中国大陆科学钻探主孔0～2000米流体剖面及流体地球化学研究

0 - 2000m fluid profiles and sources in Chinese Continental Scientific Drilling Project

地下深部流体的来源与演化的研究已成为国际地球化学领域的探索前沿和研究热点之一,中国大陆科学钻探(CCSD)为开展深部流体地球化学研究提供了珍贵的样品,构建了探索地下流体的研究平台。文中给出了中国大陆科学钻探(CCSD)主孔He、Ar、N2、O2、H2、CH4、CO2流体地球化学剖面。CCSD主孔CH4浓度的变化与H2浓度的升降没有显著相关性;CO2浓度的变化与钻井条件下的氧含量无显著相关性;CO2浓度与CH4浓度的关系有三种情况:CO2浓度与CH4浓度不相关、CO2浓度与CH4浓度负相关、或CO2浓度与CH4浓度正相关;氦浓度的增加与CO2和CH4浓度的上升呈现一定的正相关。大气中N2、O2、Ar浓度太高,掩盖了井中N2、O2、Ar气体组分浓度变化,通常情况下N2、O2、Ar浓度变化难以作为深源气体的判据。CCSD流体与KTB流体中氧一氮关系基本一致,氧、氮线性相关(r=O.97),表明这两种气体主要来源于大气。KTB中的CH4与乙烷、N2表现出非常强的线性关系,而在CCSD流体中CH4与乙烷、N2之间不存在线性相关性。两个地区间的流体成因、围岩相互作用机理等方面可能有所不同。在CCSD主孔中,目前已发现存在大量的CO2,及少量CO、CH4、C2H6、C3H8、C4H10和He、N2等气体。已确定300-2000米主孔出现多处来自于地下的气体异常,包括甲烷和C2-C4等烃类气体。

The fluid samples from the Chinese Continental Scientific Drilling ( CCSD) project were analyzed in the on-site laboratory. Mud from the hole was degassed and determined by an on-line procedure. The experiments were conducted on identification of the fluids from the drilling hole studied. The profiles of gases in CCSD were provided and the origins of them discussed. The on-site geochemical measurements indicate there is no significant correlation between CH4 concentration and H2 concentration, so is the correlation between CO2 and O2. There are positive and negative correlations between CO2 and CH4. In some cases, no such correlation can be found. One of the interesting cases is the presence of positive correlation between He concentration and the elevated concentrations of CO2 and CH4. The concentration of N2 is negatively correlated with the concentration of O2, which is similar to the correlation in KTB, but the positive correlation. As the high concentrations of N2, O2, Ar in the air conceal possible change of them from the hole, the gas components are difficult to be used as the criterion of identification of the deep fluids. The rather high concentration of CO2 and the low concentrations of CO, CH4 , C2H6 , C3HS, C4H10 , He and N2 have been found in the hole from 300 to 2000 meters. Some of them have been identified to be from the deep earth, which are primarily CH4, CO2 and He. Where the fluids are identified from the deep earth, crannies, crystal holes, fracture or fault faces can always be visible in the corresponding rock cores. The crannies, crystal holes, fracture or fault faces may be the paths of transference and the spaces of reservation of fluids under the earth and be considered as a necessary condition for keeping and finding fluids.