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为了分析重质油在低渗透砂岩中的成藏特征,通过对储层岩石学、储层物性、储层孔隙类型和原油碳同位素、饱和烃色质等方面的分析,对准东火北地区平地泉组储层特征和原油成因进行了研究.认为对致密储层而言,储层物性对原油成藏具有重要的控制作用,孔渗较好的储层利于孔隙中流体的交换,源岩低成熟产物成藏后,后期成熟度较高的原油还可成藏,导致物性差的储层中原油成熟度低,物性较好的储层中原油成熟度较高.研究结果表明:该区岩石类型主要为云质极细粒砂岩,储层孔隙不发育,孔隙度主体小于5%,渗透率普遍小于0.1 mD,孔喉半径为0.037~0.148μm,属于纳米孔范畴.该区原油姥植比为1.34~1.36,碳同位素为-30.21‰~-30.01‰,饱和烃色谱存在奇偶优势,甾烷成熟度参数C_(29)ββ/(αα+ββ)为0.24~0.27,属于本身二叠系平地泉组低演化阶段的产物.原油以近源成藏为主,储层致密导致原油侧向运移困难,凹陷深部二叠系平地泉组成熟原油未能进入火北地区成藏.对低渗透砂岩储层油气勘探,应重视低成熟烃源岩分布区.
In order to analyze the reservoir forming characteristics of heavy oil in low permeable sandstone, through the analysis of reservoir petrology, reservoir physical properties, reservoir pore types and carbon isotopes of crude oil and saturated hydrocarbon, The reservoir characteristics of Pingdiquan Formation and the genesis of crude oil are studied.It is considered that for the tight reservoirs, the physical properties of the reservoirs play an important role in controlling the formation of crude oil reservoirs, reservoirs with good porosity and permeability are favorable for fluid exchange in the pores, After the accumulation of low-mature products, the crude oil with high maturity can be also accumulated in later stage, resulting in low maturity of crude oil in reservoirs with poor physical properties and high crude oil maturity in reservoirs with better physical properties. The results show that: The rock type is mainly cloud fine grain sandstone, with undeveloped reservoir porosity, less than 5% porosity, generally less than 0.1 mD permeability, and pore throat radius from 0.037 to 0.148 μm, belonging to the nanopore category. The ratio of carbon isotope was -30.21 ‰ to -30.01 ‰, there was a even and odd advantage for the saturated hydrocarbon chromatogram, and the C_ (29) ββ / (αα + ββ) of sterane was 0.24-0.27, belonging to the Permian The product of the low-evolution stage of Pingdiquan Formation, which is dominated by near-source reservoir formation and reservoir Resulting in dense crude oil lateral migration difficult, deep depression Permian Pingdiquan group of mature crude oil failed to enter the fire area north accumulation For low permeability sandstone reservoirs of oil and gas exploration, we should pay attention to low mature source rocks distribution.