor can be tremendously high depending on field conditions. Furthermore, it is a highly challenging project despite the high dosage rate of corrosion inhibitors.
This paper presents the results using HTHP Hastelloy RC autoclaves for the performance study of corrosion inhibitors with high H2S/high CO2 and low H2S/high CO2 environments in 80 % water cut. The testing temperature was 125 °C. API 5L X52 weight-loss coupons and an electrical resistance probe system were used for corrosion monitoring.
Specially formulated corrosion inhibitors for each HTHP sour condition showed that the target corrosion rate (less than 0.1 mm/year) with no pitting corrosion was achieved for both conditions. The results of the thermal stability test showed no differences in FTIR spectra and no loss of volume from the initial observation at 125 °C.
The oil and gas industry is currently operating numerous fields that contain high concentrations of CO2 and H2S at elevated temperatures. Under such conditions, internal corrosion control has emerged as a significant challenge, leading to severe material failures in production wells and posing a substantial threat to oil and gas infrastructure.
Internal corrosion of pipelines represents a critical risk during the initial stages of production1, whit a reported occurrence of above 9,000 failures between 1990 and 20122. To combat this issue, oil and gas companies in the USA annually allocate substantial resources, approximately 1.052 billion dollars, to prevent internal corrosion1.
Corrosion inhibitors have proven to be a cost-effective method for mitigating corrosion in the oil and gas industry3. However, the efficiency of corrosion inhibitors at high temperatures above 90°C is not well-documented, and traditional inhibitors may degrade or precipitate, potentially leading to non-performance. This degradation can result in the blocking of injection systems, ultimately causing the loss of economic advantages associated with corrosion inhibitor usage4.
Various parameters influence the performance of corrosion inhibitors. These include liquid and gas flow rates, turbulent intensity, water cut, water chemistry, oil viscosity, pipeline topography, CO2 and H2S partial pressure, temperature, corrosion inhibitor type, and compatibility with other chemicals5. Notably, chloride concentration plays a crucial role in severe corrosion at high temperatures and significantly impacts corrosion inhibitor performance, requiring higher concentrations to achieve a target corrosion rate.
