Sammendrag
Cuttings-beds formation while drilling wellbores is a common challenge, especially for horizontal wells, as drilled particles have higher area to be deposited and form cuttings-beds, which can cause several problems such as increased torque and drag, pipe sticking or pipe breakage, among others. Removal of the drilled cuttings is done by circulating a suitable drilling fluid through the wellbore. This paper presents results from laboratory tests with deposited cuttings-bed and the flow of a fluid to erode the bed. The simulated cuttings-bed is a 1 m long deposited sand-bed in a horizontal section. Three different types of fluids are being used in the tests. To investigate how the rheological properties can affect the erodibility of the cuttings-bed, water (as a Newtonian fluid), a xanthan gum solution, and a water-based drilling fluid prepared for an offshore field operation (as a non-Newtonian fluids) are applied. Ultrasound measurements together with differential bed weight have been used to analyze the fluid–bed interaction. Results have shown that the cuttings-bed is eroded by dune movement. Saltation and dragging of sand particles due to the fluid flow appear to create a crest and then avalanche them down. The different types of fluids undergo different shear rates from the same pump power as the viscosity changes, as well as flow rates dependency along the dune extent.
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