Publications

CaveMan Version 3.0: A Software System for SPR Cavern Pressure Analysis

Ballard, Sanford B.; Ehgartner, Brian L.

The U. S. Department of Energy Strategic Petroleum Reserve currently has approximately 500 million barrels of crude oil stored in 62 caverns solution-mined in salt domes along the Gulf Coast of Louisiana and Texas. One of the challenges of operating these caverns is ensuring that none of the fluids in the caverns are leaking into the environment. The current approach is to test the mechanical integrity of all the wells entering each cavern approximately once every five years. An alternative approach to detecting cavern leaks is to monitor the cavern pressure, since leaking fluid would act to reduce cavern pressure. Leak detection by pressure monitoring is complicated by other factors that influence cavern pressure, the most important of which are thermal expansion and contraction of the fluids in the cavern as they come into thermal equilibrium with the host salt, and cavern volume reduction due to salt creep. Cavern pressure is also influenced by cavern enlargement resulting from salt dissolution following introduction of raw water or unsaturated brine into the cavern. However, this effect only lasts for a month or two following a fluid injection. In order to implement a cavern pressure monitoring program, a software program called CaveMan has been developed. It includes thermal, creep and salt dissolution models and is able to predict the cavern pressurization rate based on the operational history of the cavern. Many of the numerous thermal and mechanical parameters in the model have been optimized to produce the best match between the historical data and the model predictions. Future measurements of cavern pressure are compared to the model predictions, and significant differences in cavern pressure set program flags that notify cavern operators of a potential problem. Measured cavern pressures that are significantly less than those predicted by the model may indicate the existence of a leak.