--> --> The Past, Present and Future of Niobrara/Mancos B Horizontal Development in the Piceance Basin

AAPG Rocky Mountain Section Meeting

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The Past, Present and Future of Niobrara/Mancos B Horizontal Development in the Piceance Basin

Abstract

The Mancos Shale formation within the Piceance basin is one of the richest hydrocarbon-bearing formations in the world but remains a relatively unexplored play. Numerous wells have tested the liquid-rich, transitional and dry gas window, with variable results. The main drilling targets are typically the Niobrara formation, comprised mainly of marls, siltstones & shales, and the overlying Mancos B formation, comprised mainly of silty shales with relatively low carbonate content. Beginning in 2008, several horizontal wells have targeted these formations, mostly in gas-prone deposits on the southern side of the Piceance basin. Results to date have been mixed, but the highest initial production comes from the more overpressured, carbonate-prone benches, such as the Tow Creek and Rangely Bench. The wells drilled before 2014 were typically shorter with lower frac intensity, resulting lower production rates. Beginning in 2014, longer laterals with higher frac intensity resulted in higher production rates. The increased yields are due to a combination of improved frac design and drilling strategies. Importantly, the Niobrara formation is well suited to test the impact of more modern frac designs, including higher proppant and 63 Wyoming Geological Association – September 15-18, 2019 water volumes, shorter stage lengths, and plug-and-perf completion techniques. The Niobrara formation has been drilled in the liquids window along the western and northern margins of the Piceance basin from 2014 to 2018, with longer lateral lengths and higher proppant volumes, but the results have proven somewhat disappointing. Due to the lower number of wells, it is difficult to determine the exact cause of lower production rates. However, available data indicate that it is likely due to a combination of lower formation pressures, higher hydrocarbon viscosities, reservoir properties, and ill-suited completion techniques. The Piceance basin has substantial gas processing and transport infrastructure in place and can be competitive against existing US gas markets. If Piceance basin operators can merge newer completion styles with access to international LNG markets, there is unlimited potential for future natural gas production.