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摘要
Based on the pyrolysis products for the Jurassic low-mature coal under programmed temperature, and chemical and carbon isotopic compositions of natural gas from the Kuqa Depression, the genetic origin of natural gas was determined, and then a gas filling model was established, in combination with the geological background of the Kuqa Depression. The active energy of CH(4), C(2)H(6) and C(3)H(8) was gotten after the data of pyrolysis gas products under different heating rates (2 degrees C/h and 20 degrees C/h) were fitted by the Gas Oil Ratio (GOR) Isotope Model soft. When the frequency factor (At) was chosen as 1x10(14), the active energy of CH(4), C(2)H(6) and C(3)H(8) was 58 kcal/mol, 57 kcal/mol and 54 kcal/mol, respectively. The distributive ranges of the delta(13)C(1), delta(13)C(2) and delta(13)C(3) values for the pyrolysis gas products are -35.9 parts per thousand to -30.7 parts per thousand, -26.2 parts per thousand to -21.3 parts per thousand and -26.4 parts per thousand to -22.7 parts per thousand, respectively. All of the natural gases from the Kuqa Depression are dominated by hydrocarbon gases, with the high gas dryness (C(1)/C(1-4)) at the middle and northern parts of the depression and the low values at both east and west sides and the southern part. The carbon isotopes of methane and its homologs as a typical coal-type gas are enriched in (13)C, and the distributive range of the delta(13)C(1), delta(13)C(2) and delta(13)C(3) value is 32 parts per thousand to -38 parts per thousand, -22 parts per thousand to -24 parts per thousand and -20 parts per thousand to -22 parts per thousand, respectively, with the carbon isotopes of gaseous alkanes being less negative with the carbon number. With the ethane being enriched in (13)C the increasing tendency of the geological reserve of natural gas in the Kuqa Depression is observed. This observed change is consistent with the results of pyrolysate gas yield of coal as a potential gas source in the Kuqa Depression, suggesting natural gas was thermally derived from the humic organic matters and the carbon isotopes of gaseous alkanes would coarsely predict the geological reserve of gas in the Kuqa Depression. Through the simulation of kinetic processes of gas generation for the Jurassic coal in the Kuqa Depression, the gas in the Kela 2 gas field would get the threshold of gas expulsion after 27 Ma, be expelled out of source rocks as "pulse action", and then filled in the gas reservoir. The peak gas-filling history took place during the past 2 Ma.
- 出版日期2011
- 单位中国石油天然气股份有限公司勘探开发研究院
