Petroleum Engineering 405 Drilling Engineering*
Nozzle Size Selection for Optimum Bit Hydraulics:
Max. Nozzle Velocity
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Quiz A
Closed Book
1 Equation sheet allowed, 8 1/2”x 11” (both sides)
HW #7:
{ Quiz A_2001 is on the web }
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Proper bottom-hole cleaning
will result in improved penetration rates
Bottom-hole cleaning efficiency
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- Optimization -
Through nozzle size selection, optimization may be based on maximizing one of the following:
Bit Nozzle Velocity
Bit Hydraulic Horsepower
Jet impact force
these three parameters should be maximized.
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Maximum Nozzle Velocity
Nozzle velocity may be maximized consistent with the following two constraints:
1. The annular fluid velocity needs to be high
enough to lift the drill cuttings out of the hole.
- This requirement sets the minimum fluid circulation rate.
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i.e.
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Maximum Nozzle Velocity
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Maximum Bit Hydraulic Horsepower
The hydraulic horsepower at the bit is maximized when is maximized.
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Maximum Bit Hydraulic Horsepower
In general, the hydraulic horsepower is not optimized at all times
It is usually more convenient to select a pump liner size that will be suitable for the entire well
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Maximum Jet Impact Force
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3. From Plot, determine optimum q and Dpd
4. Calculate
5. Calculate
Example 4.31
Determine the proper pump operating conditions and bit nozzle sizes for max. jet impact force for the next bit run.
Current nozzle sizes: 3 EA 12/32”
Mud Density = 9.6 lbm.gal
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Pump Efficiency = 0.91
Minimum flow rate
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Calculate pressure drop through bit nozzles:
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Plot these two points in Fig. 4.36
(q1, p1) = (485, 906)
(q2, p2) = (247, 409)
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Example 4.32
It is desired to estimate the proper pump operating conditions and bit nozzle sizes for maximum bit horsepower at 1,000-ft increments for an interval of the well between surface casing at 4,000 ft and intermediate casing at 9,000 ft. The well plan calls for the following conditions:
Well Planning
1,600 hp maximum input
600 ft of 7.5-in.-O.D. x 2.75-in.- I.D. drill collars
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Hole Size: 9.857 in. washed out to 10.05 in.
10.05-in.-I.D. casing
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5,000 9.5 15 5
6,000 9.5 15 5
7,000 9.5 15 5
8,000 12.0 25 9
9,000 13.0 30 12
Interval 1
Interval 2
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Interval 3
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Table
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* Laminar flow pattern indicated by Hedstrom number criteria.
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Table
The proper pump operating conditions and nozzle areas, are as follows:
5,000 600 1,245 2,178 0.380
6,000 570 1,245 2,178 0.361
7,000 533 1,245 2,178 0.338
8,000 420 1,245 2,178 0.299
9,000 395 1,370 2,053 0.302
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Table
The first three columns were read directly from Fig. 4.37. (depth, flow rate and Dpd)
Col. 4 (Dpb) was obtained by subtracting shown in Col.3 from the maximum pump pressure of 3,423 psi.
Col.5 (Atot) was obtained using Eq. 4.85
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Surge Pressure due to Pipe Movement
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Surge Pressure due to Pipe Movement
An excessively high surge pressure can result in breakdown of a formation.
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Figure 4.40B
- Velocity profile for laminar flow pattern when closed pipe is being run into hole
psi
p
b
491
32
12
4
3