Presentation on theme: "PETE 411 Well Drilling Lesson 13 Pressure Drop Calculations"— Presentation transcript:
1PETE 411 Well Drilling Lesson 13 Pressure Drop Calculations API Recommended Practice 13DThird Edition, June 1, 1995
2Homework HW #7. Pressure Drop Calculations Due Oct. 9, 2002 The API Power Law Model
3Contents The Power Law Model The Rotational Viscometer A detailed Example - Pump PressurePressure Drop in the DrillpipePressure Drop in the Bit NozzlesPressure Drop in the AnnulusWellbore Pressure Profiles
4Power Law ModelK = consistency indexn = flow behaviour index
9API RP 13D, June 1995 for Oil-Well Drilling Fluids API RP 13D recommends using only FOUR of the six usual viscometer readings:Use 3, 100, 300, 600 RPM Readings.The 3 and 100 RPM reading are used for pressure drop calculations in the annulus, where shear rates are, generally, not very high.The 300 and 600 RPM reading are used for pressure drop calculations inside drillpipe, where shear rates are, generally, quite high.
10Example: Pressure Drop Calculations Example Calculate the pump pressure in the wellbore shown on the next page, using the API method.The relevant rotational viscometer readings are as follows:R3 = (at 3 RPM)R100 = 20 (at 100 RPM)R300 = 39 (at 300 RPM)R600 = 65 (at 600 RPM)
35DRILLSTRING ANNULUS BIT 2103DRILLSTRINGANNULUS(Static)BIT
36Pipe Flow - LaminarIn the above example the flow down the drillpipe was turbulent.Under conditions of very high viscosity, the flow may very well be laminar.NOTE: if NRe < 2,100, thenFriction Factor in Pipe (fp):Thenand
37Annular Flow - Turbulent In the above example the flow up the annulus was laminar.Under conditions of low viscosity and/or high flow rate, the flow may very well be turbulent.NOTE: if NRe > 2,100, then Friction Factor in the Annulus:Thenand
38Critical Circulation Rate ExampleThe above fluid is flowing in the annulus between a 4.5” OD string of drill pipe and an 8.5 in hole.The fluid density is 12.5 lb/gal.What is the minimum circulation rate that will ensure turbulent flow?(why is this of interest?)
39Critical Circulation Rate In the Drillpipe/Hole Annulus:Q, gal/min V, ft/sec Nre,044,154,446,756,086,099,100
40Optimum Bit Hydraulics Under what conditions do we get the best hydraulic cleaning at the bit?maximum hydraulic horsepower?maximum impact force?Both these items increase when the circulation rate increases.However, when the circulation rate increases, so does the frictional pressure drop.
43Importance of Pipe Size Eq. 4.66eor,*Note that a small change in the pipe diameter results in large change in the pressure drop! (q = const.)Decreasing the pipe ID 10% from 5.0” to 4.5” would result in anincrease of frictional pressure drop by about 65% !!
44Dpf = v 1.75turbulent flowDpf = 9.11 vlaminar flowUse max. Dpf value