Using the Optical Image Profiler (OIP) and Hydraulic Profile Tool to Visualize Complex Petroleum LNAPL Migration
The Ultraviolet Optical Image Profiler (OIP-UV) is a direct-push optical sensing tool that was recently combined with the Hydraulic Profile Tool (HPT) and Electrical Conductivity (EC) tool, also called OiHPT-UV. The OiHPT-UV tool literally sees the LNAPL in the subsurface and identifies what the hydrostratigraphic pathways are that got it there. A 3D grid of OIP-UV, HPT, and MIP probe data was combined with monitor well data, LNAPL measurements, conventional soil samples, and input into three-dimensional (3D) modeling software to clarify and explain complicated LNAPL patterns observed at various sites.
In one example, the initial LNAPL release penetrated deep below the water table and found confined stratigraphic layers that allowed it to migrate counter to the groundwater gradient. The data also showed that an air sparge and vapor extraction system had effectively cleaned up LNAPL in the smear zone but was not able to reach the confined LNAPL. Another site with randomly occurring LNAPL in monitor wells was found to have LNAPL present mostly in a perched water bearing zone and also in a deeper confined zone. The deeper confined LNAPL may have migrated there via deep wells screens. 3D models of several examples are shown that demonstrate how the HRSC tools and 3D models can be used to explain these site complexities and thus aid in remedial design.