松辽盆地长岭断陷火山岩相与天然气成藏关系

RELATIONSHIP BETWEEN VOLCANIC FACIES AND GAS ACCUMULATION IN THE CHANGLING FAULT-DEPRESSION OF THE SONGLIAO BASIN

松辽盆地盖层由上部坳陷层和下部断陷层组成。长岭断陷是断陷层的一部分,是受盆地早期发育的孙吴—双辽、松花江—四平2条岩石圈深断裂带控制的深大断陷。断陷内部及周边断裂深切岩石圈,造成多期火山活动,形成火山岩与巨厚湖相沉积岩共生。火山岩以酸性火山岩类为主,分爆发相和溢流相2种类型,两者在剖面上交替出现构成多个火山活动旋回。研究认为,喷溢相的上部亚相原生气孔发育,爆发相的空落亚相和热基浪亚相孔洞发育。火山岩相与天然气成藏关系主要表现为,喷溢相上部亚相、爆发相空落亚相和热基浪亚相控制了好储层发育,好储层又控制了气藏形成。

Caprock structure in the Songliao Basin is composed of the upper depression layers and the lower fault-depression layers. The Changling Fault-Depression （part of the fault-depression layers） is a deep-large fault-depression controlled by the Sunwu--Shuangliao and the Songhuajang--Siping Deep Fault Belts generated during basin early phase. Deep faults in and around the fault-depression cut deep into lithosphere, causing volcanic activities, resulting in association of volcanic rocks and lacustrine facies sedimentary rocks. Volcanic rocks are mainly acid, and can be divided into 2 types： explosive and outpouring. The 2 facies alternate and compose multiple volcanic activity cycles. Primary vesicles generate in the upper subfacies of the explosive facies. Pores and caverns generate in the aerial-falling and thermodynamic wave subfacies of the outpouring facies. Good reservoirs generate controlled by the upper subfacies of the explosive facies and the aerial-falling and thermodynamic wave subfacies of the outpouring facies; hence control gas accumulation formation.