Prediction Of Deep Structure And Gas Hydrate Prospects In The Hara Lake Region Of Qinghai

Natural gas hydrate is a new type of clean energy which is formed by water molecules and methane gas in high pressure and low temperature.Its shape like ice.It burns with open flames,so it can be called "combustible ice".It generally exists in the deep sea and permafrost.The study area is located in the southern Qilian basin,west side of the lake,belongs to the South Qilian orogenic belt.Tectonic characteristics of Har lake depression features of developed faults,folds and depression,low exploration degree.Because of the extreme plateau weather and complex tectonic features,people still lack of comprehensive and accurate understanding about the deep structure and the oil and gas exploration in Har Lake area.So far,comprehensive geological and geophysical exploration have not been done in this region.This study is based on the sub project”Har Lake area for oil and gas geological investigation of 2D seismic exploration project" of the”Qilian Mountains permafrost zone of gas hydrate resources in the investigation of the”which is undertaken by China geological survey of oil and Gas Resources Survey Center.We use two-dimensional seismic exploration methods to carry out the 76.7km 2D seismic data acquisition,processing and interpretation work in permafrost area of Qilian Mountains(mainly Har Lake area).The seismic data and drilling data are combined to find out the stratigraphic and structural characteristics of the study area,and to explore the relationship between the deep structure and the distribution of gas hydrateThrough this study,we revealed the deep tectonic and stratigraphic distribution of the west region in Qinghai Har lake,discussed the relationship between the deep structure and the formation of natural gas hydrate,also analyzed the anomalies of seismic velocity in the region,obtained some achievements and knowledge:1.Har Lake area belongs to the high altitude permafrost region,using the implementation of artificial seismic.Reliable seismic reflection data can be obtained by using low frequency seismic source with small distance and high density coverage2.Through the analysis of the seismic profiles and compared with adjacent area stratum,we totally summed up four sets of reflection including Permian and Triassic,Jurassic and Cenozoic strata,described the faults existing in the profile.3.The faults in the study area are characterized by multiple stages of tectonic activity,which are more complex,and most of the faults in the section are thrust faults which are almost up-right,together with wrenching strike slipping.The fault has experienced many secondary activities,the early period is the Yanshannian period and the late stage is the Himalayan period,and the fault strike is mainly from the north to the West and the west to the west.4.The study area can be divided into 4 tectonic units,namely,the southern uplift,the southern depression,the northern low uplift,the northern uplift.The Cenozoic strata are widely distributed,but partial loss in the edge of northern and southern area.Jurassic is only distributed in the southern sag.The Triassic and Permian are lost in Northern low uplift area.5.The comprehensive analysis shows that the characteristics of hydrocarbon anomaly are obvious,and the inversion of seismic wave velocity and the corresponding chaotic reflection are the reaction of gas hydrate.Complex deep structures and faults provide the migration channel and storage space for the formation of gas hydrate.Therefore,it is considered that the region is a potential prospect of gas hydrate.