When quantifying sandbody with vertical well data

the volume of sandbody often cannot be defined accurately due to the uncertainty of the interwell correlation.Horizontal well data are of significant referential value for lateral prediction of reservoir sandbody

which is difficult to be achieved by conventional vertical well data.Horizontal wells can reveal lateral variation of sandbodies

so as to assist us in quantitative characterization of sandbodies and quantitative classification of lithofacies units.This study is composed of 4 steps.Firstly

it indentified 4 types of lithofacies units according to the braided-river characteristics in the study area

coring data in vertical wells and well logging data in vertical and horizontal wells

with a view to classify lithofacies units in vertical and horizontal wells.Secondly

a quantitative research on the sandbodies was carried out with horizontal and vertical well data

and thus confirmed the configuration and scale of channel bars and braided channel sandbodies.Besides

the length-width ratio of channel bars

the width ratio of channel bar to channel and that of interbed to channel bar were well established.Subsequently

the seismic wave impedance inversion on braided-river reservoirs was carried out under the constraint of information from sandbodies encountered by horizontal well.Finally

prediction of lithofacies units was done based on the quantitative characterization of sandbodies and the results of wave impedance inversion.Results show that:(1) the horizontal well data can be used to finely characterize lithofacies distribution within reservoirs and improve the accuracy of sandbody quantification and description of internal reservoir heterogeneity;(2) the information from the laterals can increase the number of sample points in seismic inversion

thereby lower the uncertainty of interwell reservoir prediction

greatly improve the accuracy and reliability of internal reservoir seismic inversion

and increase the reliability of the reservoir lithofacies model.