Evaluation of the effect of a flow rate profile on the displacement ability of viscoelastic fluids
During technological operations related to casing strings cementing, installation of cement bridges, when pumping bundles of viscoelastic fluids into a well, several portions of non-Newtonian fluids with different rheological properties are consistently pumped. Herewith, there appear the problems of assessment of the replacement ability during their combined flow and determination of the time of the displaced fluid release at the wellhead or its achievement of the definite position in a well. The rates profile, both in pipes and the annulus is under the effect of rheological indicators as well as liquids abnormal behavior which rather often brings unpredicted results. Non-Newtonian behavior of most drilling fluids is satisfactorily described by Shvedov-Bingham rheological model (viscous-plastic liquids - VPL). The article discusses the rheological parameters effect of the dynamic yield point τ<sub>0</sub> and plastic viscosity η on the profile rates geometry and determines the boundary of separation of two successively moving VPL. Possibility of prediction of the composite flow distribution of in time and volumes of the replaced fluid in pipes and annular space will improve the quality of cementation and displacement of drilling mud batches, enriched by sludge. The article analyzes the process of one VPL displacement by another one under the condition of equality of their rheological parameters, without accounting of gravitational effects as well as examines the factors affecting the dynamics of its flow. Assessment of substitution of drilling and cement slurries is given in the article by the results of numerical modeling to determine the rates profiles for different annular cross-sections and the proposed method of control under laminar flow are shown in the article.