陆相坳陷盆地烃源岩内致密砂岩储层含油性主控因素——以松辽盆地北部中央坳陷区齐家凹陷高台子油层为例

Main Controlling Factors of Oilliness Property of Tight Sandstone Reservoir within Source Rock in Continental Depression Basin:A case of Gaotaizi oil reservoir in Qijia sag of central depression area in northern Songliao Basin

松辽盆地北部中央坳陷区齐家凹陷青山口组高台子油层是典型的烃源岩内致密砂岩油.通过对储层宏观、微观含油性分析及含油性主控因素的深入研究,表明高台子油层储层含油性主要受沉积微相、成岩作用及烃源岩质 量的综合控制,表现为有利沉积微相控制储层含油富集程度,河口坝、远砂坝微相砂体内大喉道发育,物性好,为致密 油运移提供优势通道,同时储集空间相对发育,为致密油提供更广泛的聚集场所,油气最富集,沉积微相是控制高台 子油层“甜点区”发育的关键地质条件.成岩作用控制石油差异分布,机械压实和胶结作用导致储层在油气大规模运 聚之前普遍进入致密化,局部胶结作用弱的砂岩及溶蚀作用强烈的砂岩,大孔隙及大喉道发育,后期石油充注储层发 生差异聚集,砂岩呈现不同的含油级别.烃源岩质量控制储层含油的普遍程度,好-最好烃源岩区油源充足、充注动 力强,且就近运聚,虽然砂体薄,物性差,但砂体含油更普遍,含油物性下限低,差-中等烃源岩区砂体厚度大,物性总 体较好,但受烃源岩质量及沉积、成岩作用综合控制,砂体含油普遍性差,主要以砂体中部物性好的层段含油为主,干 砂层增多.甜点区主要分布在成熟烃源岩内部,纵向多套含油层系错叠形成甜点区连片分布,中北部含油砂体累计 厚度大,物性好,向南部变差,计算甜点区资源1.5X108 t,勘探前景良好.

Typical tight sandstone oil within hydrocarbon source rocks is considered in Gaotaizi oil-layer ol Qingshankou Formation in Qijia Sag, located in central depression area ol northern Songliao Basin. Macro- and micro-analysis ol oil-bearing property and in-depth study ol the main controlling factors have been carried out in reservoir, which show that oil-bearing property ol the reservoir ol Gaotaizi oil-layer is mainly controlled by sedimentary micro-lacies, diagen-esis and quality ol source rock. Favorable sedimentary microlacies controls oil enrichment in reservoir. Macro pore throats are developed in sandbodies ol mouth bars and distal sandbars, where the physical properties are good enough to provide prelerential pathways lor migration and meanwhile relatively developed storage space can also provide more entrapment habitats. The sedimentary micro-lacies is the critical geological lactor controlling the distribution ol “ sweet spots” within Gaotaizi oil-layer. Diagenesis controls the dillerential distribution ol hydrocarbon, and mechanical com-paction and cementation led to tightness ol reservoir belore the large-scale migration-accumulation. While in local sandstones with weak cementation and heavy corrosion developed macro pores and throats. In the later charging process dillerential entrapment took place in the reservoir sandstones, having dillerent levels ol shows. Source rock quality controls the level ol oil occurrence within reservoir. Good-excellent quality source rock can provide abundant hydrocarbon and powerful charging dynamics. And, therelore the hydrocarbon can be migrated to and accumulated in reservoir within the source rocks. So, the shows are common even though the sand bodies may be thin and with bad physical properties, showing that the low-limits ol physical properties are relatively low. While in bad-middle quality source rock area the sand bodies are thick with better physical properties, but the oil-bearing property is controlled by the combination ol source rock quality, sedimentation and diagenesis. So the shows are commonly bad, only the mid-dle part with good physical properties ol sand bodies bear oil and more dry sand bodies are discovered, too. “ Sweet spot” zones are principally distributed in the mature source rock area where multiple series ol oil-layers are staggered and overlapped. A conclusion can be drawn that in the mid-north oil-bearing sand bodies are ol thick cumulative thickness and good physical properties, but to the south they get worse. In all the “sweet spot” zones 1.5x108t ol resources can be estimated, which ollers exciting exploration prospect.