Oil-gas Migration And Accumulation Dynamic System In Biyang Depression

Biyang depression is a Meso-cenozoic continental lake fault depression, which superimposes on Qinling fold belt. It is one of the small but prolifitable fault depressions in China. Under the guidance of theories of oil-gas migration and accumulation dynamic system and petroleum system and based on research of structure and sedimentary geology, drilling, seismic, logging, testing and organic geochemical data are fully utilized to analyze systematically, dynamically and quantitatively the oil-gas migration and accumulation dynamic system in this depression.In addition to structural sedimentology, compaction curve features, abnormal pore fluid pressure and geochemical characteristics, sequence stratigraphy methods are introduced to divide Biyang depression into 5 oil-gas migration and accumulation dynamic systems from top to bottom, among which the upper autogenous low mature-allogenic system, the middle and lower autogenous/ seaed systems are the most important.Oil-gas migration and accumulation condition is a static element of research of oil-gas migration and accumulation dynamic system. The effective source rocks in the study area are characterized by rich calcareous content and well developed lamellation. Organic matters mainly are ofâ…¡a andâ… type kerogens, followed byâ…¡b type kerogen, whileâ…¢type kerogen is the least. The multiple cyclic sedimentary combinations of Hetaoyuan Formation and the vertically interbeded source rocks and reservoir rocks are favorable for expulsion of hydrocarbons and migration and accumulation of oil and gas. The essential elements of the conduction system include sandbodies and faults, which combine together to form single carrier system composed of sandbody and composite carrier system composed of sandbody and fault. Hydrocarbon migration is dominated by lateral migration along bed, followed by vertical migration.The study of the oil-gas migration and accumulation is another main concern of the research of the dynamic system of oil-gas migration and accumulation. The careful correlation oil source has further proved the difference of the source rocks in the middle and lower parts in the dynamic system. Hence, the oil-gas migration and recharge mode is established, which is dominated by lateral migration along the bedding, and lateral migration along the bedding plus vertical terraced migration. It has found that there are three stages for the oil accumulation, among which the middle late stages are the main period for the oil migration and accumulation. The Biyang depression is divided into four oil-gas concentrations: eastern, middle, western and southern accumulation areas, dominated by the middle and western areas. Meanwhile, three modes of oil-gas migration and accumulation are established: autogenic lateral sealed, autogenic-allogenic sealed-semisealed vertical and autogenic-allogenic lateral-vertical migration.Based on comprehensive research of oil-gas migration and accumulation dynamic system, the main oil-gas migration and accumulation dynamic systems and accumulation of oil and gas are comprehensively evaluated and future exploration targets are presented.