摘要
升平气田下白垩统营城组火山岩的岩性学与岩相学、火山活动机制等研究结果显示,火山岩岩石类型主要为火山碎屑岩和火山熔岩,少量火山碎屑熔岩、沉火山碎屑岩、火山碎屑沉积岩和次火山岩。熔岩以流纹岩为主,少量英安岩。营城组重点含气层段营三段可划分为4个火山喷发-喷溢旋回。火山活动以喷发频率高和喷发迅速、间隔时间短和冷凝迅速、较强烈的中心式爆发与较宁静的裂隙式溢流喷发交替为特征。可识别出火山爆发相、火山溢流相、火山侵出相、火山通道相和火山沉积相5个相和溅落熔岩、火山碎屑岩、熔岩、火山重力流、火山颈和次火山岩6个亚相。高产气流井主要位于火山爆发相以及爆发相与溢流相互层地带。火山岩的储集性能主要受岩性、岩相、火山岩厚度及其空间分布特征的控制,其次受火山活动特点、古地貌、成岩作用与构造作用的影响。
Abstract
Study on lithology and petrography of volcanics and mechanism of volcanic activities in the Lower Cre-taceous Yingcheng Formation of the Shengping gas field in the Songliao Basin,indicates that rock types are mainly pyroclastics and lava,with minor pyroclastic lavas,sedimentary pyroclastic rocks,pyroclastic sedimentary rocks and sub-volcanic rocks.Lavas are dominated by rhyolite with minor dacite.Four volcanic eruption-effusion cycles can be recognized in the third member,the major gas-bearing interval,of Yingcheng Formation.The vol-canic activities are characterized by alternation of relatively quiet fissure effusion with relatively strong central eruption that features in high frequency,rapid eruptions,short intermittence,and quick condensation and consoli-dation.Five lithofacies (explosive,effusive,extrusive,volcanic conduit and volcanic-sedimentary facies)and six sub-facies(splash fall lava,pyroclastic,lava flow,volcanic gravity flow,volcanic neck and sub-volcanic) can be recognized.Wells with high gas flow rate are mainly located in areas with the volcanic explosive facies or interbe-ded explosive facies and effusive facies.The volcanic reservoir quality is mainly controlled by lithology,lithofa-cies,thickness and spatial distribution of volcanic rocks,followed by the characteristics of volcanic activity,pa-leogeomorphology,diagenesis and tectonic action.
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