Oil accumulation history in Tadong 2 oil reservoir in Tarim Basin, NW China-A case study of oil stability and cracking
Oil accumulation history in Tadong 2 oil reservoir in Tarim Basin, NW China-A case study of oil stability and cracking
复制标题
DOI：
--
复制
发表时间：
2004
影响因子：
7.5
通讯作者：
Huang Hai-ping
中科院分区：
文献类型：
--
作者：
Huang Hai-ping
塔东2井（TD 2）原油中4-甲基甾烷、甲藻甾烷及其芳香族甲藻甾烷含量较高，与轮南地区稠油及其中、上奥陶统烃源岩不同，与寒武系烃源岩具有明显的亲缘关系，但又有明显的区别。目前寒武系烃源岩成熟度高达2。67%-2. 75% VRE。埋藏史和生烃史分析表明，该套烃源岩的主要液态烃生成时间为中、晚奥陶世，油气生成过程在10 Ma内迅速完成。这些都表明高温作用对油气成藏的影响很大，高温作用导致原油致密化和裂解成气。在泥盆纪以后的地层抬升过程中，TD 2油藏被抬升至地下1730 m，储层温度下降至70℃左右（盐水包裹体均一温度50-90℃）。新形成的裂缝和构造裂缝连通了寒武系裂缝系统中早期聚集的油气，导致油气向上扩散和生物降解。原油中高浓度的25-降藿烷是生物降解作用的一个明显结果，它使原油进一步致密化。TD 2稠油的发现引发了一些新的思考。一个形成于400 Ma以上、经历过200℃以上古温度的油藏能够保存至今，表明原油的稳定性比以往认为的要高得多。
The oil from the Well Tadong 2 ( TD2 ) in the Cambrian reservoir in eastern Tarim Basin contains high concentration of 4-methyl steranes, dinosteranes and their aromatic dinosteroids, which is different from heavy oils discovered in the Lunnan area and their Middle-Upper Ordovician source rocks, suggesting a clear affinity with the Cambrian source rock extracts but distinctly. Present maturity of the Cambrian source rocks is as high as 2. 67%-2. 75% VRE. Burial history and hydrocarbon generation history analysis suggest that major liquid hydrocarbon generation time from this source rock suite was in the Middle and Late Ordovician and petroleum generation process was rapidly completed within 10 Ma. All these indicate that the oil accumulation has been severely affected by high temperature processes, which caused oil densification and cracking to gas. During subsequent stratigraphic elevation after the Devonian, TD2 oil pool was uplifted to 1730m undersurface and reservoir temperature dropped to about 70℃( brine inclusion homogenization temperature of 50-90℃). Newly formed fractures and tectonic fissures linked up early accumulated oil and gas in the Cambrian fissure system, leading to oil and gas diffusion upward and biodegradation. High concentration of 25-norhopanes occurrence in oil is one obvious result of biodegradation, which causes further oil densification. Discovery of TD2 heavy oil inspire some new considerations. An oil pool formed more than 400Ma ago, which has experienced paleotemperature of higher than 200℃, can be preserved till present, indicating much higher oil stability than previously believed.