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October 17th, 2018 11:30 AM - 1:00 PM


October 17, 2018


SPEAKER:  Kurt Rottmann   


Regional-Scale Characterization of the Arbuckle Group’s Depositional

History and Cap Rock Facies Variations and Their Role on Arbuckle

Reservoir Characteristics and Saltwater Injection



10 NW 6th Street



WEDNESDAY October 17, 2018

LUNCH 11:30am – 1:00pm






The carbonates of the Arbuckle Group were deposited in the mid-continent from shallow Cambrian and Early Ordovician seas. In places, the Arbuckle Group was deposited as a fill amongst strongly eroded pre-Cambrian geomorphic features. Deposition of a cap rock facies on the top of the Arbuckle Group consists of six primary types: porous sand (porosity >= 6%), tight sand (porosity <= 6%), shaley sand, shale, multi-storied porous sand/shale sequences, and multi-storied tight lime/tight sand/shale sequences.


During the Post Hunton (Acadian) uplift, the Arbuckle Group was uplifted with most or all of the overlying strata removed by erosion in northcentral, central and northeastern Oklahoma. This uplift and erosion created over-pressure within the Arbuckle Group relative to depth. Gases and fluids most likely escaped either into the atmosphere where the Arbuckle was exposed or through permeable sand cap facies directly overlying the Arbuckle. The Arbuckle Group was subjected to additional intervals of reburial, uplift and erosion of overlying sediments, and reburial during the Late Devonian through Early Permian Periods. Late stage Dolomitization most likely occurred during late Pennsylvanian with subsequent re-compaction of Arbuckle Group Strata.


Reservoir properties have not been well documented within the literature for the Arbuckle Group. However, increased attention has been directed towards the Arbuckle due to its importance as a reservoir for saltwater disposal and the apparent relationship between saltwater injection and seismic activity. The location of these seismic events is concentrated in northcentral and central Oklahoma. Of interest is the relationship between seismic activity and cap facies of the Arbuckle Group in areas of Arbuckle saltwater injection. Generally, in those areas where the cap rock facies is porous, seismic activity is at a minimum and in those areas where the cap facies is impermeable, seismic activity has frequently occurred. This relationship may be the result of fluid saturations within the Arbuckle Group having been dramatically changed from pressure changes and fluid loss that occurred during the Post Hunton uplift.

Additionally, pressure gradients calculated from the final shut-in pressures of 266 drill stem tests of the Arbuckle suggests lower pressure gradients in those areas with a permeable cap facies and higher pressure gradients in those areas of impermeable cap facies. However, the overall average pressure gradient is less than the average pressure gradient for other formations, which suggests an under-pressured characteristic for the Arbuckle Group.


Mr. Rottmann graduated from Western State College in 1972.  He completed advanced studies in structural geology and oceanography at the Colorado School of Mines in 1973.  Mr. Rottmann came to Oklahoma in 1974 and worked as a mudlogger until 1976 at which time he started his career as an exploration geologist.  He worked for several companies primarily in the Anadarko and Arkoma Basins.  In 1986, Mr. Rottmann worked for Beard Oil Company as a consultant and in 1993 became a full time employee in Beard’s waterflood department.  In 1995, Mr. Rottmann served as a consultant for several operators and for the Oklahoma Geological Survey where he contributed technical papers for the Survey’s series of Fluvial Dominated Delta workshops.  Since 2000, Mr. Rottmann has been principle author for workshops with the OGS that dealt with waterflooding, reservoir engineering and the Hunton Play.  He also has recently been principle author for the Survey’s workshops on the Arbuckle and the Mississippian.  In 2016, the Oklahoma Geological Survey contracted Mr. Rottmann to study the regional scale characterization of the Arbuckle Group’s hydrogeologic system from geophysical well logs.   Features of the history of the Arbuckle and overlying sedimentary rocks identified during this study appear to offer an interpretation of the underpressuring of the Arbuckle with implications for the relationship of saltwater injection and seismicity.


Attendance without reservation will not be possible.  Reservations must be cancelled by October 12, 2018 at noon to avoid being charged.  Thank you for your consideration.