北部湾盆地涠洲10-3油田及围区流三段IV油组沉积相特征

WZ10-3 oilfield is located in the southeast side of the downthrown block of No.1 fault of Weixinan Depression in the BBW Basin. Previous studies suggest that the alluvial fan is widely developed in the fouth oil group of Liu-3 Member in WZ10-3 oilfield and surrounding areas. But the location, number, and size of fan bodies are not clear. With the guidance of basic theory and methods of sedimentology, basised on the detailed core observation, combining with the comprehensive analysis of logging curve and seismic reflection characteristics, this paper clarifies the characteristics and the types of subfacies and microfacies of alluvial fan in the fouth oil group of Liu-3 Member in WZ10-3 oilfield and surrounding areas, and then discusses the characteristics and distribution of debris flow deposits. By comprehensive analyses of individual well sedimentary facies, section sedimentary facies and plane sedimentary facies, the alluvial fan sedimentary system is mainly developed in the sedimentary period of the fouth oil group of Liu-3 Member. In the depositional period of MSC1, five alluvial fans have developed in the northern part of the study area, three alluvial fans have developed in the southern part, some non-channel sandy debris flow deposits have sporadically developed in the background of sheet deposit between fans in the middle part. In the depositional period of MSC2, the total area of fans has increased compared with that in the depositional period of MSC1. The number of alluvial fans of the northern part of the study area in the depositional period of MSC2 has decreased to three compared with that in the depositional period of MSC1. The number of alluvial fans in the southern part has never changed, and the scale has changed little. The number of sandy debris flow irregularities that have developed in the middle part has increased compared with that in the depositional period of MSC1. Mid-fan glutenite bodies is the favorable oil and gas reservoir facies belt.