Large-Scale Tidal Channel Characterization of the Bioclastic Limestone Reservoir in A Oilfield, Middle East

The Sarvak formation of the A oilfield in Middle East is a block-type bottom-water bioclastic limestone reservoir with strong heterogeneity, which belongs to the rimmed shelf–type carbonate platform deposits with large scale tidal channels up to 4 km wide that accounts for 30% of the whole oilfield area. Sedimentary characteristics and reservoir development inside the tidal channel are directly related to the development strategy and well deployment of the whole oilfield. In this paper, under the guidance of the sedimentary background and the sedimentary model, and under the control of the sequence stratigraphic framework, through well-seismic combination, 2D&3D jointed and seismic profile characteristics analysis and multi-attribute optimization, analyze the internal structure characteristics of tidal channels, and classify the types of tidal channels, finely depict the boundary, trend and three-dimensional display of the tidal channel. The evolution of tidal channel is studied in combination with the changes of the paleo-structures. Combined with electrical curve, core and seismic inversion, the deposition and the favorite reservoir distribution in tidal channel are characterized. Studies have shown that the tidal channel appears as an obvious undercut on the seismic profile, including two types: shallow-cut single tidal channel and deep complex tidal channel. On the plane, the tidal channel appears as dendritic or snake-like with bidirectional bifurcation and the trend of east-west or east-north. The tidal channel becomes wider and deeper from south to north and from bottom to top, the evolution of which is controlled by paleo-structure. The reservoirs in the tidal channel are generally better than that outside the tidal channel, and the reservoir in the deep complex tidal channel is well developed. According to the research results, seven new wells are deployed in the northern complex tidal channel, and the NTGs of that are more than 91%, which are far better than the new wells outside the tidal channel. The study of tidal channels provides reliable geological basis for oilfield development.