STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

968 Drilling and Well Completions
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Figure 4-268. Sketch showing the theoretical position of strain gages for
torque measurement.
8. AR torque = 0.01 i&/gage.
9. Signal due to torque: AV = 0.002 V = 2 mV.
Example 13: Drilling Parameters-Annular Temperature
Bottomhole annulus mud temperature is recorded during drilling for mechanical
problems and for fluid entry diagnosis.
Borehole depth: 10,000 ft, deviated hole
Drill pipe rotation rate: 10 rpm
Mud heat capacity: 0.77 cal/g
Hole diameter: 12$ in.
Drainage radius: 660 ft
Mud specific weight: 12 lb/gal
Mud flowrate: 500 gal/min
Gas gravity: 0.7
z: 0.9
1. The surface measured torque is 2 kft-lb and the downhole torque is 1 kft-lb.
Assuming the heat generated is entirely transferred to the descending mud
stream, what is the temperature rise due to the pipe friction?
2. A water inflow occurs suddenly at the rate of 1,000 bbl/day. Water heat
capacity is 1 cal/g; water density is 1,00 kg/m3. The formation temperature
is 200°F and the mud reaches the drill collars at a temperature of 160°F.
Compute the annular temperature rise.
3. A gas inflow occurs suddenly when entering an abnormal pressure zone.
Compute the flowrate of gas if the formation pressure is 7,000 psi, 1 ft has
been penetrated in a 50-ft zone with 500 md, gas viscosity is 0.035 cp. Assume
no annulus pressure drop, no cutting. Compute the annular temperature drop.