Facies associations and sand-body geometries in the Ness Formation of the Brent Group, Brent Field
Facies associations and sand-body geometries in the Ness Formation of the Brent Group, Brent Field
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布伦特油田布伦特群 Ness 组相组合和砂体几何形状
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发表时间：
1989
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影响因子：
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通讯作者：
S. Livera
中科院分区：
文献类型：
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作者：
S. Livera
摘要布伦特油田的布伦特组在一个简单的缓倾半地堑构造中蕴藏着超过1000×106桶的可采石油。它厚243米(800英尺)，是在维京地块轴线附近被同沉积断块沉降放大的层序。在区域尺度上，沉积模式是一个主要的滨岸和沿海层序--RAnnoch和Etive组，位于Ness组部分时间相当的浅泻湖-涌现三角洲-平原沉积之下。然而，需要更本地化和更详细的沉积模型来预测储集层几何形状和生产行为，特别是在Ness地层。Ness组是布伦特油田最大的储集层单元，厚度可达160米(525英尺)。五个主要相组合形成储集层质量岩石：各种河道砂岩、河流席状砂岩、主要河口坝、泻湖浅滩(通常与薄滩共生并被薄滩覆盖)和泻湖席状砂岩。这些组合占富砂层序的50%-60%，埋藏在非储集层相组合中：泻湖泥岩、涌出泛滥平原泥岩和异地和原地煤。煤的范围往往很广。在放大的Ness组中，最重要的环境是以波浪和河流为主、受潮汐影响较小的泻湖三角洲。由于这种重要性，本文对这些三角洲产生的砂体进行了更详细的描述。波浪能量足以重新分配大量的沉积物，并表明在被主要淡水输入冲淡的微咸水泻湖中有显著的捕获。砂体的几何形状变化很大，既反映了对沉积物分布的局部控制，特别是紧邻压实滨面桩上方的控制，也反映了更多的区域性影响，包括粗泥沙供应、盆地过程和断块沉降。对沉积的主要控制导致三角洲平原上有规律的溺水事件，并通过产生强烈层状的储集层而产生重大影响。
Summary The Brent Group in the Brent Field contains over 1000 × 106 bbl of recoverable oil in a simple gently dipping half-graben structure. It is 243 m (800 ft) thick and represents a sequence amplified by synsedimentary fault-block subsidence close to the axis of the Viking Graben. On a regional scale the depositional model is of a major shoreface and coastal sequence, the Rannoch and Etive Formations, underlying the partly time-equivalent shallow lagoonal to emergent delta-plain deposits of the Ness Formation. However, more localized and detailed sedimentary modelling is required to predict reservoir geometries and production behaviour, particularly in the Ness Formation. The Ness Formation is the largest reservoir-bearing unit in the Brent Field, being up to 160 m (525 ft) thick. Five main facies associations form reservoir-quality rock: varied channel sandstones, fluvial sheet sandstones, major mouth bars, lagoonal shoals (which are usually associated with, and capped by, thin beaches) and lagoonal sheet sandstones. These associations make up 50%–60% of the sand-rich sequence and are embedded in the non-reservoir facies associations: lagoonal mudstones, emergent flood-plain mudstones and allochthonous and autochthonous coals. The coals are often field wide in extent. Within the amplified Ness Formation the most important environments were the lagoonal deltas which were wave and fluvial dominated with minor tidal influence. As a result of this importance the sand bodies produced by these deltas are subjected to a more detailed description in this paper. Wave energies were sufficient to redistribute large amounts of sediment and indicate significant fetch in the brackish lagoons diluted by major freshwater input. Sand-body geometries are very variable, reflecting both localized controls on sediment distribution, particularly immediately above the compacting shoreface pile, and more regional effects including coarse-sediment supply, basinal processes and fault-block subsidence. The dominant controls on sedimentation resulted in regular drowning events on the delta plains and had a significant impact by producing a strongly layered reservoir.