![]() Let us first consider the development of Beck, Nuss, and Dunn2 which incorporates the classic work of Bingham3 with the commonly applied Newtonian fluid flow equations just presented. An early worker on this subject was Pigott,1 whose data have been widely used for the construction of hydraulic tables and curves. Consequently, the Newtonian fluid equations must be altered for application to typical drilling mud systems. 7.3 Plastic Fluid Flow CalculationsĪs was pointed out in Chapter 6, the flow behavior of plastic drilling fluids is complicated by the variation of apparent viscosity with rate of shear or flow. ![]() In this case the friction factor/is obtained from Figure 7.1 or its equivalent.ĭetailed treatments of Newtonian fluid flow calculations may be found in numerous hydraulics texts and handbooks. p = fluid viscosity, cp q = circulating volume, gal/min Where Re = Reynold's number v = average velocity of flow, ft/sec, = q/2A5d2 p = fluid density, lb/gal d = pipe inside diameter, in. Definition of the existing flow pattern is given by a dimensionless quantity known as the Reynolds number: Calculation of pressure drop for pipe flow requires a knowledge of which flow pattern pertains to the specific case, since different equations apply for each situation. In turbulent flow, secondary irregularities and eddys are imposed on the main or average flow pattern. In laminar (viscous) flow the fluid moves in parallel layers or laminae which are at all times parallel to the direction of flow. 7.2 Newtonian Fluid Flow Calculationsįluid flow through pipes is considered as either laminar or turbulent. However, with a little practice and understanding the task is not particularly formidable.īefore discussing plastic fluid flow calculations let us first review the fundamental equations of Newtonian fluid flow. The solution to Equation (7.1) is rather tedious, in that separate calculations for each section are required. = pressure loss in annulus around drill pipe = pressure loss across bit water courses or = pressure loss in surface piping, standpipe, Hence the discharge pressure at the pump is defined by: Since the mud enters the drill string and leaves the annulus at essentially the same elevation, the only pressure required is that necessary to overcome the frictional losses in the system. Here it begins the long downward travel through the drill pipe and drill collars, is expelled through the water courses or nozzles of the bit, and returns up the annulus?: The annular area is relatively small around the drill collars and becomes larger in the portion containing drill pipe. 2)Irregularities of the circulating system.ĭrilling mud leaves the pump discharge, passes through the surface lines, standpipe, and mud hose, and finally enters the drill string at the top of the kelly joint.1)Mud flow property peculiarities, as discussed in Chapter 6. ![]() The standard hydraulics approach to such analyses is hindered by numerous factors, among which are: Analytical appraisal of the rig's circulating system requires an understanding of the components which consume power, so that the available energy may be used as advantageously as possible. Proper utilization of mud pump horsepower is of considerable importance to rotary drilling operations.
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