TABLE OF CONTENTS It is highly desirable for field engineers to have simple correlations for calculating gas volume requirements. These correlations have been developed for vertical and generic well trajectories. The difference between the gas rates given by a chart and correlation is normally less than 10%.
The following correlation has been developed for vertical-hole gas drilling using direct circulation methods based on Figures A-1 through A-29 and Figures B-1 through B-24:
| (2.61) |  |
where
| (2.62) |  |
The value of the correlation coefficients a 1, a 2, a 3, and a 4 are given in Table 2-2. Figure 2-2 shows the difference between the minimum required air injection rates given by charts and by the correlation. The difference is within 10% for practical gas-drilling conditions.
| Hole Size | a 1 | a 2 | a 3 | a 4 |
|---|---|---|---|---|
| Gas specific gravity 1.0: | ||||
| 17 "-15" | 7.25460750 | 0.00252683 | 0.27678264 | -1.76512350 |
| 12 "-11" | 6.66017330 | 0.00209705 | 0.19744638 | -1.23402000 |
| 11"-9" | 6.40820720 | 0.00192274 | 0.31610525 | -1.32142100 |
| 9"-8 " | 6.27980630 | 0.00182764 | -0.47922218 | 0.15480131 |
| 8 "-7 ?" | 6.04554250 | 0.00168948 | 0.35335623 | -1.18214840 |
| 7 ?"-6 " | 5.67999600 | 0.00147466 | 0.29013093 | -0.87638225 |
| 4 " | 4.95059100 | 0.00112253 | -0.33060468 | 0.28730231 |
| Gas specific gravity 0.8: | ||||
| 17 "-11" | 6.78717390 | 0.00252877 | 0.21319786 | -1.29000670 |
| 9 ?"-7 ?" | 5.92049690 | 0.00188266 | 0.44937033 | -1.21009550 |
| 7 ?"-6 " | 5.50908860 | 0.00157407 | 0.23107964 | -0.65470860 |
| 4 " | 4.69916450 | 0.00117097 | -27.29631800 | 31.61369000 |
| Gas specific gravity 0.6: | ||||
| 17 "-11" | 6.58812640 | 0.00272353 | 0.18417591 | -1.08519520 |
| 9 ?"-7 ?" | 5.71924490 | 0.00201416 | 0.44615880 |
