Methods and apparatus relating to expansion tools for tubular strings
An expansion tool for use in a wellbore includes an expansion surface made up of a concave portion, a convex portion and a straight section therebetween. The straight section is formed according to a formula Y=(1.26)(X)−0.13, where X is the wall thickness of a tubular and Y is the length of the straight section. The concave portion and the convex portion have an arc length extending the concave portion to a trailing edge of the tool. The concave and convex portions are radius-shaped. The arrangement of the shapes and their relation to each other reduces relatively high and low contact pressures and lessens the effects of axial bending in a tubular or a connection.
1. An expansion tool for expanding a tubular in a wellbore comprising:
a leading end having a first outer diameter smaller than an inside diameter of the tubular to be expanded in the wellbore;
an expansion surface including:
a concave portion extending from the leading end;
a curvilinear convex portion extending from the center section and including a portion of the tool having the largest outer diameter; and
a straight center section extending from the concave portion, wherein the concave portion and convex portion are separated by the center section.
2. The expansion tool of claim 1 , wherein the convex portion includes an arc length extending the convex portion to a trailing end of the tool.
3. The expansion tool of claim 2 , wherein the concave and convex portions are substantially equal in size and arc length.
4. The expansion tool of claim 3 , wherein the concave and convex portions are each tangent to the center section at one end.
5. The expansion tool of claim 1 , wherein the concave and convex portions are radius-shaped.
6. The expansion tool of claim 1 , wherein the center section is formed according to a formula Y=(1.26)(X)−0.13, where X is the wall thickness of a tubular and Y is the length of the center section.
7. The expansion tool of claim 1 , further including a convex pilot radius formed at the leading end of the tool, the pilot radius adjacent to and tangent to the first concave portion.
8. The expansion tool of claim 1 , wherein the expansion surface has an average angle of 3 degrees with respect to a vertical axis of the tool.
9. A method of expanding a tubular, comprising:
passing an expansion tool through the tubular in a wellbore, the expansion tool having a first outer diameter smaller than an inside diameter of the tubular;
an expansion surface including:
a concave portion extending from a leading end;
a curvilinear convex portion extending from a straight center section,
wherein the concave portion and convex portion are separated by the center section; and
including a portion of the tool having the largest outer diameter; and thereby expanding an inner diameter of the tubular.
10. The method of claim 9 , further comprising:
expanding a threaded connection between a first tubular and second tubular.
11. An expansion tool for expanding a tubular in a wellbore comprising:
a leading end having a first outer diameter smaller than an inside diameter of the tubular to be expanded in the wellbore;
an expansion surface including:
a concave portion extending from the leading end;
a curvilinear convex portion extending from the center section and including a portion of the tool having the largest outer diameter, wherein the center section is formed according to a formula Y=(1.26)(X)−0.13, where X is the wall thickness of a tubular and Y is the length of the center section; and
a straight center section extending from the concave portion, wherein the concave portion and convex portion are separated by the center section.