三塘湖盆地火山岩油气藏特征及有利成藏条件

ANALYSES ON CHARACTERISTICS AND FAVORABLE FORMING CONDITIONS OF VOLCANIC RESERVOIRS IN SANTANGHU BASIN

三塘湖盆地火山岩的分布广、厚度大,油气显示层数,含油产状多为油斑、油迹。孔隙以次生的溶蚀孔缝为主,原生孔隙为杏仁孔和气孔,大多孤立存在,一般小于5%,但裂缝发育带的孔隙度可达8.3%～22.1%。孔隙为溶蚀孔隙、风化-淋滤孔缝、孔隙-裂缝型、裂缝-混合孔隙等4种类型。油藏为裂缝性油藏,北东-东西向构造及断裂控制主要的油气藏分布,火山岩裂缝的主要发育期与排烃期相近,有利于成藏,致密火山岩提供了火山岩油气成藏良好的封盖条件。

Volcanics in Santanghu basin stretches widely with large thickness, where several layers with oil gas indication have occurrence of oil patch or oil trace. Secondary solution pores and fractures constitute the majority there, while original pores are isolated amygdaloid ones and vesicles with a porosity of less than 5%. However the porosity in some fracture abundance areas can reach 8.3% to 22.1%. There developed four types of pores: solution, weathered -leached, porous-fractured and combined fracture respectively. The reservoirs are fractured, and the distribution of which are controlled by north northeast to east-west structures and faults. The main volcanic fracture growth period was near the expulsion stage of hydrocarbon, at the same time, the tight volcanics provided good capping and sealing conditions, which are favorable for reservoir generation.