Abstract: Genetic Type of Natural Gas in Ya13-1 Gas Field, South China Sea

Gang Zhang

Ya13-1 is one of the largest gas field ever found in China in recent years. Studying on the genetic type of natural gas in the field is one of the key factors to determine the regional hydrocarbon potential--Qiongdongnan basin and Yinggerhai basin, northwest part of South China Sea. Series of geochemical methods have been undertook including the analysis of the chemical composition of the natural gas and their isotopic ratio discussed in this paper. Other related studied including geological settings, gas-source correlations, geochemistry of the condensates and extractable compounds of source rocks, and thermal simulation and evaluation of the marine shales provides further informations. It is noticeable that the higher content of mercury (44,000 ng/cubic meter) and aroma ics such as benzene and toluene may be related to the joint of condensates, which derived from coal-bearing Oligocene shales in the adjacent Qingdingnan basin.

Studies show that the natural gas in Ya13-1 gas field belong to high to post mature non-associated gas derived in marine source rocks, and mainly come from Oligocene to Pliocene marine shales in Yinggerhai basin. This is quite different with the former studies, which believe the gas derived from Oligocene coal-bearing strata of Yacheng formation, Qiongdongnan basin. The new results of the studies make sure further a pretty good potential of gas resources in the northwest part of South China Sea.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France