Wettability of chalk: impact of silica, clay content and mechanical properties
Wettability of chalk: impact of silica, clay content and mechanical properties
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DOI：
10.1144/1354-079305-696
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发表时间：
2007-02
影响因子：
1.7
通讯作者：
S. Strand;M. L. Hjuler;R. Torsvik;Janne Pedersen;M. Madland;T. Austad
中科院分区：
文献类型：
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作者：
S. Strand;M. L. Hjuler;R. Torsvik;Janne Pedersen;M. Madland;T. Austad
通过注入水从天然裂缝白垩油田提高石油采收率的成功在很大程度上取决于储集岩的润湿条件，并且在一定程度上取决于由于地层的水弱化而引起的压实。在实验室工作中，经常使用露头样品来模拟储层性质。目前的研究表明，在选择露头材料时必须小心;特别是，二氧化硅的含量将影响这些重要的属性。白垩样品奥尔堡，其中含有大量的二氧化硅和少量的粘土（6.3重量%的硅），进行了研究，通过SEM和矿物性质的二氧化硅的特征。多孔介质的表面化学不同于含有较少量二氧化硅和粘土（1.4-2.8重量%）的白垩。在具有高酸值的原油和初始地层水的存在下，奥尔堡白垩的水润湿级分在90°C下在原油中老化4周后保持接近1.0。然而，Amott-Harvey润湿指数表明，润湿条件接近中性，并且在残余饱和度下只有少量的水和油自发地吸收。由于二氧化硅和粘土的含量不同而导致的润湿条件的差异也反映在机械性能的差异上。通过大量的试验研究，似乎机械强度随着水湿度的降低而变弱。润湿性对白垩的水弱化的影响进行了讨论，在白垩溶解和化学与薄水膜。作为一个总体的结论和建议，在选择实验材料时，应仔细比较储集岩和露头白垩中的硅含量。
The success of improved oil recovery from natural fractured chalk fields by injection of water depends largely on the wetting conditions of the reservoir rock and also, to some extent, on the compaction due to water weakening of the formation. Samples from outcrops are often used to mimic the reservoir properties in laboratory work. The present study illustrates that care must be taken when selecting outcrop material; in particular, the content of silica will affect these important properties. Chalk samples from Aalborg, which contained significant amounts of silica and minor amounts of clay (6.3 wt% Si), were studied by SEM and the mineral properties of the silica characterized. The surface chemistry of the porous medium was different from chalk containing smaller amounts of silica and clay (1.4–2.8 wt%). In the presence of a crude oil with high acid number and initial formation water, the water-wet fraction of Aalborg chalk remained close to 1.0 after aging for four weeks at 90°C in the crude oil. The Amott–Harvey wetting index showed, however, the wetting condition to be close to neutral, and only small amounts of water and oil imbibed spontaneously at the residual saturations. The difference in wetting conditions due to different content of silica and clay is also reflected in differences in the mechanical properties. It appeared that the mechanical strength, as studied by a large number of tests, became weaker as the water wetness decreased. The effect of wettability on the water weakening of chalk is discussed in terms of chalk dissolution and the chemistry associated with thin water films. As an overall conclusion and recommendation, a careful comparison should be made of the Si-content in the reservoir rock and outcrop chalk when picking material for laboratory experiments.