渤中凹陷中生界火山岩特征及优质储层控制因素

Characteristics of Mesozoic Volcanic Rocks and Controlling Factors of High Quality Reservoirs in Bozhong Depression

为了探讨火山岩油气藏优质储层形成的控制因素,基于薄片分析、扫描电镜、孔渗分析以及高压压汞测试等手段,对环渤中凹陷中生界义县组火山岩的岩石学特征、孔喉结构及物性特征进行了分析。研究结果表明,环渤中凹陷中生界火山岩主要发育英安岩、粗面岩、安山岩、玄武岩、凝灰岩和隐爆角砾岩。依据储集物性和孔喉结构差异,将火山岩储层划分为4类(Ⅰ类、Ⅱ类、Ⅲ类和Ⅳ类储层),其中,Ⅰ类、Ⅱ类储层为优质储层:Ⅰ类储层为发生隐爆角砾化作用并发生大面积溶蚀作用形成的中酸性隐爆角砾岩,为高孔-中渗型储层;Ⅱ类储层为发生大面积溶蚀作用形成的中酸性粗安质隐爆角砾岩和粗面岩,为高孔-中低渗储层。优质储层的形成主要受控于岩性岩相、界面处溶蚀以及隐爆造缝三方面作用。优质储层发育在中酸性隐爆角砾岩发育溶蚀的界面位置,界面溶蚀和隐爆作用越强,越易于形成优质储层。

Based on the analyses of thin section,electron microscope scanning,porosity and permeability,and high pressure mercury injection,the petrological characteristics,pore throat structures and physical properties of volcanic rocks of Mesozoic Yixian Formation in the central Bohai depression were studied,and the controlling factors of the high-quality reservoir formation were discussed.The results show that dacite,trachyte,andesite,basalt,tuff and cryptoexplosive breccia are mainly developed in the Mesozoic volcanic rocks in the central Bohai depression.According to the differences of reservoir physical properties and pore throat structures,the volcanic rock reservoirs can be divided into four types(Type I,Type II,TypeⅢand TypeⅣ).Type I and Type II reservoirs are high-quality reservoirs.Type I reservoirs are mainly composed of intermedium-acid cryptoexplosive breccias with large-scale dissolution and belong to high porosity-medium permeability reservoirs;Type II reservoirs are mainly composed of medium-acid lava with large area dissolution,high porosity-low permeability.The formation of high-quality reservoir is mainly controlled by lithology,interface dissolution and cryptoexplosive fracture.The high-quality reservoirs are often developed at the interface of cryptoexplosive breccia of intermedium-acid rocks.The stronger the interface dissolution and cryptoexplosion,the easier it is to form high-quality reservoirs.