Oil-bearing Differences And Oil-accumulating Models Of Bedding Fractures Of Lucaogou Formation In Jimsar Sag

A large number of bedding fractures are developed in Lucaogou Formation of Jimsar Sag,which are of great significance for the accumulation of tight oil and efficient development.This paper takes the bedding fractures developed in upper and lower sweet spot bodies of Lucaogou tight oil reservoir as the research objects.Through the ways of field outcrop observation,core observation,casting thin section and image logging identification,the development characteristics of bedding fractures are studied and characterized in detail.By means of inclusion temperature measurement,TOC test,physical property test,high pressure mercury injection and physical simulation,the influencing factors of differentiated oil content in bedding fractures and oil accumulation modes of bedding fractures are studied.Four oil accumulation modes of Lucaogou tight reservoirs are analyzed and summarized.The results show that there are a lot of bedding fractures in Lucaogou tight reservoir.The density of bedding fractures in upper sweet spot body is 2.23 pieces per meter,and that in lower sweet spot body is 2.65 pieces per meter.Overall,the number of bedding fractures in lower sweet spot body is more than that in upper sweet spot body.On the whole,bedding fractures develop parallel to the stratum interface,with small opening and weak filling.Among the developed fracture types,the oil-bearing property of bedding fracture is the best,and there are oil-bearing differences between bedding fractures.The factors affecting the differentiated oil-bearing of bedding fractures include the coupling relationship between the formation of bedding fractures and hydrocarbon generation in time and the coupling relationship between bedding fractures and source rocks in space.In terms of spatial coupling,there are factors such as total organic carbon(TOC),porosity,permeability and pore throat,among which total organic carbon content is the main controlling factor.The oil accumulation model of bedding fracture is summarized by physical simulation experiment which is direct hydrocarbon expulsion,differential pressure filling and fracture reservoir formation.Bedding fracture oil accumulation is not the only model for the accumulation of tight oil in Lucaogou formation.Four accumulation models of tight oil reservoir are summarized which are intra-layer micro-fracture-pore-throat transport and differential pressure charge oil accumulation,intra-layer fracture-pore-throat transport and differential pressure charge oil accumulation,micro-fracture-pore-throat network transport and differential pressure charge oil accumulation.These four oil accumulation models are reflected in physical simulation experiments.