Powder Basin River
Upper Cretaceous Tight Oil Reservoirs

The Integrated Reservoir Solutions division of Core Laboratories is offering to interested companies participation in a project designed to optimize operators’ exploitation of low-permeability, liquids-rich, Upper Cretaceous reservoirs in the Powder River Basin. Initial activity in the basin for unconventional reservoirs focused on the Niobrara with mixed results. However, several operators have become bullish on other formations such as the Teapot, Parkman, Sussex, Shannon, and Frontier/Turner sandstones (Figure 1). The conventional reservoirs of these formations were the target of a previous core study carried out in the 1980s by Core Laboratories, which will be included in this project (Figure 2 and Table 1).

An integrated study of these unconventional reservoirs is warranted and should be directed at geology, formation evaluation and stimulation-production techniques to maximize exploitation. Some of the issues to be addressed in this project include the following:

• What are the factors controlling reservoir quality? Are they depositional facies or diagenetic?
• What are the various reservoir rock types and their petrophysical properties, and how do they vary regionally?
• What are pay recognition criteria and the appropriate water saturation model for the reservoir, and does it change by zone and/or regionally? Is there low-resistivity pay in the shaly sandstones?
• What are the optimal completion and stimulation fluids?
• What is the optimal fracture stimulation design(s) to maximize production?
• How should the reservoirs be produced in order to maximize liquids production?
• Can reservoir quality be correlated or benchmarked to production performance?

These problems can only be solved from the geological, petrophysical and completion/stimulation analysis and evaluation of wells with either conventional cores or rotary sidewall cores. The resultant data can be used to calibrate open-hole logs in order to better predict rock types and petrophysical properties essential for formation evaluation and proper well completion and stimulation designs. The rock types and their measured petrophysical properties can also serve as analogs when evaluating new reservoirs in wildcats or field step outs.

Each participating company will be required to contribute conventional core from two (2) wells for analysis and inclusion into the study. Companies may also contribute rotary sidewall cores for up to two (2) wells. All participating companies will share in the project results and interpretations.