Research on the influence of polyanionic cellulose on the microstructure and properties of oil well cement

• Published in: Construction & building materials Vol. 259; p. 119841
• Main Authors: Li, Ming, Gu, Shiyu, Jin, Jianzhou, Zheng, Youzhi, Xie, Dongbo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30.10.2020
• Subjects: Cellulose; Mechanism; Oil-based well; Polymer; Polymer; Oil-based well; Mechanism; Cellulose
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2020.119841

Most of research shows that the polymer additive of drilling fluid is one of the main causes of contamination, that is, the fluidity of the mixing becomes worse sharply (Fig (a)). However, they failed to evaluate in isolation the effect of polymer additives on the structure and properties of cement. Therefore, selecting a typical polymer additive to study the effect on structure and performance of cement is significance and value for the explanation of contamination mechanism and anti-contamination. Polyanionic cellulose (PAC), a common drilling fluid additives, which has similar molecular structure as carboxymethyl cellulose (CMC) but superior to CMC in filtration reduction, anti-salt, anti-collapse and high temperature resistance. In this work, the contamination mechanism was investigated (Fig (d)), which could be benifical to understand the interaction between PAC and cement and optimize properties. In particular, the effect of environment conditions and variety of metal ions (Al3+, Ca2+, Fe3+) produced in the process of cement hydration on the entanglement behavior of PAC was studied (Fig (b and c)). Fig (a) Optical pictures of cement contamination by PAC; The effect of different (b) Temperature/ions concentration and (c) PH on PAC entanglement behavior; (d) Schematic of cement hydration ions inducing PAC to form networks through dynamic ionic bonds. [Display omitted] •Exploring the effect of PAC on cement hydration process.•Study effect of cement hydrated ions, T and pH on entanglement behaviour of PAC.•Increasing pH could break the entanglement network to improve the contamination. Drilling fluid additive is an important factor of contamination between cement paste and drilling fluid, in which PAC is the most significant one. This work investigated the effects of PAC on the hydration process and properties of cement by using X-ray diffraction (XRD), Different scanning thermal analyzer (DSC), Fourier transform infrared spectrometer (FTIR) and Zeta-potential. Based on the results of Environment Scanning Electron Microscopy (ESEM), the evolution of the microstructure of polymer-cement could be well explained by Ohama model. Combining with the rheological and mechanical measurements, it's surmised that H2O could bind with –OH of PAC through hydrogen bond to form cross-linking structure and trapping free water, which lead to the deterioration of rheological properties and inhibit the hydration process, accompanied by reduction of C-S-H content to decrease the compressive strength. Fe3+ and Al3+ released by cement hydration induced PAC to form gel through the formation of dynamic ion bonds and hinder the homogeneous dispersion of cement particles, proving that the deterioration of rheology properties is result of coupling effects of hydrogen and ion bond. According to the mechanism, using Al3+ and Fe3+ metal masking agent or raising pH could mitigate the contact contamination and increase the safety of cementing.