Interactions between injected CO2 and shale formation during the process of CO2 sequestration with enhancing shale gas recovery (CS-EGR) may alter the physical and chemical properties of the rock, affecting the efficiency of CO2 storage as well as CH4 production. To better understand these interaction-induced changes in shale properties, two shale samples selected from a marine Longmaxi formation and terrestrial Chang-7 member of the Yanchang formation were first reacted with supercritical CO2 (scCO2) in a laboratory batch reactor at 80 °C and 15 MPa with different time intervals, and then characterization methods were designed to access the geochemical changes including optical microscope (OM), X-ray diffraction (XRD), element analysis (EA), low-pressure gas adsorption (LPGA), and Fourier transform infrared spectroscopy (FTIR). The results indicate that the nanopore structure system of the two shale samples was significantly changed after scCO2–shale interaction due to the scCO2-induced extraction of hydrocarbons, chemical reactions in minerals, and the swelling effect in clay minerals as well as organic matter. However, after exposure to scCO2, the variation trend of pore structure parameters between the marine Longmaxi and terrestrial Chang-7 sample was quite different, which was related to the huge discrepancies in terms of mineralogy and geochemical properties between them. For marine Longmaxi sample, the pore surface area and pore volume obviously decreased after a relatively short period of scCO2 treatment, whereas an opposite trend was observed in a terrestrial Chang-7 sample after long-term scCO2 treatment. In addition, an obvious decrease in fractal dimensions for marine Longmaxi sample was also observed after scCO2 exposure, reflecting the degree of pore surface roughness, and pore structure complexity were reduced, whereas the terrestrial Chang-7 sample exhibited an opposite trend. The results contribute to the understanding of the potential factors for the pore-structure evolution during long-term CO2 storage and the possible effect on the CS-EGR process.

No abstract

No abstract

No abstract

No abstract

The influences of structure parameters of polyetheramines as clay‐swelling inhibitors in water‐based drilling fluids on the application performances were studied. Interactions of polyetheramines with clays were investigated through elemental analysis (EA), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). The results showed that lower molecular weight, hydrophobic oxypropylene segment, and plentiful amino group of polyetheramines favored improvement of inhibitive properties, enhancement of adsorption abilities, and expelling interlayer bound waters of clays (as confirmed by cutting rolling test, bentonite inhibition test, EA, XRD, and TGA studies). Simultaneously, the polyetheramines did not produce adverse effect to filtration control of the drilling fluids. In addition, XRD patterns revealed that these polyetheramines could intercalate into interlayer spaces of clays and display a monolayer arrangement. The corresponding basal spacing of clays was correlated only with molecular weight of polyetheramines. The dense loading of polyetheramines in the interlayer of clays was beneficial in improving inhibitive properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

No abstract

No abstract