The Structural Characteristics And Their Controlling Effects On The Accumulation Of Oil And Gas In The West Part Of Qiadam Basin

The evaluation of oil and gas resource in the west part of Qiadam basin indicates that the Tertiary formation in the region has a very wider exploration prospect. However, not so much exploration achievement in the region has been obtained because of the limitation of many factors, for example, the structural characteristics and the evolution rule of the basin have not been known clearly so that the rules of the distribution and the accumulation of oil and gas are not fully understood. As a result, the petroleum exploration and development of the region cannot be run smoothly and the costs of both exploration and development are higher.Base on the researches on the sedimentary evolution of Tertiary structure in the west part of Qiadam basin, the distribution rule of oil and gas and its major controlling factors have been systematically discussed in this paper. The favorable exploration direction has been pointed out so as to serve the exploration and the development of oil and gas in the region.It is well known that the sedimentary evolution of Tertiary structure in the west part of Qiadam basin is controlled by Mt. Arjin and Mt. Kunlun. Different characteristics of geometry and kinematics of the mountain-creating zone have determined the complexity and the peculiarity of the sedimentary evolution of the region. On the bases of ground geological investigation, drilling data analysis, geophysical profile interpretation, key samples testing and other information, both the extension characteristics of Tertiary fault-structure and its type of cause-forming in the region have been elaborately studied. In addition, its kinematics characteristics have been fully discussed and studied. It is suggested that Miocene (12Ma) can be defined as a borderline to mark off the two stages of Tertiary structural evolution, one is sliding and separate basin (left-revolving) and the other is compressive and twisty depression basin (right-revolving). Besides, the controlling effect of fault-structure on the sedimentary evolution has been thoroughly analyzed in the paper, and the author considers that the distribution of major hydrocarbon source rock in the region is controlled by the compressing and wresting fault-zone in Tertiary strata, and the combination of reservoir rock and cap rock and the abundance of oil and gas in the region are restricted consequently. Several profitable exploration traps have been pointed o ut i n t he p aper, t hey i nclude t he t raps d eveloped i n t he 1 ower w all o f t he compressing and wresting fault-zone, the age-old structural traps, nonconformity traps and lithologic traps located at the foot of Mt. Arjin.