长江三角洲晚第四纪浅层天然气的勘探方法

Exploration methods of shallow gas in late quaternary of Yangtze River Delta

长江三角洲地区第四系覆盖区具有良好的浅层天然气勘探开发前景,气藏具有气层薄、压力小、分布广等特点,是一种典型的微生物菌解生物成因甲烷气。其勘探以静力触探及试气为主,高密度电法为辅的勘查方法。静力触探不仅可以进行75 m深度以内地层岩性、岩相划分对比,而且对砂质储层识别非常有效,同时结合触探试气,可以准确判断生气层、储气层以及气层压力大小。静力触探作为一种多用途、高效且廉价的方法,在第四系浅层气勘探中起着不可替代的作用。高密度电法能够追踪砂体展布,推断气层的厚度,有利于更准确的确定勘探范围和目标,提高勘探精度。在长江三角洲地区晚第四纪浅层天然气勘探中,通过这两种方法新发现含气面积25 km2,资源量预测约8×108m3。

The cover area of quaternary of Yangtze River Delta has good shallow gas exploration and development prospect. Due to the characteristics of thin gas bearing formation, low pressure and wide distribution, the gas reservoir is a typical methane reservoir by microbial degradation, in addition, the exploration method is mainly based on static cone penetration and gas test, and high density resistivity method is an auxiliary method. The static cone penetration not only can conduct formation lithology and lithologic facies classification within 75 m depth, but also can effectively recognize sandy reservoir, furthermore, cone penetration gas test is adopted to accurately judge the pressure of gas yielding stratum, gas storage layer and gas reservoir. Having the advantages of multi- purpose, high efficiency and low price, static cone penetration plays an irreplaceable role in quaternary shallow gas exploration. High density electric method can trace the distribution of sand body and deduce the thickness of gas reservoir, which can accurate- ly determine the exploration area and target and improve the accuracy of exploration. During the exploration of shallow gas in late quaternary of Yangtze River Delta, it concludes that gas bearing is 25 km^2 and the resource is about 8×10^8 m^3.