龙湾筒凹陷九佛堂组火山岩岩相特征研究

Study on Characteristics of Volcanic Lithofacies in Jiufotang Formation of Longwantong Sag

论文利用已有钻井取心和薄片等资料,系统研究火山岩的岩石学特征。利用新处理的地震资料和测井资料,分析火山岩相的平面展布特征,并预测有利储层的发育范围。研究表明:火山岩岩性以中性和中碱性为主,包括安山岩、粗面岩、粗安岩、火山角砾岩和凝灰岩等;九佛堂时期火山活动分为三期,早期火山作用强烈,以点式喷发为主,晚期逐渐减弱,火山岩的分布受控洼断裂和古地形的控制,岩相分为爆发相、溢流相和火山沉积相;其中,溢流相上部亚相火山岩具有裂缝和气孔两大储集空间,储集性能明显好于其它相带。

In this paper,the petrological feature of volcanic rocks was researched systematically by using the information of drill cores and rock slices which can be selected. The characteristics of surface distribution of volcanic lithofacies were analyzed before the distribution scope of advantageous reservoirs was forecasted. In the two kinds of investigative work, the seismic data and logging data that were both processed recently were utilized well. So, some new viewpoints were proposed through this study. Neutral volcanics and alkaline volcanics were the most in all volcanics of Jiufotang formation, including andesites, trachytes, trachyandensites, lava breccias, tuffs, etc. Volcanic activity has happened three times during the whole Jiufotang period. The early period volcanic activity was the strongest which erupted from a point mostly, but the activity of volcanic became weak gradually from then. The distribution of volcanics was controlled by the ancient landforms and the fractures which have ever controlled a sub-sag. The volcanic lithofacies were divided into eruption facies, overflow facies and volcano sedimentary facies. Among these lithofacies the volcanics from the upper subfacies of the overflow facies had two kinds of reservoir spaces which included fractures and air holes. The performance of this kind of volcanic reservoirs was obviously better than those of other kinds of volcanic reservoirs.