Light hydrocarbons in soils are the most important indicators in geochemical hydrocarbon exploration. However, the methods actually used to detect light hydrocarbons in soil sometimes provide data with a low signal-to-noise ratio and/or high level of interference. This research explores vacuum desorption, a new method for light hydrocarbon analysis. Vacuum desorption is a partial extraction technique designed to identify light hydrocarbons that are tightly adsorbed on soil particles. This method was used in the Huimin sag (basin) of east China. Microseepage anomalies are developed over oil pool S105 of the Shanghe field in this basin and larger seepage anomalies are developed over faults.
In contrast to the method of acid-extraction of soil hydrocarbons, the vacuum desorption method provides a low-noise background that enables a more effective identification of anomalies. The new method is also cost and time effective and is capable of covering large areas.