Deciding Where to Drill Next

In the current version of the Small County exercise, the primary sources of information that you use in selecting promising locations for drilling are contour maps of the elevations and thicknesses of the potential producing formations, namely the Quivira Dolomite, Westport Limestone, Morn Sandstone, and Sawyer Sandstone. Due to buoyancy, oil tends to rise through the stratigraphic column until it is trapped below an impermeable barrier (more information about oil accumulation). The most promising locations to drill for oil in Small County are where the tops of these permeable units exhibit anticlinal or dome-like shapes. Thus, maps of the top elevations of the permeable units will tell you the most about the potential productivity of an area. In addition, you may also want to examine maps of the thicknesses of these intervals, particularly the Morn and Sawyer Sandstones, to determine whether there is an adequate thickness of the permeable interval to support production.

One approach to locating new wells is simply to place them in areas where the elevation contour maps based on information from pre-existing wells seems to indicate anticlines in the productive intervals. However, this will lead to placing new wells close to pre-existing wells, meaning your new well will probably not provide any significant new information regarding the subsurface. At the other extreme, you could drill wildcat wells, far from existing wells, to learn more about the geological structure below Small County.