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New UW Publication Details Best Practices for Oil Drilling in Southeast Wyoming Formations

April 16, 2020

The University of Wyoming’s Enhanced Oil Recovery Institute (EORI) has published a study highlighting the best practices for drilling the Codell and Niobrara formations of the northern Denver-Julesburg (DJ) Basin in southeastern Wyoming.

This work details how best practices were obtained through optimized design and yielded better overall economics when modeled.

EORI’s Jessica Barhaug, senior engineer; and Stephen Whitaker, technical director and senior petroleum geologist, are the authors of the paper, titled “Northern Denver-Julesburg Basin Production Trends -- A Multivariate Approach,” published on EORI’s website under the “Projects” tab.

Barhaug and Whitaker initiated the study to determine the ideal drilling and completion program for a targeted reservoir and evaluate the economic results. The authors compared the current drilling and completion practices to analyze the main drivers behind cumulative oil production at different time intervals, while simultaneously considering the economics that are influencing the decision makers.

To find the highest correlation to the actual cumulative production for estimated ultimate recovery, Barhaug and Whitaker identified the attributes that have the greatest impact on production, making it possible to present an optimized well design. Their modeling also can be used to test hypothetical scenarios to determine their impact on production for the purpose of comparing the return on investment of different drilling and completion techniques.

The study raises the point that many operators may simply use the methodology of what the “guy next door” is doing, regardless of a design based on observation trends derived from publicly available data. The hope is that an operator’s data can be examined in conjunction with the results provided by this work to offer a good starting point for well design.

For the Codell, the study reveals that the attributes of proppant volume, horizontal length, gas-oil ratio and treatment rate have the greatest influence on six-, 12- and 18-month cumulative oil production. By examining the individual attribute responses, the current best design in the Codell is a lateral length of at least 9,600 feet; a job size of 12 million pounds; a treatment rate of at least 40 barrels per minute; and a gas/oil ratio of 570 standard cubic feet per barrel.

“The best ultimate recovery estimates were obtained with the optimized design and yielded better overall economics when entered into the economic model,” the authors say.

Barhaug and Whitaker’s results for the Niobrara define a 9 million-pound job size with a lateral length of 10,000 feet; a gas-to-oil ratio of 900 standard cubic feet per barrel; and a treatment rate between 40 and 45 barrel-per-minute as optimal. Due to lack of available pricing data and the inability to generate valid type curves of production, an economic analysis could not be conducted for the Niobrara.

This study differs from a report published by the Wyoming State Geologic Survey in 2017 and reveals that simple cross plots are not sufficient to properly analyze plays where a number of variables must be addressed and weighed simultaneously. The failure to properly analyze how multiple variables interrelate commonly leads to inaccurate conclusions.

In summary, Barhaug and Whitaker illustrate how, by looking at production from a multivariate approach, operators can determine which factors have had the greatest impact on maximizing production.

EORI is committed to refining and continuing this effort in the northern DJ Basin and in other basins throughout the state. Additional data gathered through operator engagement will be highly beneficial to the analyses.

Those with questions, suggestions or willingness to share data should go to www.eoriwyoming.org. Specialized analyses can be conducted to include proprietary data on a case-by-case basis.

For the full study, go to www.eoriwyoming.org/downloads/recent-projects/Northern-Denver-Julesburg-Basin-Production-Trends-A-Multivariate-Approach-web.pdf.

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