It is common for many tight sandstone reservoirs saturated with gas to have experienced an early oil charge before gas invading. To determine the effects of early oil emplacement on reservoir quality and gas migration has important role in predicting “sweet spots” of gas production in tight sand reservoirs. We investigated the palaeo and current fluids contacts accurately due to parameters from quantitative grain fluorescence in the Lower Jurassic Ahe Formation of Dibei gas field. The porosity and permeability values in palaeo-oil leg are totally higher than in palaeo-water leg, especially there being a wide gap of permeability with an order of magnitude. The variation of reservoir quality derives from the early oil emplacement, which restrained clay conversions from kaolinite or illite-smectite mixed-layer into fibrous illite that dramatically increasing flow-path tortuosity in sandstones, according to core analysis and X-ray diffraction. The early oil preserved penetrating quality of palaeo-oil leg, but the sandstones that never experienced early oil emplacement contains much more fibrous illite. It made most of early oil pathways subsequently act as the migration pathways for late gas and less than 50% of the migration pathways for gas were caused by microfractures due to quantitative grain fluorescence. Only the sandstones with medium early oil saturation did become sweet spots for gas in the tight sand reservoirs. Too much and too little oil once saturated in pores maybe adverse to the late gas migration and accumulation.

对于许多充满气体的致密砂岩油藏来说，在侵入之前要经历早期的注油是很常见的。确定早期采油对储层质量和天然气运移的影响，对预测致密砂岩储层中的天然气产量“最佳点”具有重要作用。由于地北气田下侏罗统阿河组的定量颗粒荧光参数，我们精确地研究了古流体和当前流体的接触。古油段的孔隙度和渗透率值比古水段的孔隙率和渗透率值都高，尤其是渗透率的差距较大，约为一个数量级。油藏质量的变化源于早期的注油，根据岩心分析和X射线衍射分析，它们抑制了粘土从高岭石或伊利石-蒙脱石混合层向纤维状伊利石的转化，从而显着增加了砂岩的流路曲折度。早期的石油保留了古石油腿部的穿透质量，但是从未经历早期石油注入的砂岩含有更多的纤维伊利石。它使大部分早期油路随后成为晚期气体的运移途径，而少于50％的气体运输途径是由于定量荧光导致的微裂缝引起的。只有早期含油饱和度中等的砂岩才成为致密砂岩储层中天然气的甜点。一旦孔隙中充满了太多或太少的油，可能会不利于后期的气体运移和聚集。根据岩心分析和X射线衍射。早期的石油保留了古石油腿部的穿透质量，但是从未经历早期石油注入的砂岩含有更多的纤维伊利石。它使大部分早期油路随后成为晚期气体的运移途径，而少于50％的气体运输途径是由于定量荧光导致的微裂缝引起的。只有早期含油饱和度中等的砂岩才成为致密砂岩储层中天然气的甜点。一旦孔隙中充满了太多或太少的油，可能会不利于后期的气体运移和聚集。根据岩心分析和X射线衍射。早期的石油保留了古石油腿部的穿透质量，但是从未经历早期石油注入的砂岩含有更多的纤维伊利石。它使大部分早期油路随后成为晚期气体的运移途径，而少于50％的气体运输途径是由于定量荧光导致的微裂缝引起的。只有早期含油饱和度中等的砂岩才成为致密砂岩储层中天然气的甜点。一旦孔隙中充满了太多或太少的油，可能会不利于后期的气体运移和聚集。它使大部分早期油路随后成为晚期气体的运移途径，而少于50％的气体运输途径是由于定量荧光导致的微裂缝引起的。只有早期含油饱和度中等的砂岩才成为致密砂岩储层中天然气的甜点。一旦孔隙中充满了太多或太少的油，可能会不利于后期的气体运移和聚集。它使大部分早期油路随后成为晚期气体的运移途径，而少于50％的气体运输途径是由于定量荧光导致的微裂缝引起的。只有早期含油饱和度中等的砂岩才成为致密砂岩储层中天然气的甜点。一旦孔隙中充满了太多或太少的油，可能会不利于后期的气体运移和聚集。