塔里木盆地轮南下奥陶统沥青的发现及其意义

The Discovery of Lower Ordovician Bitumen in Lunnan Low Uplift of Tarim Basin and Its Geologic Significance.

在塔里木盆地轮南低隆起某些井的下奥陶统碳酸盐岩储集层中发现有沥青,它主要充填在碳酸盐岩矿物晶间隙中,含量1%～3%,沥青反射率1.05%～1.10%.结合该区埋藏史及古地温史推算出原油沥青化形成时间发生在早海西运动期,结合油气地质背景,推断油气藏形成于晚志留世-早泥盆世时期。因此,这套储集层沥青是早古生代油气藏在早海西运动期经抬升、剥蚀、风化、氧化作用而发生沥青化,后经热变质作用而形成,它与塔北、塔中下志留统沥青砂岩属同时代产物,下奥陶统储集层沥青的发现扩大了早古生代古油气藏存在范围。对于认识轮南地区复杂的油气成因提供了新的证据。

Reservoir bitumen have been found in Lower Ordovician carbonates from some wells in Lunnan low up-lift of Tarim basin.It occurred in the pores among mineral grams,with a content of1%～3%.The measured reflectance of the bitumen ranges from1.05%to1.10%.With the combination of the burial history and palaeogeothermal evolution in this area,it is guessed that the bitumenization of the related crude oil took place at Early Hercynian,the oil reservoir was formed during Late Devonian to Early Carboniferous according to its petroleum geologic background.It is concluded that this set of reservoir bitumen was formed by the thermal maturation of bitumenized crude caused by denudation,weathering and oxidation owing to uplifting of this area during this period.The reservoir bitumen from the Lunnan low uplift has a similar origin with the Lower Silurian bitumen sandstones in Tabei uplift and Tazhong area.The discovery of the reservoir bitumen of Early Ordovician has extended the distribution of palaeo-oil and gas reservoirs of Early Paleo-zoic,and provided a new evidence for recognizing the complicated origin of oil and gas reservoirs in Lunnan area.