低成熟油页岩的生排烃作用实验模拟

Simulation of hydrocarbon generation and expulsion of low maturity oil shale

烃源岩的成熟演化特征对评价一个区域的油气产出背景意义重大。笔者选择准噶尔南部低熟油页岩作为试验样品,分别进行无水变温、等温变水及等水变温条件下的烃源岩热模拟实验,并依据油、气、固体残渣的定性定量检测,分析烃类相态与组成变化。得到以下结果:无水变温及等水变温实验中油产率均在300℃时出现最高值,而且在等水变温情况下,200℃时的产油率比不加水情况下明显增大;在等温变水情况下,生油量在加10mL水时最大;干气生成阶段,气态烃主要来自重烃裂解而不是高度演化的干酪根本身,400℃热解之后,剩余生烃率大约为5%左右;饱和烃在低温和极端高温时相对比例高,以正构烷烃为绝对优势组分;芳烃比例变化波动较大,以三环、四环芳烃为主,在400℃时达到最大值,在500℃时跌至最低值;非烃、沥青质相对比例变化与芳烃正好相反。

The study of maturation evolution of source rocks is of great significance in evaluating the regional background of oil and gas generation. Low maturity oil shale of South Junggar was chosen as sample for thermal simulating experiment of source rocks in three different conditions, that is, without water but with variation in temperatures, with various amount of water under the constant temperature, and with constant amount of water under different temperatures. Based on the qualitative and quantitative testing of oil, gas, and solid residue, the changes in the phase state and hydrocarbon compositions were analyzed. The experimental result shows that in the first two kinds of experiments, the ratios of oil generation both reached their peaks at 300 ℃, whereas the latter was higher than the former experiment of the same temperature; in the third experiment, the oil generating reached its peak with 10 mL-water; during the stage of dry gas generation, gaseous hydrocarbon mainly came from heavy hydrocarbon cracking rather than high maturity kerogen itself. After thermal craeking at 400 ℃, the remaining ratio of oil generation decreased to its minimum being 5 % ; the amount of saturated hydrocarbon was high in conditions of low and extreme high temperatures, mainly composed of n-alkanes. The amount of aromatic hydrocarbon, mainly composed of tri-aromatics and tetra-aromatics, was highly variable in different temperatures, and reached its maximum at 400℃ and lowered down to the minimum at 500℃ , whereas the changes in the amount of the non-hydrocarbon and bitumen were contrary to that.