渤海湾盆地构造演化与古生界原生油气成藏

Tectonic Evolution of the Bohai Bay Basin and the Palaeozoic Original Oil and Gas Reservoirs

在对渤海湾盆地全区分布的200余条地震剖面进行精细解释的基础上,系统分析了盆地内所发育的构造样式及其所反映的构造作用、活动时期。区内主要发育了伸展、挤压、走滑及复合等四大类若干小类构造样式,依据各类构造样式涉及的层位和构造层的相互关系,反映出古生界经历了两大期挤压、两大期拉张或走滑,并有两期明显的反转。对20条贯穿全区的地震剖面进行平衡剖面分析表明,尽管盆地内不同构造区所经历的构造作用有所区别,但总体力学性质及发育时期与构造样式所反映的构造作用较为一致,表现为T3挤压、J1+2相对稳定、J3+K1拉张、K2挤压、E—Q拉张的特点,古生界残留与埋藏正是受中新生代不同区的差异演化控制。古生界原生油气藏解剖表明,对于经历多期构造变动改造的叠合型盆地,构造演化史控制的古生界在埋藏过程中能否大量晚期二次生烃是成藏的关键之一。在古生界具备有效烃源岩的前提下,具有中生代浅埋或弱剥、新生代深埋的正负反转构造组合过渡带是古生界原生油气藏的有利成藏区。

Based on the refined interpretation of over 200 seismic profiles in Bohai Bay basin, the tectonic styles developed in the basin and the tectonics and movement times they reflect are systematically analyzed. Tension, compression, strike slip and superimposition are four major tectonic styles developed in this area. The correlation of sequence and structural layers related with the tectonic styles indicates that during the Palaeozoic this area experienced two stages of compression, two stages of tension or strike slip motion and two stages of tectonic inversion. The balanced cross section analysis for 20 seismic profiles throughout the area shows, although different structural tracts experienced different tectonic activities, their total mechanical characters, development times and tectonic styles are consistent. Generally speaking, it is mainly expressed in： compression in T3, relatively stable in J1＋2, tension in J3＋K1, compression in K2, and tension in E-Q. The diverse evolutions in different tracts during the Meso- Cenozoic time controlled the Palaeozoic remains and burial. An analysis on the Palaeozoic original reservoirs indicates that for the superimposed basin having experienced polyphase tectonic disturbance reconstruction, one of the key factors for oil and gas accumulation is whether the Palaeozoic strata can produce hydrocarbon again or not at a later time. Therefore, the inversion tectonic transition zone with effective Palaeozoic hydrocarbon source sequences, and with shallow burial or weak denudation during the Mesozoic and deep burial during the Cenozoic, is favorable for accumulations of the Palaeozoic original reservoirs.