The Lower Creataceous Valdemar field was discovered in 1977. Its chalk is with high argillaceous content and with poor reservoir qualities. The matrix permeability ranges from 0.01mD to 0.4mD with porosities ranging from 20 – 35%. The shale content varies over the different reservoir units from 4 – 70%. Formation and acid compatibility investigation indicate clay swelling and fracture face collapse. The wells (with horizontal lengths between 3,000 and 5,000 m) need to be stimulated before they can be set on production with economic rates.