Viscoelasticity of Polymers and Carrying Capacity of Drilling Fluids When Sidetracking through Surface Casing

Through-casing sidetracking is one of the important technical methods for production and efficiency enhancement. When opening windows on the walls a several layers of casing strings, large quantities of iron fillings are produced, imposing a challenge to the hole cleaning capacity of the drilling fluid used. The iron fillings produced in the windowing operation have high density and are therefore settling fast in the drilling fluid. Meanwhile, the iron fillings have different shapes, when carried up the annular space they tend to intertwine with each other to form cage-shaped structures, further increasing the difficulty of borehole cleaning. Several polymer solutions, each with different concentrations of the same polymer, have been evaluated on a laboratory dynamic carrying efficiency tester for their ability to carry the iron fillings. Through these tests, the rheological property of the polymer solutions affecting the carrying of the iron fillings during window-opening operation was studied from the viscoelasticity aspect of these polymers.