WYOMING — A recent study into oil production trends by the Wyoming State Geological Survey (WSGS) found the success of wells producing from the Codell Sandstone in southeast Wyoming depends on geology, but equally if not more important is the proper application of drilling and completion technologies and practices.
The report examines Codell Sandstone oil production in the northern portion of the Denver Basin in Laramie County. The sandstone is relatively thin, averaging 20–30 feet through most of the basin, and has historically been considered uneconomical to produce given its low porosity and permeability. However, recent advances in horizontal drilling and hydraulic fracturing methods have proved this unconventional tight sand to be an economically productive oil reservoir under the right conditions.
Between 2012 and March of this year, 119 horizontal wells owned by six operators have produced from the Codell Sandstone in the northern Denver Basin. The study, “Codell Sandstone Oil Production Trends, Northern Denver Basin, Laramie County, Wyoming,” examines characteristics associated with the highest-producing wells in an approximately 640-square-mile study area east of Cheyenne.
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“Initial production and well completion data, including the number of hydraulic fracturing stages, total slurry volume and the total amount of material used to keep an induced hydraulic fracture open during or after a fracturing treatment (proppant), were researched from well completion reports. Cumulative oil production from the Codell Sandstone was calculated for all wells, along with each well’s first 3, 6, 9, 12 and 18 months of production.” – WSGS Report.
“We compared the Codell Sandstone oil production to the wells’ respective lateral length, lateral orientation and completion techniques using both graphical and spatial analyses,” says WSGS oil and gas geologist and project lead, Rachel Toner. “The comparisons show that while traditional geologic criteria such as thickness and formation depth do not primarily influence production from the Codell Sandstone in the study area, wells with long laterals oriented north-south have consistently greater production than those drilled to shorter lengths and alternate directions.”
The goal of this study is to provide a better understanding of operational best practices that in turn can help industry and regulators in optimizing oil production from the Codell Sandstone in the northern Denver Basin in Wyoming.
The study is an open file report and therefore will be supplemented periodically as new information becomes available. Toner says the study could be extended by not only continuing to follow production trends from current wells, but also from future Codell Sandstone-producing wells currently permitted to be drilled in the northern Denver Basin.
“The WSGS is performing similar analyses on additional unconventional plays in the Powder River and northern Denver basins to determine the influence that completion techniques and geology have on production,” says Toner.
The 40-page report is accompanied by an Excel spreadsheet containing all well drilling, completion and production data used in the study.
The report, authored by Toner and WSGS geologist Dr. Erin Campbell, is available as a free download.