Study On The Relation Of Diagenesis And Lithologic Trap Of FuYu Reservoir In FuXin Area, Southern Of SongLiao Basin

The Songliao basin is a large Mesozoic-Cenozoic sedimentary basin in the eastern of China ,which belongs to depression interrior basin. Southern of Songliao Basin consist of southeastern uplift area ,the south area of central depression, the south area of western slope area and the north area of southwestern uplift area . west to Baicheng - Tongliao, north to Baicheng - Haerbin, south to Siping, east to boundaryof the basin. It include jilin province ,liaoning province ,and neimenggu province, The area of Songliao basin is about 12.4 ten thousand square kilometers . the Stratigraphical Sequence inclouding Baicheng ,Huoshilin formation of Jurassic and Shahezi ,Yingcheng ,Denlouku ,Quantou formation of lower Cretaceous and Qingshankou ,Yaojia ,Nenjiang Sifangtai ,Mingshui formation of upper Cretaceous stratums within the basin., the Target Layers this paper study is quantou formation ,there are three Sediment Provenances and six water systems during depositional stage. many small scale and Weak Reductive watersysterm are developed in arid and semiarid environment ,but not generate large scale ,uniformity Hydrostatic"flood plain"water systerm. As a whole ,it is alluvial fan– river sedimentary systerms.The research suggest that there are some differents in lithologic composition of the Fuyu Reservoir between Fuyu and Xinli area. the main lithologic composition of Fuyu reservoir sand is feldspar sandstone ,but feldspathic clast sand in Xinli. they both undergone moderate compaction,authigenic clay minerals Cementation,Siliceous Cementation,Carbonate Cementation and Metasomatism ,Dissolution and so on. Which is reach to the phase of late A2 diagenesis stage,the Diagenesis Characteristics is differdent between Xinli area and Fuyu area due to the difference in lithologic composition. the contact of grains of both Reservoir rock bodys are point–line contact. But compare to Fuyu area, the accumulate of reservoir sand in Xinli is more stronger, and suffered more stronger compaction. the content of I/S is decreasing with increasing of the depth, both clay minerals are in the second rapid transform zonation, the content of kaolinit is high because of the lithologic composition and the intensity of diagenesis ,to the contrast ,the Xinli area have the high content of greenite and illite .the Siliceous Cementation of Xinli area is stronger than fuyu area because of the different in lithologic composition and the content of clay minerals. But the Carbonate Cementation is similarity ,they all generate in the early diagenesis stage or before. and pervasive enrichment in fuyu Reservoir.The occurrence of carbonate cementation is very regular which is one important factor effecting the lithologic trap in Fuyu Reservoir. Moreover, the dissolution and metasomatism are distribute widespreadly too, which are occur in the phase of basal carbonate cementation or before .There many factors influencing on the diagenensis of Fuyu Reservoir ,not only the lithologic composition, but also The palaoclimate in the early buried phase ,lithologic characteristic and temperature pressure and so on .the diagenetic evolutionary process of Fuyu reservoir as follow: contemporaneous diagenesis: carbonate cementation play a major part in lag deposit at the bottom of channel sand and point bar sand body ,secondly is compaction. there are mainly feldspar and detrial dissolution in the middle upper part of point bar sand body .there are main compaction in natural dike and alluvial flat argillaceous sediment ,next is carbonate Cementation.Early diagenetic stage: there are mainly carbonate recrystallization because of the carbonate cementation of lag deposit at the bottom of channel sand and point bar sand body. There are mainly early stage Siliceous Cementation ,smectite cementation and compaction in the middle upper part of point bar sand body. there are mainly compaction, recrystallization, and clay minerals cementation in alluvial flat argillaceous sediment. A1 stage of late diagenesis :other superimpose diagenesises are not abviously because of the carbonate cementation in lag deposit at the bottom of channel sand and point bar sand body. The Siliceous Cementation is enhancemented,at the same time the clay minerals Cementation transformed in to kaolini cementation in the middle upper part of point bar sand body, clay minerals Cementation also play a major part in alluvial flat argillaceous sediment.the A2 stage of later diagenesis: the compaction of channel sand further consolidation. the clay minerals cementation transformed in to illite in the middle upper part of point bar sand body.We can see the difference obviously in the diagenetic evolution of different sedimentation facies from the diagenetic prccess of Fuyu reservoir. river lag sedimentation and natural dike sand become nonpermeability reservoir because of diagenesis ,lose the ablility to transport and accumulate ,and isolate from other flow units, reticular overriding reservoir sand body is isolate and noncommunicating with each other. which is effective for the generation of lithologic trap in our study area. the lithologic trap process of fuyu reservoir can be divided in to three periods according to the genesis of Fuyu reservoir sand body ,diagenetic process and present reservoir characteristic: banded-space reticulate channel sand body, meniscus lens lithologic trap and the stage of large scale lithologic trap composite and association.From the Lithologic trap mechanism of Fuyu reservoir, we can see that the at the sediment stage of forth Member of Quantou formation of meandering river meniscus point bar sand generally generate lithologic trap beacuse of the arid climate. Combination with the characteritistic of Fuyu reservoir of southern Songliao basin ,the Fuyu reservoir are mainly distribute in the middle and north of songliao basin ,the size reduce but the amount increasing from the south to north . It is proven that there are a lot of ninor faults acrossing T2 reflection horizon in the middle and north of southern songliao basin. it is very profitable to link up the Qingshankou formation source rocks and Fuyu reservoir lithologic trap. in addition, thick dark mudstone of I, II member of Qingshankou formation distribute widely and stability, so meniscus point bar sand in meandering river have the ability to store oil and gas. every depress filled with oil and the reservoir sand overriding and join in together in the southern songliao basin meandering river lithologic hydrocarbon reservoir.There are a large potential exploratation in lithologic hydrocarbon reservoir of meandering river in the middle and north of songliao basin ,but the traditional exploration ignorant the control action of the lithologic. Therefore ,it is necessity to recognite and reevaluate meandering river sedimentation of Fuyu reservoir in the middle and north of southern songliao basin, particularly we should pay more attention to the"nonstructural area",in order to make a breakthrough for explorating the hydrocarbon resources of southern songliao basin.