塔里木盆地塔河油区奥陶系原油中性含氮化合物特征与运移研究

RESEARCHES ON THE CHARACTERISTICS OF THE NEUTRAL NITROGEN COMPOUNDS AND THE OIL MIGRATION IN ORDOVICIAN CRUDE OIL FROM TAHE OIL FIELD,TARIM BASIN

塔河油区具多期成藏的特点,重质油与轻质油并存。重质油中,无论是中性含氮化合物的绝对浓度或是其比值指标都降低,严重影响了原油运移途径的判别。轻质油中,中性含氮化合物指示原油具有自南向北、自东向西的运移特点,其咔唑(CA)绝对浓度由高变低,甲基咔唑系列(MCA)与二甲基咔唑系列(DMCA)比值逐渐增大,苯并咔唑系列的[a]/([a]+[c])比值则随运移距离增加而降低。在塔河3区断裂带附近,咔唑(CA)绝对浓度较高,甲基咔唑系列(MCA)与二甲基咔唑系列(DMCA)比值较低,苯并咔唑系列的[a]/([a]+[c])比值较大,显示断裂沟通了源岩及主力油气输导层,油气运移距离短,晚期油气活跃,油质总体优于塔河4、6区。

In Tahe oil field, the oil accumulation formed in several stages. The heavy oil and the light oil are together in presence in the Ordovician reservoirs. In heavy oil, not only the absolute concentrations but also the ratio indicators of neutral nitrogen compounds are too low to distinguish the oil migration path. The distribution of the neutral nitrogen compounds in the light oil shows that the oil migrates from the south to the north and from the east to the west. In these two orientations, the absolute concentration of carbazole （CA） decreases, the ratio of methycarbazoles （MCA） and the dmethycarbazoles （DMCA） increases, and the ratio of benzo carbazole, [a] / [a] ＋ [c]）, decreases. At the fault belt in the No. 3 Block in Tahe oil field, the absolute concentration of carbazole is high, the ratio of MCA to DMCA is low, and the value of [a] / （ [a] ＋ [c]） is relative high. These features show that it is through the fault that the hydrocarbon migrates from the source rock to the reservoirs. In this way, the oil migration paths are short, and the hydrocarbon can accumulate in the late stages. Therefore, the crude oil is lighter in No. 3 Block than in the blocks of No. 4 and No. 6 in Tahe oil field.