Geophysical characterization of karst landscapes in Kentucky as modern analogs for paleokarst reservoirs

Abstract

Subsurface interpretation of paleokarst reservoirs is greatly aided by 3D seismic and other modern modeling tools and the inherent complexity of productive reservoirs requires an understanding of reservoir heterogeneities and compartmentalization. Such complexity also requires a review of karst processes and development, which can be beneficially captured via geophysical characterization of near-surface karst landscape features that certainly equate to our better understanding of high-side oil productive areas. Both electrical resistivity tomography (ERT) and refraction microtremor (ReMi) geophysical surveys at the Green River Preserve adjacent to Mammoth Cave National Park in the Mississippian Ste. Genevieve and Girkin Limestones are providing details of karst features, including horizontal passages, uvulas or karst valleys, sinkholes (dolines), vertical pits or dome caves, and associated karst system infill. Geophysical anomalies include reversals of shearwave velocities in a domal (pit) cave, and an inferred bedding-plane controlled conduit system associated with a drained sinkhole basin. Other anomalies detected in the shallow subsurface include large contrasts in geoelectrical measurements near the sinkhole basin interpreted also as a cave or conduit system. In contrast to anomalies, a mappable continuity of ERT and ReMi transects along the Green River suggests bedrock joints controlling the linear nature of bedrock highs and lows, similar to a series of grikes and clints that typify the south-central Kentucky karst.

Three-Dimensional Geophysical Characterization of Deeply Buried Paleokarst System in the Tahe Oilfield, Tarim Basin, China

“…The development of paleocaves is controlled by karstification and is subject to the transformation of subsequent geological processes, such as faulting and diagenesis [41,[70][71][72][73]. The classification of paleocaves in the runoff zone (consisting of an oscillation zone and a shallow phreatic zone, which are typically indistinguishable in paleokarst system) was carried out by following the engineering classification scheme of the paleokarst system in the Tahe Oilfield [10,18].…”

Refraction microtremor (ReMi™)–based investigation of the accumulation of Quaternary sediments on the northern edge of Isparta, Turkey

“…Sirles and Batchko (2010) depicted the soft soil and the bedrock topography beneath areas with very high traffic volume, without interrupting the vehicles by using 2D shear wave velocity section. In addition, May and Brackman (2014) used the ReMi™ technique to obtain the geophysical characterization of karstic region.…”

Improved imaging of a karst aquifer using focused source electromagnetic and differentially normalized method: a qualitative analysis

“…Some studies with conventional geophysical application have been applied in karst terrains (Nyquist, Peake and Roth ; Jacob et al . ; Ismail and Anderson ; Bumpus and Kruse ; May and Brackman ; Meyerhoff et al . ).…”

“…Properly calibrated, the electrical soundings with different electrode configuration can have excellent resolution, provided there is a significant contrast between the resistivity of the regional background and the areas of interest. Some studies with conventional geophysical application have been applied in karst terrains (Nyquist, Peake and Roth 2007;Jacob et al 2010;Ismail and Anderson 2012;Bumpus and Kruse 2014;May and Brackman 2014;Meyerhoff et al 2014). However, one sees little use of unconventional techniques.…”