不整合空间结构与油气成藏综述

不整合是由不整合面及其上、下岩石三部分组成,在空间上具有三层结构,即不整合面之上的岩石、不整合面之下的风化粘土层以及风化粘土层之下的半风化岩石。风化粘土层在上覆沉积物压实作用下岩性较致密,具有良好的封盖能力。不整合面之上的高孔渗岩石(主要为砂岩、砾岩)和不整合面之下裂隙、溶蚀孔洞发育的半风化岩石(主要为砂岩、砾岩、碳酸盐岩、火山岩及变质岩)既可作为油气运移通道,又可成为油气聚集的有效储层。由于构造部位、岩性等因素的影响,不整合空间结构复杂多变,导致不整合油气藏成藏规律复杂,因此,不整合空间结构研究对不整合油气藏勘探具有重要的指导意义。

ADVANCES IN RESEARCH OF SPATIAL STRUCTURES OF UNCONFORMITY

Unconformity generally consists of unconformity interface, overlying rocks and underlying rocks, and is spatially characterized by three stratal structures, consisting of rocks above the unconformity interface, weathered clay below the unconformity interface, and semi-weathered rocks under the weathered clay. Weathered clay is compact under compression of overlying rocks and constitutes good seals. Rocks (mainly including sandstone and conglomerate) above the unconformity interface, are characterized by better porosity and permeability, while semi-weathered rocks (mainly sandstone, conglomerate, carbonate rock, volcanic rock and metamorphic rock) below the unconformity interface, are characterized by development of fractures and solution porosity, form not only good pathways for hydrocarbon migration, but also effective reservoir beds for hydrocarbon accumulation. Due to influence of tectonic position, lithology, and so on, an unconformity spatial structure is very complicated, which renders the law that governs hydrocarbon accumulation and reservoir formation at the unconformity to be complicated too. So, research on unconformity spatial structure is beneficiary to exploration of hydrocarbon reservoirs at such unconformities.