Abstract
Understanding and improving hydrocarbon yields during enhanced oil recovery (EOR) in unconventional reservoirs is complicated by the intrinsic mineralogical and geochemical heterogeneity of shale formations. In this study, we utilized small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) to investigate the degree of oil retention and its location in the nanoporous shale matrix for two mineralogically distinct shale samples. The two samples, dubbed “dark” and “light” based on their color, were taken from adjacent strata in a Wolfcamp shale core. While both samples contained kerogen, the dark sample contained more kerogen and clay (43.7 wt %) while the light sample contained more calcite (54.9 wt %). Samples were presaturated with decane, a model hydrocarbon, prior to pressure cycling with methane. Results showed significantly more retention of decane in 1.5-10 nm radius pores of both, likely indicating that oil is retained within kerogen nanopores. Although the dark sample had a higher porosity of 8.7%, versus 3.3% for the light sample, more pores were accessible to decane and a higher percentage of the imbibed decane was removable from the light sample compared to the dark sample. The majority of decane was not recoverable for the dark sample, indicating that EOR with methane can be challenging. These new findings can help to model expected recoveries of in-place oil from heterogeneous shale formations, as well as inform improved EOR strategies.
| Original language | English |
|---|---|
| Pages (from-to) | 4937-4947 |
| Number of pages | 11 |
| Journal | Energy and Fuels |
| Volume | 37 |
| Issue number | 7 |
| DOIs | |
| State | Published - Apr 6 2023 |
| Externally published | Yes |
Funding
This work was funded by the Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory, under Grant Number FWP FE-406/408/409. Research presented in this article was also supported by the Laboratory Directed Research and Development (LDRD) program via project 20190153ER and through its Center for Space and Earth Science (CSES). CSES is funded by LANL’s Laboratory Directed Research and Development (LDRD) program under project number 20180475DR. The authors acknowledge the Center for Neutron Research (CNR) at National Institute of Standards and Technology for access to Small Angle Neutron Scattering (SANS). Access to Ultrasmall Angle Neutron Scattering (USANS) was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249. The authors would like to acknowledge Chevron for providing shale samples and Ben Bloys, Rebecca Stokes, and Michael Cheshire at Chevron for helping with experimental design. LANL is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No. 89233218NCA000001). This work was funded by the Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory, under Grant Number FWP FE-406/408/409. Research presented in this article was also supported by the Laboratory Directed Research and Development (LDRD) program via project 20190153ER and through its Center for Space and Earth Science (CSES). CSES is funded by LANL’s Laboratory Directed Research and Development (LDRD) program under project number 20180475DR. The authors acknowledge the Center for Neutron Research (CNR) at National Institute of Standards and Technology for access to Small Angle Neutron Scattering (SANS). Access to Ultrasmall Angle Neutron Scattering (USANS) was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249. The authors would like to acknowledge Chevron for providing shale samples and Ben Bloys, Rebecca Stokes, and Michael Cheshire at Chevron for helping with experimental design. LANL is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No. 89233218NCA000001). Laboratory Directed Research and Development (LDRD), DOE-FE