| Jurassic and Cretaceous in Maqiao Salient is an important stratum of hydrocarbon exploration in Junggar Basin, where Mosuowan oil and gas field and high hydrocarbon output in Pen5 have been found in recent years.The hydrocarbon exploration in practice, especially the failure of Fang5 drilling makes petroleum geologists realize that reservoir is a very important factor for hydrocarbon trap, while space-time distributing regulation of high-quality or relative high-quality sandstone reservoir is instructive for hydrocarbon exploration. So it's needed to work over the diagenetic and pore evolution mechanism of Jurrasic and Cretaceous sandstone in Maqiao Salient in order to establish diagenetic model, as a result ,to realize the type of reservoir space, the evolution of reservoir and the distribution of relative high-quality reservoir.This dissertation has studied the diagenetic and pore evolution regulation and genetic mechanism of Jurassic and Cretaceous sandstone in Maqiao Salient from the point of diagenetic mineral and basin dynamic function, and reached the following learnings:1. Jurassic sandsone reservoir is of primary pore type, which is the main type of relative high-quality reservoir space. Dissolved pore formed in acidic diagenetic enviroment is commonly observed in Jurassic sandstone. But corrosion to porosity enlarging is limited, and to permeability contribution is a little. Cretaceous sandstone reservoir is of primary pore type.2. Jurassic sandstone reservoir has such lithological characteristic as low compositional maturity, high textural maturity and low cenmentation content, which controls sandstone diagenesis and pore evolution. For instance, sandstone grain size and compositional maturity of debris controls water-rock reaction rate and scale, crushing resistance and heat resistance of reservoir. Because of low cementation, the influence of diagenetic mineral on diagenesis reflects on the ratio of diagenetic compaction. As a result of compaction,the porosity reducing in sandstone can reach to 5.5% to 6.0%.3. The burial diagenesis in vertical which is the main basin dynamic factor in Maqiao Salient and the tectonic compression in lateral are basin dynamic functions controlling sandstone diagenetic and pore evolution. The burial diagenesis are controlled by four parameters, i.e. paleogeotherm field, geological action time, loading pressure mode(or reservoir heat-evolution track) and diageneticwater-medium enviroment, and the first three parameters can be demonstrated quantificationally by heat maturity of sandstone to predict porosity. (1) Paleogeotherm field is the key factor for sandstone diagenesis. The low paleogeotherm field in Maqiao Salient determines sandstone in low diagenetic evolution phase and with high preserved porosity in such deep burial.(2) Geological action time and load pressure mode have a distinct effect on sandstone diagenetic compaction. For example, with the same overlying load pressure, compaction degree of Cretaceous is oboviously less than that of Jurassic. (3) Sandstone in acidic diagenetic enviroment has such characteristic as fast compaction rate, earlier compaction stage, prevalent grain solution and crushing, poor heat resistance and crushing resistance, small free growing space of authigenic mineral, poor reservoir properties and so on. It has undergone stronger chemical diagenesis than in alkaline diagenetic enviroment. Furthermore, its chemical-to-physical reaction is more active. So its crushing resistance is reduced. (4) Alkaline diagenetic enviroment in Maqiao Salient formed in arid climate or semiarid climate, and resulted in the cementation of carbonate and anhydrite. But acidic diagenetic enviroment formed in humid climate, and resulted in the growth of kaolinite.4. There are three types of diagenetic model in Jurassic and Cretaceous sandstone, namely arid or semiarid climate-diagenetic alkaline water medium genetic model, humid climate- diagenetic alkaline water medium genetic model and humid climate- diagenetic neutral water... |
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