Mesozoic Filling Characteristics And Basin Evolution In Tonghua Basin

The Tonghua basin lies in the eastern Jilin basin group,located between Dun-mi fault and Yalujiang fault.It is a Mesozoic faulted basin developed on the north margin of the North China plate.This paper starts from the following four parts:1.Rock and sedimentary facies typesThere are 7 major types of Mesozoic rock types in Tonghua Basin,mainly clastic rock,pyroclastic sedimentary rock and pyroclastic rock.At the same time,there are also clastic lava,lava,intrusive rock and metamorphic rock,including 15 subtypes,49 basic types;It can be dentified four types of sedimentary facies,alluvial fans,deltas,volcanoes,and lakes,including 11 subfacies,43 microfacies.2.Deposition features filled in various periodsThere are three types of sequence filling in Tonghua basin:clastic rock filling,volcanic rock filling,and mixed filling of volcanic rock and clastic rock.The sedimentary filling characteristics of the Lower Cretaceous from the bottom up in the basin are as follows:there are four third-order sequences in the Guosong formation,which are volcanic deposits.The Yingzuilazi formation identifies a third-order sequence,which is a lacustrine deposit.There are three third-order sequences in Linzitou formation,which are volcanic slope deposits.A third-order sequence was identified in the Xiahuapidianzi formation,which is a lacustrine-fan delta front deposit.There are five third-order sequences in Hengtongshan formation,which are volcanic rock-lacustrine deposits as a whole.There are six third order sequences in Sankeyushu formation,which are volcanic deposits as a whole.3.Study on the tectonic evolution of the Tonghua basinThe study found that the tectonic evolution of Tonghua Basin was divided into 6stages:in the initial depression or fault depression stage?J2h?,the range is large,which is the adjustment stage after the Indosinian orogeny.Uplift and denudation stage?J3?,inferred that the thickness of the Houjiatun formation is very large.Or during the J3,there was a certain amount of deposition that had been denudated,J2hcan be preserved today,this stage is the beginning of the Yanshan movement.The first phase is volcanic eruption?K1g?-rapid subsidence?K1y?stage,the volcanic rocks extend beyond the present basin,non-compensated debris deposits are defined within the slip faulting basin,the volcanoes in the basin are of large scale and are mixed with clastic rocks and mudstone,Guosong formation and Yingzuilazi formation were deposited in this stage.The second phase is volcanic eruption?K1l?-rapid subsidence?K1x?stage,volcanic rocks and uncompensated clastic deposits are confined to the strike-slip faulted basin,the volcano scale is smaller,the Linzitou formation and the Xiahuapidianzi formation were deposited at this stage.The third phase is volcanic eruption and slow subsidence?K1h?stage,volcanic rocks have developed,mudstones have also developed,and basins have gradually been filled,Hengtongshan formation was deposited at this stage.The fouth phase is volcanic eruption?K1s?stage,the volcano was large and was denuded,Sankeyushu formation was deposited at this stage.4.Source reservoir assemblage accumulation.The thick mudstone in Hengtongshan formation is the main favorable source rock formation in the study area.The sandstones of the Hengtongshan formation and the sandstones of the Xiahuapidianzi formation are the main developmental layers of the reservoir.There are two kinds of source reservoir assemblage,which are the self-produced and self-reservoir,low-produced and up-reservoir.The model of low-produced and up-reservoir:Xiahuapidianzi formation mudstone and Hengtongshan formation sandstone?K₁hSQ1 sandstone?.The model of self-produced and self-reservoir:Hengtongshan formation mudstones and Hengtongshan formation sandstone?K₁hSQ2 sandstone,K₁hSQ3 sandstone,K₁hSQ4 sandstone,K₁hSQ5 sandstone?.Hengtongshan formation of the Tonghua basin is the main oil reservoir.