Patent ID: 9163296
Filing Date: 2015-10-20
Classification: C21D,C22C,E21B

Abstract:
1. A coiled tube for use in a well configured to withstand axial loads, the coiled tube comprising: a plurality of strips welded together end-to-end, wherein welded together end-to-end strips are formed into a tubular shape and seam welded along their lengths to produce a continuous length of coiled tube having a first end configured to be located at a bottom of the well and a second end configured to be located at a top of the well; wherein substantially every portion along the length of the coiled tube has a yield strength configured to withstand an axial load resulting from the weight of the coiled tube from said portion to the first end of the coiled tube, the yield strength (YS) of every portion being governed by the equation: wherein at least a first portion along the length of the coiled tube has a greater yield strength than the yield strength at a second portion, where the first portion is located closer to the second end than the second portion is to the second end, and wherein the coiled tube has a tempered martensite microstructure in both the first and second portions resulting from a continuous and controlled heat treatment over the length of the first and second portions to provide for the first portion having the greater yield strength and the second portion having a lower yield strength.