Classification of thickened reservoir types and thickening modes in the northwestern margin of Junggar Basin

• 1、Fengcheng Oilfield Operation Area of Xinjiang Oilfield Company

Abstract：Through a comparative analysis of the factors that reflect the developmental environment of microorganisms of heavy oil in the northwestern margin of the Junggar Basin, the geochemical characteristics, temperature, pH, salinity, etc. of reservoir water, combining the effects of chromatographic effects on the thickening of crude oil, The crude oil thickening types in the northwestern margin are divided into four types: atmospheric water leaching, desalination and oxidation thickening, anaerobic degradation and thickening, and deep chromatographic thickening. Based on this, it is concluded that structural characteristics, caprock development, and atmospheric water infiltration are the main controlling factors for crude oil thickening in the northwestern margin. The thickening patterns of crude oil in the northwestern marginal region were analyzed, and two thickening patterns, namely, thickening of geological layer effects and secondary thickening of reservoirs after accumulation, were proposed. In which the thickening of geological layer effects, due to the long-range migration of oil and gas, the environment for hydrocarbon accumulation has undergone tremendous changes，the migration resistance of gas or light components in crude oil components is small, and they are preferentially moved to more distant areas, the heavy hydrocarbon components tend to form lithological heavy oil reservoirs in relatively dense reservoirs, such as the blocks 8 and 7, the transition to the front edge of the slope, and so on. In addition, the secondary thickening of reservoirs after accumulation is caused by poor preservation or destruction of the later stage, resulting in loss of the light group, biodegradation or oxidation, for example, heavy oil reservoir on the fault zone in the Wuxia area, and most areas in the piedmont fault zone.

Keywords： Junggar Basin the northwestern margin thickening type geological layer effect secondary alterations