Casing and Bit Size Selection

A casing and bit size program must consider the problems described in the previous section in addition to the actual casing and bit size characteristics. These characteristics include the following items:

  • casing inner and outer diameter
  • coupling diameters
  • hit sizes

A working knowledge of the relationship of these variables is important for the selection of a viable geometry program.

Pipe Selection. Casing availability is a priority consideration in hole geometry selection. High-strength casing often required for deep wells may have a small inner (drift) diameter that will influence subsequent casing and bit size selection. Unfortunately, supply and demand cycles in the pipe industry may control the pipe design rather than engineering considerations.

The outer diameter (OD) of the casing is available in numerous sizes. The drift diameter, which is smaller than the inner diameter (ID), controls the bit selection for the open hole below the casing. (The drift diameter is described in further detail in Chapter 11.) As heavier-weight pipe is required to meet certain design specifications, the available drift diameter is reduced. A rule-of-tbumb that has proven satisfactory in most field cases is to allow I in, of wall thickness to achieve a suitable design without resorting to the use of ultra-high-strength pipe (V-I50, 500-155, S00-I40, etc.). As an example, 9s/swn. casing can usually be designed properly if 8s/s-in. drift diameters arc allowed.

Hole geometry selection with the bottom-to-top approach may dictate the drift diameter of the casing as the controlling criteria. The options for this design logic are as follows:

  • try to design the pipe under the specific drift and outer diameter conditions
  • use high-strength materials
  • use special drift pipe available from some manufacturers
  • as a last resort, pipe manufacturers will prepare a special pipe design based on minimum drift requirements by enlarging the wall thickness and outer diameter

The fourth option is occasionally required in hydrogen sulfide environments where low-strength metals must be used.

Coupling Selection. Pipe couplings are generally designed to satisfy requirements such as burst, collapse, tension, and sealing effectiveness. However, coupling diameters may be a design guideline in some wells. Table 6-2 shows the outer diameter of various types of couplings and pipe sizes. API couplings are normally 1 in. larger than the pipe in sizes greater than 75/s in.

Significant advantages are often provided by using premium couplings. These couplings usually have clearances less than comparable API connections and. as such, will occasionally allow the use of smaller pipe in a well. In many cases, more expensive premium couplings can clearly reduce the total well cost by allowing smaller pipe and hole geometries. In Fig. 6— lb, the hole geometry would not be difficult to achieve if premium couplings were used, whereas clearances might be unacceptable if API couplings were used.

Bit Size Selection. Sizing the bit program is dependent on the required casing sizes. Bits are available in almost any desired size range. However, nonstandard bits or unusual sizes may not possess all of the desirable features, such as center jet or gauge protection characteristic^ In addition, bit selec-

Table 6-2 Clearances for API and Various Premium Proprietary Couplings

Coupling Size, in.

Table 6-2 Clearances for API and Various Premium Proprietary Couplings

Coupling Size, in.

Pipe Size, in.

LTC (API)1

SFf

VAIVF

IJ-4S1

4 'A

5.0

4.59

5406

5.I50

5

5.563

5.09

5.391

5.875

5 Vi

6.050

5.625

5.891

6.375

6-Vs

7.390-

6.75

7.390

7.390

7S4

8.50

7.75

8.504

8.50

8s/s

9.625

8,75

9.625

9.625

9%

10.625

9.75

10.625

! 0.625

im

1 1 750

10.875

11,748

'long thread and coupling (same diameter as STC or BTC)

'VAM (Vdllourec)

  • SFJ iHydiil) "IJ-4S (NL Atlas Bradford)
  • SFJ iHydiil) "IJ-4S (NL Atlas Bradford)

Table 6-3 Size Availability for Various Hughes Insert Tooth, Journal Bearing Bits

Hughes Bit Designation (IADC Code)

Table 6-3 Size Availability for Various Hughes Insert Tooth, Journal Bearing Bits

Hughes Bit Designation (IADC Code)

Bit Size,

J-44(6,1,7)

m.

>22(6,1,7)

J-33(5,3,7)

1-55(6,3,7)

1-77(7,3,7)

j-99(8,3,7)

4V4

X

57A

X

X

6

X

X

6Vh

X

X

61A

X

X

m

X

X

X

X

.6%

X

77/x

X

X

X

X

X

8%

X

8'A

X

X

X

X

X

8M

X

X

X

X

X

9'/j

X

X

X

m

X

X

X

X

10%

X

X

11

X

12 %

X

X

X

X

17 >/2

X

tion and availability become more difficult in odd or small bit sizes (less than 6.5 in.}.

Table 6-3 illustrates size availability for Hughes insert tooth bits. Bit sizes less than 6'/i in. restrict bit type selection. In addition, bit selection is restricted for sizes greater than 12Vi in.

Standard Bit-Casing Combinations

Fig. 6-3 can be used to select the easing and bit sizes required to fulfill many drilling programs. To use the chart, determine the casing or liner size for the last size of pipe to be run. The llow of the chart indicates hole sizes that may be required to set that size of pipe (i.e., 5-in, liner inside or b'A-in. hole).

Solid lines indicate commonly used bits for that size pipe and can be considered to have adequate clearance to run and cement the casing or liner (i.e., S'/i-in. casing in a V/x-'m. hole). The broken lines indicate less commonly used hole sizes. The selection of one of these broken paths require« that special attention be given to the connection, mud weight, cementing, and doglegs.

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Responses

  • peter
    What drill bit to use inside what size casing?
    7 years ago
  • Mafalda Lucchese
    What drill bit size fits inside casing?
    7 years ago
  • Bob
    What size drill bit for 16 inch casing?
    4 years ago
  • abaalom
    What size bit in 5.5 20 lb casing pipe?
    2 years ago
  • Largo
    How much learance to run casing oil gas?
    1 year ago
  • sofia
    What casing size to drill 12.25 hole?
    12 months ago
  • christian
    What is commonly used for deep wells in a 5" size casing or tubing?
    9 months ago
  • antonino milanesi
    What is the recomended drill bit size for the inside of 5 1/2" casing?
    8 months ago
  • troy
    What is the usual size bit for a 95/8 casing?
    7 months ago
  • gimja
    What is the standard hole size for 185/8" casing?
    5 months ago
  • reija
    What size hole is drilled to run 16" casing in oil well?
    5 months ago
  • Stefan
    What drill bit size needed to set 20" casing?
    4 months ago
  • ANKE
    Are there standard hole sizes for drilling wells?
    4 months ago
  • michael
    What hole size for 7 inch casing?
    4 months ago
  • gioele
    What hole size would you drill for 51/2 inch liner?
    3 months ago
  • FRANK
    What size drill bit will fit inside 4.5 inch casing?
    1 month ago

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