长岭断陷白垩系储层发育特征和控制因素

长岭断陷白垩系发育碎屑岩和火成岩两类储层,其储层的物性特征存在差异。研究表明,油层主要分布在白垩系浅层扇三角洲平原相的砂岩储层中,气层主要分布在营城组及以下层位溢流相和爆发相的凝灰岩和流纹岩储层中。碎屑岩储层以砂岩为主,具有成分成熟度高、结构成熟度中等、岩屑和填隙物含量高等特点;储层物性较差,多数层段为低孔低渗储层。火成岩储层,岩性主要为溢流相和爆发相的流纹岩或凝灰岩,储集层孔隙度、渗透率非均质性较强,但裂隙较发育,由裂缝连通孔洞,成为较好的储集空间。影响两类储集层发育的主控因素主要为储层岩相和成岩作用。碎屑岩储层以扇三角洲平原相的砂砾岩为主,登娄库组压实作用相对较弱,孔隙相对发育;营城组和沙河子组压实作用较强,且次生孔隙发育弱,甚至不发育。火成岩储层岩性主要以爆发相的凝灰岩和溢流相的流纹岩为主,原生孔隙与裂缝发育,为冷却成岩和热液成岩共同作用的结果。

Characteristics of Cretaceous Reservoirs and the Controlling Factors of Changling Faulted Depression

There are mainly volcanic and clastic rock reservoirs at Cretaceous in Changling faulted depression, with different physical characteristics. It is shown that oil layers are mainly developed in the shallow sandstone of fan delta plain facies. The gas layers are mainly distributed in the rhyolite and eruptive tuff of overflow and explosion facies under Yingcheng Formation. The clastic rock reservoirs are mainly made of sandstone and characterized by high maturities of composition and middle texture, high contents of rock debris and matrix, and multi-type cemention. Physical properties of the clastic rock reservoirs are not good for production, majority of which are low-porosity and low-permeability reservoirs. Volcanic rock reservoirs are mainly formed by rhyolite in overflow facies and eruptive tuff in explosion facies, with high degree of heterogeneity of porosity and permeability, and many fractures, which may be good reservoir sites owing to the fracture connection cavity. Reservoir lithofacies and diagenesis are mainly characterized with two factors in affecting reservoir development. Sandstone and conglomerate of fan delta plain facies are mainly developed in clastic rock reservoirs, with weak compaction and more pores in Deng Louku Formation. Strong compaction and less or no secondary pores are seen in Yingcheng and Shahezi Formation. Volcanic rock reservoirs are chiefly rhyolite in overflow facies and eruptive tuff in explosion facies, and primary pores and fractures are developed, which is the result of both cooling diagenesis and hydrothermal fluid diagenesis.