The underground pressure difference,concentration difference and specific gravity difference in the oil and gas field cause hydrocarbon substances to travel towards the surface. Oil andgas shows commonly seen at surface are macroscopic indicators of hydrocarbon percolation;nevertheless, more extensive hydrocarbon percolations at surface are exhibited by microscopicindicators, which can be detected only by precision instruments. Jonnes (1975) has noticed thatthe near-surface soil gas is chemically quite consistent with gas in underground gas-bearing reservoirs and gas shows in drill holes. Yan Wenbo et al. (1990) have found ultraviolet absorptionvalues of oil and gas reservoirs, saying that the values decrease in order of oil-soaked rocksedimeotary rocks over the oil reservoir→soil over the oil field→soil of the barren area. Theconcentrations or relative intensities of hydrocarbon indices determined by borehole geochemicalexploration decrease gradually from the oil and gas reservoir to the surface, and this providesaudio-visual basis for the trash of oil and gas vertical migration.