渤海湾盆地渤南低凸起西段低角度正断层分段生长特征及其油气地质意义

Segmented growth of low-angle normal faults in the western Bonan swell，Bohai Bay Basin and its petroleum geological significance

娄瑞 孙永河 张中巧

Rui LOU Yonghe SUN Zhongqiao ZHANG

为了研究渤海湾盆地渤南低凸起低角度正断层分段生长诱发的时空差异演化特征及控藏机制，基于最新三维地震资料，精细刻画表征了断层分段生长过程及差异演化特征，结合区域构造背景，探讨断层成因机制及对油气成藏的控制作用。结果表明：渤南低凸起南边界F断层和F断层均为低角度正断层，源于中生代NWW—近EW向先存逆冲断层发生负反转，在新生代发生再次活化。F断层具有平面上分段连接、垂向上多幕活动的特征，中段继承原有断面持续活动，西段和东段分别与裂陷Ⅱ幕新生NEE向断层和裂陷Ⅲ幕新生近EW向断层垂向搭接形成现今形态。低角度正断层对油气成藏的控制作用主要表现为：①低角度正断层断控侧沉积规模大，可提供充足的可容纳空间，形成规模陡坡砂体；②长期活动的低角度正断层是垂向油气运移通道，控制了油气垂向上的富集层位；③低角度正断层多期活动改造了深部储层物性，断层活动强度与优质储层的发育密切相关。

A fine characterization of the segmented growth process and differential evolution characteristics of these faults is conducted using the latest 3D seismic data to investigate the segmented growth-induced spatiotemporally differential evolution and mechanisms governing hydrocarbon accumulation of the low-angle normal faults in the Bonan swell within the Bohai Bay Basin. Furthermore， we explore the genetic mechanisms of these faults and their controlling effects on hydrocarbon accumulation while considering the regional tectonic setting. The findings indicate that faults F and F at the southern boundary of the Bonan swell are low-angle normal faults. Both originated from the Mesozoic NWW- to nearly-EW-trending pre-existing thrust faults， which underwent negative inversion and subsequent reactivation during the Cenozoic. Fault F exhibits segmented connections laterally and multiple episodes of activity vertically； its central segment inherits continuous activity from the original fault plane， while its western and eastern segments vertically overlap with the NEE-trending fault newly formed during the rifting episode Ⅱ and the nearly-EW-trending fault during the rifting episode Ⅲ， respectively. These collectively create the present morphology of fault F. The controlling effects of the low-angle normal faults on hydrocarbon accumulation are as follows： （1） The fault-controlled sides exhibit a large sedimentary scale， thus providing sufficient spaces for deposition. Consequently， large-scale sand bodies on steep slopes are developed. （2） The low-angle normal faults， which have remained active for a prolonged time， provide channels for vertical hydrocarbon migration and determine the horizons of vertical hydrocarbon enrichment. The multiphase activity of these faults has transformed the physical properties of deep reservoirs， with the activity intensity being closely related to the formation of high-quality reservoirs.

10.11743/ogg20240310