The technology to cost effectively design, construct, operate, and maintain ASTM A269 TP316L/TP316 stainless-steel pipelines for oilfield saltwater service and freshwater service was developed between 2002 and 2004.
The first installations were austenitic pipe installed within discontinued, corroded carbon steel pipelines. Primary goals were to identify a cost-effective solution for a pipe-in-pipe application. After 2004, free-standing austenitic pipeline were installed in trenches. It was determined that coils of 316L/316 tubing in lengths of 2000 meters (6500 feet) were cost effective and readily available as line pipe material to simplify the field installation and joining practices. It was also determined that internal coatings, external coatings, and cathodic protection (except for risers) were not required for corrosion protection.
Highlights from the engineering assessments and the examination of 17 cut-out samples of in-service piping will be presented to demonstrate the suitability of 316L/316 for oilfield water applications. Boundary limitations for temperature, transported fluid composition, and soil composition were defined to ensure that corrosion and stress corrosion cracking would not occur. Mechanical design and joining methods and concepts were adopted from ASME B31.3 because existing pipeline codes (e.g. CSA Z662) did not, and currently do not address this material for oilfield pipelines.
Between 2002 and 2010, 90 pipelines for freshwater service and 55 pipelines for saltwater service were installed. A review in 2021 indicated that none of the installed pipelines have experienced leaks or failures associated due to in-service degradation. Two leaks have occurred during this 19-year period; one leak was attributed to installation wear and one leak was attributed to poor installation of a mechanical fitting. Material suitability was also verified via examination of cut-out pipe/fitting samples, and the use of stainless-steel corrosion coupons for 13 years. A comparison to other materials of construction indicates that the 316L/316 pipelines performed better.
This case history will address the successful design, construction, operation, and maintenance of austenitic stainless-steel pipelines during the 2002 to 2021 period.