The distribution of phenylalkanes in the modern sediment associated with gas hydrate from the Gulf of Mexico

Phenylalkanes with carbon numbers between 16 and 19, characterized by the main carbon-18, have been identified in the modern sediments collected from gas hydrate area from the Gulf of Mexico. The structure of phenylalkanes with four isomers for every carbon number was determined by means of their mass spectra and previous studies. The distribution of the series characterized by a low molecular mass was similar to the distribution of n-alkane, alkylcyclohexanes and alkylbenzenes in each sample. There were differences in the distribution of the phenylalkane series between the S - 1, S - 4, S - 7, S - 9 samples and the S - 8, S - 10 and S - 11 samples. The phenylalkanes might be derived from Archaea associated with anaerobic oxidation of methane （AOM） processes in S - 1, S -4, S -7 and S -9 samples according to their distribution resembled with the distribution of the extract from a type of Archaea. The distribution of alkylcyclohexanes and alkylbenzenes in S - 1, S - 4, S - 7 and S - 9 sample was found to be similar to each other. The odd-over-even predominance of alkylcyclohexanes was seen as the input of some bac- terial.

Estimation of potential distribution of gas hydrate in the northern South China Sea

Gas hydrate research has significant importance for securing world energy resources, and has the potential to produce considerable economic benefits. Previous studies have shown that the South China Sea is an area that harbors gas hydrates. However, there is a lack of systematic investigations and understanding on the distribution of gas hydrate throughout the region. In this paper, we applied mineral resource quantitative assessment techniques to forecast and estimate the potential distribution of gas hydrate resources in the northern South China Sea. However, current hydrate samples from the South China Sea are too few to produce models of occurrences. Thus, according to similarity and contrast principles of mineral outputs, we can use a similar hydrate-mining environment with sufficient gas hydrate data as a testing ground for modeling northern South China Sea gas hydrate conditions. We selected the Gulf of Mexico, which has extensively studied gas hydrates, to develop predictive models of gas hydrate distributions, and to test errors in the model. Then, we compared the existing northern South China Sea hydrate-mining data with the Gulf of Mexico characteristics, and collated the relevant data into the model. Subsequently, we applied the model to the northern South China Sea to obtain the potential gas hydrate distribution of the area, and to identify significant exploration targets. Finally, we evaluated the reliability of the predicted results. The south seabed area of Taiwan Bank is recommended as a priority exploration target. The Zhujiang Mouth, Southeast Hainan, and Southwest Taiwan Basins, including the South Bijia Basin, also are recommended as exploration target areas. In addition, the method in this paper can provide a useful predictive approach for gas hydrate resource assessment, which gives a scientific basis for construction and implementation of long-term planning for gas hydrate exploration and general exploitation of the seabed of China.