Abstract
Oilfield Service companies face significant capital expenditures due to iron failures caused by corrosion, with variations in source water chemistry, fluid system additives and operational issues greatly impacting the frequency of these failures. This paper looks in depth at the root fluid system cause of corrosion in frac iron strings for different water sources in the Permian and Appalachian basins. The objective of this study is to determine the most common causes of corrosion between the two regions and determine which type of remediation technique is best suited for the conditions seen in each basin.
A suite of sensors was connected to the suction and discharge pumps of the blender in order to measure pH, conductivity, ORP, dissolved oxygen and corrosion values on the clean and slurry flow streams during the fracturing process. Treatment designs utilizing both slickwater and hybrid fluid systems were observed, with various buffers and corrosion inhibitors pumped as a corrosion control additive. Data was then analyzed based on basin, water quality and frac fluid chemistries to determine the root cause of corrosion and effectiveness of remediation methods.
The results of this study showed that the corrosion values vary significantly between the Appalachian and Permian basin due to the differences in source water quality. When utilizing produced or a blend of produced and fresh water, the Appalachian basin showed significantly higher corrosion due to higher TDS and lower pH ranges seen in the source water. The primary cause of corrosion was determined to be low pH levels in the fluid system, with buffer additives resulting in a 30% drop in general corrosion across a pad. For freshwater systems, the primary cause of corrosion was found to be increases in dissolved oxygen, with spikes in dissolved oxygen leading to a 40% increase in corrosion during certain key times in the operation. Significantly lower levels of corrosion were seen during freshwater treatments compared to produced water systems, with the primary cause of high-corrosion events due to operational introduction of oxygen into the system. Low pH fluid such as acid and varying temperature of the fluid system had significant impacts in corrosion for both fresh and produced water systems.
Utilizing real-time monitoring of dynamically changing frac fluid chemistries allows for selection of the most effective remediation method for reducing fluid corrosion in frac iron strings. This paper presents the results of the corrosion measurements of fluid systems seen across the Permian and Appalachian basins and identifies the most common root cause of corrosion in those regions.
