Kela 2 structure is the largest gas pool in Kuqa thrust belt and authigenic kaolinites are best developed in Cretaceous reservoir

with an average relative content of over 20%

and occur as book and vermicular kaoli-nites between the skeletal grains.While authigenic kaolinites are underdeveloped in Kela 3

Kela 1 and Tubei 1 traps where exploration failed.In Kela 2 structure

authigenic kaolinites have been precipitated from the dissolution of feldspar in the stratal acidic media

which have been associated with the formation of secondary pores.The diagenetic environment was in an open or half-open flow system

which allowed both the charge of acidic fluid from the underlying source rocks and the discharge of dissolved feldspar and other materials.The formation of authigenic kaolinite and secondary pores and charging of natural gas are two associated processes with closely related mechanisms.Through-going and linking-up faults pierced downward through source rock and broke upward through gypsum and halite cap rocks and constituted the major migration pathway of overpressured fluid.Areas with through-going faults had not only been provided with conditions for formation of authigenic kaolinite and secondary pores

but were also favorable for gas accumulation.Comparison of fault carrier types shows that Kelasu structural zone is more favorable for gas accumulation than Qiulitake structural zone.