摘要:
乌兰花凹陷是近年来在二连盆地南部新发现的富油凹陷,但南北两个洼槽探明的油气资源差异明显。为了准确评价乌兰花凹陷的油气资源潜力,系统地分析了乌兰花凹陷烃源灶特征,讨论了烃源灶与油藏分布的关系。研究表明,乌兰花凹陷阿尔善组至腾一上段发育C、D/E和F相源岩,受构造-层序演化的影响,南北洼槽倾油型(C相)源岩发育层段存在明显差异,南洼槽C相源岩主要发育在阿尔善组,腾一上段和下段以D/E相源岩为主,而北洼槽阿尔善组至腾一上段均发育C相源岩。多口探井热史标定结果表明,乌兰花凹陷烃源岩成熟门限在2000 m左右,南洼槽仅阿尔善组烃源岩进入成熟阶段,阿尔善组C相源岩排油强度为0.5～7.9MMT/km2,为凹陷的主力烃源岩,而北洼槽阿尔善组C相烃源岩主要发育在阿尔善组上段,成熟度较低,最大值仅为0.78%Ro,烃源灶排烃强度小于0.2 MMT/km2,不能形成规模性的油藏。乌兰花凹陷探明的原油均在南洼槽,且集中在烃源灶周围,表现为近源聚集。
Abstract:
The Wulanhua Sag is a newly discovered oil-rich sag in the southern part of the Erlian Basin, with obvious differences in proven petroleum resources in the south and north sub-sags. To accurately evaluate the petroleum resource potential of the Wulanhua Sag, the characteristics of source kitchens in the Wulanhua Sag were systematically analyzed, and the relationship between source kitchens and petroleum distribution was discussed. Studies show that source rock contains organofacies C, D/E, and F. Organofacies were primarily controlled by tectono-stratigraphy evolution of the sag. The development of high-quality oil-prone source rock（organofacies C） in the south and north sub-sags shows significant differences. In the south sub-sag, organofacies C mainly occurs in the Aershan Formation（K1ba）, and the source rocks in the first member of the Tengger Formation（K1bt1） mainly consist of organofacies D/E. However, organofacies C occurs in both K1ba and K1bt1 in the north sub-sag. Thermal history calibration results of many wells indicate that the maturity threshold of the source rock in the Wulanhua Sag is approximately 2000 m. According to this rule, only the source rock in K1ba in the south sub-sag has entered the mature stage. Oil expelled from organofacies C in the K1ba is 0.5–7.9 MMT/km~2, which makes a major contribution to proven oil accumulations. However, organofacies C is mainly developed in the upper part of the K1ba in the north sub-sag with lower maturity, and the maximum value of thermal maturity is only 0.78%Ro. The hydrocarbon expulsion intensity of the source kitchen is less than 0.2 MMT/km~2 in the north sub-sag and is not enough to form oil accumulation. The proven oil accumulations in the Wulanhua Sag are all located in the south sub-sag and concentrated around the source kitchens, indicating the accumulation efficiency of nearby source kitchens.
下载: