Kinetics and model of gas generation of source rocks in the deepwater area, Qiongdongnan Basin

In order to investigate the hydrocarbon generation process and gas potentials of source rocks in deepwater area of the Qiongdongnan Basin, kinetic parameters of gas generation （activation energy distribution and frequency factor） of the Yacheng Formation source rocks （coal and neritic mudstones） was determined by thermal simulation experiments in the closed system and the specific KINETICS Software. The results show that the activation energy （Ea） distribution of C1–C5 generation ranges from 50 to 74 kcal/mol with a frequency factor of 2.4×1015 s–1 for the neritic mudstone and the Ea distribution of C1–C5 generation ranges from 49 to 73 kcal/mol with a frequency factor of 8.92×1013 s–1 for the coal. On the basis of these kinetic parameters and combined with the data of sedimentary burial and paleothermal histories, the gas generation model of the Yacheng Formation source rocks closer to geological condition was worked out, indicating its main gas generation stage at Ro （vitrinite reflectance） of 1.25%–2.8%. Meanwhile, the gas generation process of the source rocks of different structural locations （central part, southern slope and south low uplift） in the Lingshui Sag was simulated. Among them, the gas generation of the Yacheng Formation source rocks in the central part and the southern slope of the sag entered the main gas window at 10 and 5 Ma respectively and the peak gas generation in the southern slope occurred at 3 Ma. The very late peak gas generation and the relatively large gas potential indices （GPI：20×10^8–60×10^8 m^3/km^2） would provide favorable conditions for the accumulation of large natural gas reserves in the deepwater area.

Improvement and optimization for the first order decay model parameters at typical municipal solid waste landfills in China

Landfill gas(LFG)generation is commonly modeled by using a first-order model.Methane generation potential(L0)and methane generation rate constant(k)are two key parameters in the first-order model.Coal-ash based default values or roughly analyzed values often used in China may not be appropriate for accurately estimating of LFG generation.In this study,seven groups of parameters were evaluated by comparing the theoretical predictions with real measurements from five Chinese landfills.The optimal approach for calculating L0 is the use of site-specific waste composition and the default values of degradable organic carbon(DOC)reported by the Chinese industry standard(CJJ133-2009),and the matching k can be adjusted by fitting and regression.The optimized average values were L0=67 m3 Mg−1,k=0.06 per year for landfills in Beijing and Zhengzhou in cold–dry regions,L0=69 m3 Mg−1,k=0.16 per year for landfill in Shanghai in cold–wet region,and L0=64 m3 Mg−1,k=0.21 per year for landfills in Guangzhou and Shenzhen in hot–wet regions.Monte Carlo analysis showed that the uncertainty of LFG generation at closure year varied in−22.5%to 20.5%,−17.1%to 17.1%and−28.2%to 34.7%for three climatic regions,respectively.The k value is the key influencing factor,with a 95.6%contribution ratio in the hot–wet region landfill.The results provide references for future better waste management.