Abstract: Some Considerations in the Application of Wireline Logging to Environmental Investigations

Bruce E. Gaither

Wireline log interpretation and analysis techniques were developed by the petroleum industry to identify and quantify pore fluids in petroleum reservoirs, to characterize the properties of reservoirs, and to identify lithology and aid geologic interpretation.

In subsurface environmental investigations, the information required is almost identical. Such investigations must identify and quantify pore fluids in contaminated media, quantify contaminant concentrations in groundwater, determine the hydrologic properties of aquifers, and characterize subsurface geology.

Given the great similarity of information required, it was hoped that classical log interpretation and analysis would have direct and useful application to environmental questions. However, such attempts have produced disappointing results, which can be attributed to differences in the physical environments, primarily hole and formation conditions, in which logging data are acquired by the two disciplines.

Classical wireline logging theory is based on central assumptions regarding the physical environment in which tools are operated. In environmental logging, which may occur both above and below the water table; in formations that contain air or fresh water; in holes that may be filled with air, water, or mud; and where the salinity of the formation and borehole fluids may be similar; those central assumptions are frequently not valid.

Geologists and log analysts must be aware of these differences and how they affect the various types of wireline logs. Some of these problems may be resolved by further research, rethinking of existing theory, and the development of new analytical techniques.

AAPG Search and Discovery Article #90983©1994 GCAGS and Gulf Coast SEPM 44th Annual Meeting, Austin, Texas, October 6-7, 1994