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查明南堡凹陷天然气复杂相态的成因联系,有利于本区天然气勘探成果的扩大.本文根据天然气地球化学特征、地层PVT及产能资料确定了地层条件下天然气相态类型及其分布特征,分析了天然气相态成因及相互关系;利用断接厚度和排替压力两项参数,从盖层宏观和微观封闭机理,分析了不同相态天然气的封闭下限,并以地球化学示踪的方法确定了天然气勘探方向.研究结果表明:南堡凹陷天然气的相态类型划分为溶解态的油溶气、游离态的气顶气和凝析气三大类,深层天然气以凝析气为主,中浅层天然气以气顶气和油溶气为主,并以两相共存的气顶气最容易被封闭,断接厚度为50~180m,盖层排替压力下限为1.5 MPa左右,深层凝析气形成的纯气藏次之,封闭条件要求最高的是只以单相油柱存在的油溶气.由于深层天然气相态以凝析气为主,封闭下限相对较低,并且浅层天然气发现了具有深源气的地球化学响应,反映了南堡凹陷深层天然气较大的资源潜力,故应加强滩海深层凝析气藏的勘探,并有望在陆上地区深层获得突破.
To find out the genetic relationship of complex phase of natural gas in Nanpu sag is favorable for the expansion of natural gas exploration results in this area.Based on the geochemical characteristics of natural gas, formation PVT and productivity data, the natural gas phase type and its distribution characteristics are determined and analyzed Based on the macrosemiological and microscopic sealing mechanism of caprock, the lower sealing limit of natural gas in different phases was analyzed, and the geochemical tracing method was used to confirm the relationship between gas phase origin and interdependence. Natural gas exploration.The results show that the phase types of natural gas in Nanpu sag are divided into dissolved oil-soluble gas, free-state gas-top gas and condensate gas. The deep natural gas is mainly condensate gas, Natural gas is mainly gas-top gas and oil-dissolved gas, and the capitals coexisting in two phases are the most likely to be blocked, with the thickness of 50-180 m and the lower limit of replacement pressure of cap layer of about 1.5 MPa, and the formation of deep condensate gas Of the pure gas reservoir followed by the closed conditions require only the highest single-phase oil column exists in the oil dissolved gas.Because the deep natural gas phase condensate gas-based, lower seal lower relatively, and shallow natural gas hair Geochemical response has a deep source gas, reflecting the large resource potential deep gas Nanpu Sag, it should strengthen Beach condensate gas reservoir deep sea exploration, and is expected to get a breakthrough in deep onshore.