Convection in Underground Oil Caverns: The Role of Double Diffusion

The US Strategic Petroleum Reserve (SPR) stores oil in large underground salt caverns. This oil has compositional and thermal gradients induced by geothermal heating from both the bottom surface and side walls. Temperature layering has been recorded in SPR oil caverns, which is hypothesized to be predominantly due to double-diffusive layering that occurs when a stable compositional gradient is heated from below. Initial results of a laboratory experimental program aimed at studying dynamics of such double-diffusive layers in the context of SPR are described in this paper. Of particular interest are the thickness of convecting layers, layer evolution (migration/merging) and conditions for the formation/non-formation of double-diffusive layers.