Melut盆地北部凹陷为富油气凹陷,具有岩性地层油气藏形成的基本条件。针对深层白垩系和岩性地层油气藏勘探尚未取得突破的现状,通过开展层序地层学和沉积相研究,建立了统一的层序地层格架,明确了Melut盆地北部凹陷源上、源内各主要层序岩性地层油气藏的勘探潜力与方向。研究表明:源上主要发育Yabus上段—Adar—Lau高位域,有利相带为河流、三角洲、扇三角洲,主要形成构造-岩性圈闭;源内主要发育Galhak—Algayger湖侵域,有利相带为三角洲前缘、滑塌浊积扇和洪水浊积扇,主要形成岩性和构造-岩性圈闭。综合分析认为,源内层序是寻找构造-岩性油气藏的主要勘探目标。在有利构造背景下发育良好的储盖组合是Melut盆地白垩系成藏的关键因素,辫状河三角洲前缘相带是白垩系油气成藏的优势相带,上白垩统Galhak组是白垩系油气成藏的主要目的层段。研究结果对Melut盆地北部凹陷下步勘探具有指导意义。
The northern sag of the Melut Basin is a hydrocarbon-rich depression, with the basic conditions for the formation of litho-stratigraphic hydrocarbon reservoirs. Since no breakthrough has been made in the exploration of Cretaceous deep litho-stratigraphic hydrocarbon reservoirs, a unified sequence stratigraphic framework was established after a study conducted on sequence stratigraphy and sedimentary facie, and the exploration potential and direction of the litho-stratigraphic hydrocarbon reservoirs of primary sequence above and within the source of the northern sag of Melut Basin were clarified. It was found in the study that the upper Yabus member-Adar-Lau high-stand system was mainly developed at the source, and the favorable facies belts were river, delta, and fan delta, forming tectonic-lithological traps; Galhak-Algayger lacustrine transgressive system was mainly developed within the source, and the favorable facies belts were delta front, fluxoturbidite fan and flood turbidite fan, forming lithological and tectonic-lithological traps. The comprehensive analysis suggested that the in-source sequence was the primary exploration target for finding tectonic-lithological reservoirs. Well-developed reservoir-caprock assemblage in a favorable tectonic setting was the key factor for Cretaceous hydrocarbon accumulation in Melut Basin. The facies belt of braided river delta front was the dominant facies belt for Cretaceous hydrocarbon accumulation, and the Galhak Formation of the Upper Cretaceous Series was the main target interval for Cretaceous hydrocarbon accumulation. The results of the study are of great significance for further exploration in the northern sag of Melut Bsin.
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