基于重力流相的深水水道分类方案研究*

深水水道是深水环境下的油气储集的重要场所。当前,深水水道的沉积构型及级次划分已有诸多报道,但对于单一水道分类研究较少。现有主流分类方案主要依据水道侵蚀能力,然而受地震分辨率及露头完整度影响,在实际应用中存在较大局限性。基于全球26个野外露头和西非尼日尔三角洲Akpo油田X油藏的钻井岩心资料,对不同重力流相类型进行流态学解释,将水道内部岩相简化为高密度浊流相(HTL)、低密度浊流相(LTL)以及碎屑流相(CL);在此基础上,根据不同重力流相在水道内部占比,划分出9种单一水道类型: 高密度浊流单一充填水道(HTL>70%)、低密度浊流单一充填水道(LTL>75%)、碎屑流单一充填水道(CL>60%)、块状砂质混合充填水道(HTL=40%~70%、LTL=40%~20%、CL<30%)、含砾砂质混合充填水道(HTL=40%~70%、LTL<30%、CL=15%~50%)、层状砂质混合充填水道(HTL=5%~60%、LTL=40%~75%、CL<20%)、夹碎屑砂质混合充填水道(HTL<40%、LTL=40%~75%、CL=20%~40%)、等相混合充填水道(HTL=20%~40%、LTL=20%~40%、CL=20%~40%)、含砂砾质混合充填水道(HTL<50%、LTL<60%、CL=40%~60%)。根据野外露头及划分方案在深水油田实际应用,综合分析认为不同类型水道在垂向分布具有一定规律,即碎屑流相充填的水道往往发育在水道体系底部,高密度浊流相充填的水道类型靠近水道中下部,而低密度浊流相充填的水道主要位于水道体系中上部。方案根据不同重力流相充填的百分比,对不同水道类型进行了明确定义,具有更好的适用性与可操控性,同时对于深水水道储集层预测及储集层质量评价具有重要的实际意义。

Research on classification of deep-water channels based on gravity flow facies

Deep-water channel is an important reservoir for oil and gas storage in deep-water environment. At present,there are many reports on the sedimentary architecture and classification of deep-water channels,but few studies on the classification of single channel were carried out. Current classification schemes are largely based on the erosive capacity of the channel,however,due to the limitation of seismic resolution and outcrop integrity,there are great limitations in practical application. Based on 26 outcrops in the world and the drilling core data of a deep-water basin in West Africa,different gravity flow facies with different fluid dynamics are identified,including the high-density turbidity current facies(HTL),low-density turbidity current facies(LTL)and debris flow facies(DL). According to the proportion of different gravity flow facies in the channel,nine types of single channel can be divided: single high density turbidity filling channel(HTL>70%),single low density turbidity filling channel(LTL>75%),single debris flow filling channel(CL>60%),massive sandy mixed filling channel(HTL=40%~70%,LTL=40%~20%,CL<30%),gravelly sandy mixed filling channel(HTL=40%~70%,LTL<30%,CL=15%~50%),layered sandy mixed filling channel(HTL=5%~60%,LTL=40%~75%,CL<20%),clastic sand mixed filling channel(HTL<40%,LTL=40%~75%,CL=20%~40%),isophase mixed filling channel(HTL=20%~40%,LTL=20%~40%,CL=20%~40%),sandy gravel mixed filling channel(HTL<50%,LTL<60%,CL=40%~60%). Based on field outcrops and the practical application of division scheme in deep-water oilfield,we found that the vertical distribution law of different types of channels are as follows: the channels filled by debris flow lithofacies are often developed at the bottom of channel system,and the channels filled by high-density turbidity flow lithofacies are close to the middle and lower part,and the channels filled by low density turbidity current lithofacies is mainly located in the middle and upper part. According to the percentage of different gravity flow lithofacies within channel,different channel types are clearly defined. This division scheme has better applicability and maneuverability,and is beneficial to deep-water channel reservoir prediction and reservoir quality evaluation in practice.