CHAPTER VI

COMBINATION CABLE AND ROTARY SYSTEM OF DRILLING

This system is successfully employed in drilling formations that are alternately hard and soft, or in penetrating soft or alluvial surface formations with the rotary equipment and finishing the well in the harder formations at depth with the cable tools.

The equipment used is the same as that for cable and for rotary drilling, the outfit being a combination of the two, but eliminating parts that might be duplicated in the two outfits.

The derrick and rig are the standard cable rig, except that the derrick should be 106 feet high, with the addition of a rotary engine block abutting the side sill and at a right angle from the standard engine block (see Fig. 145), and the derrick sills and floor extended to provide a slush pump platform on the opposite side of the derrick from the rotary engine block. (Refer to directions for erecting standard derricks, pages 46-48, and for rotary derricks, page 192.)

Directions for rigging up standard rigs and rotary rigs (refer to pages 97-100, 193-197), may also be followed for rigging up the combination rig, with the exception that the draw works is set up on the opposite side of the rig from the slush pumps, instead of at a right angle from the pumps, as in the rotary rig. The reason for this is that, with the combination rig, two opposite sides of the derrick are occupied by the calf wheels and walking beam on the one side and the bull wheels on the other.

Fig. 145. Side elevation and ground plan of 106-foot California Combination Rotary and Cable Drilling Rig with extra wind braces, showing machinery installed ready for drilling.

Fig. 146.

(Refer to Pages 375-377 for safe working load for Derricks.)

Fig. 147.

Interior View of Derrick-Drilling with the Rotary.