南襄盆地泌阳凹陷油气成藏作用及成藏模式

Hydrocarbon accumulation and reservoiring pattern in Biyang depression,Nanxiang basin

南襄盆地泌阳凹陷发育有岩性、背斜和断块3类油气藏。对于自生自储型的岩性油气藏来讲,上翘尖灭砂体与鼻状构造背景的构造等高线近于正交,形成了大面积砂岩上翘尖灭或侧缘上翘尖灭岩性油气藏。此类油气藏大体有3期油气充注,但以中晚期充注为主。背斜油气藏油源为核桃园组二、三段烃源岩的混源,油气先后沿层状砂体向下二门背斜运移并聚集成藏。廖庄组沉积末期是古背斜+岩性油藏形成期;上寺组沉积末期的断裂活动改造了早期油气藏,并形成了新的断层+岩性油气藏。北部斜坡因北东向、北西向断裂活动形成大小不等、形态各异的复杂断鼻、断块圈闭。此类油气藏油气源自南部的深凹,廖庄组沉积前由深凹向北作侧向运移,廖庄组沉积后经断层向浅层运移,具有晚期成藏的特征。预测凹陷南部断裂陡坡带是岩性油藏的有利地区,东部是寻找背斜油藏的有利地区,北部斜坡带是断块油藏的有利地区。

Three types of reservoirs, including lithologic, anticlinal and fault block oil/gas reservoirs, are developed in Biyang depression of Nanxiang basin. As to lithologic reservoir characterized by being generated and reservoired indigenously, the upwarping pinch-out sandbodies are nearly perpendicular to the structural contour lines of nose setting, leading to the formation of large area sandstone upwarping pinch-out or lateral margin upwarping pinch-out lithologic oil/gas reservoirs. Such reservoirs more or less experienced three hydrocarbon charging stages, with the middle -late stage as the major one. Oil and gas in the anticlinal reservoir were sourced by both the 2nd and 3rd members of Hetaoyuan Fm and successively migrated downward along the layered sandbodies and accumulated in Xia＇ermen anticline. Palaeo-anticlinal ＋ lithologic reservoirs were formed at the end of deposition of Liaozhuang Fro. Faulting at the last stage of deposition of Shangsi Fm modified the previously formed oil/gas reservoirs, leading to the formation of new fault ＋ lithologic oil/gas reservoirs. Complex faulted nose and fauh-block traps with various sizes and shapes have been formed in the north slope, due to the NE and NW faultings. Oil and gas in such reservoirs were sourced from the deep depression in the south and migrated laterally from the deep depression to the north before the deposition of Liaozhuang Fm, and migrated upward along faults to the shallow layers after the deposition of Liaozhuang Fro. Such reservoirs are characterized by late reservoiring. It is predicted that the steep slope zone in the southern part of the depression is the favorable area for discovering lithologic reservoirs, the eastern part of the depression is favorable for discovering anticlinal reservoirs, and the north slope zone is favorable for discovering fault block reservoirs.