Factors Influencing Hole Cleaning
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Pipe rotation, pipe rotation and deviated Wells is critical to Hole cleaning and the prevention of cuttings bed formation, no rotation or little rotation means that cuttings transport is restricted and limited a minimum of 120 rpm has been shown to be effective if possible higher rpm will increase Hole cleaning efficiency. Sliding for directional wood must include some pipe rotation, teamwork with the directional driller is important so that all goals are met. Hole angle and hole size, when planning a well hole angle and hole size will be determined this must include hole cleaning as an integral part of the plan. Wellbore stability is vitally important to keep the hole in good shape and a prevent hole enlargement it is important to circulate enough time for the hole to be cleaned on some deviated wells this may take three four five or even more bottoms-up, do not rely on what is seen at the shakers only to determine if the hole is clean use the parameter trends to make this determination, mud weight has a great impact on hole cleaning with mud weights greater than twenty palms per gallon no hole cleaning problems have been observed, the larger the differential between the fluid density and the cuttings the bigger the problem although increased density aids in hole cleaning it is not recommended to increase the density to clean the hole as this can lead to or initiate other problems. Drill pipe eccentricity the OD (outside diameter) of the drill pipe affects the angular velocities and cuttings transport in the annulus the smaller the difference between the drill pipe OD and the hole size the higher the angular velocity and consequently the better the hole cleaning the larger the difference will mean that the annular velocity is reduced thereby reducing hole cleaning. Cutting size and density there is no control over the size of the cuttings observations of the shakers on changes in cutting size is an important indicator of hole cleaning efficiency all hole cleaning calculations require an estimation of cutting size for the calculations to be effective and predictive.