Constructing large-scale complex aquifer systems with big well log data: Louisiana model

Abstract

This study introduces a lithofacies modeling method to construct a complex Louisiana stratigraphy model up to depth of 900 m using more than 114,000 well logs. Lithofacies intervals in one well log can be as many as 76. Louisiana comprises a number of interconnected aquifer systems and distinct geological features, such as angular unconformities, domes, and faults. The method contains processes of tessellation, discretization, translation, and interpolation to accommodate these geological features. First, the model domain is tessellated into tiles. Formations have the same dip direction within the same tile, but may have varying dip angles. Each tile is then discretized into computational cells. The data of well logs in and around a tile are translated to a non-dipping domain. A tile-lithofacies model for each tile is then constructed by interpolating well log data in the non-dipping domain. Tile-lithofacies models for all tiles are generated concurrently through parallel computing. Finally, the tile-lithofacies models are back-translated to the dipping domain and are assembled to form a complex lithofacies model. The method was applied to construct a Louisiana stratigraphy model as deep as 800 m. The model revealed two different depositional patterns in southeastern Louisiana likely due to depositional dissimilarity of the ancestral Mississippi River and Tennessee River. The major recharge zones appear to be in northwestern, southeastern, and west-central Louisiana. These recharge zones represent essential outcrop zones for Louisiana's principal aquifers. The model confirmed hydraulic connections of the Mississippi River and the Red River to their underlying alluvial sands. Hydraulic connections among different aquifer systems were also revealed. The Louisiana lithofacies model offers valuable information to improve current knowledge about Louisiana's geology and demonstrates a method potential for large-scale lithofacies modeling.