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摘要
Cementing quality is much essential to well completion in the oil and gas industry. Unfortunately, liquid or gas channelings always occur at cement-formation interface due to post cementing operations such as hydraulic fracturing. The interfacial transition zone (ITZ) is considered as a weak region at the cement aggregate interface, which is well-known in the concrete and building industry but has been taken little attention in the cement-mudcake interface. In or from this work, an effective mud cake solidification agents (MCSAs) has been designed and used as prepad fluid in the cementing job. The present work is devoted to understand the effects of MCSAs on the physical and chemical alteration of the mudcake and provide a new insight into the microstructure of ITZ between the cement and mudcake. In order to investigate the complex interaction between cement slurry and MCSAs, cement leachate (CL) was used instead of cement slurry to explore the reaction product. X-ray diffraction analysis demonstrated that the product evolved from oligomeric silicate to polymer silicate gels, indicating that MCSAs appears to improve the bonding quality between cement slurry and mudcake. Furthermore, the effect of MCSAs on the mudcake was investigated. Yield-stress test showed that MCSAs can reinforce the yield strength of the mudcake. Water-content profiles of the mudcake and FTIR analysis suggested that C-S-H gels distributed within the first 2 mm layers of the mudcake closed to cement-mudcake interface under the given experimental condition. In addition, shear bond strength test demonstrated that the bond strength at cement-formation interface of the samples was significantly enhanced by 142%similar to 2540% due to the application of MCSAs. ESEM images illustrated that chemical composition and microstructure of the ITZ was significantly changed with the application of MCSAs. Ca2+, derived from cement hydrate, was consumed by the MCSAs, resulting in decreasing of the Ca/Si ratio and the restraint of Ca(OH)(2) crystallization at the cement-mudcake interface.
- 出版日期2016-11
- 单位中国地质大学（北京）
