Viscoelastic systems for well construction

Abstract

One of the most important factors ensuring the required quality of well cementing is the use of effective flushing fluids (spacers). Among these fluids are viscoelastic systems (VES), which provide the best displacement of the drilling fluid during the cementing process.
 The article discusses the mechanism of polymerization of viscoelastic systems when using polyacrylamide cross-linked with polyvalent metal cations and the prospects for using these systems for oil and gas wells cementing. Models of the viscoelastic systems flow and their differences due to the presence of normal stresses in viscoelastic systems are shown in this article. The substantiation of the component composition of viscoelastic systems and their main properties, ensuring their efficiency as flushing fluids are given. The article also provides a description of the scientific instruments that were used during the research.
 It has been experimentally confirmed that it is necessary to use additives with the highest oxidation state when choosing a polyvalent cation as a "cross-linker" for viscoelastic systems. This will help to increase the rate of strength characteristics development. The most adequate ratios of components have been experimentally substantiated and the best solids-carrying capacity of a viscoelastic flushing fluid in comparison with other types has been proven. This eliminates the possibility of cement slurry flowing down in the annular space after the completion of the cementing process.
 The special installations proved the best degree of wellbore cleaning in vugular formation zones with a laminar flow regime. In order to minimize the negative effect of polymer films from viscoelastic systems on the adhesion of the cement stone to the casing strings it is recommended to inject a portion of the liquid containing the polymer destructor after a portion of the viscoelastic fluid.