3-D seismic evidence of the effects of carbonate karst collapse on overlying clastic stratigraphy and reservoir compartmentalization
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A multidisciplinary team, composed of stratigraphers, petrophysicists, reservoir engineers, and geophysicists, studied a portion of Boonsville gas field in the Fort Worth Basin of north-central Texas to determine how modern geophysical, geological, and engineering techniques can be combined to understand the mechanisms by which fluvio-deltaic depositional processes create reservoir compartmentalization in a low- to moderate-accommodation basin. An extensive database involving well logs, cores, production, and pressure data from more than 200 wells, 26mi2 (67 km2) of 3-D seismic data, vertical seismic profiles (VSPs), and checkshots was assembled to support this investigation. We found the most important geologic influence on stratigraphy and reservoir compartmentalization in this basin to be the existence of numerous karst collapse chimneys over the 26-mi2 (67 km2) area covered by the 3-D seismic grid. These near-vertical karst collapses originated in, or near, the deep Ordovician-age Ellenburger carbonate section and created vertical chimneys extending as high as 2500 ft (610 m) above their point of origin, causing significant disruptions in the overlying clastic strata. These karst disruptions tend to be circular in map view, having diameters ranging from approximately 500 ft (150 m) to as much as 3000 ft (915 m) in some cases. Within our study area, these karst features were spaced 2000 ft (610 m) to 6000 ft (1830 m) apart, on average. The tallest karst collapse zones reached into the Middle Pennsylvanian Strawn section, which is some 2500 ft (760 m) above the Ellenburger carbonate where the karst generation began. We used 3-D seismic imaging to show how these karst features affected the strata above the Ellenburger and how they have created a well-documented reservoir compartment in the Upper Caddo, an upper Atoka valley-fill sandstone that typically occurs 2000 ft (610 m) above the Ellenburger. By correlating these 3-D seismic images with outcrops of Ellenburger karst collapses, we document that the physical
3-D Seismic Evidence, Effects Of Carbonate Karst Collapse, Overlying Clastic Stratigraphy, Reservoir Compartmentalization
Hardage, B. A.; Carr, D. L.; Lancaster, D. E.; Simmons, J. L. Jr.; Elphick, R. Y.; Pendleton, V. M.; and Johns, R. A., "3-D seismic evidence of the effects of carbonate karst collapse on overlying clastic stratigraphy and reservoir compartmentalization" (1996). KIP Articles. 113.