Lithological Exploration and Potential in Mixed Siliciclastic-Carbonate Depositional Area of Eastern Pearl River Mouth Basin

Mixed siliciclastic-carbonate developed around Dongsha massif in early Zhujiang Formation, with the mixing types divided into compositional mixing and strata mixing. The statistic data show that the development of lithological reservoir is closely related with the distribution of mixed-sedimentation area, as 94% of the discovered lithological reservoirs are concentrated in mixed-sedimentation area. Oil and gas are accumulated in sand rocks and sealed by mud rocks or mixed rocks in lithological reservoirs.The key geological factors on lithological reservoir are studied, showing that the formation condition of lithological reservoir was controlled by terrestrial lakes, sand rocks were sourced from paleo-Pearl River, and seal rocks formed in mixed siliciclastic-carbonate sedimentation zone for its low sand ratio as the result of distal provenance, late tectonic activity and inherited structural ridges. Furthermore, integrated with oil accumulation analysis, it is suggested that lithological exploration should be focused on petroliferous sags, and centered on siliciclastic reservoirs in mixed sedimentary zone, on basis of which 3 hydrocarbon-bearing systems and 4 favorable zones are figured out in the study area.