Enrichment Regularity And Main Controlling Factors Of Tight Sandstone Oil Reservoirs In Fuyu Oil Reservoir At Central Depressions In The South Of Songliao Basin

This paper systematically studied on different types of tight sandstone oil reservoirs and its controlling factors in Quantou 4 formation and built the“Hydrocarbon generation on the top and Storage on the bottom”pattern of tight reservoir in depressed type lacustrine basin,based on the theory of“high-quality source rocks control hydrocarbon accumulation”and the idea of“explore tight oil through sweet spots”relying on hydrocarbon generation thermal simulation experiment,Constant pressure mercuryexperiment,breakthrough pressure experiment and hydrocarbon charging experiment.Building hydrocarbon source rock evaluation standard by using geochemical data and hydrocarbon generation thermal simulation experiment through source rock hydrocarbon expulsion,organic matter abundance,organic matter type,organic matter maturity and other methods.Research shows that K₂qn¹ source rocks in the central depression can be divided into high quality source rock,effective source rock,ineffective source rock 3 species.The dark mudstone which has TOC>2%?Ro>0.9%can be classified as high quality source rock that hydrocarbon expulsion quantity reaches 150²00×10⁴t/km².That kind of source rock developed at the bottom of K1qn1 formation in north Changling sunken,east slope area of Honggang terrace,wells of Hua word terrace and west slope area of Fuxin uplift area.The dark mudstone which has 0.8%<TOC<2.0%?0.8%<Ro<0.9%can be classified as effective source rock that hydrocarbon expulsion quantity reaches 50¹00×10⁴t/km².That kind of source rock developed in the central Changling sunken and Honggang terrace.The dark mudstone which has TOC<0.8%,Ro<0.8%can be classified as ineffective source rock that hardly has features of hydrocarbon generation and expulsion.The dark mudstone in K₂qn¹formation buried 1000m in late Nenjiang period.Organic matter got ripe and started to generateHydrocarbon.When buried depth came to 2000m,the peak period of hydrocarbon generation arrived with Kerogen producing natural gas.When buried depth came to2000²500m,the cumulative maximum quantity of hydrocarbon generation increased no longer,later mature stage came.Building tight sandstone reservoir standard in point of pore throat structure view by comprehensive using of Physical data of reservoir,Casting body slice data,Conventional mercury data,Constant pressure mercuryexperiment data and Scanning electron microscope data.Tight reservoir Level I possesses 10%<??12%,0.1mD<K?1mD,the pore throat radius is in range of 0.35⁰.8?m,the displacement pressure is in range of 0.3¹.5MPa,the peak value is in range of 0.16⁰.63?m.Tight reservoir Level II possesses 7%<??10%,0.05mD<K?0.1mD,the pore throat radius is in range of 0.32⁰.35?m,the displacement pressure is in range of 1.5².5MPa,the peak value is in range of 0.025⁰.16?m.Tight reservoir Level III which possesses?<7%,K<0.05mD can beclassified as ineffective reservoir because of the petroleum and natural gas filling difficultyincreased significantly.Through tight reservoirbreakthrough pressure experiment and tight oil filling experiment,overpressure was definitely confirmed the power of petroleum and natural gas migration.However,the pore throat radius is the key which decides oil filling in tight reservoir or not.The main controlling factors were drawn by summing up the distribution law of K₁q⁴ tight sandstone reservoir in study area,analysis of the relationship between it and the quality of source rock,overpressure characteristics,reservoir quality,leading system.They are“The distribution range of High quality source rock controls the distribution law of tight reservoir,Overpressurecontrolled the distribution range of tight reservoir and the discharge depth of petroleum,high quality reservoir controls the degree of tight reservoir enrichment,the source reservoir communication controls the oil-bearing of lower sand group”.On the basis of those4 parts,accumulation model as Straight row of intrusion in oil source area of sunken model and Fault block in oil source edge of slope area model were summarized from“source on the top and reservoir on the bottom”depression lake basin.