Gas hydrates were newly discovered in the Dongsha Waters of the South China Sea by drilling in 2013 and 2019. The drilling results show that the hydrates consist of microbial gas and thermogenic gas, but the source layers of the thermogenic gas are not clear. The Chaoshan depression is the largest relict Mesozoic basin under the Dongsha Waters where thick T₃—K strata, up to 5000 m, have developed under thin Cenozoic sediments. The T₃—J₁ and J₃ bear the two main layers of hydrocarbon source rocks rich in II₂-III type organic matter, mainly in the western sag, the middle low bulge, and the eastern sag. The T₃—J₁ developed bathyal - neritic mud rocks, generally greater than 400 m in thickness. The J₃ mainly developed closed and semi-closed bay type mud, also II₂-III type. Nowadays these two layers are in their mature - over mature stages, thus potentially high-producing. There have developed deep faults cutting through the Mesozoic strata and distributing fractures within the Cenozoic sediments. Analysis of geochemical and geological samples dredged from the seabed indicates a significant oil and gas leakage activity well correlated spatially with the Mesozoic-associated faults. The association of fault-fractures can act as good channels for the thermogenic gas to move upward and diffuse into the temperature pressure stabilization zone of the hydrate. Thus, sufficient gas from the Mesozoic production layers is deemed the main source of thermogenic gas. The area where the Mesozoic faults are activated is the main leakage area of thermogenic gas, thus the main target for future hydrate exploration.

Located in northern South China Sea, Pearl River Mouth Basin is a large Meso-Cenozoic basin. And in southeasters part of the basin lies Chaoshan Depression, which is mainly a residual Mesozoic depression, with a construction of Meso-Cenozoic strata over 7000m thick and good hydrocarbon accumulation conditions. The selected DHI technique, amplitude attribute of -90 degree phase component derived by phase decomposition is employed to the zone of interest (ZOI) of B structure, Chaoshan Depression. And it is found that there are evident amplitude anomalies occurring around ZOI of structure B. Phase decomposition is applied to forward modelling results of the ZOI, and high amplitudes occur on the -90 degree phase component more or less when ZOI is charged with hydrocarbon, which shows that the amplitude abnormality in ZOIs of structure B is probably caused by oil and gas accumulation. Meanwhile, another DHI attribute of spectral decomposition peak amplitude is applied also to ZOIs of B structure, and there is also amplitude anomalies coincides with those of -90 degree phase component. The two DHI attributes' coincidence strengthens the confidence of hydrocarbon accumulation prediction results.

The Chaoshan Depression situated in the Dongsha Sea region, is an important Mesozoic residual depression beneath the Cenozoic Pearl River Mouth Basin in the northern South China Sea, showing significant potential for hydrocarbon exploration. However, current drilling efforts have not resulted in hydrocarbon finds due to the absence of high-quality reservoirs. Recent quasi-3D seismic data has allowed for the first identification of Mesozoic bioherms and carbonate platforms on the Middle Low Uplift of the Chaoshan Depression. A thorough analysis was performed on their horizontal sedimentary distribution and vertical evolution. The findings indicate that the seismic reflection patterns of reefs and carbonate platforms in this area are primarily characterized by high-amplitude discontinuous to chaotic reflections, sometimes showing blank reflections or weak, sub-parallel reflections, along with notable high-velocity anomalies. Atolls, stratiform reefs, and patch reefs are found on local topographic highs of the platform, with atolls mainly in the central part of the quasi-3D area, stratiform reefs in the northeast, and patch reefs in the central-eastern region. Four vertical evolutionary stages have been identified: initial development, flourishing, decline, and submergence. The spatial distribution of bioherms and carbonate platforms was influenced by paleotectonic topography, while their developmental scale was affected by changes in relative sea level. Furthermore, reefs limestone reservoirs within the upper part of the Middle Jurassic exhibit excellent conditions for hydrocarbon accumulation, following a "lower source, upper reservoir, and upper seal" model. These reservoirs have favorable geological conditions for the formation of medium- to large-scale hydrocarbon accumulations, suggesting significant exploration opportunities.