Oil-gas shows can provide much important information to explore the related residual or secondary reservoirs.Based on field survey

geological analysis and literature investigation

this paper systematically studied the distribution of oil-gas shows in different basins/regions in China

discussed their genetic mechanisms and analyzed their petroleum geological significance.According to the degree of destruction of reservoirs

oil-gas shows can be classified into three types:partial destruction

strong destruction

and complete destruction.All these three types of oil-gas shows are widely distributed in each basin/region in China.The partial-destruction type of oil-gas shows

including oil seepage

gas seepage and mud volcano

is mainly distributed in the western and southern China.The strong-destruction type of oil-gas shows such as heavy oil is mainly distributed in the western and eastern China.The complete-destruction type of oil-gas shows

such as natural bitumen

tar sand and mineral wax

mainly occurs in the western and southern China.On the other hand

in terms of the times and extent of destruction of reservoirs

the genetic mechanism of oil-gas shows can be categorized into two types:primary-destruction and secondary-destruction.The former type of oil-gas shows include surface oil seepage

gas seepage and volcano and their formation are influenced by the intense tectonic movements

frequent earthquakes and rapid deposition.It can be further divided into four kinds according to their ways of out-flowing the surface of earth:surface-cutting fault

uplifting-denudation

diapir penetrating

unconformity outcropping.The secondary-destruction type of oil-gas shows include heavy oil

natural bitumen

tar sand and mineral wax on the surface and underground

and features in water washing oxidation and biodegradation after destroyed directly and they are usually paragenic and transitional.In the early stage of petroleum exploration

the oil-gas shows of partial-destruction type or that on thrust belt and diaper structure have greater guiding significance to discover underground reservoirs.On the one hand

although all kinds of destructive effects can destroy reservoirs to form oil-gas shows

they could also have positive influences on the redistribution and preservation of hydrocarbons.Therefore

preservation condition is the key factor to find reservoirs in areas with oil-gas shows.