To use the chart, determine the casing or liner size for the last size of pipe to be run. 6-3 can be used to select the easing and bit sizes required to fulfill many drilling programs. In addition, bit selection is restricted for sizes greater than 12Vi in. Table 6-3 illustrates size availability for Hughes insert tooth bits. Tion and availability become more difficult in odd or small bit sizes (less than 6.5 in.}. Table 6-3 Size Availability for Various Hughes Insert Tooth, Journal Bearing Bits sup>:SFJ iHydiil)'IJ-4S (NL Atlas Bradford).'long thread and coupling (same diameter as STC or BTC) Table 6-2 Clearances for API and Various Premium Proprietary Couplings 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. Bits are available in almost any desired size range. Sizing the bit program is dependent on the required casing sizes. 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.īit Size Selection. In many cases, more expensive premium couplings can clearly reduce the total well cost by allowing smaller pipe and hole geometries. as such, will occasionally allow the use of smaller pipe in a well. These couplings usually have clearances less than comparable API connections and. Significant advantages are often provided by using premium couplings. larger than the pipe in sizes greater than 75/s in. Table 6-2 shows the outer diameter of various types of couplings and pipe sizes. However, coupling diameters may be a design guideline in some wells. Pipe couplings are generally designed to satisfy requirements such as burst, collapse, tension, and sealing effectiveness. The fourth option is occasionally required in hydrogen sulfide environments where low-strength metals must be used.Ĭoupling Selection. 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.

use special drift pipe available from some manufacturers.try to design the pipe under the specific drift and outer diameter conditions.The options for this design logic are as follows: Hole geometry selection with the bottom-to-top approach may dictate the drift diameter of the casing as the controlling criteria. casing can usually be designed properly if 8s/s-in. 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.). (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. The drift diameter, which is smaller than the inner diameter (ID), controls the bit selection for the open hole below the casing. The outer diameter (OD) of the casing is available in numerous sizes. Unfortunately, supply and demand cycles in the pipe industry may control the pipe design rather than engineering considerations. High-strength casing often required for deep wells may have a small inner (drift) diameter that will influence subsequent casing and bit size selection. Casing availability is a priority consideration in hole geometry selection. These characteristics include the following items:Ī working knowledge of the relationship of these variables is important for the selection of a viable geometry program. 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.

Chart of drill bit sizes