从波动观点看塔北地区油气藏的形成演化——以英买7油藏为例

A Study of Reservoir Evolution in the Tabei Area of Tarim Basin with the Wave Analysis——A Case Study of the YM7 Reservoir

本文运用沉积波动过程分析方法,在综合分析野外露头、岩心、录井、测井、地震等资料的基础上,建立了塔北地区不同小区的岩性-时间剖面。研究表明,740～760Ma、200～240Ma、100～110Ma、60～70Ma、30Ma是控制塔北地区构造演化的主要周期。早古生代、三叠纪和第三纪以来是3次主要的沉积高峰,志留纪末—晚泥盆世早期为主要剥蚀期,剥蚀量一般>1000m,北部>1500～2000m,海西期、印支期和燕山期的剥蚀过程亦很明显。志留纪末下奥陶统顶面埋深超过2000m,下奥陶统底面约3300m。沉积—剥蚀过程的变化对油气藏的形成演化有重要的控制作用,据古地温计算,寒武系及下奥陶统在奥陶纪末期就进入生烃期,但由于整体上升,使有机质热演化处于近停止阶段,保存了二次生烃能力。三叠纪埋深速率快、幅度大,下奥陶统顶面重新超过原埋深,下奥陶统残留地层开始大量生烃,按深度计算二叠纪地层也进入大量生烃门限深度,随后发生一系列抬升过程,晚第三纪下奥陶统残留地层重新超过早古生代及三叠纪的最大埋深,第三系中下部地层也进入生烃门限。早古生代晚期抬升幅度大的地区是二次生烃的有利地区。

Based on comprehensive analyses of data from field work, coring, well-logging and geophysical exploration, the wave processes in the Tabei area of the Tarim basin have been studied with the wave analysis method, in which a set of mathematical and physical principles are used. It is shown that 740-760 Ma, 200 - 240 Ma, 100 - 110 Ma, 60 - 70 Ma and 30 Ma are the main cycles which control the evolution of the Tabei uplift. The periods of the early Paleozoic, the Tri-assic and from the Tertiary to the present are the three main periods of depositional processes, and the end of the Silurian to the early Late Devonian is the main erosional period with the average hiatus over 1000 m, greater than 1500 - 2000 m in the northern part. Erosional processes are also obvious in the Hercynian, Indosinian and Yanshanian epoches. The buried depth of the top of the lower Ordovician at the end of the Silurian exceeds 2000 m, the bottom of the lower Ordovician is about 3300 m at depth. The deposition-erosion processes play an important role in the reservoir formation. The palaeotemperature measurement proves that the Cambrian and lower Ordovician source beds began to get matured by the end of the Ordovician and maintained the ability of secondary generation of hydrocarbons because of the uplifting. Because of the highspeed deposition and great burial depth during the Triassic, the burial depth of the top of lower Ordovician surpassed the original depth, and the lower Ordovician began to generate hydrocarbons in large quantity, and at the same time the Permian source bed also reached the threshold depth of massive hydrocarbon generation according to the burial depth calculation, but a series of uplifting occurred until late Tertiary, then the remains of the Permian surpassed the maximum burial depth of the early Paleozoic and Triassic, and the lower to middle parts of the Tertiary began to get matured. Therefore, the areas where the uplifting was of a large magnitude in the late Early Palaeozoic are favourable areas for secondary generation of hydrocarbon.