基于岩石物理相的储集层分类评价:以北部湾盆地乌石凹陷东区始新统流沙港组三段Ⅱ油组为例*

目前储集层分类方法多数只是从储集层的物性特征角度进行分类,而没有从储集层的成因机制进行分类。通过利用分析化验资料、钻测井资料和测试资料,对北部湾盆地乌石凹陷东区始新统流沙港组三段Ⅱ油组(L₃Ⅱ油组)的沉积特征、成岩作用和构造特征进行分析,进而研究其对储集层物性的影响,并对储集层进行分类。结果表明: L₃Ⅱ油组主要发育扇三角洲内前缘水下分流河道、外前缘水下分流河道和席状砂3种沉积微相;成岩相主要识别出泥质杂基充填相、不稳定组分溶蚀相和强压实致密相3种成岩相;裂缝相则以无裂缝相为主,局部可观察到高角度和网状裂缝相。在此基础上通过三者的叠加对储集层的岩石物理相进行分类命名,划分出内前缘水下分流河道—泥质杂基充填相—高角度裂缝相等9种不同的岩石物理相。根据不同的岩石物理相特征,总结归纳出了Ⅰ类好储集层、Ⅱ类中等储集层和Ⅲ类差储集层共3类储集层,实现了从储集层成因机制的角度对储集层进行分类和评价。

Reservoir classification and evaluation based on petrophysical facies:A case study on the pay set Ⅱ in Member 3 of Eocene Liushagang Formation in eastern Wushi sag,Beibu Wan Basin

Currently, most of the reservoir classification are based on the physical characteristics of reservoirs,rather than genetic mechanism. Take the pay set Ⅱ in Member 3 of Eocene Liushagang Formation as the study object,the sedimentary characteristics,diagenesis and tectonic features were studied to analyse their influences on the physical properties of reservoirs based on the analysis of assaying,drlling,logging and testing data. The results showed that subaqueous distributary channel of the inner and outer fan delta front,sheet sands were developped in the Member 3 of Liushagang Formation in eastern Wushi sag,Beibu Wan Basin;three types of diagenetic facies, mud matrix filling,unstable components dissolution and strong compaction, were identified;the fracture facies were mainly composed of none fracture facies,with network fractures and high-angle fractures appeared partially in layers. Then the petrophysical facies can be classified through the superimpositions and coupling of the sedimentary facies,diagenetic facies and tectonic facies. Nine types of petrophysical facies such as underwater distributary channel of the inner fan delta front-mud matrix filling-high angle fracture were divided in this way. Three types of reservoirs—good reservoir class Ⅰ, intermediate reservoir class Ⅱ and poor reservoir class Ⅲ,were classified based on the characteristics of different types of petrophysical facies,which realized the classification and evaluation of reservoirs from the perspective of genetic mechanism.