Figure 18. Wireline porosity logs (long-spaced sonic, litho density, and neutron) of the P sand. In the P sand, the low resistivity pay is caused by fine laminations of shale that alternate with thin sand and silt laminae of higher resistivity. Most logs do not have the vertical resolution to distinguish between the shale and pay sand; they average the responses. Wireline porosity logs (long spaced sonic, litho density, and neutron) also average the shale and sand and cannot resolve low-resistivity pay. The density-neutron logs, for example, have very little crossover in these zones. There IS crossover at the top and base where the resistivity is also higher, and this portion of the P sand calculates as pay.