Abstract: As shown by coring and drilling data from numerous infill and regulation wells, significant differences in water flooding have occurred along the plane of the Bohai Sea SZ Oilfield, and there has been uneven utilization of the plane residual oil. Current methods for quantitatively characterizing plane heterogeneity are insufficient for satisfying future exploitation demands. To mitigate plane differences and realize plane residual oil potential, research characterizing reservoir plane heterogeneities was conducted during the late exploitation stage in the Bohai Sea SZ Oilfield. The results indicate that current quantitative methods for this type of characterization have been primarily based on geostatistics, with fundamental parameters, i.e., reservoir indices, obtained from wells. Because they are measured in small individual layers, they can neither sufficiently present all different properties nor effectively describe issues, such as internal structural differences in reservoir layers between wells. By examining reservoir architecture, a more comprehensive characterization of reservoir plane heterogeneity is achieved. This is integrated with plane oil-water contact relationships in different facies units in the oilfield to obtain a new quantitative characterization index and non-connected thickness, for heterogeneous layers. This index uses well profiles as basic units, thus overcoming the limitation that internal structural differences in reservoir layers between wells are not depicted. Furthermore, plotting a plane distribution map of unconnected thicknesses provides a mechanism for semi-quantitatively characterizing internal structural differences in reservoir layers. The non-thickness index is applied to closely spaced wells in the Bohai Sea SZ Oilfield in a pilot test. The predictions based on the index are consistent with the actual production results, suggesting that the index is practically applicable.

Key words: reservoir architecture, plane heterogeneity, non-connected thickness, closely spaced wells, late exploitation stage