Synergism of Mud Cake Modifier with Forming Agent of Agglomerated Cake at Cement-Formation Interface with MTA Method

Based on the method of mud cake to agglomerated cake (MTA), the synergism of mud cake modifier (MCM) with forming agent of agglomerated cake (FAAC) in oil and gas well is studied by means of X-ray diffraction (XRD), en- vironmental scanning electron microscopy (ESEM) and atomic absorption spectroscopy (AAS). The results show that the mud cake with MCM at cement-formation interface (CFI) is corroded by FAAC. And the corrosion spots and cracks are formed. The glassy substance in mud cake is depolymerized by hydrated ions from oilwell cement slurry through these spots and cracks. The soluble ionic groups in mud cake form. The diagenesis in mud cake at CFI occurs. The calcium sili- cate hydrates (CSH), ettringite, film zeolite, rod zeolite and natrolite gels in mud cake generate. Ultimately, it achieves the integrated solidification and cementation (ISC) among cement paste, agglomerated cake and formation at CFI. This paper explains why the isolation quality of CFI is improved by the MTA method.