On the Flow of CO2-Saturated Water in a Cement Fracture

IF 2.4 Q2 GEOSCIENCES, MULTIDISCIPLINARY
De Nyago Tafen, Barbara Kutchko, Mehrdad Massoudi
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引用次数: 0

Abstract

Cement fractures represent preferential leakage pathways in abandoned wells upon exposure to a CO2-rich fluid. Understanding fracture alteration resulting from geochemical reactions is critical for assessing well integrity in CO2 storage. This paper describes a mathematical model used to investigate the physical and the chemical changes in cement properties when CO2-saturated water is injected into a wellbore. This study examines the flow of a solution of CO2-saturated water in a two-dimensional fractured cement. In this approach, a micro-continuum equation based on the Darcy–Brinkman–Stokes (DBS) equation is used as the momentum balance equation; in addition, reactive transport equations are used to study the coupled processes of reactant transport and geochemical reactions, and the model for cement porosity alteration and fracture enhancement. This paper focuses on the effects of cement porosity, fracture aperture size, and surface roughness. Mineral dissolution and precipitation mechanisms are also considered. Our simulations show that smaller initial fracture apertures tend to a high mineral precipitation self-sealing. However, a complete sealing of the fracture is not observed due to the continuous flow of CO2-saturated water. The calcite precipitation mechanism of a rough fracture (random zigzag shape) differs from that of a smooth/flat fracture surface.
水泥裂缝中co2饱和水流动研究
在暴露于富含二氧化碳的流体中,水泥裂缝代表了废弃井的优先泄漏路径。了解地球化学反应导致的裂缝蚀变对于评估CO2储层井的完整性至关重要。本文介绍了一种数学模型,用于研究饱和二氧化碳水注入井筒后水泥性质的物理和化学变化。本研究考察了二氧化碳饱和水溶液在二维裂隙水泥中的流动。该方法采用基于Darcy-Brinkman-Stokes (DBS)方程的微连续统方程作为动量平衡方程;利用反应输运方程研究了化学物质输运与地球化学反应的耦合过程,建立了水泥孔隙度蚀变和裂缝增强模型。本文重点研究了水泥孔隙度、裂缝孔径大小和表面粗糙度的影响。还考虑了矿物溶解和沉淀机制。我们的模拟表明,较小的初始裂缝孔径倾向于高矿物沉淀自密封。然而,由于二氧化碳饱和水的持续流动,没有观察到裂缝的完全密封。粗糙断口(随机之字形)的方解石析出机制与光滑/平坦断口的不同。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Geosciences (Switzerland)
Geosciences (Switzerland) Earth and Planetary Sciences-Earth and Planetary Sciences (all)
CiteScore
5.30
自引率
7.40%
发文量
395
审稿时长
11 weeks
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