Building Large-scale Complex Hydrostratigraphy Model Using Big Data of Well Logs: Subsurface Characterization of the Capital Area, Louisiana

This study presents techniques to build a large-scale complex hydrostratigraphy model based on big data of well logs. The complexity also includes normal faults that displace formations, and structural dip transition from an alluvial plain to Miocene formations. The study area is the Capital Area in southeast Louisiana. More than 4,500 drillers' logs and 700 electrical logs were collected, processed, and input to the model. A quadtree grid was utilized for boundary fitting and refinement for boreholes, model boundaries, rivers, and fault traces. Each borehole falls into a single grid cell in order to capture all information from well logs. To cope with the geological complexities, the model domain was split into a set of tiles based on boundaries that define Mississippi River alluvial aquifer, Denham Springs-Scotlandville fault, and Baton Rouge fault. Angular unconformity between the alluvial aquifer and Pleistocene to Miocene formations was taken into account by developing separate models with different dip angles, which were later combined. Displacement of lithological facies at the faults were modeled through separating well log data by fault traces. Model results show significant areas that connect the alluvial aquifer to Raccourci Old Lake, False River, and Mississippi River, which are the areas of groundwater-surface water interaction. Surficial sands along Amite River at the northeast and east of the study domain represent river discharge zones to the aquifer system. Upland Terraces outcrops in the north-central area connect to Chicot Equivalent Aquifer for groundwater recharge from precipitation. In addition, the model demonstrates clear sand formation displacements across the fault zones. The complex hydrostratigraphy model will be further developed into a regional groundwater model for a groundwater availability study and a saltwater intrusion study in the Capital Area of Louisiana.

Keywords: hydrostratigraphy; modeling; well logs; groundwater-surface water connection; faults; angular unconformity; dipped formations; quadtree grid, Louisiana