| Description |
iv, 64 leaves : illustrations, maps ; 28 cm |
| Summary |
"During early Pennsylvanian time the area now occupied by Concho County was a portion of the Texas peninsula, a broad, low arch with a karst topography developing on its exposed Ellenburger surface. A mid-Pennsylvanian marine transgression inundated the arch and it became an area of clear, shallow water deposition favorable to limestone development. Local sedimentation during Strawn time was largely controlled by its position relative to the Llano uplift and surrounding basins. A variety of subsurface maps were constructed for this study essentially utilizing electric log data. The results indicate that limestones of the Strawn platform facies rapidly change in character and "reefing" appears to be associated with local pre-Strawn orogenic features. Three main parallel northeast-southwest trends apparently prevail in the western portion of the mapped area. The eastern-most trend is a prolific producer, but scattered drilling has failed to locate further potential. Accumulation is generally controlled by the absence of porosity on the updip side of fields where the limestones "reef" up, and where sandstones clean up over and wedge out against structural highs. The greatest deterrent to success in the exploration effort is the subtlety of the trap and lack of well control. If more petroleum accumulations are to be discovered in the area it will, in all probability, be due to the consideration of prevailing subsurface stratigraphic conditions"--Abstract, leaf [i]. |
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