Study On Reservoir Architecture Of The First Member Of Taizhou Formation In The South Area Of Haian Depression

The First Member of Taizhou Formation in Haian south area is the major oil layer with a comprehensive water cut of 96.2%.The overlapping of braided river delta front sand bodies at different sedimentary stages causes the unclear understanding of the transverse connectivity of the sand bodies in Bao 1 Block,and the seepage barrier inside seriously affects the later development of water injection.Based on core and logging data,it carries out the study of the analysis of architecture interface,identification and distribution of architectural element and their distribution characteristics,which reveals the correlation between reservoir architecture and distribution of remaining oil.The main conclusions and achievements are as follows.The 1^st member of Taizhou Formation is divided into 3 sand groups.The K₂t₁¹were divided into 6 sublayers.The K₂t₁³and K₂t₁²are both divided into 3 sublayers.Tai 1Member consists of the braided river delta sedimentary,which is divided into 11 types of lithofacies by the core.Its main sedimentary microfacies are the underwater distributary channel main body,the underwater distributary channel lateral margin,estuary bar and the turbidity deposite,etc.According to the genetic model,the internal 5-level architecture interfaces can be divided into 3 types:mud,physical and calcium.Based on the petroelectric characteristics of key wells,the identification and classification criteria of different types and levels of architecture interfaces and different architecture elements are established.Thick sand bodies of braided channel are dissected in order to determine the interface of each stage and clarify the spatial combination pattern characteristics of barrier type and cascade type between single stage channels.The quartz,feldspar and lithic debris are the main clastic components in the reservoir sand bodies such as the underwater distributary channel main body,the estuary dam and the mat sand of the side of the underwater distributary channel.The closer to the river side edge,the higher the content of unstable components.The main body of the river are mainly 1^st type and 2^nd type,and the lateral margin of the river is mainly 3^rd type.The 3-D model of the reservoir architecture is established by stochastic modeling method.Under its restraint,the reservoir property model is built up which reveals the feature that the reservoir physical property value of the main channel is higher than that of the channel lateral margin in the architecture elements.In addition,the architecture interfaces between the multi-proliferations are the 3-level in the single channel sandbody.The mud and physical interfaces play a control role on the local remaining oil enrichment.A mud or physical interface between single-cause sand bodies is a 4-level architecture interface.This type of interface hardly controls the local remaining oil enrichment.Due to the control of various factors in the braided river sedimentary environment,the main architecture elements of the study area are poor in physical properties,which leads to the reservoir belongs to the medium-low porosity,low-ultra-low permeability reservoir.The main body of the river in the architecture elements is type I-II good high-quality reservoir,while thelateral margin of the river are type IV reservoir.It is believed that the oil and water controlled by the structural elements are distributed along the main body of the river,and the side of the river at the high structural position is also filled with oil and gas.