英国IWCF井控培训教程1-地层压裂Formation Pressure

Annular pressure, the pump pressure required to move mud up the annulus, must be considered in well control operations.
This pressure is less than 200 psi at the reduced pump speeds used in killing a well.
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Mud gradient
Pressure & mud gradient is the amount pressure changes with depth. It is obtained by multiplying the mud weight by the constant.
MG = MW × C
0.052
0.00695
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Mud gradient
Pressure or mud gradient is obtained by multiplying mud weight by the constant C.
So, the gradient for a 12 ppg mud is : MG = 12 × 0.052 = 0.624 psi / ft
Formation pressure:
is the force exerted by fluids in the formation.
- Also called reservoir pressure, &/or
- Shut-in bottom hole pressure.
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Formation Pressure
APL = (16,000 × 8)/ 225(8.5-4.5)
+ (16,000 × 24 × 1.2)/1,500(8.5-4.5)2
= (128,000/900)+(460,800/24,000)
= 142.2 + 19.2 = 161.4 psi
161.4
1.45 PCF
16000 0.00695
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Surface
Depth, ft
Mud gradient
Pressure gradient=0.433 psi / ft Pressure gradient=0.465 psi / ft
Subnormal
Abnormal
Pressure, psi
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Annular Pressure Loss
英国IWCF井控培训教程1地层压裂
IWCF Well ControlFormation Pressure
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Pressure Concepts
The two pressures of primary concern are : Formation pressure & Hydrostatic pressure.
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Mud gradient
EX. The hydrostatic pressure of a mud with 0.624 psi/ft gradient in a 11,325 ft well would be,
HP= 0.624 × 11,325 HP= 7067 psi
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Pressure Gradient
BHP less than formation pressure causes the well to Kick, & greater than fracture pressure causes lost return.
Fracture pressure
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Mud gradient
Normal pressure gradients correspond to the hydrostatic gradient of a fresh water with a density of 8.33 ppg(0.433psi/ft) to 9.0 ppg saline water(0.465psi/ft) column.
ECD= 13.24 ppg
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Annular Pressure Loss
APL in laminar flow :
APL
L YP 225(Dh Dp )
L PV V 1500(Dh Dp )2
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Annular Pressure Loss
Ex. Calculate APL according to data’s available L= 16,000 ft (TVD), YP= 8 lb/100 ft2 , PV= 24 cp V= 1.2 ft/sec , Dh= 8.5 in. , Dp= 4.5 in.
Hydrostatic pressure refers to the pressure of drilling fluid in the wellbore.
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Hydrostatic Pressure
In the wellbore, H.P. is the result of the fluid density & true vertical depth of the fluid column.
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Equivalent Circulating Density
Another equation:
ECD MW ( APL ) 0.052 TVD
Suppose that MW=13.0 ppg , APL= 100 psi , TVD= 8,000 ft.
ECD= 13 + (100/ 0.052 / 8,000 = 13 + 0.24
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Mud gradient
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TYPICAL GRADIENT FOR S. IRAN
Formation Aghajari Mishan
Gs.(7) Gs.(6-1) Asmari Pabdeh
Gurpi Ilam Sarvak Fahliyan
GRADIENT PSI/FT
The amount of APL depends on whether the mud flow in the annulus is laminar or turbulent.
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Annular Pressure Loss
APL is higher when the mud is in laminar flow. Flow in the annulus is usually laminar,
0.83
0.54
0.56
0.74
0.54
0.56
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Pressure Gradient
Ex. Draw the lines of pressure gradients (pore, mud &fracture) for Aj. to As. formations based on table of data in previous slide. Correlate it with lithology & stratigraphic column.
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Hydrostatic Pressure
HP C MW TVD
Where:
C = 0.052, if mud density is expressed in terms of ppg, &
C = 0.00695, if mud density is expressed in terms of pcf.
Area of Lost Circulation
0.5 ppg Safety margin
Kick area Pore pressure
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Mud gradient
Normal pressure gradient: about 0.433- 0.465 psi/ft.
The gradients less than 0.433 psi/ft & greater than 0.465 psi/ft are known as subnormal & abnormal, respectively.
Pore Pres. Mud Pres. Frac. P.
0.433
0.450
0.68
0.465
0.479
0.70
0.465
0.50
0.78
0.8-1.0
0.85-1.10
1.1
0.24-0.49
0.433-0.56
0.74
0.5-0.54
0.52-0.56
0.81
0.5-0.54
0.52-0.56
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Annular Pressure Loss
When mud is being circulated, bottomhole pressure equals hydrostatic pressure plus the pressure required to move mud up the annulus.
The origin of F.P. :
It relates to how sedimentary basins are formed. As layer upon layer of sediments are deposited, overburden pressure on the layers increases, & compaction occurs. So any fluids in the formation are squeezed into permeable layers, such as sandstone. If the permeable layer is continuous to the surface (outcrops on the surface) pressure higher than normal cannot form. But if the fluid is trapped because of some anomaly, pressure higher than normal can form.
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Formation Pressure
Normal pressure Subnormal pressure - Abnormal pressure
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Hydrostatic Pressure
The term is derived from “hydro”, meaning water or liquid, & “static”, meaning at rest.
Annular pressure loss exists only when mud is being circulated & it ceases when the pump is stopped.
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Flow Path
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Annular Pressure Loss
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161.4 0.2 ppg 16000 0.052
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Equivalent Circulating Density
Another way to look at the BHP increase due to friction losses in the annulus is in terms of ECD. ECD is a combination of the original mud weight plus the equivalent mud weight increase due to pressure losses in the annulus.
because the mud velocity in the annulus during well control operations is decreased by lowering the pump speed below the speed used for normal drilling operations.