西湖凹陷中南部花港组下段储层成岩孔隙演化

Diagenetic-pore Quantitative Evolution of the Reservoir from Lower Huagang Formation in the South-central Xihu Sag

西湖凹陷中南部花港组下段储层具有丰富的致密气资源,是该区油气勘探开发的热点。基于岩石薄片、扫描电镜、物性测试和X衍射等资料,对西湖凹陷中南部花港组下段储层特征、成岩作用及孔隙演化等进行了研究。结果表明,储层孔隙度主要在7%∼10%,渗透率主要在0.10∼0.50 mD,裂缝不发育,属于致密储层。储层先后经历了早成岩A期、早成岩B期和中成岩A期,目前处于中成岩B期,压实作用、溶蚀作用和胶结作用较强。孔隙定量演化结果显示,压实作用使储层孔隙度降低了29.67%,是储层原生孔不发育的主要原因;溶蚀作用使储层孔隙度增加了15.14%,是深部储层发育的关键因素;胶结作用使储层孔隙度降低了13.55%,是储层孔隙结构变差的重要原因。综合孔隙演化结果和油气充注时间关系,该区花港组下段储层属于“先致密后成藏”的致密储层。

The Lower Huagang Formation in Xihu Sag is rich in tight gas resources,which is a hot spot for oil and gas exploration and development in this area.Based on observation of rock slices,scanning electron microscopy,physical property testing of the core and X-ray diffraction,the basic reservoir characteristics,the diagenesis and the pore evolution of the reservoir are studied.The results show the reservior porosity is mainly between 7%and 10%,the permeability mainly between 0.10 to 0.50 mD,and the fracture undeveloped,so the reservoir belongs to a kind of tight sandstone reservoir.The reservoir has experienced the early diagenesis stage A and B and the middle diagenetic stage A,and is currently in the middle diagenesis stage B,and the reservoir are greatly influenced by compaction,dissolution and cementation.The results of pore quantitative evolution show that the compaction reduces porosity by 29.67%,which is the main reason for the undeveloped primary pores;the dissolution increases porosity by 15.14%,which is the key factor for the development of deep reservoirs;with the influence of cementation,the reservoir porosity reduces by 13.55%,which is an important reason for the deterioration of reservoir pore structure.Based on the relationship between pore evolution results and oil-gas charging time,the Lower Huagang Formation in the south-central of the Xihu Sag is a kind of tight reservoir that denses before the accumulation of oil and gas.