Reservoir Architecture Research Of Braided River In Guantao Upper Formation Of West 7^th Block,Gudong Oilfield

Gudong Oilfield has entered later development period,the extra-high water cut stage.There are amount of problems need to be solved,such as serious water logging,high distribution of remaining oil,difficulty being stable and so on.Therefore,it is necessary to fine study and recognize reservoir architecture.The paper takes the braided river reservoir of Guantao upper formation of West 7th block of Gudong oilfield as research object,utilizing rock core,well logging,three dimensional seismic and dynamic data,following high resolution sequence stratigraphy and the theory of reservoir architecture.The strata of Guantao upper formation has been determined and strata framework of different levels has been established.Then,the braided river reservoir,including three levels of braided stream,braid bar and internal bar,has been finely described and dissected.The quantitative pattern of braid bar and the distribution types of interlayer has been summarized.Finally,the three-dimensional architecture model is established.The result shows that there are five types of architecture elements: braided river channel,braid bar,natural levee,infralittoral deposit and flood plain.Also,there are four types of spatial connection relationship: braided river channel-braid bar,braided river channel-natural levee,braided river channel-flood plain,infralittoral deposit-flood plain.Through quantitative analysis of prototype model,reservoir architecture of braided river of different types in research are was dissected.For anabrached river in research area,the width of braided belt is about 800m;the length range of braid bar is between 620m-790m;the width range is between 230m-310m;the average length-width ratio is 3.2: 1.For wandering river in reaserch area,the length range of braid bar is 300m-1400 m,and the width range of braid bar is 130m-620 m,while the width of single braided river channel is about 88 m.The interlayer of braid bar is devided into two genetic types,siltting layer and cross-bar channel.There are three distribution types of interlayer inside braid bar: the extensive distribution pattern of sheet siltting layer,the partly distribution pattern of sheet silting layer,the disperse distribution pattern of narrow banded cross-bar channel.