The decrease in fracturing fluid flowback rate in the process of hydraulic fracturing and the improvement of initial gas production rate after well shut-in for a period of time were investigated using weight and nuclear magnetic resonance (NMR) T2 spectra of dried shale cores and shale cores in the "as received" state after spontaneous oil and water imbibition. Experimental results indicated that the rate and weight during spontaneous water imbibition were much higher than those of spontaneous oil imbibition, contrary to capillary-driven imbibition models. Therefore, spontaneous water imbibition was related to both capillary pressure and additional hydration stress generated by clay swelling. NMR T2 spectra of different imbibition fluids (oil and water) demonstrated that signals between 0.01 ms and 1 ms were total responses of pore fluids and irreducible water, and excess imbibed water was mainly present as irreducible water in shale. Excess imbibed water flowed into the matrix and reacted with minerals to generate many micro-fractures which may connect isolated organic pores to mitigate water blocking.
Tribological properties of tetrahedral diamond-like carbon (ta-C DLC) coating were investigated to assess the effects of the counter surfaces under the boundary condition in the presence of biodegradable oil. The tribological tests were performed using steel/steel, steel/DLC and DLC/DLC contacts, and found that the coefficient of friction was 0.062, 0.059 and 0.048, and the wear loss was 5.57 × 10−4, 9.81 × 10−4 and 6.02 × 10−4 mm3, respectively. DLC/DLC contacts showed the lowest friction coefficient and steel/steel contacts showed the lowest wear. The high wear of steel/DLC compared to the other two contacts might be due to the high affinity between iron and carbon. The high content of oleic acid may maintain the low friction in self-mated ta-C DLC contacts and tribochemical wear was prevented by nano-scale graphitization. Therefore, material combinations are important for tribological properties and canola oil is an effective lubricant for contacts coated with ta-C DLC films.
Recently, the use of carbonated water injection has been considered for enhanced oil recovery (EOR), and it provides a great potential for reducing CO2 emissions. Both laboratory and field applications on EOR using carbonated water injection have been reported, and various mechanisms have been suggested for oil recovery. However, the interaction between the carbonated water and rock and its influence on EOR remains unclear. Therefore, the objective of this study was to evaluate the carbonated water-rock interactions through core flooding experiments and using an advective-reactive transport model. The experimental results pertaining to permeability of the core sample, and effluent pH value and calcium concentration were presented as a function of the amount of injectant. The effect of oil present in the core sample, ageing, and kind of injectant, on the interaction and oil recovery were analyzed. The results showed that calcite in the carbonate rock dissolved owing to its interaction with carbonated water; this increased the porosity, and thus, the permeability of the rock, and effluent pH value and calcium concentration also increased. The simulation results for effluent calcium concentration and pH agree well with experimental data, indicating the applicability of the model for further understanding the interactions in the carbonate reservoir.
Toluene hydrogenation reaction for methylcyclohexane (MCH) synthesis via Pt-loaded Al2O3 and TiO2 (Pt/Al2O3 and Pt/TiO2) catalysts were investigated in a fixed bed reactor at 398-473 K and ambient pressure. Partial pressures of toluene, hydrogen and MCH were 60 to 91, 9 to 23, and 9 to 17 kPa, respectively. Pt-loaded catalysts showed higher activities in the order of Pt/Al2O3>Pt/TiO2 (anatase-rutile mixture, AR) = Pt/TiO2 (anatase, A)>Pt/TiO2 (rutile, R) above 423 K, whereas Pt/TiO2 (anatase) showed remarkably higher activities at 393 K. To estimate the effects of support species, kinetic analysis using rate-based model was conducted. The correlation between adsorption behavior and catalytic activities was investigated using a Langmuir-Hinshelwood model. The kinetic constants for each catalyst were almost same. It was considered that only kinetic constants cannot explain the catalytic activities. Coverage of toluene and MCH were independent of the reaction rates, however the reaction rates increased as hydrogen coverage increased for all catalysts.
Organosolv treatment of Japanese cedar wood with silica–alumina catalyst in a water/1-butanol mixture and conversion of the recovered lignin fractions into phenolic compounds by catalytic cracking over an iron oxide catalyst were investigated. Organosolv for separation of lignin fractions from solid cellulose was carried out in an autoclave reactor at 423-523 K with/without silica–alumina catalyst. The average molecular weights of the lignin fractions obtained with/without the catalyst were 2060 and 2501, respectively, indicating that the catalyst was effective for depolymerization of lignin. Cellulose was significantly decomposed over 503 K with the catalyst, increasing the difficulty of separating lignin and cellulose. Therefore, the optimum treatment temperature was determined around 473 K to separate lignin fractions from solid cellulose. Moreover, the lignin fractions were extracted predominantly into the 1-butanol phase based on analyses of the molecular weight distributions and pyrolysis-GC-MS of the liquid products. Next, catalytic cracking of the obtained 1-butanol phase, which was rich in the lignin fractions, was performed over an iron oxide catalyst using a high-pressure fixed-bed flow reactor at 673 K. Consequently, degradation of the lignin was observed and the carbon yield of phenolic compounds after the reaction improved to 9.6 C-mol% based on the lignin fractions.
A modified Petlyuk process with a reboiler at the bottom of the prefractionator eliminates the need for a vapor interconnection between the main column and the prefractionator and thus improves operability. However, the effect of this configuration on the operability has not been clarified. The present study examined the operability of a modified Petlyuk process with a reboiler at the bottom of the prefractionator for the separation of benzene, toluene, and p-xylene ternary mixture. The effect of the bottom-out to feed ratio of the prefractionator on the separation characteristics of the modified Petlyuk process was evaluated for different feed flow rates. The operation range of the modified Petlyuk process was clarified by presenting the conditions satisfying the product specifications as a contour plot for the feed flow rate and the bottom-out to feed ratio of the prefractionator. The operability of the modified Petlyuk process was compared with that of the original Petlyuk process. Based on the obtained results, a dynamic simulation verified that the product specifications can be satisfied simply by adjusting the bottom-out to feed ratio of the prefractionator for a disturbance of the feed flow rate.