As the US Strategic Petroleum Reserve (SPR) storage caverns age, the integrity of the cavern wells has emerged as a significant issue, which requires mitigation. SPR has been holding nitrogen on several cavern storage wells since November 2012.

Pressure prediction as a function of time for WH117A. Inset shows model predictions during the nitrogen test as it compared to the observed wellhead pressure data.

Pressure prediction as a function of time for WH117A. Inset shows model predictions during the nitrogen test as it compared to the observed wellhead pressure data.

These wells exhibited some level of anomalous pressurization behavior in the last year that caused concern for their near-term pressure integrity. Some cavern wells passed routine mechanical integrity tests (MITs), but these wells may exhibit long-term pressurization rate that indicate small leak rates below the routine MIT limit of detection.

Sandia developed a hydrostatic column model for SPR cavern wells undergoing long-term nitrogen testing. The goal of this model is to detect small leaks below the limit of detection inherent in routine MITs. DOE Strategic Petroleum Reserve Program Office allowed Sandia to test the new leakage-detection methodology on a cavern well at the West Hackberry site, Louisiana. The well was undergoing a MIT. This test demonstrated that the Sandia model combined with long-term nitrogen modeling can be used to detect leaks smaller than the minimum detectible leak rates for routine MITs.

This work was sponsored by the DOE Office of Fossil Energy.