利用生烃动力学方法确定海相有机质的主生气期及其初步应用

Kinetic method for determining the main gas-generation period of marine organic matters and its application

利用已获得的国内外典型海相有机质(原油与干酪根)的生气动力学参数,采用生烃动力学方法,计算地质历史中天然气的产率和产气速率,利用EasyRo方法计算成熟度。经过二者的耦合,确定Ⅰ型干酪根主生气期的Ro值为1.4%～2.4%,Ⅱ型干酪根主生气期的Ro值为1.5%～3.0%,原油裂解气主生气期的Ro值为1.6%～3.2%。以塔里木盆地塔西南地区为例,初步探讨系统的开放度对主生气期的影响及天然气“死亡线”的问题,研究结果,模拟系统开放度对主生气期的动力学参数计算有一定影响,开放系统Ⅱ型干酪根主生气期的Ro值为1.4%～3.1%,天然气主生气期比封闭系统要早。根据研究结果,初步确定海相有机质天然气“死亡线”为Ⅰ型干酪根Ro值约为3.5%,Ⅱ型干酪根Ro值为4.4%～4.5%,海相原油Ro值约为4.6%。

The natural gas fields and generation rates in the geological history are calculated by use of kinetic methods and the acquired kinetic parameters of typical marine organic matters （oil and kerogen） of China and other areas in the world, and the maturity is calculated by Easy Ro method. The coupling of the two results shows that Rois 1. 4%-2. 4% during the main gas- generation period of type I kerogen, R0, is 1. 5 %-3. 0% during the main gas-generation period of type Ⅱ kerogen, and Ro is 1.6%-3. 2% during the main gas-generation period of oil cracking gas. Taking the southwestern area of Tarim Basin as an example,the influences of the openness of simulation system on the main gas-generation period, and the ＂dead line＂ of natural gas generation are also discussed. The results indicate that the openness of simulation system has a definite influence on the kenetic parameters calculation of the main gas-generation period. Ro is 1.4%-3. 1% during the main gas-generation period of type Ⅱ kerogen in the open system, which is earlier than that in the closed system. The ＂dead line＂ of natural gas generation is determined as R0 is 3.5%o for type I kerogen, Ro is 4.4%-4.5% for type Ⅱ kerogen and R0 is 4.6% for marine oil.