新疆两大盆地石炭—二叠系火山岩特征与油气

新疆准噶尔盆地与塔里木盆地石炭—二叠系火山岩十分发育,分布广,厚度大。准噶尔盆地石炭系火山岩广泛分布于盆地的西部隆起、陆梁隆起、中央隆起及东部隆起等广大地区,可分为上、下石炭统共5个组;二叠系火山岩较少,只在某些层位见到凝灰岩、凝灰质砂岩。塔里木盆地石炭系火山岩主要见于盆地周缘地区,二叠系火山岩在全盆分布广泛,不仅厚度大,而且岩石类型多;主要岩石类型为基性和超基性岩,其次为中酸性岩;其分布具有平面分带性和垂向旋回性。火山作用促使不成熟的生油岩提前进入生油门限,也可使成熟的生油岩过早转化为高成熟。中酸性火山溶岩是石炭系的主要储层,岩浆活动为油气运移提供了通道。火山岩储层可形成亿吨级的大油田,因此在新疆的油气勘探中,应关注石炭-二叠系火山岩的成藏和分布,并把他作为石油勘探的重要领域之一。 

CHARACTERISTICS OF THE CARBONIFEROUS-PERMIAN VOLCANIC ROCKS AND HYDROCARBON ACCUMULATIONS IN TWO GREAT BASINS, XINJIANG AREA

The Carboniferous-Permian volcanic rocks were very well developed with wide distribution and big thickness in the Junggar and Tarim basins,Xinjiang area.The Carboniferous volcanic rocks are widely distributed in the West Uplift,Luliang Uplift,Central Uplift and East Uplift of the Junggar Basin,which can be divided into upper and lower Carboniferous(total 5 formations).The quantity of the Permian volcanic rocks is small.The tuffs and tuffaceous sandstones are shown in only certain layers.The Carboniferous volcanic rocks of the Tarim Basin are mainly distributed at the margin of basin but the Permian volcanic rocks are common in the whole basin with large thickness and variety of rock types.The main types are basic and ultrabasic rocks and then are intermediate-acid rocks.Their distribution is characterized by lateral zonation and vertical cyclicity.The volcanism accelerated immature source rocks to enter oil generation threshold in advance,at the same time it also caused mature source rocks became over matured.Intermediate-acid volcanic lava is the main reservoirs of the Carboniferous.Magmatism activities provide the pathway for hydrocarbon migration.The volcanic rocks can form big oilfields of 100 million tons so we should focus on study of reservoir-forming and distributions of the Carboniferous-Permian volcanic rocks in oil-gas exploration of Xinjiang area and regard these reservoirs as one of important targets in petroleum exploration.