Abstract
Hydraulic fracturing of low-permeability rocks significantly enhances hydrocarbon production from unconventional reservoirs. However, fluid transport through low-permeability rocks and the influence of geochemical transformations on pore networks are poorly constrained. Mineral reactivity during interactions with injected water may alter the physical nature of the rock, which may affect hydrocarbon mobility. To assess alterations to the rock, we have previously conducted a hydrothermal experiment that reacted cubed rock samples (1 cm3) with synthetic hydraulic fracturing fluid (HFF) to simulate physicochemical reactivity during hydraulic fracturing. Here, we analyze unreacted and reacted rocks by small-angle neutron scattering and high-pressure mercury intrusion to determine how the pore networks of unconventional reservoir rocks are influenced by the reaction with hydraulic fracturing injectates. Our results suggest that fluid-rock interactions exhibit a two-fold influence on hydrocarbon recovery, promoting both hydrocarbon mobilization and transport. Pore-matrix interfaces smooth via the removal of clay mineral surface asperities, reducing the available surface area for hydrocarbon adsorption by 12-75%. Additionally, HFF-induced dissolution creates new pores with diameters ranging from 800-1400 nm, increasing the permeability of the rocks by a factor of 5-10. These two consequences of mineral dissolution likely act in concert to release hydrocarbons from the host rock and facilitate transport through the rock during unconventional reservoir production.
| Original language | English |
|---|---|
| Pages (from-to) | 15811-15819 |
| Number of pages | 9 |
| Journal | ACS Applied Materials and Interfaces |
| Volume | 13 |
| Issue number | 13 |
| DOIs | |
| State | Published - Apr 7 2021 |
Funding
This material is based upon the work supported by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DE-SC0014664. RJHT and QRSM were supported by the SCGSR Fellowships. RJHT also acknowledges the support by the SER, and QRSM was also supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Chemical Sciences, Geosciences, and Biosciences Division through its Geosciences program at the Pacific Northwest National Laboratory (PNNL). Contributions to the measurements of experimental data and manuscript preparation by GR were supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division. JPK was supported by the UW SER and a Nielson Energy Fellowship. This research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.
| Funders | Funder number |
|---|---|
| Office of Science Graduate Student Research | |
| SCGSR | |
| UW SER | |
| U.S. Department of Energy | DE-SC0014664 |
| Office of Science | |
| Basic Energy Sciences | |
| Workforce Development for Teachers and Scientists | |
| Oak Ridge Institute for Science and Education | |
| School of Energy Resources, University of Wyoming | |
| Pacific Northwest National Laboratory | |
| Chemical Sciences, Geosciences, and Biosciences Division |
Keywords
- fluid-rock interface
- fractal geometry
- hydraulic fracturing
- hydrocarbon recovery
- nanoporosity
- pore network
- small-angle neutron scattering
- unconventional reservoir
