| The Lufeng Sag,located in the northeast of Zhu Ⅰ depression in the Pearl River Mouth Basin,is one of the most explored sag at present,but most of the studies on this area focus on the southern part of Lufeng Sag,and there are few studies on the differences of tectonic features in different areas in the north and south.Meanwhile,as the number of conventional oil and gas reservoirs decreases,the importance of fractured oil and gas reservoirs gradually emerges,but previous research on the fractures inside the Lufeng Sag is less,and the distribution pattern of the fractures is not very clear,which requires the use of suitable methods to predict the fractures.The paper is guided by the theories of tectonic geology and tectonic analysis of the oil region,and based on the collection and collation of 3D seismic data,relevant well data and core data in the study area,it studies the differences in tectonic features and tectonic evolution in the north and south regions,analyzes the distribution characteristics of stresses in different periods in the study area,makes quantitative prediction of fracture development density in different periods,and analyzes the formation of different tectonic features in the north and south of the Lufeng Sag.The study shows that(1)the internal structure of the Lufeng Sag is dominated by semi-graben,and different sub-lying areas exhibit different structural features at different stages of rifting,influenced by the controlling effect of boundary fractures.(2)There are some differences in the tectonic evolution of the north and south of the Lufeng Depression: during the Wenchang Period,the rifting center is in the south of the Lufeng Sag;during the Enping Period,the rifting center is in the north of the Lufeng Sag.(3)There are three levels of fractures in the Paleocene of the Lufeng Sag,and the fractures have different activities in different periods: in the Wenchang period,the fractures in the southern part of Lufeng Sag are more active than those in the northern part,and in the Enping period,the fractures in the northern part are more active than those in the southern part.(4)Through finite element numerical simulation studies,it was verified that the change of regional extensional stress direction led to different stress strengths in different periods in the north and south regions within the Lufeng Sag.(5)The identification and description of fractures in the study area by core and imaging logging data,combined with regional stress distribution characteristics and rock fracture guidelines,quantitative prediction of fracture development in different periods in the study area,and hierarchical classification of development areas according to fracture density,the main fracture development areas are Lufeng 15 Sub-Sag,Lufeng 13 east Sub-Sag,Lufeng 13 east Sub-Sag western gently sloping zone.(6)In summarizing the results of the previous work.Based on the summary of previous studies,the development patterns under the control of two different styles of fracture systems in the north and south of the Lufeng Sag are proposed.The differences in the properties of the basement rocks in the study area lead to the differences in nature of the pre-existing fractures,which determine the differences in the tectonic characteristics of the north and south of the Lufeng Sag. |
