Abstract: The application of oil and gas microbial detection technology in the complex water net area,such as the Beihanzhuang Oilfield of the Subei Basin,has shown great advantages to the commercial culturing technology system. As a case study,we selected an oil developing area and an unknown area,where no oil shows have been found,for sample collection,analysis and evaluation. Methane anomalies are found in the oil developing area covered by the complex water net and the proxies in the unknown area without oil discovery are ten times higher than those in the oil developing area. It leads to the conclusion that the area without discoveries so far is not valueless,but has great potential for oil and gas accumulation. It also indicates that the microbial oil and gas detection technology is applicable and should be promoted in the studied region.