Y. X. Sun et al. / Natural Scien c e 2 (2010) 1394-1399

Copyright © 2010 SciRes. Openly accessible at http:// www.scirp.org/journal/NS/

1398

2

*

(m) = 115.072 (kPa).

At angle gaining interval within the depth of =

1604.82 (m), its surge pressure:

2

L

P2 = = 0.1917859 (kPa/m) *

2

1

22

*

s

PLPd L

(sin84° – sin8°)* 1604.82 (m) = 263.254 (kPa).

The total annular surge pressure value at the pipe shoe

is:

P = P1 + P2 = 115.072 (kPa) + 263.254 (kPa) =

378.326 (kPa).

The corresponding addition mud density is:

ρ = P/gH = 378.326 (kPa)/{9.8 (N/kg)*2204.82(m)} =

0.0175 (g/cm3).

5. CONCLUSIONS

Based on the rheological mode of Casson flow, the

flow rate computation models of axial laminar flow in

eccentric annulus apply to horizontal well were success-

fully established. Finally, we developed a new model of

predicting surge pressure imposed on different intervals

in horizontal well, of which the numerical model could

be calculated by the program called Mathematica con-

veniently. And the magnitude of the predicting surge

pressure provided a criterion in determining the addition

mud density.

After calculating the actual example using this new

model and comparing with traditional predicting method,

it is obvious that this new model can be computed easily

by the field engineers. Across the steps of derivation of

this new model, we concluded that it can calculate flexi-

bly, it provides a method of predicting surge pressures in

vertical well and directional well after being simplified.

And this new model can also direct the secure produc-

tion on location through predicting surge pressures under

different working conditions of drill string.

6. ACKNOWLEDGEMENTS

We would like to thank the drilling engineers Shurui Zhang and

Guobin Li from Daqing Oil Field for their supports to the field test and

operations

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