A new strategy of crosswell correlation for channel sandstone reservoirs — An example from Daqing oilfield, China

Abstract

Crosswell correlation for subsurface channel sandstone reservoirs is a difficult problem for geologists worldwide because it is hard for us to know the subsurface sand-body distribution situation. Different correlation methods or strategies result in different sand-body stacking and reservoir connecting models. Sand-body correlation for channel sandstones with only static geologic methods is prone to cause high uncertainties in the analysis for sand-body distribution and connection due to their complexity and heterogeneity. Combining outcrop images and wireline logs, we have evaluated seven channel correlation models. We developed a new channel sand-body correlation strategy with four steps with a case study, combining channel architecture patterns, different correlation models, and tracer test data. The four-step correlation method consists of channel-belt correlation, isolated channel sand-body correlation, barrier and baffle analysis, and impacts of reservoir structure. Furthermore, the channel reservoir connectivity was also analyzed in terms of connection efficiency derived from tracer test data as well as in terms of barrier and baffle obtained from channel-body correlation results. We found that the new correlation workflow integrated with our correlation models reduced the uncertainty of subsurface channel sand-body correlation in the study area. In addition, the channel correlation strategy can approach the subsurface sand-body connection reality of the reservoir distribution and reflect the real production performance in the study area. The correlation strategy and models in the paper could be applied to other analogous subsurface channel reservoirs.