Study On The Sedimentary Facies Of Fuyang Members In Block D16-2in Fuyu Oilfield

Fuyu oilfield is located in Ningjiang, Songyuan City,Jilin Province which is near the beautiful Songhua River.D16-2regional area is located in the East South Central of Songliao Basin which is the Eastern edge of depression. Fuxin upheaval of the Fuyu III structure is a dome anticline which is complicated by faults and it’s a fractured, low permeability sandstone reservoir.The reservoir is shallow.The average burial depth is from325to540m. The study area D16-2is located in the east of Fuyu oilfield. The purpose layers spring three&four which belongs to Cretaceous are also called Yang DaChengZi&Fuyu.It’s blocked by faults in the East and west sides.So the reservoir has thin sand,poor lateral connectivity,low permeability&porosity, high heterogeneity and low oil abundance. Reservoir is controlled by tectonic.The study area is3.04km2.The formation temperature is31.5℃.The pressure coefficient is1.06. The original formation pressure is4.4MPa. The saturation pressure is3.6MPa under the normal oil pressure system.It has1184.1×104t geological reserves,but only390.7×104t could pick out.The main layers of Fuyu is4,7,8,10,11,12and14,16,19,21,24,25layer of Yang DaChengZi. Physical characteristic is extremely different.The porosity is between22%to30%and permeability is between20×10-3to200×10-3μm2.The average initial oil saturationis is72%. Statistics by December2011, it has drilling496,357oil wells and139water wells. The extent of recoverable reserves recovery is72.9%.After30years waterflood, moisture content became higher and the development is facing a severe situation..No matter what stage, reservoir description is based on the reasonable layer division and contrast. Through detailed analysis of layer division and contrast in D16-2of Fuyu oilfield in spring four&three show the principle of the method.From the old layer to new,Yang DaChengZi oil layer divided into6sand groups,Fuyu oil layer divided into4sand groups.More detailed,the6sand groups include13members and the4sand groups include17members.We can see various layers thickness variation is not obviously from the layer contrasting cross-section.This shows that the overall depositional environment should be more stable in the D16-2. In order to keep up with the pace of production, summed up five methods in plane and two methods in plane setion to identify the single sand body after the division of the layers. Five methods are depositing a thin layer of sand between the river, the difference in elevation of the river, the river in the lateral evolution of different thickness, the superposition of the river, the river from a thick thicken thinning.Two methods are argillaceous discontinuity and calcareous discontinuity. So on the basis of layer contrasting,they are splited into early and late expect1,2,5layers,So the D16-2summarizes57blocks monolayer.Since the D16-2block has been discovered for a long time. On the basis of previous work,ultimately makes the layer division results more reasonable.Combines rock and mineral identification information and heavy mineral assemblages comprehensive found Fuyang reservoir source direction mainly from the south East of the Changchun-Huaide delta system and the direction of Tongyu Baokang System which is the main source of material.By the study of the sediment petrology, sedimentary rhythm, particle size analysis, sedimentary structures, fossil features, mud color and other aspects found that spring four is delta facies and delta front has underwater distributary channel, overbank sand, mouth bar, split between the Bay; delta plain can be subdivided into distributary channel, overbank sand, crevasse splay, split between the Bay. Sedimentary evolution from bottom to up is water into the delta facies.Spring three is meandering river.There are riverbed facies,bank facies,river-man facies.Further subdivided into7micro facies. Such as:bed residence, while beaches, natural levee, crevasse splay, floodplain, river lakes and rivers diffuse diffuse swamp.Using spontaneous potential, gamma ray, sonic, resistivity and other logging curve to summarizes the characteristics of each phase of the microfacies.Then considering coring wells facies. Finally, these features apply to the non-coring wells, in order to better cross-section of all the wells in the region with an objective understanding.The river is an important area of sedimentary microfacies. Throughout this study and previous research on this block of D16-2, summarizes three eventually be used to identify a single river boundary method:(1) channel sand elevation difference between the top surface layers (2) discontinuous sand body between the river (3) differences in channel sand body size. Sedimentary microfacies have a crucial impact on the distribution of reservoir sands in the vertical plane and the exhibition bout on points. Overall sandstone thickness, effective thickness, pore throat radius,heterogeneity coefficient is showing a strip as same as the river and sedimentary facies distribution is made to EN-WS direction. The distribution of these parameters in the overbank sand, abandoned channel sand bodies of these micro-phase development weaker than the river, microfacies strong hydrodynamic this point dam formation. Sedimentary microfacies affect the performance of these reservoirs exist, such as distributary channel, mouth bar, point bar are advantage microfacies for the oil and gas accumulation zone.