Environment – Assisted Cracking (EAC), also referred to as stress corrosion cracking, is a growing problem for oil and gas producers given the increased incidence of drilling in HPHT areas. It is a complex issue that is attributable to the interaction of sensitive, stainless steel metallurgy under applied or residual stress, with the various clear brine packer fluids used in today's critical completions. Applications of standard corrosion tests and experiments have generated very few of the answers needed to help producers predict how various combinations of tubular metallurgies and fluids will perform together in the well. Much more specific empirical data is needed to understand the mechanisms causing these failures, and how they can be avoided.

In an effort to find the difficult answers, two leading manufacturers of martensitic stainless steel tubulars, and clear brine fluids JFE and TETRA, have joined their technical resources to scientifically examine the phenomena of stress corrosion cracking. The technical alliance, which is called the ChemiMetallurgy™ research program, has developed an accelerated EAC test methodology that replicates known tubular failures that have occurred in the field over the past few years. Lessons learned have permitted extensive testing of multiple combinations of metallurgies and packer fluids to determine their interactions under actual well conditions.

By early in 2005, the testing protocol will have conducted more than 3000 tests gauging the interactions of more than 16 fluid combinations with 6 different chrome tubulars. These tests are being run under high stress, varying temperatures, with the additives, gases, and typical formation fluids that would be found in a well.

The testing to date has delivered some interesting surprises. Of special relevance is the importance of subtle differences in fluid and metal composition upon their susceptibility to EAC. Indications are clear: small differences can promote significant cracking consequences.

Results of these studies matching fluid with metallurgy not only minimize the risk of failure in the field, but also provide compelling economic benefits. Given a choice of several equidensity fluids that have been tested to be EAC compatible with specific tubulars, a fluid can be selected for use based on lower cost and/or other performance considerations.

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