Determining the integrity of geomembrane-sealed reservoir basins using suspended resistivity profiling

As geomembranes have emerged as a prevalent solution to mitigate reservoir seepage, maintaining the structural integrity of geomembrane anti-seepage systems (GAS) is essential for reservoir safety. Conventional geophysical methods often struggle to detect anomalies in GAS deposits beneath deep water layers due to limited resolution and insufficient penetration depth. This study presents the suspended resistivity profiling (SRP) method, which enables rapid, high-resolution underwater surveying unaffected by water depth using small electrode spacing near targets. With the measurement cable suspended 1-2 m above the target, a 1 m thick cover layer was accurately detected in both synthetic and field experiments using a nonconventional array with a 2 m electrode spacing. Field investigations reveal that the thickness of cover layer varies between 0.7 and 1.6 m. An integrity index, computed from these thickness variations, indicates that a significant portion of the reservoir basin lies within the normal range. However, notable disparities across the reservoir reveal sedimentation risks in the northeast and erosion risks in the west. The potential discrepancies associated with SRP are evaluated by examining the influence of electrode positioning on geometric factors; results showed relative errors of less than 2%, which underscores the reliability of the SRP method. Furthermore, a summary from various publications highlights the capability of the SRP approach for high-resolution underwater imaging at survey speed of 4 km/h. These findings provide a robust framework for decision makers to develop more cost-effective strategies for assessing and restoring the integrity of GAS.