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Analysis On Evolution And Hydrocarbon Potential Of Southern Songliao Basin And Its Deep Petroleum Systems

Posted on:2006-03-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:X H HeFull Text:PDF
GTID:1100360182956863Subject:Structural geology
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Songliao Basin is one of the main hydrocarbon bearing basins in China. The Daqing oil field of it yields over 5000 × 10~4t every year over 20 years and 66×10~8t proven reserves had been found in the basin till now. It contributes to China much more. All of those are attributing geologically to the zones in middle and upper sequences of the basin. As for the deeper sequences of it, there is a huge resources and lower degree in exploration. A lot of questions about the deeper parts are waiting for answers, especially in petroleum conditions, what look like the pool models and regularities of hydrocarbon accumulation, where the leads and how to find and appraise them. So the thesis sets the southern part and its deep sequences as the study area and involves in four tectonic units of the first order. The geodynamics analysis covered almost whole area of the Northeast China. The advanced methods such as basin dynamics analysis, sequence stratigraphy analysis, basin modeling and Petroleum system analysis are employed and comprehensive appraising for prospects of the area was done. As results new ideas are proposed in theory and some prospecting leads available for drilling are found out in practice.Main researches accomplished during the study:1. Dividing the basin stratigraphy assembly in Northeast China , ascertaining the time of basin forming, analysis of the original basin type and probing into the tectonic background of Northeast China in Mesozoic.2. From the view of the system analysis based on the west Pacific Ocean tectonic domain and regarding of the evolution of the paleo-Asiatic tectonic domain in Pre-Mesozoic especially between Carboniferous and early, middle Jurassic, researching for the geodynamic environment and process of Songliao basin's forming under the "twodifferent eras and schemes" (respectively as to the pre-Mesozoic, Mesozoic and Cenozoic). A new idea about the origin of Songliao basin was given.3.Generalizing and specifying the petroleum features of the deep parts of Southern Songliao basin in the aspects of the structure, sedimentary system, source rock, reserve rock, petroleum system, controlling factor and accumulation regularity for hydrocarbon accumulation.4. Well done the petroleum analysis on the featuring Shiwu fault-depression situated in Southern Songliao basin. The work included high resolution sequence stratigraphy analysis for the depositing system and its space distribution and pattern changing, modeling the resource distribution and generalizing the pattern of pool forming and concerned influential factors. The prospecting leads were predicted and located.Following achievements were obtained:The Mesozoic sequence was divided into four sets (P2-T2^ T3-J2% K^ K2—Ei). They were deposited in marine, continental environment and both. Among all the tectonic movements occurred in the area, the early episode of the Indosinian movement, the first, second and third episode of the Yanshanian movement and the first episode of the Himalayan orogeny are the most important for the basin forming in the area. Three tectonic development stages and four original basin forming periods were defined in according to the geodynamic scheme, tectonic deforming feature, volcanic activities and sedimentary body in this area. The four stages are T3-J2 -. Ki \ Ki2 and K2—E1 of which the third and the fourth are proven as the growing time of the mega oil field of Daqing and the second is the forming time of the deeper part of Songliao basin and other basins in the area.Five main geodynamic stages were experienced in the evolution of the Songliao basin under the tectonic background of the eastern China. First one is the stage of micro-plate combining and collision and in this time of late Paleozoic and early Mesozoic the Paleo-Asia ocean diminished out and the base of the Songliao basin was formed. Also there was an increased crust over there due to the plate convergence, combination and continental squeezing orogeny. The residual of the Triassic and the Middle and Lower Jurassic mostly were attributed to molasses formation and some may be foreland formation. The second is the period of the formation of the continental rift basin resulted from the activity of the mantle plume and the lithosphere delaminating with the intense crust extension which occurred during late Jurassic and the early part of early Cretaceous. That is the time Western Marginal Pacific Tectonic Domain imposed its subduction impact on the area. Thefault depressions and huge volcanic and magma formations were formed in the area that time. The third one is featured with thermal subsidence after rifting in the time from Quangtou period to early Paleocene in which the depression, in another word the middle and upper part of the Songliao basin, was formed as a result of the decreasing activity of mantle plume, new crust growing and cooling. The fourth phase was the period between the late Paleocene and early Neocene (Oligocene and Miocene). This is the time that the Pacific plate subducted down to the Eurasia plate with the different direction and rate from the former one, which ignited a direct impression on the eastern China. The pressing process shaped the architectures of the middle and upper part of Songliao basin such as Daqing anticline and other reverse structure belts trending NE in the basin. Also the reversion of the boundary fault of the fault depression and uplifting happened at the same time. The last one is the period of regional uplifting after the North China Movement. This event began from the late Miocene till now and its result is the regional uplifting and final withering of the Songliao basin.Studying and analysis reached the conclusions that Songliao basin is an active continental rift of Mesozoic as to its deep part. The scheme of its deformation may be simple shear extension or crust detachment extension. The geodynamics is involving the activity of the mantle plume resulting from the subduction of the paleo-Pacific ocean plate and crust delaminating commonly occurred in the eastern China in Yanshanian period.The petroleum features of the deep part of the Songliao basin are that the source rocks are located in the fault depressions which are contained by the basement faults. The depressions are in one of three shapes of listric, graben and the combination of these two types. The structure of the fault depression and its evolution controlled the filling-type sedimentary system in it and imposed the effect on the deposition environment and faces which were closely related to the type, abundance of the organic matter in rock and the type, quality of reserve rock. The size and thickness of the deeper part of the basin play an important role in the hydrocarbon potential of fault depressions. One petroleum system can be recognized which is further divided into the three hydrocarbon bearing assemblies. Each assembly is featuring in the pool formation and hydrocarbon accumulation. Among the factors influencing the formation of the pools the source rock, structure, trap and reservation are the critic ones. The view of the source rock being critic for the formation of pool is an illustration for the Chinese continental petroleum theory.The most favorable prospect area for hydrocarbon exploration is the Changlin fault depression located in the Central Depression zone and followed by the Shiwu faultdepression and Dehui fault depression in the ES Depression zone. All of them both have gas and oil potential with the character of gas dominated resource configuration. The studying way of the basin modeling for the migration and accumulation of the hydrocarbon in depression actually is another expression of the macro geodynamics in small scale geological body. A typical petroleum analysis for the Shiwu fault depression was well done. The depression is characteristic of listric structure and experienced three phases of evolution of rifting, thermal subsiding afterwards and structural reversion. The last phase is correspondent to the stage of the architecture forming and basin withering periods.Four reversion structure belts, that is of Pijia-Zhangjiatun, Bawu-Shiwujiazi, Gujiazi-Houwujiafu and Qiangjiatun, were formed in the fault depression stage and shaped in the last period of the basin evolution, and the home of the leads and pools. The filling-type sequences of the fault depression are subdivided into 3 units of the first order, 2 units of the second and 5 units of the third. The main depositional systems are fan delta and fluvial delta. The integral petroleum system of Shiwu fault depression can be divided into four sub-systems of Kih(Kih+Kish+Kiy)(!), K!sh(Kih+Klsh+Kiy)(!), K,y' (K,sh+K,y+ Kid) (!) and Kiy2(Kiy+K!d+Kiq)(!). The comprehensive prospect appraising demonstrated that the Guhouba block of the central structural zone, Pijia block and Zhangjiatun block of north steep slope zone are the most favorable objects for progressive exploration in Shiwu fault depression. The deep part of the Houwujiafu structure is the best one among the subtle traps for the drilling.
Keywords/Search Tags:Songliao basin, Tectonics Dynamics, Basin Modeling, Petroleum System Resource
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