渤海海域渤中19-2大型岩性油田发现与成藏新认识

New insights into the discovery and reservoir formation of the BZ19-2 large lithologic oilfield in the Bohai Sea

随着渤海海域勘探程度的增加,寻找浅层规模岩性油气田难度日益加剧。2021年,在渤中凹陷西南部洼中隆,发现了渤中19-2大型河流相岩性油气田。利用地震、薄片、地化等资料,对渤中19-2油田关键成藏条件进行分析。结果表明:①明下段大型曲流河频繁迁移,不同期次河道交切叠置,控制了规模性岩性圈闭的形成;②深浅汇油背景垂向叠置,为浅层油气富集提供有利构造背景;③渤中19-2构造明下段北西向河道砂体与关键断裂具有良好的“断-脊”配置关系,形成烃柱高度大的“一级充注”;④渤中19-4构造紧邻油源断裂形成“双脊继承-强活动断层-局部砂体”成藏模式,渤中19-2构造远离油源断裂形成“双脊接力-强活动断层-连片砂体”成藏模式。渤中19-2油田的发现,证实了渤海海域洼中隆起区浅层岩性油气藏勘探潜力,有助于类似地区大面积岩性勘探取得新突破。

As exploration in the Bohai Sea area intensifies,discovering shallow and scale lithologic oil-gas fields has become increasingly challenging.In 2021,the BZ19-2 large fluverine lithologic oil-gas field was discovered in the central uplift of the southwest Bozhong Sag.This study analyzes the key reservoir formation conditions of the BZ19-2 Oilfield using seismic,thin section,and geochemical data.The results indicate that:①The formation of large-scale lithologic traps is controlled by frequent migration of large meandering rivers and cross-cutting superposition of sub-channels over different periods.②A vertically superimposed deep and shallow sink oil setting provides a favorable structural background for shallow oil and gas accumulation.③The NW-trending channel sand body in the lower member of Minghuazhen Formation within the BZ19-2 structure formed a“first-order charging”with large hydrocarbon column height facilitated by an optimal“fault-ridge”configuration.@The BZ19-4 structure is adjacent to the oil-source fault to form a“double ridge inheritance-strong active fault-local sand body”reservoir formation model,whereas the BZ19-2 structure is far away from the oil-source fault to form a“double ridge relay-strong active fault-continuous sand body”reservoir formation model.The discovery of the BZ19-2 Oilfield confirms the exploration potential of shallow lithologic reservoirs in the mid-depression uplift area of the Bohai Sea,which is helpful to achieve new breakthroughs in large-scale lithologic exploration in similar regions.