徐深气田营城组一段沉火山碎屑岩地层划分及其成因分析

STRATIGRAPHIC DIVISION OF SEDIMENTARY PYROCLASTIC ROCK INYINGCHENG 1 MEMBER AND ITS ORIGIN

通过对徐深气田E21区块火山岩储层开展的精细描述,进一步深化了对火山岩气藏的内在地质认识,发现在营城组一段火山岩顶部发育一套沉火山碎屑岩地层。这套地层是一套电性上具有中伽马、中低阻,地震上具有平行-亚平行反射特征的致密非储层。它的划分有两点意义:①进一步刻画了营城组一段火山岩储层顶面构造形态,提高了构造解释精度,减少了分层误差;②剥除了本层密度反演产生的储层预测误差,反映出真实的火山岩储层面貌。分析认为:沉火山碎屑岩地层的形成与火山喷发时古地貌密切相关。它的发现为开发方案井位部署,特别是水平井的部署实施提供了坚实的设计依据和成功保障。

In this study,a fine description to volcanic reservoir of E21 block in Xushe gasfield is carried out;an inuimic geo-logical understanding to volcanic reservoir is further deepened;and a set of sedimentary pyroclastic rock stratum is developed at the volcanic rock of top Yingcheng 1 Member.The stratum is a tight and non reservoir characterized by middle gamma,middle to low resistivity,along with parallel and subparallel reflection.It is significant to divide it:one is to peint out the structure framework of top reservcir,to increase the structural inte^retation accuracy and to decrease the division error;another is to remove the reservoir-prediction error generated from density inversion,to reflect the true volcanic reservoir.It is considered that the formation of sedimentary pyroclasfic rock is closely related to palcogeomorphy when volcanic eruption.This conclusion can provide solid evidence and assurance forwellsite deployment,especially for horizontal well.