莫索湾地区侏罗系油气成藏主控因素分析

准噶尔盆地腹部莫索湾地区具有良好的油气成藏条件，目前已在侏罗系发现了大量油气。依据物化特征可将侏罗系原油分为Ⅰ、Ⅱ、Ⅲ类。Ⅰ类原油密度低，成熟度高，生物降解程度弱；Ⅲ类原油密度高，黏度大，生物降解严重；Ⅱ类原油密度中等，成分复杂，具混源特点。断裂性质对研究区的油气成藏具重要影响，莫索湾凸起断裂属张扭性质，断距小，封闭性差，未能有效封堵油气；而莫北凸起断裂以伸展为主，断距大，逆牵引构造明显，封闭性好，控油作用强。异常压力分析表明该区超压发育，封隔层位于侏罗系三工河组三段，实测压力系数大于1.96，由于地层压力过高，八道湾组难以形成规模油气聚集。流体包裹体均一温度证实侏罗系油气藏有三次充注事件，第一次成藏的油气遭受生物降解，第二、三次成藏保存条件较好。总之，多旋回的构造运动、不同的断层性质和封闭强度、过高的异常压力及多期的成藏过程是控制莫索湾地区侏罗系油气成藏的主要因素。

AN ANALYSIS OF DOMINANT CONTROL FACTORS OF HYDROCARBON RESERVOIRING IN JURASSIC OF MOSUOWAN AREA

Favorable hydrocarbon reservoiring conditions exist in Mosuowan area of the central Junggar Basin, where large amount of oil and gas have been discovered in Jurassic so far. According to the physical and chemical features, crude oil in the Jurassic can be divided into 3 types, including type Ⅰ、Ⅱ and Ⅲ. Type Ⅰis characterized by low density, high maturity and weak biodegradation, type Ⅲ features high density, large viscosity and strong biodegradation, while type Ⅱ is characterized by moderate density, complex components and mixed sources. Fault properties have major influences on hydrocarbon reservoiring in the study area. The faults on Mosuowan uplift are transtensional and cannot effectively seal hydrocarbons due to their short fault displacement and poor sealing ability. While Mobei uplift are dominated by extensional faults, with large fault displacement, pronounced drag structure, good sealing ability and strong control on oil accumulation. Abnormal pressure analysis shows that overpressure is well developed in the study area and the barriers are located in the 3rd member of Jurassic Sangonghe Formation with a measured pressure coefficient over 1.96. Scale hydrocarbon accumulations cannot be formed in the Badaowan Formation due to high formation pressure. Homogenization temperature of fluid inclusion demonstrates that the Jurassic pools were charged in 3 stages. Hydrocarbons charged in the first stage were biodegraded, while that charged in the second and third stages were well preserved. Multicyclic tectonic movement, different fault properties and sealing abilities, abnormal high pressure and multiphase hydrocarbon accumulation are the major factors that control the formation of Jurassic oil and gas reservoirs.