حساب انخفاض ضغط مثقاب الحفر-DRILL BIT PRESSURE DROP CALCULATION
Drill Bit Pressure Drop computation
computation of both hydraulic power and impact force are substantially depend on calculating pressure drop across the bit. A major chance of normal circulating pressures is lost by pumping through the snoots when spurt bits are used. The pressure loss isn't frictional pressures but rather acceleration forces. hypotheticals generally made are
drill bit pressure drop computations
1) the changes in pressure performing from a change in elevation are negligible.2) the upstream haste(V.) is negligible compared to downstream( as below figure).
Grounded on these hypotheticals, bit pressure drop is calculated according to below Equation
Working for snoot haste, VN
Laboratory studies show the pressure drop through the snoot doesn't correspond precisely according to Eqs. over. As a result, a discharge measure factor, Cd is applied to make laboratory results correspond to theoretical pressure drops. The discharge measure will vary, depending on snoot type and size, A value of0.95 is representative, still, for utmost field situations.
Applying Cd above equation becomes
Where:
AT = total nozzle area, in^2
Q = flow rate, gal/min
VN = nozzle velocity, ft/sec
Using Eq. 1&2 And solving for PB:
In drilling Hydraulics, Impact Force can be calculated through this equation.
Mud weight = 14.5 Ib/gal
Flow rate = 300 gal/min
Jet sizes = three 12/32 in. jets
Solution:
1. Determine the nozzle area, AT:
AT = 3 x π /4 x (d)^2 = 0.331 in^2
2. Eq.3 is used to calculate the pressure drop at the bit:
PB = (300)^ 2 x 14.5 / ( 0.95^2 x 0.331 ^2 x 12028) = 1097 psi
3. Calculate the hydraulic horsepower expended at the bit from Eq.4
HHP = (1097 psi x 300 gal/min) / 1714 = 192 hp
4. The hydraulic impact force due to pressure loss through the drilling bit is computed from Eq.5
Fi = 0.01823 x (0.95) x (300) x ((14.5)(1,097))^(1/2) = 654 Ib
Applying Cd above equation becomes
Where:
AT = total nozzle area, in^2
Q = flow rate, gal/min
VN = nozzle velocity, ft/sec
Using Eq. 1&2 And solving for PB:
Drill Bit Hydraulic Horsepower & Impact Force Calculation
Hydraulic power at the drill bit
A measure of the energy per unit of time that's being expended across the bit snoots. It's generally calculated with the equation HHP =P * Q/ 1714, where P stands for pressure drop in pounds per forecourt clout, Q stands for inflow rate in gallons per nanosecond, and 1714 is a conversion factor necessary to yield HHP in terms of power. Bit manufacturers frequently recommend that fluid hydraulics energy across the bit snoots be in a particular HHP range, for illustration2.0 to7.0 HHP, to insure acceptable bit tooth and bottom- of- hole cleaning( the minimal HHP) and to avoid unseasonable corrosion of the bit itself( the maximum HHP).Impact Force computations at the drill bit
Impact pressure which affect impact force is the instigation change of the drilling fluid distributed over the impacted area at the hole bottom. This pressure, acting over and to the sides, attempts to overcome chip hold-down pressure and remove cutting from beneath the bit. pressure and remove cutting from beneath the bit.In drilling Hydraulics, Impact Force can be calculated through this equation.
Example On How To Calculate bit pressure drop, Hydraulic Horse Power And Impact Force
Calculate the drill bit pressure drop, hydraulic horsepower and impact force for the following set of conditions:Mud weight = 14.5 Ib/gal
Flow rate = 300 gal/min
Jet sizes = three 12/32 in. jets
Solution:
1. Determine the nozzle area, AT:
AT = 3 x π /4 x (d)^2 = 0.331 in^2
2. Eq.3 is used to calculate the pressure drop at the bit:
PB = (300)^ 2 x 14.5 / ( 0.95^2 x 0.331 ^2 x 12028) = 1097 psi
3. Calculate the hydraulic horsepower expended at the bit from Eq.4
HHP = (1097 psi x 300 gal/min) / 1714 = 192 hp
4. The hydraulic impact force due to pressure loss through the drilling bit is computed from Eq.5
Fi = 0.01823 x (0.95) x (300) x ((14.5)(1,097))^(1/2) = 654 Ib
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