松辽盆地长岭断陷龙凤山地区油气分布有序性及其主控因素

Orderliness of hydrocarbon distribution in the Longfengshan area of the Changling fault depression, Songliao Basin, and its main controlling factors

对于松辽盆地油气分布有序性的研究较为薄弱,其主控因素尚不明确,制约了该区的油气勘探进程。为此,以该盆地油气勘探新区——长岭断陷龙凤山地区为例,从油气藏类型、储量丰度、油气相态等方面刻画了该区油气分布的有序性,结合油气成藏条件划分出S2、S203和S201等3个油气运聚单元,并利用层次分析法对不同成藏要素的配置关系进行定量评价,明确了油气分布有序性的主控因素。研究结果表明:(1)自北部洼陷带向西部构造带,该区油气分布在相态上体现为气藏—油气藏—油藏的有序变化,油气藏类型上则表现为岩性油气藏、构造—岩性油气藏、岩性—构造油气藏、构造油气藏的渐变特征,油气富集程度上呈现出储量及其丰度逐渐增加的趋势;(2)该区油气分布有序性受控于3种因素,断—源时空配置的有效性控制了油气相态分布的有序性,不同运聚单元边界条件的差异性控制了油气藏类型分布的有序性,断—源—砂—盖配置的差异性则控制了油气富集程度的有序性。结论认为,S201运聚单元的油气成藏条件最为优越,源—断—砂—盖配置最好,勘探潜力最大,可作为下一步油气勘探的重点区块。

The orderliness of hydrocarbon distribution in the Songliao Basin has benn rarely studied and its main controlling factors have not defined yet, which impedes the oil and gas exploration in this area to certain extent. In this paper, the Longfengshan area in the Changling fault depression, a new exploration area in the Songliao Basin, was taken as an example to describe the orderliness of hydrocarbon distribution from the aspects of reservoir type, reserves abundance and hydrocarbon phase state. Then, based on hydrocarbon accumulation conditions, three hydrocarbon migration–accumulation units（S2, S203 and S201） were classified. Finally, the configuration of hydrocarbon accumulation elements was assessed quantitatively using the analytic hierarchy process, and the main factors controlling the hydrocarbon distribution regularity were defined. The following results were obtained. First, from the sag belt in the north to the structural belt in the west, the hydrocarbon phase state changes in an order of gas reservoir–oil gas reservoir–oil reservoir, the reservoir type presents a gradual change of lithologic reservoir–structural-lithologic reservoir–lithologic-structural reservoir–structural reservoir, and the hydrocarbon reserves and abundance increase gradually. Second, the orderliness of hydrocarbon distribution in the study area is controlled by three factors. The orderliness of hydrocarbon phase state is controlled by the effectiveness of fault–source space–time configuration; that of reservoir type is controlled by the diversity of boundary conditions of hydrocarbon migration-accumulation units; and that of hydrocarbon enrichment degree is controlled by the diversity of fault–source–sandstone–caprock configuration. From the sag belt in the north to the structural belt in the west, the fault–source–sandstone–caprock configuration turns better and the hydrocarbon migration–accumulation capacity becomes stronger. In conclusion, S201 is the best in hydrocarbon accumulation conditions, source–fault–sandstone–caprock configuration and exploration potential, so it can be taken as a main target for future exploration.