Correlating productive oolitic zones throughout Folsomville field is difficult because lithologies in the upper part of the Ste. Genevieve Limestone are variable both laterally and vertically. The problem is further complicated by thickness variations of this interval that result in juxtaposition of porosity zones when geophysical logs are correlated. Subsurface slice mapping, now an infrequently used method of subsurface analysis, can resolve complex geometries of oolite bodies and account for seemingly incongruous patterns of hydrocarbon production.

Interpretation of six porosity zones in the upper Ste. Genevieve Limestone and one in the overlying Paoli Limestone (Mississippian) shows that the five oldest zones contain significant oolite bodies that accumulated over an area of positive relief on the sea floor. Integrating isopach and lithofacies maps with fluid-production histories permits more accurate description of individual reservoirs and should contribute to more effective oil recovery from the field.