Research On Sedimentary Facies And Reservoirs Of H₃Voil Zone Of B125Block In Gucheng Oil Field

The Gucheng oil field locates in the northern slope of Biyang Sag, Nanxiang basin, The B125block is horst fault nose structure, of which oil bearing area is1.3km2, and geological reserves is416×104t. The layers of this block contain Shangsi formation of Neogene system、Hetaoyuan formation of Palaeogene system and Dacangfang formatiom. By weather-worn effected, the member1and2of Hetaoyuan formation and the Ⅰ、Ⅱ oil group of member3of Hetaoyuan formation have been completely denuded, the Ⅲ-Ⅷ oil field of the member3Hetaoyuan formation. The oil layer is mainly distributed in H3formation, and the H3Ⅳ oil group、H3Ⅴ oil group H3VI oil field have been put into the development. The purpose of this research interval is H3Ⅴ oil group, of which the oil-bearing area is1.07km2and the geological reserves are236×104t.The sedimentary period of H3Ⅴoil field, the landform of B125block is north high and south low of slope districr, the provenance is from northwest Of the Gucheng district, the sedimentary system is fan delta, and the the intrafacies belongs to delta front.By Statisticsing of five Wells core physical property data, the range of porosity H3V oil group is3.45-44.55%, of which the average is26.31%, the main distribution range of porosity is20-35%; the Permeability range is1-9000md, and the average of Permeability is694md.The H3Ⅴoil group of B125district is typical high permeability reservoir, The areal Heterogeneity, in-layer heterogeneity and inter-layer heterogeneity is strong, the longitudinal monolayer onrush phenomenon is serious, the plane easily along the high permeability zone formed large channel. After water flooding development in1989, the H3V oil field has high recovery degree, determining the development stage, by the oil well water rising fast, the stable production oil field is difficult, and the poor development effection, this block is urgently needed to deepen the sedimentary facies, sand body and reservoir distribution of research, which lay a solid geological foundation for adjust the potentialities and planning or subsequent.The main contents of this study are the small layer segmentation contrast, sedimentary facies, sand body distribution, reservoir physical characteristics and distribution law of research.The features of the oil group contrasted:in the H3Ⅴoil group of upper formation sedimentary period, the study area is relatively deep shallow lake water and half deep lake area, which is characterized by large set of mudstone; in the sedimentary period of H3V oil group, the earth of the study area crusted overall uplift, sedimentary environment transformed delta front subfacies, sandstone thickness, thin mudstone layers; in the late sedimentary period of H3V oil group, the earth overall crusted decline, the water was darker, again the sedimentary environment transformed the shallow lake and the half deep lake facies, mainly mudstone deposition, sandstone low-development. As a result, the stratigraphic correlation of the H3V oil group is very clear. The sedimentary rhythm of internal oil group is clear, by the sand and mud interbed, the small layer is contrasted easily.Through core observation showed, the lithology of objective interval in the study area is sandstone and mudstone interbed, the colour of sandstone is mainly gray, grizzly or brown-black, dark brown; the colour of mudstone is mainly gray green, gray black, the layer of mudstone is thin, the lithology is brittle. Rock color features reflect reducing sedimentary environment as a whole.Rock lithology are mainly medium sandstone, fine sandstone and siltstone and pelitic siltstone. The detrital minerals in rocks are mainly quartz and feldspar, among them, the quartz content is53%; the feldspar content is22.5%; the cuttings content is13.5%, the cuttings content metamorphic rock and volcanic rock are relatively high; the filler content is11%. According to the rock mineral composition, it is to know that the lithology of H3V oil group is mainly feldspar sandstone and lithic feldspar sandstone.Rock lithology are mainly medium sandstone, fine sandstone and siltstone and pelitic siltstone. The detrital minerals in rocks are mainly quartz and feldspar, among them, the quartz content is53%; the feldspar content is22.5%; the cuttings content is13.5%, the cuttings content metamorphic rock and volcanic rock are relatively high; the filler content is11%. According to the rock mineral composition, it is to know that the lithology of H3V oil group is mainly feldspar sandstone and lithic feldspar sandstone. The grain of sandstone detrital has well classify and medium psephicity, the shape is subangularity and subround, the contact between particles is mainly point contact, with a small amount of line contact.The types of bedding Various, the main types are large scale cross-bedding, oblique bedding, massive bedding and graded bedding, etc, and wash surface is development. The scale bedding is a relatively large and the bedding developed in strong proximal delta front distributary channel of which water power is relatively.According to core observation and description, it is to compile one single well facies which the core length is longer. Chooseing the combination gamma ray neutron laterolo and the self-potential curve as the dentification of logging facies. the curve of distributary channel is bell and box underwater; the curve of overbank and front sand sheet and is dactylic, the curve of distributary and lacustrine facies mud is orthoscopic conformation.The combination gamma ray neutron laterolo amplitude and natural potential amplitude of sandstone of objective interval abnormal conducts obviously, it is generally easy to identify sandstone reservoir, but there are also high-abnormal combination gamma ray neutron laterolo, no natural potential amplitude anomaly amplitude of mud shale, and the medium to small-abnormal of combination gamma ray neutron laterolo、high-abnormal natural potential of sandstone. As a result, there is a big difficulty of sandstone identification, in order to accurately identify sandstone reservoir, extracting the natural potential、combination gamma ray neutron laterolo acoustic time, microelectrode and resistivity curve reflect the characteristics of sandstone, by this approach, the difficult problem of sandstone recognition has been solved in this area.This study has been achieved nine sections of sub-layer division and contrast, compiled nine sub-layers of sedimentary microfacies and sand body distribution, porosity distribution, permeability distribution, and according to the core analysis data and laboratory test data, mercury injection, reservoir physical property interpretation data, the pore structure and type, reservoir heterogeneity characteristics have been studied.By the analysis data of core physical property, the logging interpretation models of porosity and permeability have been established, the porosity and permeability interpretation contains the gamma ray correction and self-potential correction, therefore, the interpretation accuracy of porosity and permeability has been increased maximum.