Basin-Scale Static Models for Unconventional Resource Plays, Examples From Permian Midland and Delaware Basins

Abstract

Evaluating unconventional resource prospectivity of entire basins has traditionally been carried out using 2D mapping. In this study we used workflows that integrate data from petrophysical analysis of several hundred wells and structural control from over 2000 wells in basin-scale static models. The resulting static models yield significant insights into lateral and vertical changes of resource plays across the basins.

Major large-scale trends in these basins have been identified previously; e.g., Midland Basin NW to SE trends: the decreasing potential of the Middle Spraberry, increase of organic shales with high TOC in the Lower Spraberry, or the decrease of carbonates with an accompanying increase of TOC in the upper Wolfcamp. These broad trends, however, do not fully capture the small scale vertical variability within specific units.

The significant advantage of an integrated static model is spatial detail. Smaller scale features can be evaluated in addition to some of the earlier mentioned basin scale trends. An excellent example is local carbonate slumps on basin flanks often with higher concentrations of organic shales than predicted by large scale trends. Using a geostatistical approach, that honors the relationships measured in cores, in petrophysical analysis, and in property distribution in the static model, quantifies the predictability of the static model.

Core measurements from over 100 wells were used to construct petrophysical models that are interval, region, and facies specific reflecting the variability in the basins. The consistency of the petrophysical models supports evaluation of variability vertically and laterally across the basins. Facies categories were distributed in the static models reflecting the different depositional environments on the basin margins, flanks, and central basin as well as the changing rock associations vertically. Facies distribution was further constrained by depositional models, statistical parameters, and production data.

3D grids with petrophysical properties (e.g., lithology, porosity, saturation, and TOC) are combined with existing production to create a predictive tool for estimating productivity in undeveloped areas.

Lithological and derived property models provide critical rock properties for wellbore and hydraulic fracture stimulation treatment design.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018