黄骅坳陷二氧化碳气成因类型及富集规律

Genetic Type and Concentration Regularity of Carbon Dioxide Gas in Huangnua Depression

黄骅坳陷二氧化碳气的特征是:层位分布较普遍、丰度和成因类型较多、高纯度气藏分布地域较集中和气藏规模较小。依据R/Ra与δ13CCO2关系图,参考二氧化碳含量及产区地质条件,对黄骅坳陷二氧化碳成因类型进行了区分。通过对二氧化碳含量与碳同位素、氦气含量及其同位素、CO2/3He比率、氩同位素、伴生烷烃气成因分析,认为港151井二氧化碳气藏属幔源成因。根据本区大地构造及构造活动性特征分析,认为岩浆期后的地幔脱气可能是黄骅坳陷幔源二氧化碳气的主要来源方式。对二氧化碳气富集规律的研究发现,沧东断裂是沟通深部幔源流体的重要通道,盆地内二级断层的活动性对二氧化碳富集具有关键的作用,两组区域性深断裂交会处是无机成因二氧化碳富集的最有利场所。

The carbon dioxide gas in Huanghua depression features in more reserving layers, high abundance, multi-genetic types, highly pure reservoirs located in a small areas, and small gas reservoir. According to the relation between R/Ra and δ Cco2, the content of CO2 and geological conditions of gas producing areas, the genetic types of CO2 in Huanghua depression arc classified. CO2 gas reservoir in Gang-151 well is considered to be mantle-derived CO2 based on the analyzing the ratio of the content of CO2 and the carbon isotopes to the content of helium and the helium isotopes, the genesis of the argon isotopes and the associated alkane gas. The author believes that mande degassing after magmatism may be the main source of CO2 in this depression on the basis of analyzing the structure of Huanghua depression and its structural activity features. Based on the study of the concentration regularity of in this depression, it is found that Cangdong fault is the primary pathway connecting deep mantle-derived fluids. The activity of the secondary faults inside basin is vital to the concentration of CO2. The juncture of the two sets of regional deep fractures is favorable for the concentration of inorganic CO2.