Reef reservoir and fluid identification technology and its application to no-well deep water area in Western South China Sea

Deep-water bioreef reservoirs in the western South China Sea have great oil and gas potential. However, the physical properties of and the fluid in the reef reservoirs remain difficult to be identified though great endeavors have been made by predecessors. In this study, the correlation of seismic reflection characteristics from a point to an area is carried out based on paleo-geomorphological background. Large reefs were found in the stepped Songnan low uplift. As the depth migration velocity is considered, bioreefs should be bounded by high velocity boundaries with an inner part of uneven low velocity. Based on the results of petrophysical forward modeling and semi-quantitative judgment by well-free inversion from Berryman (1992) and Kuster-Toksöz (1974) model, it is found that the reservoirs are dominated by medium-low porosity reefs. Prestack elastic inversion, combined with the pursuit of matching relationship between Vp/Vs attribute anomalies and deep structures, it is predicted that the hydrocarbon-bearing area should be located in the southern part of the reef group. Combining paleo- geomorphology together with seismic velocity, forward and inversion processing, a set of technology system suitable for bioreef reservoir and fluid identification in a well free deepwater areas in the western South China Sea was developed, with which some reef lithologic traps have been found in the Songnan low bulge area of Qiongdongnan Basin.