A Multidisciplinary Approach to Unconventional Petrophysical Reservoir Integrated Saturation Measurements

A multidisciplinary approach is being used to characterize unconventional reservoir rock, providing high-quality porosity, saturation, and grain density data. Higher-frequency (23 MHz) NMR with 2D T1/T2 mapping provides a bird’s-eye view of residual core fluids, including additional characterization detail regarding hydrocarbon and water mobility. Multi- Heating Rate Pyrolysis (MHR), a specialized staged temperature ramp pyrolysis method, provides added clarity and separatory power of mobile vs. immobile hydrocarbons to aid in the HF NMR segmentation process and understanding hydrocarbon producibility. Ongoing workflows elucidate the efficacy of the HF NMR over the historical GRI approach in saturation determination and understanding the formation dependent nuances in determining mobile hydrocarbons in conjunction with MHR pyrolysis. This integrated workflow uncovers the power of using a multifaceted approach to understanding the microporous unconventional reservoir media. The study underpins the particle-size-dependent nature of fluid losses, both water and hydrocarbon, determined by carrying out experiments with HF NMR on intact and crushed reservoir rock of different mesh sizes before going through the GRI extraction and measurement process. Additionally, while particle size is an import factor of fluid loss, XRD results and additional formation information indicate that both clay, rock quality, and fluid quantity and quality are also controls on fluid losses. Hydrocarbon producibility can be better determined in different formations using HF NMR and MHR pyrolysis in conjunction. In unconventional samples, where the hydrocarbon has low molecular mobility, the HF NMR and MHR pyrolysis show good agreement between the two methods, and the MHR results can define the fractions of hydrocarbon that are likely to be produced. In formations where hydrocarbons have high-molecular mobility, the volatile components suffer losses due to the sample-size reduction in pyrolysis preparation. The nonvolatile components are preserved and can be identified by MHR pyrolysis. The producible fractions can then be uncovered by using the difference in the full hydrocarbon volumes determined by HF NMR and the low-molecular mobility hydrocarbons determined by MHR pyrolysis.