Global Evaporites Development Characteristics and Their Effects on Formation of Giant Oil Fields

Evaporite rocks are widely developed in petroliferous basins around the world and closely relate to the formation and distribution of the global giant oil and gas fields.By study of the relative changes in sea level,the changes in climate condition and the evolution of various basins,the development characteristics of evaporite rocks are analyzed.That is,the formation and distribution of evaporite rocks are commonly controlled by the restricted topographic lows inner basins,the relatively stagnant water bodies and the hot arid climate.Through research of sealing ability,thermal conductivity and incompetence of the rocks,the effects of them on formation of giant oil-gas field are analyzed,integrated with the case studies of giant oil-gas fields in eastern Siberia,Campos and Zagros basins.It is suggested that tight evaporites can be as cap rocks that effectively seal the underlying hydrocarbons;the thermal conductivity can keep the temperature balance,being helpful to complete organic matters' transformation;the incompetence may cause it decollement and deformation,which allows the overlying reservoirs to have developed fracture systems,greatly improving the quality of reservoirs;the intense deformation could also form salt structures,shaping new traps for oil and gas.It is concluded that the development of evaporite rocks restricts or influences the formation and distribution of the global giant oil and gas fields in time and space,and with the deepening of the oil and gas exploration,the large and giant oil-gas fields related with the evaporites will inevitably become the targets for petroleum exploration in the future.