Finedescription Of Low-permeability Reservoir Of Shahejie Formation In Block He146,Bohai Bay Basin

The lenticular lithologic reservoirswith low permeability,which generally resulted from the manysand bodies,smaller area,thinner thickness,sporadic and occasional distribution,vertical multiple layers,interbedded dry and oil layer and heavily heterogeneity,would usually have the worse adaptability of well pattern and space,obvious discrepancy between injection and production liquid quantity,and poor production effects.The issues,such as geologic features,mainly-dominated controlling factors and the distribution pattern of residual oil,will result in the efficient development for this particular oil reservoir if they could not be solved.For the above reasons,the development of such reservoirs has become the recognized world oil problem.This paper,however,based on the acquired research achievements,through the comprehensive application various disciplines which include as petroleum geology,high-resolution sequence stratigraphy,reservoir geology,sedimentary petrology,mineral petrology,development geology,well logging and reservoir engineering,and combined the integrated data such as seismic,drilling,logging,cores test & analysis,oil test and production,production test and performance,the fine description and characterization for reservoir geologic features has been conducted,fine 3D geological model has been established,and the characteristics and control factors of remaining oil distribution have been cleared in He146 faulted-block reservoir Which have some typical features,such as thin layer,lenticular,Medium porosity,low permeability,slumping deep-water gravity flow deppsite sandstone and lithologic in middle sub-member of third Shahejie Formation of Paleogene system of Xianhezhuang Oilfield.The innovative results and recognition have already been achieved as followings.(1)In this paper,rootless slumping deep-water turbidite fan sand bodies to sand geometric section contrast pattern have been established.At the same time,the formation of contrast and dividing about 126 wells have been finished.The studies have shown that the formation can be divided into 5 groups of sand layers,46 small layers or 64 single sand layers.The studies also indicated that the structural configuration of He146 faulted-block is monoclinal uplift structure dip from southwest to northeast complex cut by several faults with nearly east-west dip,and the formation dip is 5-10°.(2)In this paper,the sedimentary type of the slumping deep-water gravity flow deposits has beenidentifyied,the rootlessslumping deep-water turbidite fan sand body genetic model andthe water channel slumping deep-water turbidite fan sand body genetic model in dongying depression gentle have been established.At the same time,the six periodsedimentary evolution rule in middle sub-member of third Shahejie Formation of Paleogene system has been cleared.The studies have shown that the formation have 2 types deep-water gravity flow sedimentary systems,such as the far shore gentle slope flooding deep-water turbidite fan,which is controlled by the eastern sediment source,and the slumping deep-water turbidite fan,which is controlled by the eastern and middle sediment source.Among them,the slumping deep-water turbidite fan belongs to dongying delta front slumping deep-water turbidite fan sedimentary system,mainly developmed rootlessslumping deep-water turbidite fan sedimentary facies and water channel slumping deep-water turbidite fan sedimentary facies.The sedimentary periods from 4 to 1 in middle sub-member of third Shahejie Formation of Paleogene system were the main development period of theslumping deep-water turbidite fan,and the change of base level,the ancient terrain,sediment supply and tectonic movement on the types of sedimentary facies and sedimentary characteristics have important control action.(3)The reservoir lithology is mainly clastic feldspar sandstones with dark grey or grey,fillings are argillaceous miscellaneous and diagenetic cements,the dominant porosity types are original,and the pore structure belongs to fine pore,micro to micro-fine throat.The microcosmic heterogeneity is stronger,and the lower the reservoir property,the stronger the microscopic heterogeneity.The analysis of conventional reservoir physical data shows that the average porosity of the core is 18.2% and the air permeability is 32.7m D in the reservoir.Among them,the 2nd,3rd and 4th sandstone bodies are advantageous in reservoir quality.Thusthe reservoir types is definite as the medium porosity and lower permeability resulted from the comprehensive evaluation.Reservoir heterogeneity is serious resulted from the control of deposition and diagenesis,its planar distribution is dominant by the continuous and isolated sandstone bodies,in which the heterogeneity of sandstone distribution patterns are central and zonal model for minor and major reservoirs respectively.(4)The comprehensive classification evaluation criterion for this special thin layer lenticular lithologic reservoir has been established,which is on basis of some features parameters,such as the types of sedimentary facies,sand-body distribution,heterogeneity pattern,single sand-body area,single sand-body thickness,was formed in order to divide the reservoirs into 3 classes,which named the class I sandstones are water channel slumping deep-water turbidite fan,sandstones appear the strip,sheet,irregular or regular continuous distribution,the heterogeneity pattern is strip type,and smaller size while bigger area;thesedimentary microfacies types of class IIIsandstones are rootless slumping deep-water turbidite fan,their shape appear the little potatoes(lens body shape),the central heterogeneous model,privileged quantity while small area;the sedimentary microfacies types of class II sandstones arewater channel or rootless slumping deep-water turbidite fan,their shapes appear the bigger potatoes(lens body shape)and strips and former are dominant,the heterogeneity model is strip,center and the latter is dominant,their quantity and area scope is from class I to class II.(5)The effective thickness interpretation standards in the oil formation has been established.The study suggests that when the formation whose Physical parameters include Reservoir rock?Siltstone,Oil content?Oil immersion,SDT?260?s/m,Rcond?3?·m,R4m?4?·m,Icond?3,I4m?3,??14.5%,So?50%belongs tooillayer.It is believed that the oil content is mainly controlled by reservoir lithology and physical property.In space,the reservoir shows such distribution characteristics which includes there are many layers,scattered and thin,with few main layers.The main layer contains oil sands,which is large in scale,and the oil sands in the non-main layer are scattered,with smaller distribution characteristics,and the reservoir development and distribution characteristics are mainly controlled by sedimentation.(6)Under the costraints of the faces by step by step,the property modeling method has been proposed,which controlled by microfacies,sandstone facies,and fluid facies.Application of the modeling method,the target reservoir fine 3D geological model is established,and remaining oil distribution and main influencing factors in the different types oil sands body have been cleared.The studies have shown that the remaining oil distribution in the class I reservoirs lies in water-bearing in medium and lower degree and affected by the manual fractures,by applying the numerical stimulation and reservoirs engineering to analyze the production performance,will affected by the sedimentary facies at higher water-bearing degree,wholly,the residual oil lies at the margin of channel way,fan lobe and other area without well-space controlling;while the residual oil from the class II and IIIreservoirs are obviously affected by the combination of sedimentary facies with deployment pattern of oil-water well,lies in the area without drilling involved.The interlayer remaining oil is mainly influenced by degree of well pattern control.Therefore,the remaining oil exists in the class I,the partially covered and large class II oil sands body.Considering larger remaining recoverable reserves and less development difficulty,the part of the remaining oil is a major potential object in lenticular lithologic reservoir.(7)In this paper,a series of fine description technology of reservoir is created.According to the technical requirements,the process is mainly divided into the following five steps.(1)The acies type and sedimentary microfacies characteristicsare studied,and sedimentary facies models are established,by means of the sedimentary type identification and microfacies research method about the slumping deep-water turbidite fan.(2)Under the costraints of the water channel slumping deep-water turbidite fan sand bodies such as elevation contrast pattern and the rootless slumping deep-water turbidite fan sand bodies to sand geometric section contrast pattern,the single sand layer is finely contrasted and divided.(3)The comprehensive classification and evaluation of oil-bearing sand body was carried out by the comprehensive classification evaluation criterion for this special thin layer lenticular lithologic reservoir.(4)Three-dimensional fine geological model is established by the fine geological modeling technology which include the property modeling method under the costraints of the faces by step by step.(5)The distribution of residual oil was revealed by the oil-bearing sand body as the basic unit using uumerical simulation through reservoir.The research results and recognition not only for the target of reservoir remaining oil potential in follow-up study provides provide abasic model,but also for similar reservoir to conduct fine reservoir description,residual oil distribution and efficient development technology research provide a solid theoretical foundation and technical supporthas important theoretical and practical significance.Therefore,the research in this paper has importanttheoretical and practical significance.