南海北部含油气构造上方化探异常研究

在南海北部利用地球化学方法作为油气勘探的一种辅助手段。在6个航次中采集了沉积物、底层海水及海面大气样品，测定了近50种化探指标，并采用稳健统计方法进行了数据处理和异常圈定。化探结果在油气藏上方发现了清晰的、具不同指标组合的综合化探异常，与邻近空构造形成鲜明的对照。圈闭顶部的块状异常和圈闭周绿的环状、半环状异常是下伏油气藏的良好指示，而剖面上呈锯齿状、平面上呈线状的异常则与断裂带有关。实践表明，建立已知油气藏上方的化探异常模式及解剖已知空构造上方的地球化学特征对于指导本区或邻区的化探异常评价是十分必要的。

A STUDY ON GEOCHEMICAL ANOMALIES AT OIL/ GAS-BEARING AND BARREN STRUCTURES IN NORTHERN SOUTH CHINA SEA

Geochemical methods have been used to assist petroleum exploration insedimentary basins of the northem South China Sea. Sea-surface air, near-bottom water,and seabed or near-surface sediments were sampled in 5 cruises. About 50 chemicalindices have been determined, and data were analyzed by robust stahstical methods.Results show that composite geochemical anomalies with various association of indicesappear over all of the oil/gas fields studied, in a clear contrast with the geochemicalfeatures of their adjacent barren traps. Anomalies of halo or circular/half circularshapes appearing on top or surrounding structural traps are often indicative ofunderiying oil/gas prospects, while linear anomalies with rugged profiles are closelyrelatod with fault belts. The establishment of model anomalies over known oil/gasfields and barren structures are necessary in providing analogue for the interpretationof anomalies in target areas.