Abstract:

Use of soil iodine for oil and gas prospecting in the past 40 years has demonstrated that soil iodine is an auxiliary index for tactical oil and gas prospecting, but its relevance to the strategic oil and gas prospecting has never been reported before. With analysis of near surface factors influencing soil iodine, multi-purpose geochemical prospecting data over an area of 81,500 km² in the central part of Songliao Basin was used to verify the significance of geochemical anomalies in surface soil iodine (1 point/4 km²) and soil iodine (1 point/16 km²) to the indication of oil and gas, leading to the discovery of a regional geochemical anomalies of soil iodine in the form of a huge ring related to oil and gas for the first time. Investigation indicates that the regional geochemical anomaly in soil iodine is mainly linked to medium to large oil and gas fields and hydrocarbon-rich depressions, and the deep soil sampling density of 1 point/16 km² is fairly sufficient to strategic oil and gas prospecting. The main factors which have bearing on soil iodine include topography and landscape, soil type, soil pH, human farming, rivers.

Key words: Songliao Basin, strategic oil and gas exploration, iodine survey in soil, huge ring of geochemical anomaly, geochemical mega-province