Undergraduate Honors Theses

Thesis Defended

Spring 2015

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Geological Sciences

First Advisor

David Budd

Second Advisor

Charles Stern

Third Advisor

Barbara Buttenfield

Abstract

In recent years, the Niobrara Formation and the Codell Sandstone of the Carlile Shale Formation have been targets of oil and gas production in the Wattenberg Field of the Denver-Julesburg Basin. Horizontal drilling of these units has become more popular since 2010, with Niobrara wells extending to northeastern Colorado and Codell wells remaining within Wattenberg. It is likely that exploration in the Codell will follow the same trend of the Niobrara; therefore it is important that lateral facies variability within the Codell is determined as facies can be applied to reservoir potential. I described and logged five cores along a northeast-southwest transect through Wattenberg to northeastern Weld County for grain size, lithology, bioturbation, sedimentary structures, and sorting. Six facies were found between the five cores and represent a regressive marine shelf environment. A basic vertical sequence was found in all five cores and represented environments at the storm wave base up to the fair weather-lower shoreface transition. Two different facies were found in the northeast core, including a purely shoreface sand. This shoreface sand facies is of particular importance because it is pure sand consisting of preserved sedimentary structures with no bioturbation. Porosity and permeability within this unit are likely higher than the bioturbated facies because silt and mud have not been worked into the pores of the shoreface sand. The presence of the two different facies show evidence of lateral variability in the Codell to the northeast, and the shoreface sand could mean better reservoir potential to the northeast.

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