Study On Flow Units Of Low Permeability Reservoir Of The Middle Es₃ Member In Block Fan 29,Daluhu Oilfield

Block Fan 29 in Daluhu Oilfield is a typical low permeability turbidite reservoir,with complicated and small pore structure,poor reservoir physical properties and serious longitudinal in homogeneity.There are some prominent problems in part of the block,such as poor water injection and rapid rise in water cut,which affect the oil and gas exploration and development in the study area.Finding out the differences of water flooding effect,fluid seepage characteristics and fluid distribution between layers is of great significance to reservoir development and remaining oil prediction.Due to the complexity formation mechanism of the turbidite reservoir,13 parameters are selected based on the factors that affect the distribution of flow units.And using the method of factor analysis,five principal component factors are extracted which include reservoir factor,flow factor,sedimentation factor,and interlamellar factor.Then using the 70 sets of learning samples as the input of the model and the flow units prediction model are established based on the method of support vector machines.The established model is tested by 52 groups of predicting samples and the accuracy rate of the results reaches 90.38%.Studies show that prediction model of flow units can more comprehensive consideration of the complex mapping relationship between various geological factors and flow units.The support vector machine has broad prospects in the study of flow units.The vertical and lateral distribution patterns of the flow unit are established,based on the division result of flow unit.The research shows that the flow units of the Middle Es₃ reservoir are dominated by type III units,accounting for about 60%of the whole area.Type I,type II and type IV units is less distributed.The poor reservoir seepage capacity is consistent with the characteristics of low permeability reservoir.There are obvious differences in the distribution of flow units between the layers,the permeability of the 4² and 4³ reservoir is strong,and the seepage of the 4⁴ and 4⁵ reservoir is weak.Three kinds of rhythms are mainly developed on the section,which contains prosodic rhythm,reverse rhythm and complex rhythm.There are two kinds of division modes in the lateral direction.One is that the flow units are in direct contact with the non-seepage layer and often develops in the in the sedimentary cycles of 4⁴and 4⁵ reservoir,belongs to the outer rim of the fan and fan margin.The sandstone bodies are isolated and dispersed.The other is the lateral contact between the flow units,which mainly develops in the sedimentary cycles of 4² and 4³ reservoir,and belongs to the turbidite sand body.Flow units have a significant control over the remaining oil distribution.Among them,The water flooding of type I units have good development effect,quick flooding and high degree of exploitation.So it is no longer regarded as the main target area for potential exploration.The remaining oil is mainly concentrated in Type II and Type III units,it is the main target area for adjusting and tapping potential in the next step.Type IV units developed poorly and flooding is weak,but the original oil saturation is low,so it will not serve as the target area for remaining oil development of the next step.In addition,the marginal joints of different types of flow units and the hyperosmotic sites surrounded by the low permeability flow units tend to be favorable areas for remaining oil enrichment.