Cable Tool Drilling

4.1 Introduction

The first oil well in the United States was drilled with cable tools in 1859 to a depth of 65 feet. This was the historic Drake well located near Titusville, Pennsylvania; it is credited with having started the American petroleum industry. The cable tool (also called churn or percussion) drilling method, however, did not originate in this country, but is believed to have been employed first by the early Chinese in the drilling of brine wells.1

In this method, drilling is accomplished by the pounding action of a steel bit which is alternately raised by a steel cable and allowed to fall, delivering sharp, successive blows to the bottom of the hole. This principle is the same as that employed in drilling through concrete with an air hammer, or in driving a nail through a board.

The original percussion drilling apparatus consisted of a spring pole anchored into the ground at an angle, with the bit suspended from the free end by a rope. To impart the necessary reciprocating action to the bit, the Chinese employed a number of men who alternately jumped on and off the spring pole beam from a ramp. Many early brine wells in the United States were drilled in the same manner, except that the spring pole was equipped with stirrups where two or three men stood and literally kicked the well down.

As more and deeper wells began to be-drilled, efforts were made to improve the drilling equipment. Steam engines began to be used; walking beams replaced the spring pole; steel cables replaced manila ropes; and other improvements followed. Although the modern cable tool rig is a far cry from the ancient Chinese model, the changes have been in materials and equipment, for the basic operating principle is unchanged.

4.2 Equipment and Basic Technique

To discuss the equipment and technique of this method we will refer to Figure 4.1 which shows the American

To discuss the equipment and technique of this method we will refer to Figure 4.1 which shows the American

Cable Tool Percussion Drilling Method
Fig. 4.1. American standard cable tool rig. After Brantly,2 courtesy AIME.

standard cable tool rig. Although rigs of this type have been almost completely replaced by lighter, more portable models, the standard rig is still the yardstick of percussion drilling.

4.21 The Drill String

The drill string of a cable tool rig is composed of the bit, drill stem, jars, and a rope socket enabling their attachment to the drilling line or cable. The main parts of the drill string are

1. The drill bit: A heavy steel bar, generally four to eight feet long, having the lower or drilling end dressed to varying degrees of sharpness depending on the formation to be drilled. Sharper bits are used in hard rock drilling while soft rock bits are quite blunt. Cable tool bits are made from high carbon and molybdenum-silicon alloy steels in a number of patterns by various manufacturers. Naturally these bits require frequent sharpening or dressing which is either performed at the well by the driller and the tool dresser or in the nearest blacksmith shop. Two typical cable tool bits are shown in Figure 4.2.

Cable Tool Drilling

Fig. 4.2. Typical cable tool bits. Courtesy Spang and Company. (A) Straight regular pattern. (B) Twisted Mother Hubbard pattern.

(A) (B)

  1. 4.2. Typical cable tool bits. Courtesy Spang and Company. (A) Straight regular pattern. (B) Twisted Mother Hubbard pattern.
  2. The drill stem: A cylindrical steel bar generally 10 to 20 feet long which is screwed directly above the bit. Its diameter depends on the hole size and the amount of weight desired. The purpose of this member is to furnish additional weight for the downward drilling blow.
  3. Jars: Heavy steel links which telescope within each other much like two links in a chain. Their function is to produce a sharp upward blow on the tools, causing them to be jerked loose from soft, sticky formations, and allowirig a clean, sharp drilling blow. Long stroke jars having two to six feet of telescope action are often used in fishing jobs (retrieving of tools, etc. lost or stuck in the hole). Drilling jars normally have strokes of less than one foot and are often omitted in hard rock drilling. This piece of equipment is responsible for the affectionate title Jarheads which rotary drillers often apply to their cable tool counterparts.
  4. Tool joints: Connectors for the bit, drill stem, etc. These consist of tapered, coarse threaded connectors machined on the ends of the tools. The thread design allows easy makeup, and the necessary tightness is obtained from the metal-to-metal fit at the flat shoulders of the joint. Proper tightness of these joints is essential to prevent the severe drilling vibrations from unscrewing the tools.

The drilling line is also part of the drill string, but for convenience it is discussed in the next section.

4.22 Rig Lines

The standard rig has three lines or cables used for various purposes. These are the drilling line, the sand line, and the calf or casing line. Before discussing the individual functions of these, let us look at wire lines in general.

A steel cable is composed of a number of wire strands wound helically around a hemp or independent wire rope center with a uniform length of lay. A lay is the length of rope required for individual strands to make one revolution g,bout the center and is further specified as right, left, or Lang lay, as shown in Figure 4.3.

Regular Lay Lang Lay

Right lay, Lang lay

Fig. 4.3. Illustration of right and left, regular and Lang lay. Courtesy API.8

Right lay, Lang lay

Fig. 4.3. Illustration of right and left, regular and Lang lay. Courtesy API.8

Right Lay Cable

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« X 1* WARRINGTON WITH FIBER COBB

6x1* SEALE WITH FIBER COBB

S X 1* SEALE WITH INDEPENDENT WIRE-ROPE COBB

6x1* SEALE WITH FIBER COBB

S X 1* SEALE WITH INDEPENDENT WIRE-ROPE COBB

« X 11 FILLER WIRE WITH FIBER CORE

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  • Sebastian
    Where was the first cable tool drilling method used and what was it used for?
    2 years ago
  • iris mcintosh
    What is meaning of drilling lines in cable tool method?
    3 months ago

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