Integrated Reservoir Evaluation Using Advanced Wireline Technology to Optimize Landing Points and Reservoir Drainage in an Unconventional Reservoir: A Powder River Basin Case Study

Abstract

An enhanced reservoir characterization requires advanced measurements and customized workflows. While having detailed measurements in the reservoir is helpful, an integration of data is required for a full petrophysical analysis. The optimization of landing points and reservoir drainage is critical during the exploitation of unconventional plays, which nowadays play a critical role in the world’s hydrocarbon reserves.

Customized reservoir characterization workflows for specific reservoir attributes and diagenetic configurations are the solution to overcome rock and reservoir quality uncertainty, a common scenario in unconventional reservoirs. This paper describes the integration of organic shale petrophysics using geochemical spectroscopy and focused magnetic resonance measurements, for the characterization of unconventional reservoirs. Accurate quantification of the mineralogy, lithology and total organic carbon for a better understanding of saturations and reservoir quality was achieved during the integration and validation. Advanced magnetic resonance and geochemical spectroscopy characterization are correlated with open hole and core information to show the precision of the customized workflow.

The application of this customized workflow assisted in providing an enhanced reservoir evaluation of sweet spots, that allows future planning for drilling and completions strategies. Sensitivity analysis improves the integrated workflow and customization, increasing the knowledge of the unconventional shale reservoir behavior and the corresponding impact on the reservoir drainage performance.

The Powder River Basin in the Rocky Mountains region of United States extends throughout the states of Montana and Wyoming, covering approximately 200 miles from north to south and 120 miles from west to east. Figure 1 illustrates the extent of the Powder River Basin. It is well known for its ash deposits (bentonites), as well as its coal deposits, which account for 40 percent of the United States production.

The Basin it is not only notorious for its coal production, but also for its hydrocarbon potential in conventional reservoirs, such as the Turner Member and Parkman Sandstones in the Upper Cretaceous, and unconventional reservoirs such as the Niobrara (87–82 My) and Mowry (100–94 My) Shales. According to the Wyoming State Geological Survey, the basin had its first oil discoveries in the late 19th century (1889 North of Salt Creek) and did not produce natural gas until the later discoveries of gas-bearing coals in the 1990s.