Thick marine siltstone to mudstone formations are common to most sedimentary basins around the world. These thick marine sections are also sometimes associated with high amounts of organic carbon particles, which "cook" into hydrocarbons when subjected to pressure and heat. Examples of these source rocks are found in many parts of North America, including the Barnett of Texas, the Utica formation in Quebec and the Horn River source rock of NE British Columbia.
Up to 600 Meters Thick
The Whangai Formation is a poorly bedded, siliceous or slightly calcareous mudstone of Late Cretaceous age, with localized development of greensand and well bedded calcareous facies. The formation is 300 to 600m thick throughout much of the onshore East Coast Basin. The Whangai has an average TOC of 0.8% in the western, onshore sub-belt, with maximum measured values of 1.7% TOC and 336 HI. Although its TOC content is lower than the Waipawa, the Whangai Formation has been geochemically linked to many onshore oil and gas seeps, validating its potential as an unconventional reservoir. In addition, the Formation is heavily fractured, providing both increased reserve potential as well as natural pathways to enhance flow rates. The fact that the Formation is typically some twenty times thicker than the overlying Waipawa formation adds immensely to the potential of its overall oil and gas generation.