当前在含水合物地层固井用相变微球低热水泥浆设计时，未充分考虑相变微球粒径及质量分数对水泥浆性能的影响，导致水泥浆性能降低和成本增加，从而引发一系列固井质量问题，因此，分析相变微球对固井水泥浆性能影响及调控机制尤为关键。

为排除相变芯材储热效应的干扰，以自制的多级粒径相变壁材微球为研究对象，研究壁材微球粒径和质量分数对水泥浆性能的影响，建立了不同水化龄期水泥浆的Dinger-Funk方程(DFE)模型，揭示了壁材微球对固井水泥浆性能的调控机理。

结果表明：(1)相较于质量分数，微球粒径对固井水泥浆流动性能和力学性能影响更大，在进行相变微球低热固井水泥浆设计时，需重视微球粒径对固井水泥浆性能的影响。(2)微球质量分数增大对水泥浆体系存在2种不同的效应，一方面是堆积密度增大导致的水泥石力学强度提升以及水泥浆流动性能减弱效应，另一方面是微球引入本身强度缺陷导致的水泥石强度下降效应，这2种效应的主导地位取决于微球的质量分数和粒径，其中质量分数对两种效应起决定性作用，当质量分数较小时，堆积密度上升效应占主导，当质量分数超过4%时，强度缺陷效应占主导，2种效应共同作用下，水泥石单轴抗压强度呈现先上升后下降的趋势。(3)最紧密堆积DFE模型与水泥浆流动性能和力学性能有较强的相关性，当固井水泥浆DFE模型处于较优状态时，通常意味着该体系具有较好的流动性和力学性能。研究结果为热敏地层低热相变微球固井水泥浆设计提供有益参考。

The current design of low-heat cement slurries prepared by adding microspheres with phase change materials as wall materials for well cementing in strata bearing natural gas hydrates (NGHs) fails to fully account for the impacts of the particle size and mass fraction of the microspheres on the performance of cement slurries. This leads to impaired cement slurry performance and increased costs, further inducing many problems with well cementing quality. Hence, it is significant to analyze the impacts and controlling mechanisms of the microspheres on cement slurry performance.

To eliminate the interference of the heat storage effect of the core materials also made of phase change materials, this study independently developed microspheres with polymethyl methacrylate (PMMA) as the wall materials (PMMA microspheres) with varying particle sizes. It explored the impacts of the particle size and mass fraction of the PMMA microspheres on the performance of cement slurries, established Dinger-Funk Equation (DFE) models for cement slurries with different hydration ages, and revealed the mechanisms behind the control of the cement slurry performance by the PMMA microspheres.

The results indicate that compared to the mass fraction of the PMMA microspheres, their particle size exhibits more significant impacts on the fluidity and mechanical properties of cement slurries, thus warranting more attention in the design of low-heat cement slurries with PMMA microspheres. The increase in the mass fraction of the PMMA microspheres causes two distinct effects on the cement slurry system. On the one hand, the increase in bulk density enhances the mechanical strength of set cement and reduces the cement slurry fluidity. On the other hand, the inherent strength defects caused by the introduction of the PMMA microspheres decrease the strength of the set cement. The predominant role of both effects depends on the mass fraction and particle size of the PMMA microspheres. Specifically, in the case of a low mass fraction, the bulk density effect predominates in the cement slurry system, whereas the strength defect effect becomes dominant when the mass fraction exceeds 4%. Under the joint action of both effects, the uniaxial compressive strength of set cement trends upward initially and then downward. The closest packing theory (CPT)-based DFE model is strongly correlated with the fluidity and mechanical properties of cement slurries. Generally, an optimal DFE model suggests high fluidity and favorable mechanical properties of the cement slurry system. The results of this study provide a valuable reference for the design of low-heat cement slurries prepared by adding microspheres with phase change materials as wall materials for well cementing in strata susceptible to temperature changes.