松辽盆地断陷层火山机构类型及其气藏特征

Classification of Volcanic Edifices and Its Characteristics of Gas Pool in Faulted Sequence of the Songliao Basin,NE China

松辽盆地断陷层(火石岭组和营城组)火山机构类型见3类6型。营城组以酸性火山机构为主,其中:盆地北部酸性熔岩火山机构占33%,南部占38%,北部的中基性火山机构比例小于南部。火山岩气藏类型主要为构造-岩性气藏,气水界面是一个起伏变化的界面。气藏内部特征受火山机构类型控制:酸性碎屑岩火山机构的气层厚度变化较小,其形态为板状或席状;酸性复合和熔岩火山机构气藏的气层厚度变化小,其形态为丘状和席状;中基性熔岩火山机构的厚度变化较大,其形态为丘状或楔状。松辽盆地火山岩气藏成藏主控因素为有效烃源岩、通源断层和储层物性。从松辽盆地发现的火山岩工业气藏来看:火山岩气藏主要集中在酸性熔岩火山机构中,北部贡献率为50%,南部贡献率为38%;盆地北部中基性火山机构的成藏效率高于南部。火山岩勘探方向应该聚焦在具有烃源岩和通源断层的区带,首先针对酸性火山机构,其次是中基性火山机构。

Volcanic edifices of the Yingcheng Formation and the Huoshiling Formation in the Songliao basin are classified into 3 types. They are pyroclastic, composite and lava volcanic edifices. According to chemical composition of rocks, each type is subdivided into acid subtype or intermediatebasic subtype. Most of volcanic edifices of the Yingcheng Formation are acid subtype. The percentage of acid lava volcanic edifice is 33% in northern basin and 38% in southern basin. The proportion of intermediate-basic volcanic edifices in northern basin is more than that in southern basin. The volcanic gas pool of Songliao basin isstructural lithological type. The depth of gas-water interface changes greatly. Internal characteristics of gas pools are controlled by volcanic edifices type. The shape of gas layer within acid pyroclastic volcanic edifice is sill or tabular, and the thickness changes little. The shape of gas layer within acid composite and lava volcanic edifice is mound or sill, and the thickness changeslittle. The shape of gas layer within intermediate-basic lava volcanic edifice is mound or wedge, and the thickness changes rapidly. The volcanic gas pool forming in Songliao basin is controlled by effective source rocks, faults of communicating source rocks, porosity and permeability. The industrial gas pool of Songliao basin is accumulated in acid lava volcanic edifices, which contributes 50% in northern basin and 38% in southern basin. The efficiency of gas pool formation of intermediate-basic volcanic edifices in northern basin ishigher than that in southern basin. The acid composite edifices have the maximum productivity of single well. The productivity of acid volcanic edifices is higher than intermediate-basic. The volcanic exploration direction should be focused on the targets with effective source rocks and faults of communicating source rocks. Firstly, aim at the acid volcanic edifice. Secondly, find the intermediatebasic volcanic edifice.