f Surface Geochemical Evaluation of Murzuq Basin (Libya)

The surface geochemical surveys as having a growing importance in petroleum exploration, primarily determine and evaluate the light hydrocarbon (C1-C4) surface microseeps from active oil and natural gas reservoirs at depth. A surface geochemical prospection was conducted in northern Murzuq basin (Libya) and a total of 700 soil gas samples were collected over a 500 km2 survey area from a depth of 1.2 meters with a specially desinged soil gas probe system and analysed by gas chromatography for methane, ethane, propane and n-butane. Selected components were used to produce light hydrocarbon contour and dot maps, pixler diagrams etc. in order to evaluate the distribution, magnitude and the type of the hydrocarbons trapped in the subsurface reservoirs beneath. Since the surface anomalies can also be originated from the fractured rocks and faulted zones, these linear anomaly features in the study area were characterized and differentiated by using the subsurface geological and geophysical data. As a conclusion, the Murzuq basin survey has revealed that both the correlation of the results with the post drilling activities, low costs and short project deadlines gives a positive indication for the more extensive use of the method in the petroleum exploration.