Yili Comprehensive Analysis Of Petroliferous Basins

Based on the theory of plate tectonics and principles of that hydrocarbon basin being researched integratedly, dynamicly and comprehensively, by mease of the study which ranges from the regional structure background of Yili basin formed to the Yili-Zhongtianshan micro plate, to the Yili block, to the Yili basin, the formation and evolution characteristics of the different structure units and their different controlling effects to the formation of oil and gas basis are analyzed in this dissertation. Meanwhile, the history from filling and thermal to hydrocarbon generation and hydrocarbon accumulation in Yili basin are researched systematicly. Finally the requirement of hydrocarbon accumulation is further analyzed in Yili basin and it is compared with other basins in Xinjinag and the exploration prospects have been evaluated comprehensively.Yili basin is a independent unit of the Yili-Zhongtianshan micro plate, which is subject to the Zhunger-Kazakstan plate .It is a superimposed basin which formed on the basis of the folded pre-Permian basement, underwent rifting and breaking in Permian ,depressing and uplifting and multiple deformation and reformation after Permian . This basin had undergone three phases, the rifting phase in Permian, the depression phase from Mesozoic to early Neozoic and the phase which formed the intermountain basin by thrusting reformation latter Neozoic. The evolutionary process of the basin was affected by multiple structural movements, of which the Yining movement was the strongest. This movement made this basin enter the territorial depositional period, in which the temperature decreased, the traps, the places oil and gas can be accumulated were formed. Occurred in the Neozoic, the strong Himalayan movement made the first order and the second order structure units uplift to form maintains in the basin, which are unfavorable to preserve oil and gas. The basin is controlled by four groups of fault (NEE, NWW, nearly EW, NW and the fault groups like letter X) which divided the basin into three first order structure units, including northern sub-basin, the central uplift and the southern sub-basin. The two sub-basins can be divided into smaller structure units, in which the Yining depression is the most favorable in Yili basin.The development and distribution of the source rock and the reservoir rocks of the strata are strictly controlled by the evolution of the structure and its characteristics. Three sets of source rocks had been formed juring the steady sinking of the basin .The first source rock, being clay and calcium clay stone in Tiemulike formation of Permian was formed in deep lake environment; the second source rock ,being clay stone in Xiaoquangou group of middle to upper Triassic was formed in the offshore and the shallow lake environment; and the third source rock ,being coal beds in Badaowan formation of lower Jurassic was formed in the lake-swamp environment .The first one is the most potential, since it has the biggest thickness, thehighest organic matter abundance, high maturity and the highest hydrogen generating capacity. Because of the above mentioned reasons, the first one should be considered the main source rock in Yili basin. By means of the modeling of the buried history and the history of thermal evolution, it can be concluded that this set of source rock had entered the ceiling of the oil-generating window in the early Triassic period and reached its peek in the middle and end of Triassic period, befor entering the highest maturity in the early and middle Jurassic period , and had generating gas in the end of Jurassic period. As for the second and the third source rock, they both have little potential, because they both have low maturity.The distribution of the reservoir is controlled by the depositional environment and the faces which are mainly alluvial, delta and river. Determined by the diagenesis and the latter reformation, the physical property of the reservoir in general is poor, ranked as Class 3-4. Vertically, a number of reservoir and cap ro...