Standard API Drill Pipe

Standard API Drill Pipe

Appendix B gives the dimensions and mechanical properties for standard API drill pipe. This is the drill pipe used in most rotary drilling operations (shallow and deep). API drill pipe are fabricated by various API certified manufacturers around the world, principally for use in the drilling of deep wells for the recovery of oil and natural gas. Table B-3 gives the drill pipe dimensions (outside diameter, inside diameter, and weight per unit length) of the pipe body of various drill pipe sizes. API drill pipe size is denoted by the outside diameter of the pipe body and its associated nominal (pipe body) weight per unit length. The nominal weight per unit length defines the wall thickness and the inside diameter. The lengths of drill pipe elements (pipe body and tool joints) are defined in the API range designation of Table 1-1. When tool joints (box and pin) are added to a pipe body the average actual weight per unit length of the drill pipe element is increased above the pipe body nominal weight per unit length. API drill pipe is also classified by API material (steel) grade. Table 3-2 gives the API material grade designations and respective standards for minimum yield, maximum yield, and minimum tensile strength of the steel grade. The actual steel used to produce the various API grades for drill pipe fabrication is one of the AISI grade classifications of steel produced in US steel mills. For an AISI grade of steel to be used to fabricate drill pipe of a particular API grade the AISI grade must satisfy the minimum and maximum specification given in Table 3-2.

Table 3-2 shows that for API E75 grade the minimum yield is 75,000 psi, the maximum yield is 105,000 psi, and the minimum tensile (ultimate) strength is

100,000 psi. Similar data is shown for API X95, API G105, and API S135 steel grades [1, 2].

Table B-4 gives the dimensions and mechanical properties of various drill pipe sizes (and nominal weights) and tool joint combinations for API grade E75 [1, 2]. The approximate (actual) weight per unit length data given in the table is for a 30 ft drill pipe element (Range 2). In general, API grade E75 drill pipe elements are used on single rotary drilling rigs. These drill pipe elements are usually Range 1 lengths (see Table 1-1). Table B-4 also shows the drill pipe body to tool joint type (either external upset or internal upset), the tool joint connection, outside diameter, inside diameter, tensile yield of the pipe body and tool joint (threaded connection), and the torsion yield of the pipe body and tool joint (threaded connection). The data given for tensile yield and torsion yield are based on the minimum yield of the API grade E75 (i.e., 75,000 psi).

An example will be used to demonstrate how to use the API drill pipe tables in Appendix B. Table B-4 gives data for E75 grade steel drill pipe. In Column (1) of Table B-4 is given a 2 3/8 inch nominal size drill pipe (also pipe body size given in Table B-3). In Column (2) is given 6.65 lb/ft nominal unit weight, (also nominal unit weight given in Table B-3). In Column (4) is given the upset type (in this case EU is external upset) and in Column (5) is given the connection type (in this case NC26 (IF)). Column (3) shows that this drill pipe has an actual unit weight of 6.99 lb/ft. Column (6) gives the connection tool joint outside diameter of 3 3/8 inches and Column (7) gives the connection tool joint inside diameter of 1 3/4 inches. Column (8) gives a drift inside diameter of 1.625 inches (the outside diameter of the largest survey or other tool that can pass through the drill pipe element) for this drill pipe. This diameter is governed by the tool joint inside diameter. Column (9) gives an axial tensile force of 138,214 lb to yield the steel of the drill pipe body and Column (10) gives an axial tensile force of 313,681 lb to yield the steel of the tool joint. Thus, the weakest part of the drill pipe element to axial tension is the pipe body. Column (11) gives a torque of 6,250 ft-lb to give torsion yield of the steel of the pipe body and Column (12) gives a torque of 6,875 ft-lb to give torsion yield of the steel of the tool joint box. Thus, the weakest part of the drill pipe element to torque is the pipe body.

Table B-5 gives similar data as in Table B-4 but for the higher strength grades of drill pipe steel (i.e., X95, G105, and S135). In Column (1) of Table B-5 is given a 4 1/2 inch nominal size drill pipe (also pipe body size given in Table B-3). In Column (2) is given 16.60 lb/ft nominal unit weight, (also nominal unit weight given in Table B-3). In Column (4) is given the upset type (in this case EU is external upset) and the steel grade S135. In Column (5) is given the connection type (in this case NC50). Column (3) shows that this drill pipe has an actual unit weight of 18.62 lb/ft. Column (6) gives the connection tool joint outside diameter of 6 5/8 inches and Column (7) gives the connection tool joint inside diameter of 3 1/2 inches. Column (8) gives a drift inside diameter of 3.375 inches (the outside diameter of the largest survey or other tool that can pass through the drill pipe element) for this drill pipe. This diameter is governed by the tool joint inside diameter. Column (9) gives an axial tensile force of 595,004 lb to yield the steel of the drill pipe body and Column (10) gives an axial tensile force of 1,183,908 lb to yield the steel of the tool joint. Thus, the weakest part of the drill pipe element to axial tension is the pipe body. Column (11) gives a torque of 55,453 ft-lb to give torsion yield of the steel of the pipe body and Column (12) gives a torque of 44,673 ft-lb to give torsion yield of the steel of the tool joint box. Thus, the weakest part of the drill pipe element to torque is the pipe body.

Table B-6 gives a summary of the API connections available for both drill collars and drill pipe. These connections are all API recognized and are used by a variety of fabricators of drill collars and drill pipe. The table gives the outside diameter, inside diameter, and thread data for each connection type and size. Also given are the detailed dimensions of the box and pin of each connection. These dimensions are not used in machining box and pin connections. Readers are referred to Reference 6 to obtain information regarding API connection dimensions and tolerances for machine shop.

Table 3-2: API drill pipe steel grades minimum and maximum mechanical properties [1].