辽河坳陷古近系碎屑岩储层孔隙演化特征探讨

Discussion on pore evolution features of clastic rock reservoir of the Paleogene in Liaohe Depression

辽河坳陷古近系的主要沉积特征是物源多、沉积体系多、砂岩成熟度低及砂体规模小。通过成岩作用和成岩相研究,储层成岩相可划分为4种,即碳酸盐胶结相、自生粘土矿物胶结相、石英胶结相和粘土矿物转化相。这4个相可进一步划分为7个亚相自生粘土膜胶结亚相、晶粒状碳酸盐胶结亚相、自生高岭石胶结亚相、石英胶结亚相、嵌晶状碳酸盐胶结亚相、伊/蒙混层亚相和伊利石亚相。不同成岩相分布明显受深度控制,具有在垂向上相连的展布特征,垂向上可组成6个成岩相带。通过大量的砂岩和泥岩孔渗数据统计分析,建立了6个对应的高孔渗带(ABCDEF)与6个低孔渗带(abcdef),它们与6个成岩相带在空间分布上具有一一对应关系,即A-a、B-b、C-c、D-d、E-e和F-f分别与晶粒状碳酸盐相带、自生高岭石相带、石英胶结相带、嵌晶状碳酸盐相带、伊/蒙混层粘土矿物相带和伊利石相带相对应。可见,不同成岩相带对应不同孔隙度发育带的孔隙演化,并从有机质演化的角度解释了上述对应关系。应用这一规律在鸳鸯沟地区有利储层孔隙预测中取得了较好效果,验证了该区储层孔隙演化特征及其对油气运聚的影响。

The sedimentary features of Liaohe Depression are characterized by the small-scale sandbody, multi-provenance, multi-sedimentary systems and low degree of sandstone maturity. Analysis on the diagenesis and diagenetic facies shows that the reservoir diagenetic facies in Liaohe Depression can be divided into four types, i.e. carbornate cemented facies, authigenetic clay mineral cemented facies, quartz cemented facies, and clay mineral transformed facies. These facies can further be divided into the following seven subfacies, i.e. the clay authigenetic film cemented facies, crystalline grained carbonate cemented facies, authigenetic kaolinite cemented facies, quartz cemented facies, mosaic carbonate cemented facies, illite and montmorillonite mixed layer facies and illite facies. The distribution of these facies are obviously controlled by their depths, and is characterized by a vertical connection, which can constitute six diagenetic bands. Six high porosity-permeability bands （ABCDEF）and six low porosity-permeability bands （abcdef）are established by a great deal of statistic analysis on sandstone and mudstone porosity and permeability. They .correspond respectively to six diagenetic facies zones, i.e. ： band A- a, band B- b, band C- c. band D- d, band E - e, band F- f respectively correspond to the crystalline carbonate facies band, authigenetic kaolinite facies band, quartz cemented band, poikilitic carbonate cemented facies band, illite and montmorillonite mixed layer facies band and the illite facies band. Different diagenetic facies bands in the sandstone reservoir correspond to the different evolutions of different porosity development bands, and the relationship between them can be illustrated by the viewpoint of organic evolution. A satisfactory effect has been obtained by using the above regulation in the prediction of favorable reservoir pores in Yuanyanggou area. As a result, the effect of reservoir pores evolution on oil and gas migration has been proved in the area.