摘要 :
Casing deformation has been found to be a very significant issue in the development process of shale gas in China, while the coupling effect of transient temperature-pressure has a significant impact on casing stress, and worthy o...
展开
Casing deformation has been found to be a very significant issue in the development process of shale gas in China, while the coupling effect of transient temperature-pressure has a significant impact on casing stress, and worthy of study. This paper presented a new numerical investigation to understand the coupling effect of transient temperature-pressure on casing string during volume fracturing. A wellbore temperature model was established to obtain the required input parameters of dynamic temperature boundary. The numerical model considers the coupling effect of transient temperature-pressure and the various cement sheath shapes. The results showed that the temperature of casing changed drastically during fracturing. Under the influence of the coupling effect of transient temperature-pressure, (a) when the cement sheath shape was integrity, the casing stress increased greatly and showed dynamic changes: first increased and then decreased, (b) when there was deficiency in cement sheath, with the increase of the eccentric distance or deficiency angle, the casing stress increased aggravating risk of casing deformation. Rotating the casing string during the cementing process to avoid the deficiency in cement sheath or using warm fracturing fluids to minimize the influence of the coupling effect of transient temperature-pressure are possible innovative strategies to solve these difficult problems.
收起
摘要 :
Experimental and numerical studies are performed on autoignition and extinction of non-premixed n-dodecane spray cool flames. A novel phenomenon of repetitive autoignition-extinction instability of near-limit non-premixed spray co...
展开
Experimental and numerical studies are performed on autoignition and extinction of non-premixed n-dodecane spray cool flames. A novel phenomenon of repetitive autoignition-extinction instability of near-limit non-premixed spray cool flames is observed and examined. The repeated autoignition and extinction cycles are mostly the results of the competition between timescales of fuel spray vaporization and low-temperature oxidation, where the dynamics of large droplets in poly disperse spray play an important role. It is also found that with the increase of the oxygen mole fraction or the oxidizer temperature, the spray cool flame stabilization time increases, and the cycles of autoignition and extinction become less frequent. Over a critical oxidizer temperature and oxygen mole fraction, the repetitive autoignition and extinction instability disappears, and a stable spray non-premixed cool flame can be observed. A one-dimensional two-phase model with detailed chemistry is employed to reveal the spray flame structure and dynamics. It is shown that the large droplets can penetrate the flame front and result in the autoignition-extinction instability. The experimental evidence and numerical results provide the insights of this novel phenomenon of repetitive autoignition-extinction instability of near-limit non-premixed spray cool flames. The results will contribute to the development of advanced low-temperature combustion engines and spray combustion models.
收起
摘要 :
The growing demand of efficient and clean propulsion systems has sparked an interest in understanding the low temperature combustion of alternative fuels under high pressure conditions. Diethyl ether (DEE) is a potential alternati...
展开
The growing demand of efficient and clean propulsion systems has sparked an interest in understanding the low temperature combustion of alternative fuels under high pressure conditions. Diethyl ether (DEE) is a potential alternative biofuel, for being used in blend with conventional fuels in internal combustion engines. DEE oxidations are studied at 10 and 100 atm, over a temperature range of 400-900 K, at fuel lean, stoichiometric, and rich conditions by using a supercritical pressure jet-stirred reactor (SP-JSR). Experimental data shows that DEE is very reactive and exhibits an unusual oxidation behavior with two negative temperature coefficient (NTC) zones. Furthermore, a weaker NTC behavior is observed at 100 atm and the intermediate temperature oxidation is shifted to lower temperature at 100 atm. The existing DEE model in literature well-predicts the experimental data at low temperature; however, it underpredicts the fuel consumptions at intermediate temperature. The H_2/O_2 subset in the existing DEE model is updated in this study based on the Princeton updated HP-Mech. The updated model improves the overall predictability, especially at intermediate temperature.
收起
摘要 :
Major ion chemistry, δ~(11)B, ~(87)Sr/~(86)Sr, δD and δ~(18)O of brines together with clay mineral XRD were analyzed from the Carboniferous, Ordovician and Cambrian basinal brines in the Bachu Uplift, Tarim Basin, NW China. The...
展开
Major ion chemistry, δ~(11)B, ~(87)Sr/~(86)Sr, δD and δ~(18)O of brines together with clay mineral XRD were analyzed from the Carboniferous, Ordovician and Cambrian basinal brines in the Bachu Uplift, Tarim Basin, NW China. The brines are thought to originate from seawater evaporation and have subsequently mixed with meteoric water. The brines show B, Li and Sr enrichment in the Carboniferous and Ordovician and K enrichment in part of the Ordovician relative to seawater, and have δ~(11)B from +19.7 per thousand to +32.2per thousand. With increasing depth, B concentrations increase, δ~(11)B values decrease and illite percentages increase among clay minerals, thus B with low δ~(11)B values is interpreted to have been added from thermal degradation of kerogen (Williams et al. 2001). However, those most K-enriched brines have the highest B and Li and lowest δ~(11)B, suggesting that the additional B, Li and K may have the same source, for which the basalts in the Cambrian and Lower Ordovician cannot be ruled out.
收起
摘要 :
Major ion chemistry, δ~(11)B, ~(87)Sr/~(86)Sr, δD and δ~(18)O of brines together with clay mineral XRD were analyzed from the Carboniferous, Ordovician and Cambrian basinal brines in the Bachu Uplift, Tarim Basin, NW China. The...
展开
Major ion chemistry, δ~(11)B, ~(87)Sr/~(86)Sr, δD and δ~(18)O of brines together with clay mineral XRD were analyzed from the Carboniferous, Ordovician and Cambrian basinal brines in the Bachu Uplift, Tarim Basin, NW China. The brines are thought to originate from seawater evaporation and have subsequently mixed with meteoric water. The brines show B, Li and Sr enrichment in the Carboniferous and Ordovician and K enrichment in part of the Ordovician relative to seawater, and have δ~(11)B from +19.7 per thousand to +32.2per thousand. With increasing depth, B concentrations increase, δ~(11)B values decrease and illite percentages increase among clay minerals, thus B with low δ~(11)B values is interpreted to have been added from thermal degradation of kerogen (Williams et al. 2001). However, those most K-enriched brines have the highest B and Li and lowest δ~(11)B, suggesting that the additional B, Li and K may have the same source, for which the basalts in the Cambrian and Lower Ordovician cannot be ruled out.
收起
原文获取