Establishment of the Depositional Model of Sandy Braided River: A Case from the H Block in Orinoco Heavy Oil Belt, Venezuela

Key words: 
• modern sedimentation /
• empirical equation /
• horizontal well /
• depositional model /
• sandy braided river /
• Orinoco heavy oil belt

Abstract: The lower member of formation Oficina of H block in Venezuela's Orinoco heavy oil belt is dominated with extensively distributed sandy braided river deposits. The heavy oil resources within the reservoir is rich and has a huge potential for development. At present, the oilfield is at the stage of reservoir evaluation before the development and it has relatively large well spacing with no 3D seismic coverage, only a limited number of newly drilled horizontal wells exist within part of the block. According to the existing data available in the study area, first of all, the paper analyzes the formation and evolution of the sand bar and channel from the dynamic point of view, focusing on the differences between the three statuses of active channel, sandy channel fill and the abandoned channel fill. On this basis, study methods such as modern sedimentation analogy, empirical formula utilization, application of horizontal well data are used to characterize the key parameters of the main units in braided river and to restore its scale. Based on the above research results, this paper summarizes the depositional model of sandy braided river and accomplishes the establishment of a 3D geological model under its guidance. This model is combined with prediction of reservoir distribution in the study area and good application results have been achieved. It is of great importance to guide the implementation of subsequent development plan and to improve the sand encountering ratio for the new wells to be drilled.