四川盆地东北部地区长兴组碳酸盐岩成岩作用及储层孔隙演化

Diagenesis of the Changxing Formation Carbonate Rocks in the Northeastern Sichuan Basin and Reservoir Porosity Evolution

以四川盆地东北部长兴组碳酸盐岩为研究对象,应用薄片、铸体、阴极发光和X射线衍射等室内分析技术,对其成岩作用、成岩演化序列、储层孔隙演化及其特征进行了详细研究。研究区常见的成岩作用有:压实压溶作用、胶结作用、充填作用、交代作用、白云化作用、重结晶作用、溶蚀作用、破裂作用等成岩作用。其中对储层孔隙发育影响较大的主要是胶结作用、溶蚀作用、充填作用、白云化作用和重结晶作用。长兴组礁滩组合储层主要发育泥晶灰岩、泥晶颗粒灰岩、亮晶颗粒灰岩、礁灰岩及礁白云岩等,由于物质成分的差异,其孔隙演化具有不同的特点。根据成岩现象间的先后顺序、矿物间的相互切割关系以及成岩作用过程中孔隙演化特点,总结出长兴组的成岩序列及孔隙的演化规律。

The object of this work is the Changxing Formation carbonate rocks in the northeastern Sichuan basin.Our purpose is to study their diagenesis,diagenetic sequence,porosity evolution characteristics by use of analytical techniques of thin sections,casting,cathodoluminescence and X-ray diffraction.The widespread diagenesis in this area principally includes compaction,cementation,filling,replacement,dolomitization,recrystallization,dissolution and fracture diagenesis.Of all the diagenesis,cementation,dissolution,filling,dolomitization and recrystallization contribute greatly to the porosity development of reservoirs.In the reef-beach reservoir of the Changxing Formation,micrite limestones,micrite grain limestones,sparry grain limestone,reef limestone and reef dolostones developed well.Because of the composition differences,the pore evolution owes different characteristics.According to the diagenetic order,mutual cutting relation between minerals and the porosity evolution characteristics in the diagenesis process,this paper sums up the diagenetic sequence and porosity evolution rule in the Changxing Formation.