三塘湖盆地石炭系火山岩油藏储集空间特征与成因机理

Reservoir Space Characteristics and Genesis Mechanism of Carboniferous Volcanic Reservoir in Santanghu Basin

三塘湖油田牛东区块上石碳统(C_2k)卡拉岗组火山岩油藏储层岩性主要为杏仁状安山岩、杏仁状玄武岩、自碎角砾状安山岩及自碎角砾状玄武岩,其储集空间可分为两大类:一类为孔洞类,主要有钠沸石未完全充填的气孔、杏仁体溶蚀孔、粘土矿物及葡萄石杏仁收缩孔、基质溶孔、以及火山玻璃和长石类矿物颗粒微孔;一类为裂缝类,主要为未被钠沸石及绿泥石完全充填的火山岩自碎缝、收缩缝、构造缝以及各类缝充填物溶蚀形成溶蚀缝。通过研究,岩浆的物质成份、喷溢相带以及后期改造作用是形成火山岩优质储层的主要因素。粘度大,流动性差,气体逸散较慢的中性岩浆,形成的安山岩是最佳储层,而喷溢旋回末期是形成杏仁体、气孔及自碎缝的有利时期,喷溢旋回间期的风化淋滤为各类溶蚀孔形成提供了条件。火山岩储集空间的形成机理对寻找火山岩储层具有重要意义。

The main rock kinds of volcanic reservoir of the Carboniferous Kalagang formation of block Niudong in Santanghu basin are amygdaloidal andesite, amygdaloidal basahs, auto-breeeiated andesite and auto-breceiated basalts. Reservoir space is divided into two types. One type is pore-cave space system, including air hole not fully filled by natrolite, amygdaloid body corrosion pore, clay mineral and prehnite almond＇s sinkhole, matrix dissolved pore, and volcanic glass and feldspar mineral grain＇s micropore. The other is fracture space system, including volcanic auto-fracture not fully filled by natrolite and chlorite, shrinkage fracture, structural fracture as well as corrosion fracture formed by corrosion of filling in various fractures. By analyzing, main factors forming high quality volcanic reservoirs are the magma composition, eruptive facies belt and deuteric alteration. Andesite, formed by intermediate rock with high viscosity, slow fluidity and slow gas dispersion is the optimum reservoir. Optimum period of forming amygdaliod body, gas hole and auto-fracture is in the end period of eruptive cycle. The weathering and eluviations in the period of eruptive cycle provide forming condition for various corrosion pores. The forming mechanism of volcanic reservoir space is of significance for seeking volcanic reservoirs.