The Connectivity Characterization Of Distributary Channel Sand Bodies On The Shallow Delta Plain

Shallow lacustrine delta is a unique sedimentary system different from the normal delta and typical fluvial facies;the plain distributary channel sand bodies were well developed and characterized by rapid bifurcation and frequent migration,which caused various stacked styles and complex connectivity.This paper,taking the northern part of Eastern Xingliu Block as an example,started with the Ordos Oolong River sedimentary outcrop of similar background,built the quantitative geological knowledge database and qualitative superimposition,then applied the results into subsurface reservoir study and guided the well-to-well sand correlation combining with core,logging and dynamic data,then established the property model controlled by architecture elements in order to evaluate the connectivity of element sets in the sand.The main research contents and the results are as follows:(1)The thickness of single bodies performs larger changes along the lateral extent if the datas of TCF(thickness variation factor)are widely distributed,whereas the thickness has no obvious change and the single body is tabular if the data of TCF are clustered close to zero.The apparent width/thickness ratio is between 28.42~85.87 in parallel source direction,and between 21.24~35.60 in vertical direction.(2)The barriers present two different features in vertical direction :(1)the reversed S-shaped,the angle between 1.13~4.01°;(2)the incised filling formed,low-angle progradation in the top and along the pinch-out direction,the angle between 2~3.47°;whereas have little difference in oblique or parallel source direction: being forward in low angle between 0.96~4.63°.(3)There are two types in 8 kinds of sand-stacking patterns on the cutting degree and channel migration direction indicated by barriers:(1)stacking without cutting in the same direction,stacking with little cutting in the same direction,stacking with deep cutting and connecting in the same direction,stacking with deep cutting and no-connecting in the same direction;(2)stacking without cutting in the different direction,stacking with little cutting in the different direction,stacking with deep cutting and connecting in the different direction,stacking with deep cutting and no-connecting in the different direction.(4)Used the outcrop result to direct well-to-well correlation of subsurface sandbodies,firstly identified baffles,classified the vertical stages individual well,proposed three methods of correlation:by the combination of well logging curves shape,by the stacking styles of sandbodies,by mutual authentication of dynamic and static data.(5)Built the property models,ranked architecture elements in three hierarchies: superior,medium,inferior,finally four typical sets of architecture elements of the single sand body were sorted: superior-superior-superior type,superior-medium-inferior type,superior-inferior-medium-superior type,superior-inferior-superior type.The connectivity is decreasing,and linked to the position of the perforation.Thus a systematic set of connectivity characterization method about distributary channel sand bodies on the shallow delta plain is summed up,that is: using the outcrop result to direct well-to-well sand body prediction,analyzing the sand stacking patterns and connectivity,then phased stochastic simulation to get data to evaluate connectivity in sand bodies.