Application of Diagenetic Facies Analysis to Reservoir Prediction in Deep Water Area of the Northern South China Sea: A case study from Baiyun Sag, Zhujiangkou Basin

Key words: 
• diagenetic facies

Abstract:  Analysis of diagenetic facies method aims at establishing the genetic link between the clastic reservoir diagenesis and the porosity evolution. The model reflecting this genetic link could provide important basis for explanation on mechanism relevant to porosity evolution and its main controls as well as vertical and horizontal distribution of favorable reservoir zone. The result of this research shows that mechanical compaction, cementation and dissolution are principal diageneses, and according to their associations, five diagenetic facies associations could be recognized as :①Early carbonate cement dissolution facies;②Weak compactionstrong dissolution facies(﹤1 800 m);③ Intermediate compactionstrong dissolution facies(1 800~2 800 m)④ Slightly strong compaction slightly strong dissolution facies(2 800~3 800 m) and ⑤ Strong compactionweak dissolution facies(﹥3 800 m). The reservoir distributed in deep water area are controlled by slightly strong compaction slightly strong dissolution facies with measured porosity ranging from 10%~20%.Type Ⅲ reservoir constitutes the major reservoir zone with some Type Ⅱand Ⅰinterlayer. Generally, Zhuhai Formation(E23zh)is dominated by slightly strong compaction slightly strong dissolution facies, and the high quality reservoirs are mainly composed of delta plain channel and beach sandstones due to porosity enhancement caused by the first secondary porosity zone. For the same reason, type Ⅲ with minor type Ⅱ and Ⅰreservoirs form the relatively favorable zone in the delta plain facies. Due to weak hydraulic dynamics and finer grain overlapped by strong compaction, type Ⅲ reservoir prevails in the delta front area.