We describe the development of a nanosilica-based oil and gas well cement additive which reduces the risk of casing-casing annulus (CCA) and sustained casing pressure (SCP) through gas migration mitigation. Nanosilicas added to oil and gas well cement have been shown to accelerate cement hydration and reduce the cement porosity and permeability. While these qualities can potentially reduce the risk of zonal isolation loss, there are known rheological effects associated with adding nanosilicas to cements. It is known that cements loaded with nanosilicas produce gels prematurely, which has the deleterious effect of leading to air entrainment in cement and can also effect the pumpability of the cement slurry. This property can also interfere with gas migration mitigation because it is the formation of the gel that reduces the hydrostatic pressure on the formation. This can, in-turn, allow for fluid from the formation to invade the cement prior to building enough mechanical strength to resist the fluid influx. The nanosilica product described in this article has been developed to display no gelation effect in the cement and a rapid hydration onset. These performance attributes are due to a specialized functionalization or coating on the nanosilica particle. At temperatures equal to or below 120°F (49°C), this functionalization renders the nanosilica inert from the cement until its timed degradation and thus does not interact with the cement phases responsible for the gelation behaviour observed with other commercially available nanosilicas in the process of cement placement.

中文翻译：

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纳米二氧化硅功能化以从休眠状态转变为活性状态，以缓解波特兰水泥中的气体迁移

我们描述了一种基于纳米二氧化硅的油气井水泥添加剂的开发，该添加剂通过减缓气体迁移来降低套管-套管环空 (CCA) 和持续套管压力 (SCP) 的风险。添加到油气井水泥中的纳米二氧化硅已被证明可加速水泥水化并降低水泥孔隙度和渗透率。虽然这些特性可以潜在地降低层状隔离损失的风险，但在水泥中添加纳米二氧化硅会产生已知的流变效应。已知载有纳米二氧化硅的水泥过早地产生凝胶，这具有导致水泥中夹带空气的有害影响，并且还会影响水泥浆的可泵送性。这种性质也会干扰气体迁移缓解，因为凝胶的形成降低了地层的静水压力。这反过来又允许地层中的流体在建立足够的机械强度以抵抗流体流入之前侵入水泥。本文中描述的纳米二氧化硅产品已被开发为在水泥中没有凝胶化效果并且快速水化开始。这些性能属性归因于纳米二氧化硅颗粒上的特殊功能化或涂层。在等于或低于 120°F (49°C) 的温度下，