Abstract
Sudden blow-out of tubing after only six days of production tests of the 12,000-foot Walter Marr Well No. 1, Pincher Creek Field, Canada caused an investigation of causes for failure. Examination of the removed 9 percent nickel steel tubing showed no obvious defects and calculations showed failures not due to excessive triaxial loading.
Investigators, after discarding embrittlement as a. cause, initiated tests to determine if stress corrosion cracking was the cause, because well fluids and gases included 10 percent hydrogen sulfide and 6.3 percent carbon dioxide by volume. Specimens of 9 percent nickel steel tubing were submerged in tap water containing hydrogen sulfide and carbon dioxide in a cell at 5000 psi and 190 degrees F. All specimens failed in six days.
Numerous other tests of the tubing and other steels at varying loadings were conducted, including pre-stressed and re-heat treated but not pre-stressed samples. These tests developed the following tentative conclusions: 1) Tubing failures at the Marr well resulted from stress-corrosion cracking. 2) Susceptibility to failure in hydrogen sulfide environments is not limited to 9 percent nickel steel. Steels treated to produce Rockwell C24 to 26 may be rendered susceptible. 3) Plastic deformation greatly increases susceptibility to failure, but is not essential if protective corrosion products films are removed. 4) Embrittlement is not a primary cause of failure but may be contributory. 5) Susceptibility may be reduced, by composition changes.
