The appropriate choice of materials for well completions in sour fields is an important factor in the economic success of oil and gas activities. The choice is governed by mechanical properties, resistance to both corrosion damage and sulphide stress cracking (SSC), availability and cost. Resistance to SSC is often the principal factor affecting the choice of materials for H2S containing environments, since the occurrence of SSC can result in a catastrophic and potentially hazardous failure. This often necessitates the selection of highly alloyed, highly priced materials. Therefore, it is important to have a method of assessing candidate materials that leads to the most cost-effective choice being made.

An alternative approach has been developed in which the emphasis is put on failure prediction. This approach combines the results of constant extension rate tensile (CERT) testing with fracture mechanic assessments. On the basis of this approach a "fitness for purpose" evaluation of a range of materials has been undertaken, thus allowing the selection of the most suitable/cost-effective material for the intended duty. Furthermore, the present concept has led to a better definition of operational limits of tubular goods for sour service applications over a wide range of testing conditions.

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