Abstract: The sandy braided channel bar is an important reservoir type for oil and gas development with complex internal inhomogeneity. To address the problems of poorly understood sedimentary characteristics, architecture model and residual gas distribution rule of the braided channel bar in the Lower He8 Member of the Sulige Gasfield, a study was conducted with the analytic hierarchy process as a guide, in combination with the analysis of architectural elements and the data from ancient outcrop, modern sedimentation, coring and dense well pattern logging. The results show that the braided river sand bodies have the characteristics of mutual superposition in the longitudinal direction and large contiguous distribution in the horizontal direction, and the variation of the accommodable space controls the contact relationship of the sand bodies, and four types of sand body vertical superposition patterns are proposed during the rise and fall of the datum; as the sand body is internally hierarchical, the different seepage barriers (interbeds) are formed during the deposition of the braided river, which are divided into five types, such as river bottom stagnant mud and gravel deposits, channel bar silt layer, side-deposited fine-grained deposits, abandoned river fill deposits and overbank fine-grained deposits, and the silt layer is the main factor controlling the oil and gas seepage inside the channel bar; according to the difference of water flow energy characteristics and deposition characteristics in different locations of the channel bar, the channel bar is divided into the architectural elements such as head, center, wing, tail and silt layer, etc. The tail is obviously more inhomogeneous than the head, and the upper part of the channel bar with more developed silt layer is more inhomogeneous than the lower part; the tail and upper parts of the channel bar are the residual gas enrichment areas. The results of the study are useful for the exploration and development of reservoirs in the study area and similar braided river depositional environment.

Key words: braided river deposits, channel bar, reservoir internal architecture, seepage barrier, residual gas type, He8 member, Sulige Gasfield