The velocity of the fluid in each of these intervals can be determined with the following equations.The first step in hydraulics calculations is to determine which stage of flow is occurring in each geometric interval of the well.for Annular Flow of Bingham Fluid 102 Critical Reynolds Number for Annular Flow.
#Drilling hydraulics annular reynolds series#
–Different equations are also required to calculate the pressure losses in the annulus and drillstring because of different geometries. THEORY AND APPLICATION OF DRILLING FLUID HYDRAULICS The EXLOG Series of. –These differences make it necessary to use different equations to determine the pressure losses in laminar and turbulent flow. Fluids in laminar flow “act”differently than fluids in turbulent flow.–This is especially true in extended-reach drilling. It is imperative to optimize drilling fluid hydraulics by controlling the rheological properties of the drilling fluid to avoid reaching this theoretical limit.–The pressure ratings of the pump liners and surface equipment and the number of mud pumps available limit the circulating system to a maximum allowable circulating pressure. Many wells are drilled under pressure limitations imposed by the drilling rig and associated equipment.The critical pressures are total system pressure (pump pressure), pressure loss across the bit and annular pressure loss (converted to ECD).Once the rheological properties for a fluid have been determined and modeled to predict flow behavior, hydraulics calculations are made to determine what effect this particular fluid will have on system pressures.rheological properties of water-based drilling fluids and the hydraulic behaviors. Even when a cuttings bed is formed, the annular velocity increases, and the bed is eroded until the system is in equilibrium. To improve the understanding of cuttings transport in HDD annulus. Each increase in annular velocity shows a corresponding decrease in the total cuttings concentration. The three flow rates shown in Figure 1 are 115, 172, and 229 fpm. Any increase in such term decreases the size of the cuttings bed formed on the low side of the hole and in some cases may prevent it.
Mud engineers often use other equations forms:Īnnular velocity is the variable that will affect hole cleaning the most. V = 0.024 x gal/min / (Annular Volume, bbl/ft) It is calculated from the following equation:Īnnular Volume, bbl/ft = capacity open hole, bbl/ft minus (capacity of drill pipe and displacement of drill pipe, bbl/ft)Īnnular Velocity, ft/min = ( pump output, bbl/min) / (Annular Volume, bbl/ft) This important term must be considered carefully when selecting a flow rate: excessive-velocity opposite open hole promotes erosion, while insufficient one in the larger annulus near the surface can cause inadequate cuttings transport. The usual expression of this annular velocity is in feet per minute. A general annular Reynolds number expression was derived from this method for. Chapters 3 through 10 analyze specific hydraulic considerations of the drilling process, such as viscometric measurements, pressure losses, swab and surge.
It will be recalled that the upward velocity of the mud in the annulus between the drill pipe and wall of the hole is an important consideration with that function of drilling fluid of removing drilling cuttings. Drilling hydraulics calculation involving many factors, such as drilling fluid rheology, the variation of.
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