The Carbon Isotopic Equilibrium Method of Evaluating the Biogasgenerated Quantity and the Generation Period: its application

Key words: 
• biogas

Abstract: The biogas generation period plays a very important role in its accumulation. But now there is not a creditable and effective method to appraise it. Aiming at this difficult problem, and considering it′s a carbon isotope balance process, regardless of the formation mechanisms of biogenic gas. The 13C and 12C amount of initial organic matter before generation and that of residual organic matter and other productions after generation should keep conservation. Carbon isotopic equilibrium method (model) is explored and established to assess biogenic gas in this paper, which is demarcated and applied according to the abundant analyzed data in Songliao basin. Results show that the accumulatively generated biogenic methane ofⅠ, Ⅱ and Ⅲ types organic matters are 193.94 ml/g, 175.64 ml/g and 161.71 ml/g, respectively. The biogasgenerated quantity of source rock in the research area is about 385.4 ×1012 m3. The major period of biogenic gas generation occurs before the end of Nenjiang period. The possible biogas resource is between 11.40×1011m3 and 24.8×1011m3.