Controlling factors and distribution patterns of lithologic pools in the fluvial facies of the 3<sup>rd</sup> and 4<sup>th</sup> members of the Quantou Formation in the Songliao Basin

doi:10.11743/ogg20110314

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Controlling factors and distribution patterns of lithologic pools in the fluvial facies of the 3^rd and 4^th members of the Quantou Formation in the Songliao Basin
Vol. 32, Issue 3, Pages: 411-419(2011)
Online First：28 June 2011，

Published：2011
DOI： 10.11743/ogg20110314
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DOI：

Controlling factors and distribution patterns of lithologic pools in the fluvial facies of the 3^rd and 4^th members of the Quantou Formation in the Songliao Basin[J]. 2011, 32(3): 411-419. DOI: 10.11743/ogg20110314. DOI：

摘要

依据大量钻井、测井、地震及实验室分析资料，应用陆相层序地层学、沉积地质学及油气成藏理论，通过成藏条件研究认识到，松辽盆地扶杨油层为河流相低孔、低渗储层，上覆的白垩系青山口组一段湖相泥岩既是烃源岩又是区域性盖层，因此具有上生下储式成藏特征。油–源对比表明，油气垂直下排最大距离可达550 m，平均约300 m。明水组沉积末期，盆地反转应力场产生了大量断穿烃源岩及扶杨油层的断层并在源岩及储层内产生大量裂缝，同时源岩进入生烃高峰期，于是在构造应力及生烃超压作用下油气沿断层及裂缝下排到扶杨油层而成藏。因此，明水组沉积末期成为油气成藏的主要时期。曲流河点砂坝具有较好的物性，是油气的主要储集体。受浅水湖泊形成的泥岩盖层影响，形成了两套含油层系，油藏主要发育在近油源的扶余油层，盆地范围内具有统一的油–水界面。青山口组一段高成熟烃源岩控制了油藏主要分布在中央坳陷区，较低的砂地比决定了扶杨油层以发育岩性油藏为主。

Abstract

Based on data from drilling

logging

seismic and lab

we make a study of the Fuyang oilbearing interval in Songliao Basin by using theories of continental sequence stratigraphy

sedimentary geology and hydrocarbon accumulation.The Fuyang oilbearing interval in Songliao Basin is a lowporosity and lowpermeability reservoir of fluvial facies.The overlapping mudstone of lacustrine facies in the 1

 member of the Cretaceous Qingshankou Formation is both source rock and regional seal

and therefore hydrocarbons generated in the upper source rocks migrated downward and accumulated in the lower reservoirs.Oilsource correlation shows that average distance of downward vertical migration of hydrocarbons is 300 m with the longest distance of 500 m.At the end of the Mingshui Formation deposition

stress field inversion resulted in various faults cutting through source rocks and the Fuyang oilbearing interval and many fractures inside the source rocks and reservoirs.At the same time

source rocks reached the peak of hydrocarbon generation.Driven by tectonic stress and overpressure due to hydrocarbon generation

the hydrocarbons migrated downward along the faults and fractures and accumulated in the Fuyang oilbearing interval.Hence the major period for hydrocarbon accumulation is the late period of the Mingshui Formation deposition.With favorable reservoir quality

meandering river point bars are major reservoirs for oil and gas.The existence of mudstone seals of shallow lacustrine facies leads to the formation of two sets of oilbearing intervals.Oil pools mainly developed in the Fuyang oilbearing interval which was close to the oil source and have a uniform oilwater contact in the basin.High mature source rocks in the 1

 member of the Qingshankou Formation determine that oil pools are mainly distributed in the central depression zone.Relatively low nettogross ratio leads to the predominance of lithlogic oil pools in the Fuyang oilbearing interval.