The Geology of the Arbuckle Group in the Mid-Continent: Sequence Stratigraphy, Reservoir Development and the Potential for Hydrocarbon Exploration

Fritz, Richard D.; Medlock, Patrick; Kuykendal, Michael; Wilson, James L.

The Arbuckle Group of the Mid-continent comprises the mid-southern portion of the "Great American Carbonate Bank" (GCAB) and consists mostly of carbonates with a few laterally consistent sandstones. The Arbuckle Group is found in the Anadarko, Ardmore, and Arkoma basins and surrounding environs in the Texas Panhandle, Oklahoma and Arkansas. These basins represented a significant downwarp associated with early rifting in the area now located in the southern one-half of both the states of Oklahoma and Arkansas. Similar to other portions of the GACB the thick, widespread Cambro-Ordovician Arbuckle Group was deposited as mostly shallow-water, restricted marine carbonates.

Reservoirs in the Arbuckle are complex and porosity is controlled both by original depositional fabric, diagenesis, paleokarst and fracture overprint. Upper subtidal and lower intertidal facies typically have the most conducive depositional fabric to reservoir development. Diagenetic changes are a continuum that begins with early diagenesis, including hypersaline/evaporative conditions, vadose and phreatic conditions and followed by deep phreatic to late thermal diagenesis. There is evidence that porosity formed during multiple diagenetic phases. Dolomitization and precipitation events also occurred throughout various levels of the profile. Dolomite is the most abundant mineral and can be subdivided into (1) early (syngenetic to penecontemporaneous) hypersaline dolomite, (2) shallow burial mixed-water (phreatic) dolomite, and (3) deeper burial to thermal (baroque and xenotopic) dolomite.

The post-Arbuckle unconformity is recognized as evidence of a globally eustatic sea level drop and has been used to mark the boundary between the Sauk and Tippecanoe depositional sequences. The Arbuckle Group contains multiple unconformities and disconformities at major sequence boundaries. Paleokarst is especially prevalent beneath the post-Arbuckle unconformity regularly within the Arbuckle Group especially along major sequence boundaries with related unconformity surfaces. Paleokarstic features in the Arbuckle Group have been identified on outcrop in The Arbuckle Mountains of Southern Oklahoma and in the southern Ozark Uplift in northeastern Oklahoma. Numerous cores and logs indicate collapse breccias that are interpreted to have formed in response to karst conditions.

The Arbuckle Group is an important petroleum reservoir in the Mid-continent and it has great potential especially for natural gas. Exploration is enhanced by understanding the complex relationships of depositional process, stratigraphic relationships, paragenesis and structural overprint. Reservoir development is typically along sequence boundaries especially where facies have strong diagenetic overprints from dolomitization and dissolution associated with paleokarstic events. There are no major source rocks below or within the Arbuckle Group so the best reservoirs are structurally related with strong fracture overprints and juxtaposed to source rocks or along migration pathways.

The Arbuckle Group is an important petroleum reservoir in the Mid-continent and it has great potential especially for natural gas. Exploration is enhanced by understanding the complex relationships of depositional process, stratigraphic relationships, paragenesis and structural overprint. Reservoir development is typically along sequence boundaries especially where facies have strong diagenetic overprints from dolomitization and dissolution associated with paleokarstic events. There are no major source rocks below or within the Arbuckle Group so the best reservoirs are structurally related with strong fracture overprints and juxtaposed to source rocks or along migration pathways.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013