Abstract: In recent years, the theory of composite sandbody architecture proposed by CNOOC has contributed to several major oil and gas discoveries.This paper systematically introduces the context for proposing this theory, its fundamental concept, main content and characterization method as well as practical application, and discusses the significances of this theory.Ground penetrating radar reveals that the common architecture element of modern and ancient meandering river deposits is point bar composite instead of a single point bar.When their scales being larger than seismic resolution, they commonly correspond to a single channel belt or composite channel belts and represent a sub-layer or sand group.A sand body of this kind is defined as a composite sand body and is treated as a separate development unit.The composite sand body is originated from abrupt change in accommodation and source supply caused by tectonic uplift or subsidence of basin valley.The relationship between depositional process and composite sand body architecture pattern is revealed by river terrace geomorphology.This paper illustrates architecture unit, architecture bounding surfaces, architecture model, scale characteristics and their controlling factors, and defines modern sedimentary geomorphic markers of architecture bounding surfaces.Fine characterization of composite sand body architecture is the key to precisely describing remaining oil distribution and quantifying development index, and further optimizing injection-production pattern and increasing success rate of infilling drilling.

Key words: river terrace, architecture hierarchy, characterization method, composite sandbody architecture, remaining oil distribution