“Don’t forget about the Fort Hays.” Those words were the refrain from noted Niobrara geologist and expert, Dr. Steve Sonnenberg, Professor and Charles Boettcher Distinguished Chair in Petroleum Geology at the Colorado School of Mines.
Speaking at the Niobrara Completions and Well Spacing Congress in Lakewood, Colorado on November 18, 2014, Dr Sonnenberg presented a talk titled: New Reserves in an Old Field, The Niobrara Resource Play in the Wattenberg Field, Denver Basin, Colorado.
In his talk, Dr. Sonnenberg covered the Niobrara basics for the audience, namely the Niobrara reservoirs: A, B, C, Fort Hays chalks and the Codell sandstone. The source beds: A Marl, B marl, C marl, and Recovery Factors: Porosity, Thickness, Saturation, Lateral Length, orientation, spacing & completion, pressure, and mechanical stratigraphy.
He went on to describe the Niobrara Petroleum System where the chalks are greater than 70% calcium carbonate, low in porosity and permeability and only producible due to recent advances in drilling technology. The marls he said, were 30 to 70% calcium carbonate and excellent source rocks with TOC (Total organic carbon) content of 4 to 6 % by weight.
A history of drilling in the Niobrara was covered with many maps and diagrams presented.
Dr. Sonnenberg went on to discuss the origin of the natural faults and fractures that make the Niobrara a premier shale play. The fractures are the result of Tectonic forces, a regional stress field, and diagenetic factors. Sonnenberg specifically pointed out the Niobrara exhibits polygonal fault systems (also exhibited in 100 other basins) that can form early as a result of compaction and dewatering.
The effects of the Colorado Mineral Belt and the Wattenberg Thermal Anomaly were also discussed.
The talk was concluded with a Q&A session. When asked about the current lack of success by some operators in the Greenhorn formation, Dr. Sonnenberg said he “would not give up on the Greenhorn at all. Its early on. It’s a play of the future” He also said that the best shows from drill stem tests in the DJ basin come from the Greenhorn formation, and that they “got his attention”.