The role of clay minerals in influencing porosity and permeability characteristics in the Bridport Sands of Wytch Farm, Dorset
The role of clay minerals in influencing porosity and permeability characteristics in the Bridport Sands of Wytch Farm, Dorset
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DOI：
10.1180/claymin.1982.017.1.05
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发表时间：
1982-02
期刊：
影响因子：
1.5
通讯作者：
K. Morris;C. M. Shepperd
中科院分区：
文献类型：
--
作者：
K. Morris;C. M. Shepperd
布里德波特砂岩是一种广泛分布于英格兰南部大部分地区的下侏罗纪海相砂岩。它是一种非常细的、中等分选的石英砂岩，其特征是易碎和坚硬的钙质胶结层交替出现。这些沙子构成了多塞特郡Wytch Farm Field的上部水库，目前产量约为每天4000桶。对岩心材料的研究表明，与空气渗透率相比，液体渗透率显著降低，从而评估了注水开采油气的适用性。这些减少从最佳质量储层的30%或更少到低渗透砂岩的70%以上不等。Bridport Sands中的粘土矿物主要包括高岭石和伊利石-蒙脱石和伊利石-蒙脱石类型的混合层粘土。也有少量的蛭石和蛭石。高岭石被发现作为松散的附着，离散的颗粒，而混合层粘土形成斑片状的孔隙内衬。渗透率降低可解释为：（i）水的吸附和结晶不良的混合层伊利石-蒙脱石的膨胀导致孔隙空间堵塞（这种降低在很大程度上是可逆的）和（ii）堵塞孔喉的自生高岭石晶体聚集体的物理运动（这种降低在很大程度上是不可逆的）。孔隙尺寸分布、粘土颗粒尺寸、孔隙空间内粘土的分布以及粘土的组成都是控制Bridport Sands中脆弱储层段的孔隙度/渗透率关系和渗透率降低的重要因素。
Abstract The Bridport Sands is a widespread marine sandstone of Lower Jurassic age found in much of southern England. It is a very fine grained, moderately sorted quartz-arenite and is characterized by the alternation of friable and hard calcareous-cemented layers. The sands form the upper reservoir in the Wytch Farm Field, Dorset, which is currently producing at the rate of around 4000 barrels per day. Investigation of core material to assess the suitability of water injection for gas/oil recovery has shown that significant reductions of liquid permeability compared to air permeability occur. These reductions vary from 30% or less in the best quality reservoir to more than 70% in low-permeability sandstones. Clay minerals in the Bridport Sands comprise mainly kaolinite and mixed-layer clays of both the illite-chlorite and illite-smectite types. Small amounts of vermiculite and chlorite also occur. The kaolinite is found as loosely-attached, discrete particles, whilst the mixed-layer clays form patchy pore linings. The permeability reductions may be explained by: (i) the adsorption of water and expansion of poorly-crystalline mixed-layer illite-smectites causing blockage of pore space (this reduction is largely reversible) and (ii) the physical movement of authigenic kaolinite crystal aggregates blocking pore-throats (this reduction is largely non-reversible). The pore-size distribution, clay particle sizes, the distribution of the clays within the pore space, and the composition of the clays are all important factors in controlling porosity/permeability relationships and permeability reductions in the friable reservoir intervals in the Bridport Sands.