榆林页岩生物模拟产气条件优化和产气机理

Optimization of simulated biogenic gas production conditions and study of gas production mechanism of shale

摘要:

目的 研究页岩生物产气的影响因素和产气机理。方法 以榆林页岩为研究对象，利用实验室前期富集的产甲烷微生物作为功能菌群，通过正交试验优化页岩的生物产气条件。采用气相色谱(gas chromatography, GC)、X射线衍射(X-ray diffraction, XRD)、傅里叶变换红外光谱(Fourier-transform infrared spectroscopy, FT-IR)、拉曼光谱(Raman spectroscopy, Ram)以及核磁共振波谱(nuclear magnetic resonance spectroscopy, NMR)分析了页岩的生物模拟产气特征，并对产气前后页岩的理化性质变化进行了分析。结果 页岩最优产气条件为：接种量15%、页岩粒度小于0.125 mm、培养温度35 ℃，50 d累计净产甲烷量为81.22 μmol/g页岩。产气前后工业和元素分析结果表明，产甲烷菌通过消耗页岩中的有机组分来产气。XRD分析结果显示，页岩中无机矿物组分也参与了厌氧降解产气过程。FT-IR与拉曼光谱显示，页岩有机物多为长链脂肪烃。产气时，部分化合物的羰基、醚键反应生成含羧基的中间产物。产气后，页岩样品的D、G峰不明显，表明干酪根的石墨化程度与成熟度增加。NMR结果表明，脂肪醇或脂肪胺在产气过程中被微生物利用。结论 榆林页岩中的有机组分可以被微生物利用产生甲烷，同时无机矿物组分也被消耗。产气过程中，有机组分的化学结构发生变化，生成较小的化合物。

Abstract:

Objective To study the influencing factors and mechanism of biogenic gas production in shale.Methods The shale in Yulin was chosen as the object of this study, and methanogens specifically enriched by our research team in the preliminary stage were used as functional microbiota. An orthogonal design was adopted to optimize the biogenic gas production conditions. The simulated biogenic gas production characteristics and changes in physical and chemical properties of the shale before and after gas production were comprehensively analyzed by gas chromatography (GC), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy (Ram), and nuclear magnetic resonance spectroscopy (NMR).Results The optimal conditions for gas production from shale were as follows: 15% inoculum, a shale particle size of less than 0.125 mm, and an incubation temperature of 35 ℃, under which a cumulative methane yield of 81.22 μmol/g shale was achieved within 50 days. Industrial and elemental analyses conducted before and after gas production revealed that methanogens consumed the organic components of shale to produce methane. XRD results indicated that the inorganic mineral components in shale also contributed to the anaerobic degradation process associated with gas production. FT-IR and Ram results showed that the organic matter in shale was mostly long-chain aliphatic hydrocarbons. During gas production, the carbonyl and ether bonds in some compounds reacted to form intermediate metabolites containing carboxyl groups. After gas production, the D and G peaks in the shale samples were not obvious, indicating that the graphitization degree and maturity of kerogen in the shale increased. In addition, NMR results confirmed that fatty alcohols or fatty amines were utilized by microorganisms in gas production.Conclusion Microorganisms can utilize the organic components of the shale to produce gas, while also consuming the inorganic mineral components. This leads to chemical structure organic components, leading to formation of smaller compounds after gas production.