松辽盆地北部岩性油藏形成条件与分布规律

Formation Conditions and Distribution Law of Lithologic Oil Reservoirs in Northern Part of Songliao Basin

松辽盆地中浅层大型坳陷湖盆河流—三角洲、湖泊沉积体系的沉积地质背景决定了其具有形成大面积岩性油藏的地质条件。纵向上,由于各时期基准面升降造成可容空间在不同时期差别较大,因此发育的砂体类型也有一定的差别;同时由于储层埋藏深度以及与烃源岩的相对位置不同,各含油组合岩性油藏成藏条件与分布规律也存在一定的差异。平面上,岩性油藏的类型受构造部位和砂岩的发育程度控制。凹陷中三角洲外前缘相带主要形成岩性油藏,凹陷周边是各种隐蔽油气藏发育的主要地区。针对三角洲前缘相带砂泥岩薄互层岩性油藏的实际情况,以高分辨率层序地层学为指导,对松辽盆地北部姚家组一段葡萄花油层展开了精细地质研究,认识到油气藏具有成带分布的特点,并划分出构造油气藏分布带、构造—岩性油气藏分布带和岩性油气藏分布带,为隐蔽油气藏勘探指明了方向。

Against the sedimentary background of fuvial and deltase dimentary systems in largede pression-type lake bas in,Songliao Basin certainly has the geological conditions for forming lithologic oil reservoirs in large areas. Vertically, the lifting and descending of datum level in various periods causes big difference in allowable space in the different stages.Therefore, there is a certain difference in the types of developed sandbodies. Meanwhile, the migration and accumulation conditions and distribution law of those lithologic oil reservoir of each assemblage are quite different owing to the difference in the buried depth of reservoirs and locations of hydrocarbon source rock. On the plane, the types of lithologic oil reservoirs are controlled by structural positions and maturity of sandstone. The lithologic oil reservoirs are formed mainly in the frontal facies zone outside the delta in the depression. The surrounding areas of the depression are the main locations for development of various subtle oil and gas reservoirs. Guided by the high-resolution sequence stratigraphy, the detailed geological study was made on Putaohua oil layer of Yaojia Formation in the northern part of Songliao Basin in the light of the actual conditions of the sandy-shale thin interbedded lithologic oil reservoir in the frontal facies zone of the delta. It is found that the oil and gas reservoirs are distributed in belts. Therefore, distribution of oil and gas reservoirs is divided into the belt for structural oil and gas reservoirs as well as the belt for structural-lithologic oil and gas reservoirs and lithologic oil and gas reservoirs, clarifying the orientation for exploration of subtle oil and gas reservoirs.