Effective hole cleaning in horizontal and extended reach wells (ERD) often requires use of high circulation rates, which may not be always achievable due to the risk of circulating bottom hole pressure reaching the fracture limit of the rock. Achieving good hole cleaning while keeping the circulating bottom hole pressure within the safe operational window is very often the major engineering challenge. A drag reducing fluid with good hole cleaning ability could be a potential solution in this case.

In order to see if it is possible to use a drag reducing fluid and still achieve a good hole cleaning, an experimental program was designed and conducted. The main objective of this experimental study was to compare the hole cleaning performances of water and a drag reducing fluid.

The hole cleaning experiments were conducted using a 9m long horizontal flow loop with concentric annular geometry (Outer Pipe ID = 95 mm, Inner Pipe OD = 38 mm, ID/OD ratio = 0.4). The drag reducing additive was a commercially available partially hydrolyzed polyacrylamide (PHPA). Water and two drag reducing fluids with 0.07% V/V and 0.1% V/V PHPA concentrations were used. Critical velocities for the initiation of cuttings movement with rolling, saltation/dunes, and suspension modes were determined and compared when using water and drag reducing fluids as a carrier fluid. Critical velocities for the initiation of cuttings movement were found to be lower with water than that of drag reducing fluid in all transport modes.

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