CHARACTERISTICS OF SEQUENCE STRATIGRAPHY AND PREDICTION OF FAVORABLE GAS ZONES FOR THE SOUTH EDGE OF THE JUNGGAR BASIN

Presently sixty-eight major natural gas fields have been discovered in marine and transitional continental-oceanic sequences in China and marine sedimentary sequences are favorable for exploration of natural gas.The marine sedimentary sequences in three cratonic basins are composed of two major cycles of transgression and regression,in which multiple combination of source rocks,reservoirs and seals was formed.In addition,as a result of tectonic movement many unconformities were formed and stratigraphic-lithological gas pools were developed.There are 4 kind of gas fields in marine sequences:(1) stratigraphic-lithological gas traps related with old uplift;(2) anticlinal gas pools related with old uplift and late tectonic movement;(3) lithological gas pools of reef,oolite beach or sandbody;(4) large anticlinal gas pools under compressional background.In one word,distribution of natural gas is closely related with old uplift,reservoir conditions and tectonic activity.