反转构造盆地裂缝特征——以松辽盆地大庆三肇地区为例

FRACTURE FEATURES OF REVERSED BASIN:TAKING SANZHAO AREA OF SONGLIAO BASIN FOR EXAMPLE

松辽盆地主要经历了伸展构造期和反转构造期。伸展构造期主要形成一组近NS向的拉张破裂裂缝和两组斜交共轭剪裂缝。反转构造期主要形成NE ,NW向两组共轭剪裂缝和一组近EW向的横张裂缝。盆地东部生长断层的活动到青山口组末期才基本结束。由于生长断层活动期间泉头组三段、四段尤其是青山组的沉积物基本处于塑性状态 ,因此构造裂缝不发育。伸展期形成的裂缝由于经历了较长时间的成岩作用 ,裂缝多被方解石充填 ,有效程度低。进入反转构造期后 ,盆地内储层已经成岩 ,在挤压作用下形成了构造裂缝。因此 。

Songliao basin has principally experienced extensional and reverse stages. A set of near NW tension fractures and two sets of oblique shear fractures were chiefly formed in the stage of extensional structure, whereas two sets of near NE and NW shear fractures and one set of EW spreading fractures were developed in the stage of reverse structure. Fault growth activities could not cease basically until the late Qingshankou Formation. Structural fractures were not well developed due to sediments in plasticity in the Third Forth Member of Quantou Formation and Qingshankou Formation in particular. Most of fractures formed in the stage of extensional structure are discovered to be filled with calcite and in inefficient due to prolonged process of diagenesis. During the reverse stage, structural fractures were extensively formed by compressional process because the reservoir in the basin was already in deep diagenesis. Therefore, fractures in Sanzhao area were mainly formed in the reverse stage.