Modeling Method of Point Bar Internal Architecture of Meandering River Reservoir Based on Meander Migration Process Inversion Algorithm and Virtual Geo-surfaces Automatic Fitting Technology

摘要

This paper developed a new modeling method of the point bar internal architecture of meandering river reservoir based on a new meander migration process inversion algorithm and virtual geo-surfaces automatic fitting technology. Firstly, we proposed a new inversion simulation algorithm of meander migration process based on the river hydrodynamics which can backward simulate the migration centerlines of channel at each time step starting from the centerline of the terminal abandoned channel. Considering the fact that lateral accretion interlayers have the same strike with the ancient channel where they draped, through extracting restored channel centerlines at very high density combined with 3D geometry characterization, the 3D virtual geo-surfaces of lateral accretion interlayers inside the point bar were built. After examining the extent of match-up between each virtual geo-surfaces and well data in 3D space, the virtual geo-surfaces which don’t conform to well data were removed and the virtual geosurfaces which conform to both well data and predefined rules were retained as the final geo-surfaces model of real lateral accretion interlayers. In order to test the reliability of this method, we applied this method to study the reservoir architecture of the west region of NmI3 depositional unit of M oilfield in Bohai Bay Basin, East China. M oilfield is one of the biggest oilfield in Bohai Bay Basin, East China. A total of 140 wells penetrated the NmI3 depositional unit. The average well spacing is about 400m. Constrained by the well spacing and the size of the channel and the point bar, we only characterize the 4th order architecture unit by means of interwell 3D correlation. And the lateral accretion interlayers model was built using the inversion simulation method. Based on the internal architecture model of the point bar, we explained the big difference of fluid production rate between 2 prodution wells which are in the same point bar and have roughly the same distance to the injection water well. The results show that the the injected water flows along the strike of lateral accretion interlayers, suggesting an advantageous flow path was formed inside the point bar. So the relative spatial position between wells and lateral accretion interlayers is a key factor that influences production dynamic. This rule can be used to guide well placement and waterflooding optimization in point bar reservoir.