171 / 2013-04-20 23:56:22

The Jump-out Failure Analysis Of Long Round Thread Casing

long round thread, jump-out, fine element method

There was a directional well in China western oil field with depth of 3000m.It was run casing (139.7 × 7.72 mm J55 LC) to 1852m, casing string fall off. The 2 short section samples of failure were taken, respectively the field end pin, the box and mill end pin. The sample geometric parameters and thread contour were measured using thread gauge and profilometer. Material chemical composition, mechanical properties and metallographic of sample were researched. According to the results of test, the main influencing factors of long round thread jump-out were analyzed by nonlinear finite element. One was the quality of thread itself, including thread parameters, the material properties and geometry dimension; the other was field casing running operation and make-up. The numerical simulation results were consistent with the field failure sample measured morphology. So we knew that the main reasons for the jump-out failure were that the material yield strength of sample was less than API5CT specified value and field end pin make-up turns was shortage .