Figure 1. Present-day structural cross-section showing log-based lithostratigraphic correlation of the San Andres reservoir interval in Vacuum field. The reservoir was originally subdivided into 4 major lithologic units: 1) the porous "lower San Andres" carbonates (LSA), 2) the Lovington sandstone (LVSS), 3) the porous "upper San Andres" carbonates (USA), and 4) one or more other sandstones in the upper San andres (SASS). The "lower San Andres" was recognized as being the best and most continuous reservoir.