Reactivity of CO₂ with Utica, Marcellus, Barnett, and Eagle Ford Shales and Impact on Permeability

Abstract

In order to reduce greenhouse gas emissions while recovering hydrocarbons from unconventional shale formations, processes that make use of carbon dioxide to enhance oil recovery while storing carbon dioxide (CO2) should be considered. Here, we examine samples from three shale basins across the United States (Utica and Marcellus Shales in the Appalachian Basin, Barnett Shale in the Bend Arch-Ft. Worth Basin, and Eagle Ford in the Western Gulf Basin) to address the following questions: (1) do changes from reaction with CO2 and fluids at the micrometer and nanometer scale alter flow pathways and, in turn, impact hydrocarbon production, CO2 storage, and seal integrity and (2) can CO2 or fluid reactivity be predicted based on physical or chemical properties of shale formations? Experiments were conducted at 40 °C and 10.3 MPa to characterize the interaction between CO2 and shale using X-ray diffraction (XRD), carbon and sulfur analysis, in situ Fourier transform infrared spectroscopy (FT-IR), feature relocation scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), mercury (Hg) intrusion porosimetry, and Brunauer–Emmett–Teller (BET) surface area and pore size analysis coupled with density functional theory (DFT) methods. Changes in mechanical, physical, and flow properties of shale cores due to CO2 exposure were addressed using a New England Research Autolab 1500 and Xenon X-ray computed tomography (CT) scanning. Results showed that CO2 did not promote significant reactivity with the shale if water was not present; only shales with swelling clays or residual interstitial pore water reacted with dry CO2 to promote reactivity in shale. When water was added as a reactant, CO2 formed carbonic acid and reacted with the shale to dissolve carbonate pockets, etched and pitted the shale matrix surfaces, and increased the microporosity and decreased nanoporosity. Porosity and permeability increased appreciably in core shale samples after exposure to CO2 saturated fluid due to dissolution of carbonate. Shale mechanical properties were not altered. Trends were not observed that could tie CO2 or fluid reactivity to physical or chemical properties of the shale formations at the basin scale from the samples we examined. However, if the shale contained significant amounts of carbonate and water was available to react with the CO2, pore sizes were altered in the matrix and permeability and porosity increased.

Impact of Supercritical CO2 on Shale Reservoirs and Its Implication for CO2 Sequestration

“…It is self-explanatory that, for the progress of civilization, utilization of available energy resources cannot be terminated, and to accommodate this with the PCA objective, negative GHG emissions is to be achieved in the coming decades. − Luderer et al estimated that, even after phenomenal efforts by several countries, the fossil fuel contribution to emission until the end of century would remain ∼1000 Gt CO 2 . In this context, carbon capture and storage (CCS) in geological reservoirs has been identified as a feasible near-term option to combat the rising GHG emissions. ,− …”

Investigating Enhanced Oil Recovery in Unconventional Reservoirs Based on Field Case Review, Laboratory, and Simulation Studies

“…Figure shows the distribution of wells in the field, where eight horizontal wells were completed in the Eagle Ford between 2011 and 2013, as shown by the black line in Figure . Similar to the Bakken, the Eagle Ford formation has an extremely tight rock matrix, where the permeability is at a nano-darcy to micro-darcy level. − The crude oil produced from Eagle Ford shale is also volatile because of the high percentage of light components in the oil. , At this site, the oil production rate dropped nearly 90% in the first 5 years of production, from a peak rate of 40,863 bbl/month (6.5 × 10 3 m 3 /month) (in August 2011) to 4500 bbl/month (0.715 × 10 3 m 3 /month) (in April 2016).…”

“…A variety of laboratory experiments and simulation studies were performed to investigate EOR mechanisms and predictive potential EOR responses in unconventional reservoirs. − ,,− However, very few of these studies were correlated with actual field performance. One of the reasons was the limited access to actual field data. , In this section, a series of experiments were collected for gas injection pressure, MMP, and oil recovery factor assessment in the Bakken and Eagle Ford, and then a set of new experimental and simulation activities were carried out to correlate the laboratory/simulation observations with actual field performance.…”

Comprehensive Review of Property Alterations Induced by CO2–Shale Interaction: Implications for CO2 Sequestration in Shale

“…In addition, CO 2 adsorption induced swelling will decrease the permeability of shale. , Thus, the permeability of a shale gas reservoir is influenced by multiple factors, leading to diversified complex characteristics in the permeability evolution of shale. Some researchers have found that the permeability of shales increased after CO 2 exposure and increased with increasing reaction time, temperature, and pressure. ,− However, other researchers argue that the permeability of shale decreased with the increase of CO 2 exposure time, and the reduction of permeability caused by ScCO 2 is stronger than that caused by SubCO 2 . ,, It is obvious that there are two distinct and opposite variation trends of permeability in shale, which can be interpreted by the different experimental conditions for them and the difference in dominant factors for the different shales. On the one hand, the extraction and dissolution effects of CO 2 exposure play dominant roles in permeability variation; thus the permeability showed an increasing trend after CO 2 exposure.…”