文档介绍：Air Drilling(空气钻井)
1 Hole Cleaning
2 Equipment
3 Drilling Practices
4 Problems
5 Gas Type
6 Mist Drilling
Section 2 – Page 1
“Dry air is labeled as such here to recognize its use as one of the mon types of UB fluids. However, most of the info here applies to any gas used as the UB fluid as well as to air.”
Gas Behavior
Where T is expressed in degrees R.
P1 x V1
T1
=
P2 x V2
T2
1 ft3 of gas
@ 10,000 ft TVD
BHP = 5200 psi
2 ft3 when
circulated to 5000 ft
Unload condition!!
Length of
Fluid Column
= Length of Gas
Gas Rising in
An Open Wellbore
If the injection rate of N2 is 900 scf/minute at 700 F and an injection pressure of 600 psi. What is the volume flowrate of this gas downhole at conditions of 5200 psi and a temperature of 2500 F.
V2 = ( x 900 x 710 ) / ( 5200 x 520 ) = ft3/m
A standard cubic foot has a pressure of psi at a temperature of 600 F
To convert Fahrenheit to Rankin add 460
Section 2 - Page 2
Gas Law
Hole Cleaning
Hole cleaning with air is plicated subject. In simple terms, the upward air flow exerts a drag force on the cutting. If the drag force is greater than the gravitational force, the cutting will move upward and out of the hole.
Cuttings removed on most air drilling operations tend to be very fine. The term “dusting” is often used to describe the removal process. The bit generates parable in size to overbalance drilling; however, they tend to remain in the hole until ground down to a small enough size for the air flow to lift from the well.
The pressure of the air increases with depth, causing the density of air to increase as well. The increased pressure reduces the air velocity; however, the increase in density assists with the cuttings transport.
Increased Air
Velocity at Less
Air Pressure
Less Effective
Hole Cleaning
As Depth Increases
Drag Force
Due to Air Velocity
Gravitational
Settling Force
Cutting
Resulting
Cutting Velocity
Section 2 - Page 3
Air/Gas Injection Requirements
Air injection