Oil well pipe connection structure and oil well pipe

Abstract

Provided is means for connecting oil well pipes together with a compact/simple structure and the strength that significantly exceeds the limits of prior art even without the flange, etc. An oil well pipe coupling structure includes a first oil well pipe and a second oil well pipe, the external thread portion has a first external thread portion, a substantially tapered second external thread portion, and a third external thread, the internal thread portion has a first internal thread portion, a substantially tapered second internal thread portion, and a third internal thread portion the first external thread portion is screwed to the first internal thread portion, the second external thread portion is screwed to the second internal thread portion, the third external thread portion is screwed to the third internal thread portion, and the first oil well pipe and the second oil well pipe are coupled

1 . An oil well pipe coupling structure comprising:
 a first oil well pipe having an external thread portion on an outer circumferential surface; and   a second oil well pipe that has an internal thread portion that is screwed to the external thread portion on an inner circumferential surface and can be connected to the first oil well pipe,   wherein the external thread portion is made up of a first external thread portion having a diameter of a predetermined dimension and a substantially tapered second external thread portion that is disposed on one end portion side with respect to the first external thread portion and gradually contracts radially toward one end side,   the internal thread portion is made up of a first internal thread portion that is disposed on an opening end side and has a diameter of a predetermined dimension and a substantially tapered second internal thread portion that gradually contracts radially from the first internal thread portion side toward an inner side,   the first external thread portion is screwed to the first internal thread portion, the second external thread portion is screwed to the second internal thread portion, and the first oil well pipe and the second oil well pipe are coupled together;   wherein the external thread portion has a third external thread portion that is disposed on the one end side with respect to the second external thread portion and has a diameter of a predetermined dimension,   the internal thread portion has a third internal thread portion that is disposed on the inner side with respect to the second internal thread portion and has a diameter of a predetermined dimension, and   the third external thread portion can be screwed to the third internal thread portion, wherein the external thread portion has a first circular region including the first external thread portion,
 a second circular region including the second external thread portion, and a third circular region including the third external thread portion that are virtually divided in a radial direction, 
   an area of the first circular region is equal to or smaller than a third of a total cross-sectional area of a transverse section of the first oil well pipe,   an area of the second circular region is equal to or larger than a third of the total cross-sectional area of the transverse section of the first oil well pipe,   an area of the third circular region is equal to or smaller than a third of the total cross-sectional area of the transverse section of the first oil well pipe,   the internal thread portion has a fourth circular region including the first internal thread portion, a fifth circular region including the second internal thread portion, and a sixth circular region including the third internal thread portion that are virtually divided in a radial direction,   an area of the fourth circular region is equal to or smaller than a third of a total cross-sectional area of a transverse section of the second oil well pipe,   an area of the fifth circular region is equal to or larger than a third of the total cross-sectional area of the transverse section of the second oil well pipe, and   an area of the sixth circular region is equal to or smaller than a third of the total cross-sectional area of the transverse section of the second oil well pipe.   
     
     
         2 . The oil well pipe coupling structure according to  claim 1 ,
 wherein the first external thread portion and/or the third external thread portion have a thread with a symmetrical shape,   the first internal thread portion has the thread shape corresponding to the thread of the first external thread portion, and the third internal thread portion has the thread shape corresponding to the thread of the third external thread portion.   
     
     
         3 . The oil well pipe coupling structure according to  claim 1 ,
 wherein a sealing structure is provided between an outer circumferential surface of a tip portion of the first oil well pipe and an inner circumferential surface on a base end side of the internal thread portion of the second oil well pipe and/or between an outer circumferential surface on a base end side of the external thread portion of the first oil well pipe and an inner circumferential surface of the tip portion of the second oil well pipe.   
     
     
         4 . The oil well pipe coupling structure according to  claim 1 ,
 wherein a sealing structure is provided between an outer circumferential surface of a tip portion of the first oil well pipe and an inner circumferential surface on an inner side of the internal thread portion of the second oil well pipe and/or between an outer circumferential surface on a base end side of the external thread portion of the first oil well pipe and an inner circumferential surface of the opening end side of the second oil well pipe, and   in the sealing structure, a length in an axial direction of the outer circumferential surface of a tip portion of the first oil well pipe is set to shorter than a length in the axial direction of the third internal thread portion of the second oil well pipe and/or a length in the axial direction of the outer circumferential surface on the base end side of the external thread portion of the first oil well pipe is set to shorter than a length in the axial direction of the inner circumferential surface on the opening end side of the second oil well pipe.   
     
     
         5 . An oil well pipe having a hollow structure, comprising:
 an external thread portion on an outer circumferential surface,   wherein the external thread portion is made up of a first external thread portion having a diameter of a predetermined dimension and a substantially tapered second external thread portion that is disposed on one end portion side with respect to the first external thread portion and gradually contracts radially toward one end side, and   the external thread portion is screwed to a different member having an internal thread portion;   wherein the firstexternal thread portion andhas a third external thread portion that is disposed on the one end side with respect to the second external thread portion and has a diameter of a predetermined dimension, wherein the external thread portion has a first circular region including the first external thread portion, a second circular region including the second external thread portion, and a third circular region including the third external thread portion that are virtually divided in a radial direction,   an area of the first circular region is equal to or smaller than a third of a total cross-sectional area of a transverse section of the oil well pipe,   an area of the second circular region is equal to or larger than a third of the total cross-sectional area of the transverse section of the oil well pipe, and   an area of the third circular region is equal to or smaller than a third of the total cross-sectional area of the transverse section of the oil well pipe.   
     
     
         6 . The oil well pipe according to  claim 5 ,
 wherein the first external thread portion and the third external thread portion have the thread having a symmetrical shape.   
     
     
         7 . The oil well pipe according to  claim 5 ,
 wherein, on a tip side and/or a base end side of the external thread portion, an outer circumferential surface that can be brought into close contact with an inner circumferential surface of the different member substantially throughout an entire circumference when the external thread portion has been fitted into the internal thread portion of the different member is provided.   
     
     
         8 . The oil well pipe according to  claim 5 ,
 wherein, on a tip side and/or a base end side of the external thread portion, an outer circumferential surface that can be brought into close contact with an inner circumferential surface of the different member substantially throughout an entire circumference when the external thread portion has been fitted into the internal thread portion of the different member is provided, and   a length in an axial direction of the outer circumferential surface on the tip side of the external thread portion is set to shorter than a length in the axial direction of the third external thread portion and/or a length in the axial direction of the outer circumferential surface on the base end side of the external thread portion is set to shorter than a length in the axial direction of the first external thread portion.   
     
     
         9 . An oil well pipe having a hollow structure, comprising:
 an internal thread portion on an inner circumferential surface,   wherein the internal thread portion is made up of a first internal thread portion having a diameter of a predetermined dimension on an opening end side and a substantially tapered second internal thread portion that gradually expands radially along a direction away from the first internal thread portion, and   the internal thread portion is screwed to a different member having an external thread portion;   wherein the internal thread portion has a third internal thread portion that is disposed on the opening end side with respect to the second internal thread portion and has a diameter of a predetermined dimension,   wherein the internal thread portion has a fourth circular region including the first internal thread portion, a fifth circular region including the second internal thread portion, and a sixth circular region including the third internal thread portion that are virtually divided in a radial direction,   an area of the fourth circular region is equal to or smaller than a third of a total cross-sectional area of a transverse section of the oil well pipe,   an area of the fifth circular region is equal to or larger than a third of the total cross-sectional area of the transverse section of the oil well pipe, and   an area of the sixth circular region is equal to or smaller than a third of the total cross-sectional area of the transverse section of the oil well pipe.   
     
     
         10 . The oil well pipe according to  claim 9 ,
 wherein the first internal thread portion and the third internal thread portion have the thread having a symmetrical shape.   
     
     
         11 . The oil well pipe according to  claim 9 ,
 wherein, on the opening end side and/or an inner side of the internal thread portion, an inner circumferential surface that can be brought into close contact with an outer circumferential surface of the different member substantially throughout an entire circumference when the internal thread portion has been fitted into the external thread portion of the different member is provided.   
     
     
         12 . The oil well pipe according to  claim 9 ,
 wherein, on the opening end side and/or an inner side of the internal thread portion, an inner circumferential surface that can be brought into close contact with an outer circumferential surface of the different member substantially throughout an entire circumference when the internal thread portion has been fitted into the external thread portion of the different member is provided, and   a length in an axial direction of the inner circumferential surface on the opening end side of the internal thread portion is set to shorter than a length in the axial direction of the third internal thread portion and/or a length in the axial direction of the inner circumferential surface on the inner side of the internal thread portion is set to shorter than a length in the axial direction of the first internal thread portion.