Basin-level unconventional resource evaluation has traditionally been carried out using 2D mapping. In this study, we use workflows integrating petrophysical analysis of several hundred wells with structural control from over a thousand wells creating a basin-scale 3D geocellular static model. The resulting static model generates insight into lateral and vertical variability not previously realized by traditional basin level analysis of resource plays.
Traditional methods have previously identified major large scale trends in basin analysis; e.g., the NW to SE trends in the Midland Basin, including: the decreasing reservoir potential of the Middle Spraberry, the increase of organic shales with increasing TOC in the Lower Spraberry, and the decrease of carbonates with increasing TOC in the Wolfcamp A. However, these trends do not fully capture the significant smaller scale variability within these specific units.
We have successfully applied a geostatistical approach honoring relationships of calculated petrophysical properties, core measurements and appropriate property distributions. The spatial detail provided by this integrated model results in ‘well level’ reservoir characterization that basin scale trends alone are not able to quantify.
The study area, approximately 105 miles NS and 75 miles EW, includes wells from twelve counties within the Midland Basin. 317 vertical wells with modern triple combo logging suites were included in the petrophysical analysis. Locations of study wells are shown on map (Figure 1). The interval of interest for this study includes the Middle Spraberry through the Wolfcamp B. This is early Permian Leonardian and Wolfcampian ranging from approximately 300 my to 275 my. The analysis interval averages about 1700 feet in thickness; however, this thickness varies significantly within the basin. The interval of investigation is more than 2200 feet thick in Reagan County in the southeastern part of the basin and decreases in thickness by more than 1000 feet in the northwest part of the basin to a total of approximately 1200 feet.
