The Distribution Of Water-Soluble Gas In Geothermal Water In Weihe Basin

There are abundant geothermal water resource and water-soluble gas resource in WeiheBasin. Among the water-soluble gas resource, helium gas and combustible gas are the mostpotential industrial value compositions. Firstly, this thesis researches the stratum, sedimentaryfacies, fracture, geothermal features of Weihe Basin and the formation conditions ofwater-soluble gas from the six aspects including source rock, reservoir, caprock, trap,migration and conservation condition. Then the thesis summarizes the influencing factors ofthe water-soluble gas distribution and peculates the resource distribution favorable areas ofthe helium gas and combustible gas.The Weihe Basin is the Cenozoic rifted basin which formed on the basis of the Paleozoicstrata. Because the basin is under the influence the four large structural systems whichinclude Qinling latitudinal tectonic system, Qi Lu Helan epsilon type structural system, theNeocathaysian structural system and Longxi vortex structural system, it is well-developedfractures that affect on the tectonic unit of the Weihe Basin and the migration andpreservation of the water-soluble gas. Considering on the complex composition and genesisof the water-soluble gas in the Weihe Basin，this thesis mainly researchs the deep rich heliumwater-soluble gas and shallow combustible water-soluble gas in this area.The research shows that the rich helium water-soluble gas affected by the distribution ofsource rock and fracture is in the southern base of the intersection of the uranium-rich graniticand deep fracture zone. It includes Xi’an-Chang’an and Lantian distribution favorable areas ofthe helium gas. Besides, the helium gas is distributed only in the reservoirs which are belowZhangjiapo group due to the joint control of reservoir and caprock. The main reservoir of thehelium gas is Lantian-Bahe group and Gaoling group is secondary. Another type of thewater-soluble gas in Weihe Basin is combustible gas which is the biogenic methane gasbelong to the lake sediment of Zhangjiapo group in Gushi Depression, Weinan area. Due tothe control of the sedimentary facies and hydrocarbon, the source rock the combustible gas isdistribution in the source rock area in Gushi Depression. Zhangjiapo group is its source rockand reservoir as well. The methane content of this gas can be more than95%with hugeresource potential,and after the separation of water and gas can be directly ignited at the mouth of well. This distribution favorable areas of the combustible gas resource isWeinan.Another potential combustible gas resource is local atXi’an-Xianyang.