Supercritical carbon dioxide extraction of petroleum on kieselguhr

The ability of an injected gas to dissolve crude oil hydrocarbons may be a major factor controlling the success of enhanced oil recovery (EOR) projects in unconventional reservoirs. Multiple laboratory gas injection tests were conducted using Bakken crude oil in which the gas-dominated upper phase in equilibrium with the bulk crude oil was collected and analyzed to determine dissolved crude oil concentrations and their molecular weight distributions. Dissolved concentrations varied greatly among the test gases, as well as at different pressures for all of the fluids except propane. The ranges of total dissolved hydrocarbons at 10.3, 20.7, and 34.5 MPa were methane (8–67 mg/mL), ethane (40–228 mg/mL), propane (230–278 mg/mL), and CO2 (13–254 mg/mL). The oil solubility in a representative produced gas (69.5/21/9.5 methane/ethane/propane) ranged from 9 to 145 mg/mL. The gases and pressures that mobilized the lowest total hydrocarbon concentrations were also the least effective at mobilizing heavier hydrocarbons. For example, the C20–C36 fraction of the crude oil that was mobilized with each gas exposure at 10.3–34.5 MPa was methane (<1–6%), ethane (12–95%), propane (58–99%), produced gas (<1–33%), and CO2 (<1–40%), indicating concentration of the heavier hydrocarbons in the residual crude oil after exposure to gases (and pressures) that are less effective. Residual crude oil viscosities after gas exposure showed significant increases (with the notable exception of propane at all three pressures), also consistent with each test gas’s ability to dissolve heavier hydrocarbons. Consideration of each gas’s density changes with pressure correlated well with their abilities to dissolve crude oil, and increases in pressure always increased oil solubilities regardless of each gas’s minimum miscibility pressure (MMP) value with the crude oil used for these mobilization experiments. Multiple exposures of a crude oil sample to fresh test gas showed declining dissolved hydrocarbon concentrations demonstrating that crude oil solubilities were not controlled by saturation solubility, but were controlled by equilibrium partitioning of hydrocarbons between the gas-dominated and oil-dominated phases.

Section: Introductionmentioning

confidence: 99%

Comparison of CO₂ and Produced Gas Hydrocarbons to Dissolve and Mobilize Bakken Crude Oil at 10.3, 20.7, and 34.5 MPa and 110 °C

Hawthorne

Miller

2020

“…Morselli et al 10 investigated the effects of SC-CO 2 extraction on the yields of saturates and aromatics in the crude oil at different temperatures, pressures, and concentrations of co-solvent (acetone). Ni et al 11 compared the SC-CO 2 extraction to Soxhlet solvent extraction of petroleum. SC-CO 2 showed a lower extraction yield than dichloromethane (DCM) Soxhlet extraction, while the SC-CO 2 extracts could reserve lighter components because they did not require a desolvent procedure.…”

Section: Introductionmentioning

confidence: 99%

“…The SC-CO 2 extraction on the small saturates and aromatics broke the original equilibrium state and eventually led to the deposition of large compounds. Ni et al 11 reported the molecular compositions in the SC-CO 2 extracts and their saturate, aromatic, resin, and asphaltene (SARA) fractions. However, the molecular selectivity at different extraction conditions was still unclear.…”

Section: Introductionmentioning

confidence: 99%

Molecular Selectivity in Supercritical CO₂ Extraction of a Crude Oil

Cao¹,

Bo²,

Ma³

et al. 2017

Self Cite

Supercritical CO2 flooding has been considered as a promising enhanced oil recovery (EOR) method because it can effectively improve the oil recovery and promote greenhouse gas sequestration. However, the solubility of different petroleum components in supercritical carbon dioxide (SC-CO2) has not been well investigated. This paper presents the molecular selectivity of SC-CO2 extraction on crude oil under different pressures and temperatures. The crude oils were loaded on the surface of kieselguhr and extracted by SC-CO2. The extracts and residues from SC-CO2 extraction were analyzed by gas chromatography–mass spectrometry and Fourier transform ion cyclotron resonance mass spectrometry. Our results showed that the operating pressure (20–30 MPa) affected the extraction yields more than the temperature (50–70 °C). SC-CO2 preferentially extracted small molecules with relatively low aromaticity and polarity. Compound classes containing multiple heteroatoms had lower extraction yields than hydrocarbons. The carbon number distribution ranges of various compound classes in the residues were largely different. Carboxylic acids and phenolic compounds were found to have poor solubility in SC-CO2. The risk of asphaltene precipitation in CO2 EOR is also discussed.

“…A total of 128 scans of FT-ICR data sets were accumulated to enhance the signal-to-noise ratio and dynamic range. Methodologies for FT-ICR MS mass calibration, data acquisition, and processing were described elsewhere. , …”

Section: Methodsmentioning

confidence: 99%

Composition and Transformation of Sulfur-, Oxygen-, and Nitrogen-Containing Compounds in the Hydrotreating Process of a Low-Temperature Coal Tar

Chen

Wang

et al. 2018

Self Cite

A low-temperature coal tar was subject to a three-stage catalytic hydrotreating reactor. The raw coal tar and its hydrotreating products from each reactor section were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The removal efficiencies of sulfur, nitrogen, and oxygen were 99.4%, 88.4%, and 78.1%, respectively. The molecular transformation routes of each heteroatomic species are different. Sulfur species were removed from low double bond equivalence (DBE) values to higher values through the whole hydrotreating process. Furanic compounds and basic nitrogen compounds carried out the saturation of aromatic rings before the hydrogenation of low DBE species. Neutral nitrogen compounds were resistant in the processing and cannot be removed completely in the end of the hydroprocessing. The phenolic compounds were the most resistant to hydrotreating during the whole process. The transformation capabilities of heteroatom compounds in the processing were as follows: phenolic compounds > neutral nitrogen compounds > furanic compounds > basic nitrogen compounds > sulfur compounds.