Page 72 - Drilling Technology in Nontechnical Language

Chapter 3 – DRILLING A LAND EXPLORATION WELL 63

losses might be so severe that no mud returns are seen at the surface while
pumping over 1,000 gal/min (3,785 l/min) down the drillstring!

Drill pipe tally for well XYZ BHA length = 296.75
Length Total Total with BHA

31.32 31.32 328.07
30.98 62.30 359.05
31.44 93.74 390.49

31.62 125.36 422.11
31.69 157.05 453.80
31.50 188.55 485.30
31.45 220.00 516.75

30.96 250.96 547.71
31.66 282.62 1579.37
31.57 314.19 610.94
Fig. 3–15. Example of a tally sheet

Losses are discussed in more detail in chapter 13.
Once at the required depth, drilling is stopped. Mud is still circulated
around until all of the drilled cuttings are cleaned out of the well. If this
is not done and the drillstring is just pulled out, several major problems
become likely:

▪ As the drillstring is pulled out of the hole, the cuttings left in
the annulus will fall down and very likely be jammed between
the hole and the drillstring. This will stick the drillstring and
also prevent mud from circulating (because the annulus will be
blocked). In this condition, the drillstring will be stuck and might
not be freed, in which case the well might have to be abandoned.
▪ Cuttings will settle on the bottom and thus make the well
shallower than drilled. This might prevent the surface casing
being run to the required depth.

_Devereux_Book.indb 63 1/16/12 2:06 PM