Geoscience for QGIS is a free plugin enabling you to:

Desurvey drill holes
Display downhole data
Convert down hole structure data
Create local grids
Use other tools to simplify your life

Install Geoscience for QGIS from the Plugins->Manage and Install Plugins menu directly within QGIS.

See the help pages from the Geoscience for QGIS menu to get started.