| In the regional tectonic, Suganhu depression is in Uplift of Northern Margin ofQaidam Basin, The area of Suganhu depression is7000km2. The area of the mainstudy is323km2in Mesozoic. the Through previous studies, There exists Jurassic ofMesozoic and Paleogene and Neogene and Quaternary of Cenozoic，we know thehydrocarbon source rocks were developed in the Middle and Lower Jurassic, andthere has hydrocarbon show according to the drilling, but well testing results showsnon-ideal. Formation condition analyses and reservoir-forming rule are unclear,Base on previous study，by the data on regional geology,drilling,geophysics andexperimental analysis,we had researched the characteristics of source-reservoir-sealcombinations and reservoir forming characteristics,and establish oil and gaspool-forming models of Suganhu.1、Research of source rocksBased on the logging data and the research of the past, It is concluded that thedark mudstone in the middle–lower Jurassic stratum is the only source rock of thisregion. The upper Jurassic stratum and the above one is all red clastic rocks. Thesource rock is mainly consisted of lake facies mudstone, charcoal mudstone and coal.The geochemistry characteristics is analyzed and it is concluded that the type ofsource rock in Suganhu area isⅡ-Ⅲ, the dark mudstone in the upper Jurassic stratumhas the highest abundance of organic matter, and is in a n the high evolution degree.most of them is good-middle source rocks. 2、Reservoir studyThe reservoir of Suganhu mainly distributed in J2and J3, which has poorphysical property and few Crack, it belongs to super low pore dense reservoir and lowpore low permeability dense reservoir, the stage of diagenesis of reservoir is A2, Inthe paper, sedimentation and diagenesis control the physical properties of reservoir inSuganhu, near source coal system strata sedimentary lead to the content of heterobaseis slightly higher, because of this, the sediments is easier to compaction,during theDiagenesis period, primary pore has reduced by compaction andcementation.although,the physical properties has improved by the secondary porewhich production of the dissolution, pore throat of the reservoir is too fine to flowingof the acid dissolved substances, face this kind of circumstance,the dissolution haslimited transformation effect, the comprehensive factors of sedimentation anddiagenesis ultimate lead to the present situation of the reservoir of Suganhu.3、Seal evaluationThe styles of cap rocks is mudstone seal, the sedimentary environment of upperjurassic in Suganhu is more stable,the thickness of single udstone is high andcontinuous distribution,this can be a series of local cap rock;The mudstone ofpaleogene is over1300m in buried depth, the compared of mudstone and strata isnearly70％,the large thickness of single udstone can be reach85m or73m. Accordingto the quantitative evaluation of microscopic of cap rock, the sealing property of caprock in Suganhu is good, especially for the oil,bad to gas.4、Hydrocarbon accumulation periodReconstruction of Burial History of the Suganhu, the area has twice big upliftand denudation in middle cretaceous and middle late pliocene by Yanshan movementand Xishan movement. Microscope observation and testing for fluid inclusion showsthe homogenization temperature of salt-water inclusion is between64.6℃and89.6℃,the Histogram has two main peak which are65-70℃and75-80℃, according to burialhistory and thermal history,the temperature of two main peak is close, the reservoirforming time should be just once,the time is early cretaceous period. 5、Factors controlling oil accumulation and oil and gas pool-forming modelsThe source-reservoir-cap assemblage of Suganhu has two models，they areself-generation&self-reserving lower intervals generation and upper intervalreserving.The trap in the center of Sutan1well is beneficial to the Formation of oiland gas reservoir. The stage of main oil generation is at the late period of EarlyCretaceous, the oil and gas go into the sandbodies nearby after the generation andformed a self-generate, self-reservoir reservoir swiftly. After that, by the influence ofHimalayan movement, the oil and gas migrated to the upper Jurassic formation andformed a lower-generate, upper-reservoir reservoir. |
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