Abstract

Hydrodynamic containment principle for the storage of oil products in underground cavern is one of the key principles for the success of whole project. The key idea of hydrodynamic containment is straightforward i.e. to maintain gradient of total hydraulic head toward storage cavern high thus flow of ground water overpass the leakage of oil or gas. Where hydraulic gradient would not be naturally maintained, artificial hydraulic gradient and containment should be provided by so called water curtain system. In such a case, design of water curtain system should incorporate the onsite hydrogeological condition and structures, however in most cases it is based on the assumptions, which are homogeneous and isotropic condition probably due to limited information during the planning and basic design stages. Therefore success of system is heavily relying on steady monitoring and verification of system with comparison of model predictions and measurements. Inevitably, there will be discrepancy of actual measurement and model prediction, which could cause the amendment of design to cope with actual hydrogeological condition and probable performance degradation of system. We have observed that there are actual measurements and monitoring results inconsistent with the prediction based on homogeneous and isotropic hydrogeological model. In this paper, we have attempted to draw some lessons that would be food for thought to similar oil storage caverns from the experiences of detail design, investigations, construction and monitoring of hydrodynamic containment with focus on heterogeneous hydrogeological condition of natural ground.

1. Introduction

It would not be an over exaggeration that success of unlined oil product storage cavern construction project is entirely relying on the hydrodynamic containment capability of natural ground condition or artificial system that emplaced in the cavern storage. To turn underground cavern into oil storage container, hydrodynamic containment principle is devised, which relies on the immiscibility and buoyance due to density differences of water and oil. Basic idea of the principle is as simple as by inducing water flows along joints against the oil or petro gas leakage, so that oil or gas remains inside cavern. For this, containment principle requires two things, full saturation and hydraulic head gradient to overcome the leakage. In locations, where condition is not naturally given, it should be provided by so called water curtain system to ensure full saturation and necessary hydraulic gradient.

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