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Beneficial Effects of Chemical Treatment And Maintenance Pigging Programs In Returning an Offshore Pipeline to Pre-Hurricane Ike Conditions Following a Breach And the Ingress of Seawater And Sand, And the Effects of Bacteria Generated H2S
Powell, Daniel (Williams Midstream) | Fincher, Dale (Williams Midstream) | Gonzales, Raymond (Williams Midstream) | Melancon, Burkin (Williams Midstream) | Winters, Robert H. (Champion Technologies) | Rodrigue, Brad (Champion Technologies) | Brown, Elliot (EB Scientific Enterprises)
ABSTRACT ABSTRACT When Hurricane Ike crossed the Gulf of Mexico in September 2008, one of the major laterals in an offshore gas gathering system was ripped from the trunkline. As a consequence of that breach, approximately 75,000 BBL (11.9 MM liters) of seawater entered the trunkline, and approximately 40,000 BBL (6.4 MM liters) of seawater entered the lateral. A previous paper (NACE #10064) described the repairs, the high levels of hydrogen sulfide (H2S) that were generated by microbiological activity, the monitoring program, and the chemical treatment and maintenance pigging programs, which were implemented to re-establish control over the SRBs and the H2S they generated. This paper is a follow up to that report. Although inhibitor residuals have been very high, sand production appears to have temporarily increased as the sand from within the lateral and trunkline is slowly transported uphill to the onshore gas processing facility, “one girth weld at a time.” Of interest, the iron counts have become elevated. This may be attributed to the maintenance (cleaning) pigs, which are slowly pushing the sand that entered the pipelines when the pipeline was breached. The pigs, coupled with the transportation of the sand, are apparently scraping and “sand blasting” the walls of the trunkline, thus removing the oxides and corrosion products from the pipeline. This paper also presents results from destructive metallurgical examination of a hot tap coupon or “cut-out” obtained from the trunkline when a new 6” (15.2 cm) OD subsea tie-in (SSTI) was made at the 3:00 o’clock orientation in 2010. INTRODUCTION In an earlier paper we described an offshore gathering system within the Gulf of Mexico, which filled with seawater during the passage of Hurricane Ike on September 13, 2008 when one of the laterals was ripped from the trunkline.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Health, Safety, Environment & Sustainability > Health > Noise, chemicals, and other workplace hazards (1.00)
- (2 more...)
Controlling The Formation Of A Non-Sulfur Based Black Powder Within A New Natural Gas Processing Plant's Waste Heat Recovery Unit And Minimizing Any Threats Of A Possible Metal Dusting Corrosion Mechanism Within Process Tubing
Powell, Daniel (Williams Midstream One Williams Center) | Stapley, Larry A. (Williams Midstream One Williams Center) | Hughes, Jason (Williams Midstream One Williams Center) | Brown, Elliot (EB Scientific Enterprises)
ABSTRACT "Black powder" is commonly used to describe iron sulfide or iron oxide compounds, which may form within natural gas pipelines. Extensive "black powder" problems were reported following the startup of a new gas processing facility in 2009. Specifically, an extensive dark to black powdery dust or flakes were found clogging the waste heat recovery unit (WHRU) heat exchangers and the downstream filters and piping. The "black powder" was not observed in the inlet filters to the plants or the amine systems, but was observed within the mole sieve dehydrators (Presumably, the powder was transported there during the regeneration cycle.) A sample of the gas from within the outlet header of the WHRU was also collected and analyzed, and found to contain 7% (mole) hydrogen gas. Investigations focused on the processes, which could result in the formation of the black colored powders, as well as potential threats to the integrity of the process equipment and piping, including possible metal dusting mechanisms. This paper will summarize the result of those investigations, the changes in the processes, which significantly reduced further formation of the black-colored powdery material to manageable levels and enabled the units to be returned to service, and initiatives to ensure the continuing integrity of the process equipment and piping. Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. INTRODUCTION When a new gas processing facility in North Central Colorado initially started up, a "black powder" formed, clogging the waste heat recovery unit heat exchangers, the downstream system filters, and the facility piping.