We propose a novel cement additive made of graphite nanoplatelets (GNPs) for improved hydraulic isolation and durability of oil and gas wells. The primary role of the cement sheath, which is zonal isolation, can be significantly affected by the permeability of set cement (hardened cement slurry). On one hand, it is the inherent microstructural defects of cement, including pores and microcracks, that results in the intrinsic permeability of cement, and on the other hand, cracking, micro-annuli, or other flow paths developed through the disturbed cement by connecting the pre-existing microstructural defects determine the equivalent permeability of set cement. The purpose of this research is containing or at least minimizing the intrinsic and developed flow paths through the cementitious matrix with the help of surface-modified GNPs. GNPs possess high surface area to volume ratios. In this study, we focus on the effect of surface-modified GNPs on the overall mechanical properties of both cement slurry and hardened cement slurry affecting the permeability of cement. We present two dispersion methods on the basis of physical and chemical treatments of the surface properties of GNPs. The efficiency of proposed methods on the overall properties of the cement is examined before and after its setting. To mimic downhole conditions, cement slurries are cured at 3,000 psi and 190°F for 24 hours. Also, some experiments were repeated under the pressure and temperature conditions up to 5,160 psi and 126°F, respectively, to examine pumpability and behavior of cement slurry at bottomhole conditions. To examine the role of spatial distribution of GNPs on the hardened cement nanocomposite, samples with different concentrations of GNPs were tested. We investigated the effect of modified GNPs on the unconfined compressive strength (UCS), shear bond strength, thickening time, rheological characteristics, and the free fluid content. We measured zero free fluid at room temperature for different concentrations of GNPs, demonstrating uniform dispersion of nanoparticles within the cement matrix. On the other hand, the squeeze of water out of the lower parts of the cement slurry and its upward migration can develop preferential paths for oil and gas migration. Therefore, eliminating the above-mentioned water separation can enhance cement sealing properties. We found that an optimum 0.2 vol% concentration of acid-functionalized GNPs improves the compressive and the shear bond strength of the prepared cement by approximately 42 and 175% as compared to the plain cement, respectively.

我们提出了一种由石墨纳米片（GNP）制成的新型水泥添加剂，以改善液压隔离和油气井的耐久性。水泥护套的主要作用是区域隔离，它会受到固化水泥（硬化水泥浆）的渗透性的显着影响。一方面，水泥的固有微结构缺陷（包括孔和微裂纹）导致水泥的固有渗透性，另一方面，裂缝，微环空或通过连接而通过受干扰的水泥形成的其他流动路径预先存在的微观结构缺陷决定了凝固水泥的等效渗透率。这项研究的目的是借助表面修饰的GNP抑制或至少减少通过胶结基质的固有和发达流动路径。GNP具有高的表面积体积比。在这项研究中，我们集中于表面改性的GNPs对水泥浆和硬化水泥浆的整体力学性能的影响，从而影响水泥的渗透性。我们在对GNPs的表面性质进行物理和化学处理的基础上，提出了两种分散方法。在凝结之前和之后检查提议的方法对水泥整体性能的效率。为了模拟井下条件，水泥浆在3,000 psi和190°F下固化24小时。另外，分别在高达5160 psi和126°F的压力和温度条件下重复了一些实验，以检查井底条件下水泥浆的泵送性和性能。要研究GNP的空间分布在硬化水泥纳米复合材料上的作用，测试了具有不同浓度的GNP的样品。我们研究了改性的GNP对无侧限抗压强度（UCS），剪切粘结强度，增稠时间，流变特性和自由流体含量的影响。我们在室温下测量了不同浓度的GNP的零自由流体，证明了纳米颗粒在水泥基体内的均匀分散。另一方面，水从水泥浆下部挤出并向上迁移可以为油气的迁移开辟优先路径。因此，消除上述水分离可以增强水泥密封性能。我们发现最佳值为0。