Structural Characteristic And Seal Evaluation Of Fault In The North Of Chaidamu Basin

Bye use of geological date such as seismic, well logging, produce testing etc, the structural characteristic is studied and the evolving process of the north of Chaidamu basin is reversed, the type, the action time and the distribution of fault are summarized, the development characteristic of fault is analyzed, the result shows that up member of Xiaganchaigou formation and Shangganchaigou formation are mainly detachment zones in the north of Chaidamu basin, fault that slip from the shallow detachment zone majority throw to earth surface. From throw level to see, fault type is very simple in the north of Chaidamu basin, that mainly have three types, first is basement involution fault that throw to the earth surface, second is basement involution fault that throw to de up member of Xiaganchaigou formation and Shangganchaigou formation, third is overlying formation slip fault that throw to the earth surface from two detachment zones, up member of Xiaganchaigou formation and Shangganchaigou formation.The lateral seal and vertical seal mechanism of fault and effecting factor are analyzed, the result shows that the evaluation method of fault lateral seal is Allan that is the base, using shale content calculation result to forecast fault rock type, the evaluation method of fault vertical seal is to calculate fault plane normal pressure and analyze fracture seal. Fault seal of type area in the north of Chaidamu basin is dissected, the result shows that Nabaxain area mainly develops clay smears and phyllosilicate-framework fault rock, the lateral seal is good, the vertical seal is bad because of secondary fracture, Mabei area mainly develops clay smears and phyllosilicate-framework fault rock, the lateral seal is good, fault buried depth is contrast shallow in Youshashan formation, vertical seal is bad, because partly fracture formed in up member of Xiaganchaigou formation, Shangganchaigou formation and lower member of Xiaganchaigou formation, vertical seal is bad, Yahu area mainly develops clay smears and phyllosilicate-framework fault rock, the lateral seal is good, fault vertical seal is good expect thatâ‘¢fault vertical seal is bad becauseâ‘¢fault buried depth is shallow. The distribution of oil-gas reservoir is obviously controlled by fault, fault act in early time that provide the condition of oil-gas migration and accumulation, formation multiple types oil-gas reservoirs, Fault act in late time that confined oil-gas reservoirs'preservation and destruction.