深层海相天然气成因与塔里木盆地古生界油裂解气资源

Origin of Deep Marine Gas and Oil Cracking Gas Potential of Paleozoic Source Rocks in Tarim Basin

我国海相地层时代老,演化程度偏高,高过成熟干酪根热降解生气潜力有限。针对深层海相天然气成因,提出了有机质接力成气机理,具体包含3方面涵义,生气母质的转换、生气时机的接替和气源灶的变迁。源内分散液态烃型气源灶继承了原生气源灶的特征,而源外分散和聚集型液态烃气源灶与原生气源灶相比,则发生了空间上的迁移。上述三部分液态烃在高—过成熟阶段均可裂解成气,但后者通常埋藏较前者浅,裂解成气的时机晚于前者,有利于晚期成藏。通过不同有机质丰度、不同岩性烃源岩生排烃模拟实验研究,建立了不同有机质丰度烃源岩的排油率图版,为源内、源外分散液态烃分配比例和数量研究提供了依据;从3个方面,生烃潜力评价指标S1、热成因沥青和储层的荧光特征,论证了塔里木盆地古生界地层中分散可溶有机质的数量、分布、裂解程度,肯定了塔里木盆地古生界海相烃源岩有机质接力成气的现实性;并用正演研究思路计算了塔里木盆地中下寒武统分散可溶有机质裂解成气数量。有机质接力成气机理的应用大大提高了塔里木盆地台盆区古生界找气的潜力和希望。

The marine strata in China is of old age and in high evolution period, and the potential of gas generated from high-overmature source rocks is limited, but the gas exploration of this marine strata in Tarim, Siehuan and Ordos basin has greatly effective with large oil and gas fields constantly discovered. This paper brings up the successive gas generation machanism for the origin of deep marine gas, including three meanings of transformation of gas generation matter, replacement of gas generation time, and change of gas source kitchen. The gas source kitchen of dispersive liquid hydrocarbon inside of source rocks inherits the characteristics of original gas source kitchen, but the gas source kitchen of dispersive ＆ concentrated liquid hydrocarbon outside of source rocks has occurred the spacial change comparing with original gas source kitchen. The above three liquid hydrocarbon can be cracked into gas at high-over mature stage, but the latter is embeded flatter and its time of cracking and gas generation is later than the former, which makes for the late gas accumulations. This paper creates expulsion oil rate plates of different organic matter abundance through simulation experiments of hydrocarbon generation and expulsion of different organic matter abundance and different lithology source rocks, providing the basis for the reasearch of allocation proportion and quantity of dispersive liquid hydrocarbon inside ＆ outside of source rocks. This paper demonstrates the quantity, distribution and cracking degree of dispersive soluble organic materials of Palaeozoic strata in Tarim basin from the evaluating indicator S1 of hydrocarbon generating potential, heat-origin asphalt and the fluorescence characteristic of reserviors, and makes sure of the reality of successive gas generation of organic matter of Palaeozoic marine source rocks in Tarim basin, and also calculates the cracking gas quantity of dispersive soluble organic matter in middle and lower Cambrian of Tarim basin. The application of successive gas generation mechanism of organic matter can greatly increase the gas exploration potential and hopeness of palaeozoic strata in Tarim basin.