双北地区沙三段层序充填样式与目标选择

以层序地层学理论为指导,对双北地区9条地震剖面进行地震层序解剖,结果表明,高位体系域地震反射具有低频、中振幅、连续性好的特征;钻井揭示岩性组合为砂砾岩与泥岩互层,分异性好,砂体横向延伸较远。水进体系域地层厚度向洼陷方向楔状增厚特征明显,地震反射具有高频、中低振幅、连续性差的特征,可识别出丘状、透镜状、楔状反射地质体及上超反射地震相,钻井揭示砂泥岩混杂,泥质含量高,分异性差,为滑塌成因。结合层序发育特点,明确沙三段高位体系域以微幅度构造控制下的岩性–构造圈闭为目标,水进体系域以砂岩上倾尖灭型岩性圈闭及砂体透镜体型岩性圈闭为目标。

Sequence filling style and target selection of 3~(rd) member of Shahejie formation in Shuangbei area

Based on the theory of sequence stratigraphy, the seismic sequence analysis of 9 seismic profiles in Shuangbei area was carried out. The results show that the seismic reflection of high-level system domain has the characteristics of low frequency, medium amplitude and good continuity. Drilling data revealed that the lithologic combination was interbedded between sand conglomerate and mudstone, with good anisotropy and further lateral extension of sand bodies. The formation thickness of the water-entering system domain is obviously wedge-shaped thickening in the direction of depression, and the seismic reflection has the characteristics of high frequency, medium and low amplitude and poor continuity. The conical, lenticular, wedge-shaped reflected geological bodies and super-reflected seismic phases can be identified. Drilling data revealed that the sand and mudstone are mixed with high shale content and poor anisotropy, which is the cause of collapse. Combined with the sequence development characteristics, it is clear that the upper system tract of 3~(rd) member of Shahejie formation is targeted at lithology-structure traps under the control of micro-amplitude structure, while the upper system tract of water inflow is targeted at lithology traps of up dip pinch-out type sandstone and lenticular type sand body.