Cotton Valley Lime (Oolitic Shoal) Play
Analogue
As mentioned earlier, Exxon controls much of the play, and Figure 14 shows a typical Exxon completion in the trend. The McCain Unit has the almost universal tite lime “caprock” in the upper 100 feet of the Cotton Valley Lime interval. Below lies the main porosity of the bar build-up, sitting on top of tite lime again. None of the low resistivity rock is perforated, and indeed much of this porosity is wet. The well has been a below average producer and will yield about 2 BCFGE. It is interesting how this well has never had water problems in years of production, even though the lowest perf is only 30 feet above water. It is apparent that it is not “free water.” There are examples in the trend where operators have avoided anything less than 10 ohms, despite the fact that this is the best quality reservoir in the section.
One of the best insights to the play can be gained by looking at some petrophysical data and production for a former Exxon unit, the Jackson G.U. 1-2. Figures 15, 16, and 17 are components of the log for reference, while Figure 18 is the core log for the same well. Both logs show the Exxon perforated interval, followed in time by the Apache perforated interval. Of importance is the fact that rock with less than 2.5 ohms is perforated and fraced.
Figure 19 demonstrates the corresponding production response after the re-completion.