Depositional Environment and Production Characteristics, Parkman Sandstone, Southern Powder River Basin, Wyoming

Matthew Steidtmann and Lesli J. Wood - Colorado School of Mines

The Upper Cretaceous (lower Mesaverde) Parkman Sandstone of the Powder River Basin is a deltaic succession that displays overall progradational parasequence set stacking. Depositional environments range from offshore marine to coastal plain and show strong wave and some tidal influence. Shoreface facies are excellent reservoirs, so excellent in fact that they are dominantly wet across the Powder River Basin except for a few structural and stratigraphic traps. Consequently, interest in the Parkman was pretty minimal until the discovery of Savageton Field in 2002 when the lower Parkman became a significant tight oil play. The reservoir facies at Savageton is the distal portion of a single parasequence at the base of the lower Parkman sandstone. Before oil prices dropped in 2014, the lower Parkman was the most economic play in the Powder River Basin (Andy Finley, pers. comm.). Several papers were published on the Parkman in the 1960’s and 70’s prior to the advent of sequence stratigraphy, since then, nothing has been published except for the publication on Savageton Field.

The Parkman is well displayed in outcrops along the western Powder River Basin at Teapot Dome and there is abundant subsurface data to the east within the basin. Initial study of Parkman outcrops suggests it may be more complicated than a single prograding parasequence set as there appears to be a sequence boundary near the top of the lower Parkman in outcrop. Above the sequence boundary a postulated valley fill facies grades up from estuarine to multiple stacked fluvial successions. Relief along the basal scour has not yet been determined. The fluvial successions display relief on the order of 10’s of meters.

Observations and interpretations made on Parkman outcrops will be integrated with core and well log data to develop a better understanding of the Parkman in the Powder River Basin and potentially aid in production enhancement.

Abstract

Map of Outcrop StudiesTeapot Dome, Wyoming

Parkman Wells by OperatorParkman Wells by Production

Abundant hummocky cross stratification throughout Parkman Cross bedding above HCS

Multi-story channel incisions with lateral accretions

Scour surface (sequence boundary) with roots

View of lower Parkman (with thickening up parasequences) and upper Parkman coastal plain

Connectivity of Parkman reservoirs• How does the connectivity of the Parkman reservoir system vary spatially and temporally?• How does the connectivity of the Parkman reservoir system vary by facies association/depositional system over time?

Correlation approaches• What is the most useful correlation technique for the Parkman? Lithostratigraphically, biostratigraphically, chemostratigraphically or sequence

stratigraphically?• Are there some key flooding events we need to use?

Partitioning of Reservoirs• What is the spatial distribution and character (thickness, etc.) of the inter parasequence shales in the producing area? Where do the sequences cross-

communicate and where are they separated.• What is the basinward extent of the quality sands distal of the thick shorefaces? And how are the sands partitioned (high heterogeneity or low)?

Future Work

Cross-section of measured sections showing valley incision on the left and absence of incision on right.