Equitrans Midstream Provides Rager Mountain Storage Facility Update

Equitrans Midstream Corporation (NYSE: ETRN), today, submitted information to the Pipeline and Hazardous Materials Safety Administration (PHMSA) regarding the root cause investigation and analysis related to the Rager Mountain Storage facility incident that occurred in November 2022. The comprehensive root cause analysis (RCA) was initiated promptly following resolution of the natural gas storage well venting incident and was conducted by an independent, third-party company with expertise in reservoir management and well and corrosion engineering. Additionally, the RCA activities were coordinated with PHMSA and the Pennsylvania Department of Environmental Protection (PADEP).

The third-party RCA team consisted of subject matter experts in several disciplines, including metallurgy, failure analysis, well construction and reservoirs, well logging, chemistry, and microbiology. The RCA was conducted using a systematic, evidence-based approach consisting of three phases: 1) analysis of Equitrans' Storage Integrity Management Plan (SIMP) and related processes; 2) data collection and analysis of physical evidence; and 3) use of the Apollo RCA method that integrated previous well logging data, drilling analysis, well deliverability and kill attempts, failure analysis, metallurgical observations, microbiological assessments, and reviews of Equitrans' internal standards/procedures and regulatory guidelines.

RCA Summary of Findings:

The direct cause of the venting from Rager well #2244 was due to water- and oxygen-induced corrosion on the outside diameter of the top joint of the well and the infiltration of organic/inorganic matter into the annulus, which resulted in a failure of the well casing. The primary root causes for this failure were identified as follows:

• Magnetic wireline testing is the industry-standard used to identify potential corrosion on storage wells, and, in 2016, Equitrans’ contractor performed wireline testing of all wells at Rager Mountain. The contractor processed the 2016 logging data using the algorithm technology available at the time, and the wireline report received by Equitrans for well #2244 identified limited corrosion levels, which did not require remedial action. Following the venting incident in 2022, the previous logging data for well #2244 was reprocessed using a recently available and updated algorithm technology, which revealed more extensive corrosion at the top of the well, confirming that the previous 2016 report was inaccurate.
• The top joint corrosion could have potentially been mitigated by injecting corrosion inhibiting gel into the annular space between the inner and outer casings of well #2244.
• Given the location of well #2244 and its vent, Equitrans’ practice of keeping the annulus vent open to allow for the safe venting of gas permitted water, air, and solids to enter the annular space, which may have contributed to the potential exacerbation of corrosion.

Based on results of an inventory verification test conducted after the venting incident was resolved, Equitrans' initial gas loss estimate for well #2244 was approximately 1.29 Bcf. Following completion of the RCA, the cumulative gas loss was determined to be approximately 1.164 Bcf. Due to the restriction of the annulus valve, the RCA indicates approximately 1.037 Bcf of the total cumulative gas loss was vented to the atmosphere and roughly 0.127 Bcf was diverted to and contained within formation(s) located at approximately 1,800' and/or 3,000' below ground.