Deepwater Lacustrine Architectural Elements and Subsystems Identified in the Subsurface from Borehole Images – An Example from Weizhou Field, Beibuwan Basin, South China Sea

Outcrop work on deepwater deposits often shows mass-flow systems are more complicated and heterogeneous than generally accepted. However it is difficult to recognize the different architectural elements and subsystems in the subsurface at reservoir scales. At a reservoir scale, the finer details of heterogeneity are important for accurate reserves calculation, completion strategies and development well placement. This paper describes how high-resolution resistivity borehole images are able to identify deepwater subsystems and architectural elements in the subsurface. The study sections consist of four wells located offshore Beiwuban Basin in the South China Sea (Figure 1). Borehole images were recorded in all these four wells. Detailed observations from borehole image logs reveal the occurrence of turbidites, slumps, and debrite facies in a deep-lacustrine setting. Openhole logs could not resolve the heterogeneity and different facies in the reservoir.