三肇凹陷扶杨油层油气“倒灌”运聚成藏规律研究

Research on Migration and Accumulation Mechanism of Hydrocarbon "Reversed Migration" in Fuyu and Yangdachengzi Formation in Sanzhao Depression

松辽盆地三肇凹陷扶杨油层有着丰富的油气资源,但由于油"倒灌"运聚成藏的复杂性,使得如何进一步扩大储量区和已探明区块如何开发成为困扰勘探家的两大难题。扶杨油层油成藏的特殊性体现在两个方面:一是断层密度大、规模小且密集成带;二是三肇凹陷扶杨油层处于物源交汇区,主要的储集体河道砂展布规律难以预测。本研究在系统油源对比的基础上,以断裂形成演化为核心,标定油源断层,分析断裂与砂体的配置关系及其控油规律,建立了成藏模式。油源对比表明,三肇凹陷扶杨油层油主要来自青山口组烃源岩,成藏关键时刻为明水组沉积末期,因此断陷期形成坳陷期和反转期活动的断层以及坳陷期形成反转期活动的断层为主要的油源断层,油在超压作用下沿着油源断层"倒灌"运移,下排的深度一般为200m,因此只有扶杨油层的顶部才是有利的目的层。扶杨油层断裂具有密集成带的特征,油源断层多为断裂密集带的边界断层,是主要的控藏断裂。油沿油源断层"倒灌"运移动力条件、断裂多期变形机制以及反转期青山口组泥岩水平拆离作用形成的水平裂缝的输导作用决定油主要富集在油源断层下盘河道砂中,在油源断层控制的地垒型断块中油最富集,断裂密集带处于构造低部位,不是主要的富集区。

There is abundant oil and gas in F, Y Formation of Sanzhao depression in Songliao Basin, how to further enlarge reservoir area and how to exploit proven territory, are two problem puzzling explorer because of the complexity of reversed migration. The distinctiveness of accumulation of F, Y Formation are manifested in two aspects： first, higher density fault, smaller scale and concentrated in zone; second, it＇s difficult to forecast distribution of the fluvial channel sand since F, Y Formation located in convergence of provenance. This paper based on the correlation of oil and gas, centering on the formation and evolution of fault, oil source fault is calibrated, the allocation of fault and sand body and regulation of controlling oil has been analyzed and the accumulation model is established. It＇s considered that the oil of F, Y Formation mainly comes from the hydrocarbon source rock of K1qn, the key period of accu- mulation is last sediment stage of K2m, consequently, the main oil source faults are those among the periods of fault depression to depression and depression to inversion, reversed migration happened along the oil source fault under the action of overpressure, the depth downward is usually 200m, so the favorable formation of interest is the top of F, Y Formation. Faults in F, Y Formation is featured by concentration in zone, oil source faults , the ones controlling accumulation, are mainly the boundary faults. The force condition of ＂ reversed migration＂, namely, oil along oil source faults, multiple phases of deformation of faults and transportation of horizontal fracture caused by the decoupling of mudstone of K1 qn in reversed period determined the concentration of oil in footwall channel sand of fault, oil in horst controlled by oil source fault is highly concentrated, whereas the concentration zone of fault which is the lower tectonic place is not concentration area of oil.