深水断陷盆地层序地层分析与岩性-地层油气藏预测—以中国南海C盆地深水区古近系T组为例

依据Vail经典层序地层学理论,充分结合多井浅水区和无井深水区地质、地球物理资料,提出浅水区钻井资料与深水区地震资料井-震结合验证对比的思路,对中国南海C盆地深水区古近系T组进行层序地层精细划分。结果表明,该思路可成功解决深水区地层-地震资料品质差、无井资料、断层复杂、高温高压造成地层破碎层序界面不明显、追踪对比困难等难题,建立研究区目的层三维等时层序地层格架。研究中将T组划分为4个三级层序,并在等时层序地层格架内识别出辫状河三角洲、扇三角洲、下切谷、盆底扇、浊积扇、滩坝及滨岸砂7种沉积砂体类型。这些特征砂体与广泛分布的海侵体系域泥岩在空间上形成单断式、多断式和斜坡式3种成藏模式,形成了众多的岩性-地层油气藏。

Sequence stratigraphy analysis and lithologic-stratigraphic reservoir predication in deepwater faulted basins -an example from the Paleogene T Formation of the deepwater C Basin in South China Sea

Guided by Vail's classical theory of sequence stratigraphy,the authors proposed to finely divide the Paleogene T Formation of the deepwater C Basin in South China Sea by tying wells in the shallow water area to the seismic sections in deepwater area.The results show that the proposed method works effectively in dealing with such problems as poor seismic data quality,lack of well data,complexities of faults,vague sequence boundaries caused by high temperature and high pressure,difficulties in stratigraphic tracing and correlation,and so on.By using the method,the authors also established fine three-dimensional isochronous stratigraphic sequence framework of the study area,divided the T Formation into four third-order sequences,and recognized seven kinds of sandbodies:braided deltas,fan deltas,incised valley,basin floor fan,turbidite fan,beach bar and shore sands.These sandbodies together with widely distributed mudstones of TST formed many lithologic-stratigraphic reservoirs in three kinds of accumulation mode:single fault,multiple fault,and slope.