Combining Geophysical and Well Data for Identifying Best Well Locations

Abstract

Geoelectric and well data are combined and used to delineate “best” well location areas. The best location is selected based on a compromise solution for two conflicting objectives: (1) maximum well yield (i.e., maximum sustainable pumping rate); and (2) maximum wellhead protection (i.e., maximum total travel time related to a fixed setback distance). The methodology combines hydraulic conductivities and layer thicknesses obtained from well logs, well-performance tests, and geoelectric measurements to estimate and map well yield and travel time. Hydraulic conductivities, layer thicknesses, and the estimated yields and total travel times are considered as spatially correlated random variables. Expected value and 75% reliability maps are developed for yield and total travel time. The best well location areas are identified based on a trade-off map that is calculated as a combination of the yield and travel time maps. The relative importance of well yield versus wellhead protection is incorporated in the trade-off relationship. The methodology is illustrated for a study area located near Ashland, Nebraska.