平落坝香二气藏成藏条件剖析

ANALYSING THE RESERVOIR FORMING CONDITIONS OF PINGLUOBA XIANG 2 GAS RESERVOIR

平落坝气田是川西龙门山前缘发现的又一个中型气田。文章从沉积构过发展、孔隙演化、油气运聚史、圈闭类型和特征、储层地质模型、封盖性能、水文地质条件等方面剖析了平落坝香二气藏的成藏机制。该构造紧邻上三叠统生烃凹陷，本身也具有良好的生烃条件，早期聚气条件好，晚第三纪以来有丰富的“晚成气”补给；属短轴高丘状背斜构造类型，褶皱适中、圈闭完整，无破坏性大断层切割；香二段气层上覆香三段泥质岩厚度大，宏观特征和微观结构研究认为属封盖能力强的优良盖层；香二段储层发育６种类型次生储集空间，孔隙结构较好，选择性溶蚀导致信层的非均质，具较高的有效储集概率；张开、半充填低角度裂缝发育，与次生溶蚀孔形成有机的配置，裂缝是重要储集空间和渗滤通道，是气并产能的重要控制因素；天然气的保存条件优越。

Pingluoba gas field is another midium one found out in the front of Longmen Mountain in West Sichuan after Zhongba gas field.The reservoir forming mechanism of Pingluoba Xiang 2 gas pool is analysed in the aspects of sedimentary structure development,pore evolution,oil-gas migration history,trap type and features,reservoir geological model,captock's performance,hydrologic geology condition etc.The structure is closely linked with a source sag of Upper Triassic Series.Itself is of good hydrocarbon generating condition and good gas storage condition at early stage.Abundant'paulopost gas'recharge has existed since Tertiary period.It belongs to the structure with minor axis high mounded shape, moderat folds,complete trap and without destructive major fault cut.The mudstone of Xiang 3 member overlying the gas bearing formation of Xiang 2 member,with a big thickness,belongs to good caprock through studying its macrofeatures and microstructures.Xiang 2 member gas reservoir has 6 types of secondary storage space,better pore structure,selective kartification made it heterogeneous and with a higher effective storage probability.Opened and semi-pecked small angle fractures are developed and formed a good coordination with secondary karst pores. The factures are main storage space, percolation channel and the main control factors of gas well production capacity. Gas preservation conditions are good.