Abstract:

In southern Dagang area, Dagang oildfield, the lithology of Guantao Formation is complex, and shale content of reservoir is high, and the resistivity difference is little, so it is difficult to identify the oil-bearing reservoir and water-bearing reservoir by well logging interpretation. Lithology, petrophysical property and water property data are used to analyze genetic feature of low resistivity reservoirs, because illite/smectite formation is the main clay mineral type of Guantao Formation, and formation water salinity is small, so high clay-bound water and additional conductivity of clay are two main causes of low-resistivity reservoirs. Based on analysis of genetic feature, three-pore conductivity model is used to evaluate the electrical conductivity of water saturation, and movable water saturation method is integrated to identify the low-resistivity oil-bearing reservoirs. According to three-pore conductivity mode and movable water saturation method analysis, the conclusions of well-logging interpretation is consistent with the test oil results.

Key words: low-resistivity oil reservoirs, genesis of low resistivity, three-pore conductivity model, well logging