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Unformatted text preview: A T M PETE 661 Drilling Engineering Lesson 20 Surge and Swab 2 A T M Surge and Swab Three Different Forms of Surge and Swab Pressures Kick Detection on Trips Well Shutin Procedures when a KICK is Detected A Blowout Case History 3 A T M Surge and Swab Read: ADE Ch. 6 Reference: Advanced Well Control Manual, SPE Textbook, ~2003... Homework # 11  due Nov. 25 Homework # 12  due Dec. 02 Project  due Dec 6 4 A T M Surge & Swab The actual mechanics are complicated, but can be sufficiently described by: 1. Pressure to initiate movement in a thixotropic mud 2. Steadyflow viscous drag between moving pipe and a static borehole, 3. Dynamic pressures resulting from mud acceleration or deceleration 5 A T M Annulus Mud Velocity Profile during downward movement of drillstring resulting in surge pressure Function of: pipe speed system geometry flow regime whether the pipe is open or closed 6 A T M Inertial effects of pipe movement Swab due to acceleration when P/U off of slips Deceleration effects while breaking Peak Velocity Pipe at rest 7 A T M Example B1 The following conditions apply to a drilling liner job on a deep well. Present depth = 16,000 ft Last casing setting depth = 12,100 ft Last casing inner diameter = 8.835 in Liner outer diameter = 7.625 in Drillpipe outer diameter = 5.0 in Liner length = 4,300 ft Mud density = 15.8 lbm/gal Average running speed = one min. for a 90 ft stand Maximum acceleration = 0.60 ft/s 2 12,100 16,000 8 A T M Example B1 Assume the mud has developed an average gel strength of 30 lbf/100 ft 2 & use the following Fann multispeed viscometer data: 600 = 65 lbf/100 ft 2 300 = 39 lbf/100 ft 2 200 = 27 lbf/100 ft 2 100 = 17 lbf/100 ft 2 6 = 5 lbf/100 ft 2 3 = 4 lbf/100 ft 2 9 A T M Example B1, solution When dealing with tapered string geometries (liner strings, drilling assemblies, etc.), the maximum surge or swab pressure is usually experienced when the bottom of the string reaches the depth of interest. So, determine the surge pressure at 12,100 ft for each of the three effects and calculate the equivalent density based on the highest value. 10 A T M Example B1 Equation B1 yields the pressure required to break the gel strength: psi p ) . . ( ) , , )( ( ) . . ( ) , )( ( p g g 558 203 355 5 8835 8 300 300 4 100 12 30 625 7 8835 8 300 300 4 30 = + =  + = ( 29 1 2 300 d d L p g g = d 1 d 2 11 A T M Example B1 We estimate the maximum string velocity using Equation B4: V p = 1.5 (90/60) = 2.25 ft/s = 135 ft/min avg , p max , p v . v 5 1 = 12 A T M Example B1 From Equation B2, the relative velocity opposite the liner for Newtonian fluids is: ft/m in. 394 625 . 7 835 . 8 ) 135 ( ) 625 . 7 ( 2 2 2 = = a 2 2 2 2 p p p a d d v d v = 13 A T M Example B1 The linercasing clearance expressed as a ratio is (7.625/8.835) or 0.863. Assuming power law behavior, Schuhs extrapolated mud clinging constant is about 0.48. Hence the effective annular velocity from Equation B5 is: V = 394 + (0.48)(135) = 459 ft/min ....
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 Fall '11
 Dr.JeromeJ.Schubert

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