The Waltersburg sandstone produces oil from isolated sand bodies and has produced nearly eight million barrels of oil from those of the Rochester, Mounts, and Fleener Fields. From the overlying "little Menard" Limestone to the Vienna Limestone below, the Waltersburg interval is most commonly 70 feet thick, but ranges from 14 feet in the north to 116 feet in the south. Increasing interval thickness is strongly correlated with increasing sand percentage. The maximum sand accumulation occurs in elongate sand bodies up to 100 feet thick,one-fourth to one mile wide, and two to five miles long. Elongate sand bodies are commonly oriented northeast-southwest, nearly perpendicular to strike. Sheet sand bodies are less than half as thick and usually produce only from small structural highs.Structure contour maps of the Vienna and "little Msnard" Limestones show that a 16 square mile plunging anticline bearing N30E exists along with other minor folds on a regional slope dipping about 40 feet per mile into the Illinois Basin. The structure of the "little Menard" may be associated with structural features of the Vienna, with isolated thick sand bodies or both where they occur together. Structural features of the "little Menard" that are not seen on the Vienna are usually attributed to differential compaction over sand bodies. The overall similarity in folding of both limestones suggests that deformation occurred after Waltersburg deposition as a result of differential compaction over older sediments combined with regional tilting as sediments subsided into the Illinois Basin.Oil production occurs in sands 10 to 60 feet thick that are structurally high. Structural elevation is therefore more important to production than sand thickness. Since most structural traps have been exploited, the most favorable locations for potential production are where thick elongate sands thin up-dip to form stratigraphic traps. Although a few locations for possible stratigraphic traps exist within the study area, extending exploration in recommended places may lead to more promising production outside the study area.On the basis of petrography, subsurface geometry, and log signatures of the Waltersburg sandstone, the depositional environment is suggested as being a fluvial dominated delta plain facies. The various types of thick elongate sand bodies are attributed to fluvial distributary channels. The interdistributary area is represented by mostly shale and silt, with crevasse-splay sands and possible minor mouth bar/crevasse-splay couplets.
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/182397 |
| Date | 03 June 2011 |
| Creators | Johnston, David Kent |
| Contributors | Pierce, Walter H. |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | x, 135 leaves : ill. ; 28 cm. |
| Source | Virtual Press |
| Coverage | n-us-in |
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