Pioneer Natural Resources' South Texas Asset Team has drilled and completed >200 Eagle Ford wells with relatively good prediction of performance based on a series of key play maps (thickness, brittle minerals fraction, and HC yield). These maps are paramount in an appraisal phase of any unconventional resource play; however, they do not explain the observed subtle reservoir variability or necessarily what particular parameter is driving the wells' performance. The purpose of this paper is to highlight the combination of key performance drivers across Pioneer's Eagle Ford trend. This study includes reservoir characterization and subsurface structural models, geo-steering data, and drilling and completion considerations. In order to achieve this, Pioneer made an early strategic decision to maintain the same completion design across all geologic areas in our trend to allow for elimination of potential ambiguity from changing the completion design. Collectively, these data are plotted against well performance rankings (forced rankings), determined by diagnostic production plots that leverage both rate and pressure (Productivity Index).
Results of this extensive data set yield that geology controls performance across the trend, but not one geologic parameter alone can be used to describe the entire trend. For example, TOC is the primary performance driver for our strongest wells; whereas poorest performing wells clay content is the dominant parameter. On a first order, clay content (< 35' of Vbrit thickness) differentiates the poorest 20% of wells in the area of interest but TOC (>40' of TOC thickness) further delineates average wells from the top 35%. This work primarily focuses on the identification of TOC driving performance, but extends the workflow to pinpoint other performance drivers across the trend and their impact on development and our understanding of the reservoir.
Once the performance driver(s) for a given area is identified we then use log-to-seismic relationships to generate seismic attribute maps which provide a much finer resolution than our log-derived maps (which rely solely upon pilot well control). These new maps, log-to-seismic relationships (3D seismic attribute volumes), and mapped well rankings greatly enhance our understanding of the Eagle Ford reservoir as well as aids in our appraisal and development drilling program.