In Situ Validation of PSDM Seismic Volumetric Curvature as a Tool for Paleokarst Heterogeneity Studies: Results from an Extended-Reach Lateral at Bemis-Shutts
Jason Rush, Mina Fazel Alavi, Dennis Hedke, and Lynn Watney
This DOE-funded project evaluates the utility of seismic volumetric curvature (VC) for predicting stratal and structural architecture diagnostic of paleokarst reservoirs. VC has been championed for identifying faults (offset <¼ λ) that cannot be imaged by conventional 3-D seismic attributes such as coherence. The objective of this research is to prove-up VC-techniques for reducing uncertainties in reservoir compartmentalization studies and seal risk assessments. A 2000-ft horizontal lateral was purposefully drilled across VC-imaged lineaments-interpreted to record a fractured and a fault-bounded doline-to physically confirm their presence. The 15 sq mi study area is located in southeastern Bemis-Shutts Field, which is situated along the crest of the Central Kansas Uplift (CKU) in Ellis County, Kansas. The uppermost Arbuckle has extensive paleokarst including collapsed paleocaverns and dolines related to exceedingly prolonged pre-Simpson (Sauk–Tippecanoe) and/or pre-Pennsylvanian subaerial exposure. A lateral borehole was successfully drilled across the full extent (~1100 ft) of a VC-inferred paleokarst doline. Triple combo, full-wave sonic, and borehole micro-imager logs were successfully run to TD on drill-pipe. Interpretations of the PSDM volume, VC-attributes, and wireline logs provide an integrative assessment of karst landscape evolution along the CKU. In contrast to the southeastern part of the study area, the northwest part is characterized by large dolines (>1000-ft wide) that coincide with radiating lineaments as imaged by the VC-attribute map. Dolines likely functioned as small river basins. Surface water would have been focused into dolines along channels that preferentially formed along radial fractures created by sagging and brittle failure across paleocavern roofs. A karsted plateau likely developed as runoff was diverted into a groundwater system via dolines, moved laterally along an aquitard, before emerging as springs along an escarpment.
AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013