深水内波、内潮汐沉积类型及其油气意义

深水内波、内潮汐沉积可归纳为水道型和非水道型两种基本沉积类型。水道型沉积常发育双向递变层序和单向递变层序,单砂层较厚,它不仅是油气的良好储层,而且常与深水重力流沉积和深水背景泥岩沉积一起构成有利的地层或岩性圈闭,应当列为深水沉积区油气勘探的重点目标。非水道型深水内波、内潮汐沉积一般发育由砂泥频繁薄互层所构成的对偶层双向递变层序和对偶层单向递变层序,单砂层很薄,油气勘探意义可能不大。广泛分布的大型沉积物波(分为粗、细粒两种)和水道口附近的内潮汐砂坝,是两种比较特殊的内波、内潮汐沉积建造。根据现有研究实例和沉积成因水流理论分布范围等,建立了深水内波、内潮汐综合沉积模式。

Classification of Internal-wave and Internal-tide Deposits in Deep Water and Significance to Petroleum Prospecting

According to current researching status, internal-wave and internal-tide deposits in deep water have been divided into two basic types of sedimentation, namely channel type and non-channel type. The former generally composes of bidirectional or unidirectional grading sequences with relatively thick single sand layer, so they are good petroleum reservoirs. Besides, together with deep-water gravity flow deposits and background mudstone, they may be the elements of favorable subtle traps, therefore they should be important oil exploration target in deep-water sedimentary area. The latter develops bidirectional or unidirectional grading sequences displayed by lots of very thin sand-mud rhythmites. Because of very thin single sand layer, they are little significant to oil exploration. Internal wave and internal tide deposits may also build up special positive bed forms on deep-water seafloor, i.e. large-scale sediment waves (including coarse-grained and fine-grained ones) spread widely and internal-tide sand bars that are located in channel-mouth environment. An integrated sedimentation model for internal-wave and internal-tide deposits was established based on researched examples and theoretic distributing environments of sedimentary currents.