塔东地区构造热事件及其对原油裂解的影响

塔东地区目前共有7口探井钻遇油气勘探潜力较大的寒武系-下奥陶统碳酸盐岩地层。主要对这7口井古生界的有机质成熟度资料做了系统分析，发现其中2口井古生界有机质成熟度剖面呈直线型，属于正常的地热演化剖面；另外5口井古生界有机质成熟度存在非常明显的拐点；7口井古生界与中新生界的有机质成熟度之间不连续，即有明显的“断层”，表明塔东隆起区及斜坡区古生界地层的有机质成熟度增加并不是由于沉积埋藏造成的，而是由于深部的异常热事件造成的。从成熟度变化分析，异常热事件在垂向上主要影响下古生界地层，在平面上异常成熟度现象分布在走滑性深大断裂带附近，远离走滑性深大断裂带的井中有机质成熟度表现为正常的热演化剖面，说明在塔东地区异常热事件与深大断裂有关，称之为构造热事件。构造热事件成为塔东隆起或斜坡区在中新生代时古生界原油裂解的主要热动力。7口探井中多期沥青的存在，进一步说明该地区有过后期原油裂解，同一样品中沥青反射率存在明显的差异，反映沥青是在不同阶段形成的。其中1期沥青分布区域没有受到异常热事件影响，沥青只是早期正常埋藏成因；对2期沥青分析说明有1期后期异常热事件，与该区断裂主要活动时期（J3末）是一致的；对3期沥青分析说明存在2期后期异常热事件，与车尔臣断裂带的2期活动（S₃-D₂、J₃末）一致。

Tectono-thermal Event and Its Influence on Cracking of Crude Oil in Eastern Tarim Basin

Up to now,there are 7 wells with the Lower Paleozoic carbonate strata in eastern Tarim Basin(Tadong).The trap drilling prospect is optimistic in these strata,especially in the Cambrian-Lower Ordovician.After analyzing comprehensively the data from maturity of organic matter in these 7 wells,the results show that the maturity of organic matter is normal thermal evolution and the sections look like a single beeline in 2 wells,and there are very distinct inflection points in the other 5 sections of maturity.The sections of maturity in 7 wells are all discontinuous between Paleozoic and Mesozoic-Cenozoic,that is to say,there is a fault between them.This denotes that the increase of maturity of Paleozoic organic matter doesn't owe to sedimentation and burial in the uplift and slope region in Tadong,but to the abnormally thermal events in the deep.According to the variety of maturity,the abnormally thermal events mainly distribute in the Lower Paleozoic in the vertical,and near the deep grand strike-slip fault zones in the lateral,and the sections of maturity are normal in those wells apart from the faults.All these show that the abnormally thermal events have a close relationship with the deep grand faults,so the author calls it tectono-abnormal thermal events.It is the main thermal propulsion for cracking of Paleozoic crude oil in the Cenozoic in the uplift and slope region in Tadong.Multistage bitumen in these 7 wells proves clearly that there is a late cracking of crude oil in Tadong.The bitumen reflectivity has an obvious difference even in one sample,and this phenomenon shows that the bitumen is formed in different stages.Furthermore,there is no abnormally thermal event in the areas where only have one stage bitumen,and the bitumen is formed by the early sedimentation.There is one late abnormally thermal event in the areas where have two stages bitumen,and the time of thermal event is consistent with the movements(the terminal Late Jurassic) of the faults in this area.There are two late abnormally thermal events in the area where have three stages bitumen,and the time of thermal events is consistent with the movements(S3-D2,the terminal Late Jurassic) of Churchen Fault System.