Microporous and Mesoporous Materials ( IF 5.2 ) Pub Date : 2019-04-01 , DOI: 10.1016/j.micromeso.2019.03.050 Mona W. Minde , Merete V. Madland , Udo Zimmermann , Nina Egeland , Reidar I. Korsnes , Eizo Nakamura , Katsura Kobayashi , Tsutomu Ota
Seawater injection into chalk-reservoirs on the Norwegian Continental Shelf has increased the oil recovery and reduced seabed subsidence, but not eliminated it. Therefore, understanding rock–fluid interactions is paramount to optimize water injection, predict and control water-induced compaction.
Laboratory experiments on onshore and reservoir chalks have shown the need to simplify the aqueous chemistry of the brine, and also the importance of studying the effect of primary mineralogy of chalk to understand which ions interact with the minerals present. In this study, the mineralogy of the samples tested, are simplified. These experiments are carried out on pure calcite powder (99.95%), compressed to cylinders, flooded with MgCl2, at 130 °C and 0.5 MPa effective stress, for 27 and 289 days.
The tested material was analysed by scanning and transmission electron microscopy, along with whole-rock geochemistry. The results show dissolution of calcite followed by precipitation of magnesite. The occurrence and shape of new-grown crystals depend on flooding time and distance from the flooding inlet of the cylinder. Crystals vary in shape and size, from a few nanometres up to 2 μm after 27 days, and to over 10 μm after 289 days of flooding and may crystallize as a single grain or in clusters.
The population and distribution of new-grown minerals are found to be controlled by nucleation- and growth-rates along with advection of the injected fluid through the cores. Our findings are compared with in-house experiments on chalks, and allow for insight of where, when, and how crystals preferentially grow.
中文翻译:
用MgCl 2充注方解石粉的矿物学变化,以研究在孔尺度上提高采收率(EOR)的机理
挪威大陆架上的粉笔储层中注入海水增加了石油采收率并减少了海床沉陷,但并没有消除它。因此,了解岩石与流体的相互作用对于优化注水,预测和控制水致密实性至关重要。
陆上和储层白垩的实验室实验表明,需要简化盐水的水化学反应,并且研究白垩的主要矿物学作用以了解哪些离子与存在的矿物相互作用的重要性也很重要。在这项研究中,被测样品的矿物学得到了简化。这些实验是在130℃和0.5 MPa有效应力下,将纯方解石粉(99.95%)压缩成圆柱状,并用MgCl 2充注,进行27天和289天。
通过扫描和透射电子显微镜以及全岩石地球化学分析了受测材料。结果显示方解石溶解,随后菱镁矿沉淀。新生长晶体的出现和形状取决于注入时间和距圆柱体注入口的距离。晶体的形状和大小各不相同,从27纳米后的几纳米到2μm,以及淹水289天后的超过10μm,都可能结晶成单个晶粒或成簇。
发现新生长矿物质的分布和分布受成核速率和生长速率以及注入岩心对流作用的控制。我们的发现与白垩上的内部实验进行了比较,从而可以洞悉晶体优先生长的位置,时间和方式。