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源岩条件是低熟气形成的重要因素,准噶尔盆地东部地区侏罗系烃源岩分布范围广,厚度大,有机质为腐殖型烃源岩,RO值绝大多数都小于1.0%,具备有利于低熟气形成的源岩基础。通过地球化学分析,发现侏罗系烃源岩埋深为2 200~4 500m,RO值变化幅度很小,基本都在0.5%~0.8%之间。同一口井和不同区域的侏罗系烃源岩,都表现出随着埋深增加RO值变化范围较小,还未达到常规意义上的生气高峰阶段,并且在此演化阶段保持了很长的地质历史时间。针对实际地质情况,开展温度和时间条件下低熟气形成的热解生烃模拟实验研究,实验结果表明,330℃和350℃时,烷烃气产量较低,随着时间增加(3~30d)产气量变化很小,加热温度370℃和390℃,随着时间增长,气体增加量在14~21d达到最高峰,之后到30d呈缓慢增加或基本保持不变,相对同一温度3d时产气量增加2~2.5倍,即RO值增高0.2%~0.3%时,烷烃气生成量有显著增加,说明时间效应对低熟气形成有重要作用,并且受温度条件的限制。
The source rock conditions are important factors for the formation of low-grade gas. The Jurassic source rocks in the eastern part of the Junggar Basin are characterized by a wide range of distributions, thicknesses and organic matter as humic hydrocarbon source rocks. Most of the RO values are less than 1.0% Conducive to the formation of low-grade gas source rock foundation. Through geochemical analysis, it is found that the buried depth of Jurassic source rocks ranges from 2 200 m to 4 500 m, and the variation range of RO value is very small, ranging from 0.5% to 0.8%. The same well and Jurassic source rocks in different regions all show that the range of RO varies little with the increase of burial depth and has not reached the peak of gas generation in the conventional sense and remains very long in this evolutionary stage Geological history time. According to the actual geological conditions, the pyrolysis hydrocarbon generation simulation experiment of low-mature gas under the condition of temperature and time is carried out. The experimental results show that the yield of alkane gas is low at 330 ℃ and 350 ℃, and increases with time (3 ~ 30d) The change of gas production is very small. The heating temperature is 370 ℃ and 390 ℃. With the increase of time, the amount of gas increases reaches its peak at 14 ~ 21d, then slowly increases or remains unchanged at 30d, and the gas production increases at 3d 2 ~ 2.5 times, that is, when the RO value increases by 0.2% ~ 0.3%, the amount of alkane gas production increases significantly, indicating that time effect plays an important role in the formation of low-grade gas and is limited by temperature conditions.