Composite drill pipe

A drilling string for drilling a well bore, comprising:

• a plurality of fiber reinforced synthetic tubes, each tube having a leading end and a trailing end spaced axially from the leading end,
• the leading end of the first one of the tubes being engageable with a bit for drilling a bore through the earth when a force is applied to the trailing end of the last one of the tubes;
• coupling means associated with the adjacent ends of each successive pair of tubes for serially connecting the tubes and defining a drilling string of desired length, the coupling means including a pair of interchangeable fittings respectfully attached to the pair of tubes, the end of one of the pair of tubes having an internal taper and its respective fitting having an external taper;
• and
• an adhesive bond between the internal taper of the tube and the external taper of the fitting.

A drilling string for drilling a well bore, comprising:

• a plurality of fiber reinforced synthetic tubes, each tube having a leading end and a trailing end spaced axially from the leading end,
• the leading end of the first one of the tubes being engageable with a bit for drilling a bore through the earth when a force is applied to the trailing end of the last one of the tubes;
• coupling means associated with the adjacent ends of each successive pair of tubes for serially connecting the tubes and defining a drilling string of desired length, the coupling means including a pair of interchangeable fittings respectfully attached to the pair of tubes, the end of one of the pair of tubes having an internal taper and its respective fitting having an external taper;
• and
• a metal sleeve extending around the internally tapered end of the tube and the externally tapered end of the fitting when the fitting is seated in the tube.

A drilling string for drilling a well bore, comprising:

• a plurality of fiber reinforced synthetic tubes, each tube having a leading end and a trailing end spaced axially from the leading end,
• the leading end of the first one of the tubes being engageable with a bit for drilling a bore through the earth when a force is applied to the trailing end of the last one of the tubes;
• coupling means associated with the adjacent ends of each successive pair of tubes for serially connecting the tubes and defining a drilling string of desired length, the coupling means including a pair of interchangeable fittings respectfully attached to the pair of tubes, the end of one of the pair of tubes having an internal taper and its respective fitting having an external taper;
• and
• a pin extending radially through the internally tapered end of the tube and the externally tapered end of the fitting.