东海陆架盆地大春晓油气田成藏动力学特征及成藏模式

油气成藏动力学是动力学研究的前沿,大春晓油气田成藏动力学是东海陆架盆地油气成藏特征研究的热点,也是长期研究薄弱环节。通过井震解释和数值模拟,分析了大春晓油气田成藏动力学三大能量场:温度场、压力场和应力场的成藏动力学要素特征。研究表明区内具有地温梯度高特点,达36～40℃/km,且发现60个岩浆侵入岩,导致局部增温作用促进油气成藏;烃源岩热成熟度不一致性明显,数值模拟结果表明,早期大春晓地区东北部和东南部成熟度高,其中,天外天构造和春晓-断桥构造烃源岩成熟时间最晩,大春晓构造烃源岩晚成熟;早、中期NNE向拉张应力场产生拉张正断层,有利于油气运移和保存;晩期NWW向张剪性应力场所形成平移断层有利于油气保存。区内发育典型超压并存在大型超压囊,提出了超压-压力囊模式,超压与断裂体系促进了油气运移。采用数值模拟技术阐述油气运移的时代、过程与结果。通过大春晓油气田含油气系统关键时刻和事件、成藏动力学机制与过程综合分析,建立了大春晓油气田成藏动力学模式和成藏模式。

Dynamic characteristics and model of hydrocarbon accumulation in the large Chunxiao oil and gas field in the East China Sea Shelf Basin

The research on the dynamics of hydrocarbon accumulation is a frontier of kinetics research.The study on the dynamics of hydrocarbon accumulation in the large Chunxiao oil and gas field is also a hot topic,but a bottleneck as well,in the study of hydrocarbon accumulation features in the East China Sea Shelf Basin for a long time.Through well-to-seismic tie interpretation and numerical simulation,we concluded three energy fields supporting the accumulation in the oil and gas field,including temperature field,pressure field and stress field, the dynamic elements of which were analyzed as well.It's pointed out that the study area is characterized by high geothermal gradient,up to 36~40℃/km,and 60 magmatic intrusive rocks are found therein,leading to the promotion of hydrocarbon accumulation by locally increasing temperature.The thermal maturity of source rocks is significantly inconsistent.The results of numerical simulation show that the maturity is high in degreein northeast and southeast of large Chunxiao area;the Tianwaitian and Chunxiao-Duanqiao structures come to the last in terms of the maturity of their source rocks,and the large Chunxiao structure is also late in this aspect;the NNE-trending tension stress field in the early and middle stages produces tensile normal faults,which are conducive to hydrocarbon migration and preservation.In the later period,the NWW-trending tension-shear stress field forms translational faults,which are also favorable for hydrocarbon preservation.Typical overpressure is developed and a large overpressure sac exists in the area,and an overpressure-pressure sac model is proposed to demonstrate the effect of overpressure and fracture systems on promoting hydrocarbon migration.In addition,the numerical simulation method is used to reveal the era,process and results of hydrocarbon migration.The key moment and events,and dynamic mechanism and process of hydrocarbon accumulation in the study area are integratedly analyzed,leading to the establishment of the dynamic model of hydrocarbon accumulation in large Chunxiao oil and gas field as well as its accumulation model.