莺歌海盆地内波内潮汐与重力流沉积特征及其油气地质意义

Sedimentary characteristics of gravity flow and internal wave and internal tide and the significance to petroleum geology in Yinggehai basin

为进一步研究莺歌海盆地深水沉积中内波内潮汐与重力流沉积特征,将成像测井引入对内波内潮汐和重力流沉积序列的研究中,结合岩心、地震和核磁测井资料建立了内波内潮汐沉积解释模型,在海底扇(水道和朵叶体)沉积背景下,对内波内潮汐和重力流沉积进行了系统分类,并对不同沉积相背景的储层物性特征做了定量分析。研究发现,莺歌海盆地中央坳陷带西北部上中新统黄流组一段沉积微相可精细划分出5种水道类型和3种朵叶类型;内波内潮汐沉积受控于基准面变化,基准面相对较高时或古构造埋深较深时更容易形成该类沉积,从下到上可以形成4个沉积序列:内波内潮汐(改造)沉积(S1),重力流沉积(S2),内波内潮汐(改造)沉积(S3)和远洋泥沉积(S4)。同重力流沉积相比,内波内潮汐形成的储层物性更好,勘探评价时应优先考虑。

To further study sedimentary characteristics of deep water gravity flow and internal wave and internal tide in Yinggehai basin, borehole image logging is used to study the sedimentary sequences. Integrated with core, seismic and NMR log, the interpretation model of internal wave and internal tide deposition is established. Based on the sedimen- tary facies of submarine fan （channel and lobe）, the deep water gravity flow and internal wave and internal tide depo- sition are systematically classified and reservoir physical properties of different facies are quantitatively analyzed. Re- sults show that five types of channels and three types of lobes are identified in Huangliul Formation, Upper Miocene, northwest of central depression in Yinggehai basin. The internal wave and internal tide deposition is controlled by the change of base level, and this deposition is more easily formed under the condition of relatively higher base level or deeper buried paleo structure. Four sedimentary sequences can be identified vertically from bottom to top. internal wave and internal tide （reworked）deposition （S1）, gravity flow deposition （S2）, internal wave and internal tide （re- worked）deposition （S3）, and pelagic shale deposition （S4）. Compared with the gravity flow, the physical property of internal wave and internal tide deposition is better and it should be considered prior for exploration evaluation.