Since the Niobrara is a typical low porosity and permeability self sourced oil reservoir formation, there are factors that must be in place for a successful oil well. The key factors in searching for areas of the Niobrara Formation where oil can be produced are (Sonneberg 2011):
- Thermal Maturation – a measure of the degree to which organic metamorphism has progressed (The “oil window” for Type-II organic matter is commonly considered to be in the range of 0.60 to 1.35 percent Ro – Vitrinite Reflectance (Hunt, 1996))
- Natural Fracturing as a result of movement along basement faults (expressed on the surface in lineaments) and wrench faults
- Natural Fracturing as a result folding and faulting caused by tectonic faults, diapiric slumping, and the dissolution of evaporites (salts)
- Natural Fracturing due to a regional stress field and regional uplift
In a talk by Stark and Coskey at the Denver Petroleum Club on February 11, 2011 a slide was presented that outlines the prime area for Niobrara hydrocarbon generation in the Denver Basin in the form of a banana shaped zone from the Southern Wyoming border angleing down towards Colorado Springs, Colorado. This area appears to be the main focus of current oil company lease acquisition programs. As drilling programs in the Niobrara progress, this hydrocarbon window will be refined. Areas around this “banana” zone are prime areas for exploration leasing programs.
Factors controlling target “sweet spots” for exploration can be discerned by the mapping of lineaments from satellite imagery, measuring vitrinite reflectance using electrical resistivity from well logs, 3D and 3C seismic imaging to pick up fault and folds that will cause natural fracturing.